NCHurricane2009's Blog

2013 Atlantic Hurricane Season Birdseye Discussion #29

By: NCHurricane2009, 9:16 AM GMT on June 30, 2013

...SUNDAY JUNE 30 2013 5:15 AM EDT...
Tropical wave activity remains on the upswing...with one crossing the Lesser Antilles with decent activity (and being mentioned in the NHC Tropical Weather Outlook within the last 24 hours)...another that has seen an increase in activity as it enters the western Caribbean (also mentioned the NHC Outlook in the last 24 hours)...and yet another vigorous tropical wave rolling off of Africa. However their is no near-term development anticipated from any tropical wave....see tropical belt discussion below for details.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_29_2013_2345Z_zps1ef03a45.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0129Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_29_2013_2345Z_zpsa604c8e8.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Large frontal cyclone and upper trough is parked offshore of the west US coast...with warm air advection ahead of it producing a building upper ridge over the SW US. Upper vorticity has ejected eastward from this system days ago...which is currently an upper vortex over the Great Lakes. Eastern divergence of this upper vortex supports a 1002 mb frontal cyclone centered over the US/Canada border. Western convergence of this upper vortex supports a surface ridge building into the western US and western Canada as shown by the red-zig-zag line in the upper-left corner of the above atmo chart. NW Atlantic upper ridge is supported by warm air adevction ahead of the 1002 mb cyclone...which has a relatively new extension near the the SE US coast.

P2...During the previous discussion...vorticity of upper trough crossing Hudson Bay was consumed by upper trough mentioned in paragraph P3 and Great Lakes upper vortex mentioned in paragraph P1...with the associated east Canada surface front diminshing. This early morning...east Canada surface front has been re-invigorated as a 1002 mb frontal cyclone by another upper trough crossing Hudson Bay.

P3...Upper trough previously over the high seas midway between Greenland and Canada is currently SE of Greenland. Its western convergence supports surface 1033 mb ridge SE of Greenland.

P4...Large upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1031 mb...is NE of the Azores. It is supported by northeastern convergence of eastern Atlantic upper ridge mentioned in paragraph P9. This surface ridge continues to have a westward extension currently located across the W Atlantic...western Cuba...and Gulf of Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraph P1...including east side of NW Atlantic upper ridge and east side of SW US upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical wave over the central Caribbean during the previous discussion is moving into the western Caribbean. This was previously a special feature on this blog with anticipation that favorable upper winds would develop in the western Caribbean...but then was cancelled as a special feature during discussion #26 when models showed that upper winds would no longer be favorable due to amplification of paragraph P1 upper vorticity. Indeed paragraph P7 of discussion #28 confirmed that upper winds had become less favorable. However...latent heat release from eastern Pacific t-storm activity has amplified upper ridging from the southwest that is once again making upper winds a bit more favorable...albeit the tropical wave is still under some unfavorable westerly shear. To the east of the wave axis...t-storms have increased due to split flow upper divergence between the upper ridging building from the SW and paragraph P7 Lesser Antilles-Bermuda upper vortex...resulting in the tropical wave being introduced into the NHC Tropical Weather Outlook in the last 24 hrs. Despite the slight increase in favorability from the upper ridging building from the SW (and shown in the GFS model to persist for another 48 hrs after which time the paragraph P1 Great Lakes upper vortex and paragraph P7 Gulf upper vortex amplify in unison and erode the favorable upper ridging)...no development is expected with lack of computer model support...the fact that the upper ridging is not quiet enough to eliminate the westerly shear...and that it will soon be interacting with the Yucatan...Central America...and SE Mexico landmasses.

P7...Upper vortex persists midway between the Lesser Antilles and Bermuda. Upper vortex over the Bay of Campeche has shifted northward into the Gulf of Mexico due to eastern Pacific upper ridging building from the southwest as mentioned in paragraph P6 above.

P8...Tropical wave continues crossing the Lesser Antilles and will be in the eastern Caribbean later today. As paragraph P9 below explains...favorable upper ridging to the east has built into the central tropical Atlantic. These favorable upper winds previously enhanced the thundestorm activity of this tropical wave...but recently the thunderstorms became more associated with the eastern divergence of the paragraph P7 Bermuda-Lesser Antilles upper vortex. Even more recently...the thunderstorms have diminshed as the tropical wave is entering the non-divergent region directly south of the upper vortex...causing the NHC to remove this wave from their tropical weather outlook as of 2 AM EDT.

P9...Tropical wave SW of the Cape Verde Islands continues to be located in a favorable low shear deep-layered easterly wind current supported by south side of paragraph P5 surface ridge and south side of anticyclonic upper ridge in the eastern Atlantic. The paragraph P4 upper vortex and pararagph P7 Leser Antilles-Bermuda upper vortex have weakened enough to allow this favorable upper ridge to expand westward into the open central tropical Atlantic. Despite the favorable upper winds...this tropical wave remains suppressed by dry Saharan air (seen by brown shading in lower-right of above thermo chart) advected from Saharan Africa by aforementioned deep-layered easterly wind current.

P10...Metoesat-9 satellite imagery continues to suggest a vigorous tropical wave rolling off of the west African coast and into the eastern tropical Atlantic. Despite its early impressivenes...currently their is no computer model support for devleopment...and it could easily cough on dry air that lies ahead in its path much like the tropical wave mentioned in paragraph P10 above.

2013 Atlantic Hurricane Season Birdseye Discussion #28

By: NCHurricane2009, 1:30 PM GMT on June 29, 2013

...SATURDAY JUNE 29 2013 9:30 AM EDT...
Tropical wave activity is on the upswing...with one approaching the Lesser Antilles with an increase in thunderstorms (and being mentioned in the NHC Tropical Weather Outlook within the last 24 hours) and yet another vigorous tropical wave about to roll off of Africa. However their is no near-term development anticipated from any tropical wave....see tropical belt discussion below for details.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_28_2013_2345Z_zps495780ab.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0119Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_28_2013_2345Z_zps24013ffc.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Large frontal cyclone and upper trough is parked offshore of the west US coast...with warm air advection ahead of it producing a building upper ridge over the SW US. Upper vorticity has ejected eastward from this system days ago...which is currently an upper vortex over the Great Lakes. Eastern divergence of this upper vortex supports a deepening 996 mb frontal that has moved from the NE US and onto the US/Canada border. Western convergence of this upper vortex supports a surface ridge building into the western US as shown by the red-zig-zag line in the upper-left corner of the above atmo chart. NW Atlantic upper ridge mentioned in paragraph P3 of the previous discusison has shifted northward from Bermuda while supported by warm air adevction ahead of the 996 mb cyclone.

P2...Vorticity of upper trough crossing Hudson Bay (paragraph P2 of the previous discussion) has been consumed by upper trough mentioend in paragraph P3 and Great Lakes upper vortex mentioned in paragraph P1. As a result...the associated surface frontal cyclone has been absorbed by the 996 mb cyclone mentioned in paragraph P1...with what is left of it a dissipating front north of the cyclone. 1022 mb surface ridge over Hudson Bay was formerly supported by western convergence of the absorbed upper trough.

P3...Upper trough moving into the far NW Atlantic (paragraph P3 of the previous discussion) is currently over the high seas midway between Greenland and Canada.Its eastern divergence supports a deepening 1000 mb frontal cyclone that has moved from SE Nefoundland north-northeastward to the waters just offshore of Greenland's south tip. Its western convergence supports 1024 mb ridge just E of Newfoundland.

P4...Surface troughing SSE of Newfoundland has dissipated.

P5...Large upper vortex persists in the open central Atlantic.

P6...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1036 mb...is NE of the Azores It is supported by eastern convergence of NE Atlantic upper ridge wave that is currently a northward extension of the eastern lobe of tropical upper ridging described in paragraphs P9 and P10 below. This surface ridge continues to have a westward extension currently located across the W Atlantic...Florida Straits...and Gulf of Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraphs P1...including east side of NW Atlantic upper ridge and east side of SW US upper ridge.

...TROPICAL BELT DISCUSSION...
P7...Western of the two Caribbean tropical waves in paragraph P7 of the previous discussion has crossed Central America into the eastern Pacific...continuing the upheaval of eastern Pacific activity (see www.nhc.noaa.gov for latest info on eastern Pacific activity...which is not covered on this blog). Eastern of the two Caribbean tropical waves is currently in the open central Caribbean. Meanwhile...amplification of paragraph P1 Great Lakes upper vorticity has triggered a chain reaction that has made upper winds over this tropical wave less favorable. Due to the amplifcation....fragment of paragraph P1 SW US upper ridge has been pushed southward into the US Gulf coast...which has pushed the paragraph P8 Bay of Campeche upper vorticity southward...which in turn has de-amplified the western lobe of low-latitude upper ridging such that the tropical wave is currently under hostile westerly shear north of the upper ridge axis. However...the de-amplified western lobe of the upper ridge continues supporting a flare up of t-storms over Central America and to the south of this tropical wave.

P8...Upper vortex between Bermuda and the Bahamas has shifted SE such that it is now midway between Bermuda and the Lesser Antilles. Surface trough and t-storms north of the Lesser Antilles associated with this vortex's eastern divergence have diminished in the last 24 hrs. Upper vortex also persists over the Bay of Campeche.

P9...Tropical wave midway between the Lesser Antilles and Cape Verde Islands in the previous discussion is nearing the Lesser Antilles...and will be crossing the Antilles later today. As paragraph P10 below explains...the eastern lobe of this upper ridging is continuing its expansion into the open central tropical Atlantic. These favorable upper winds have reached this trpoical wave within the last day such that the associated thunderstorms have tremendously increased...and these thunderstorms are also becoming more associated with the eastern divergence of the paragraph P8 Bermuda-Lesser Antilles upper vortex. Even though the NHC mentioned this system in their tropical weather outlook during the last 24 hrs...no devleopment is expected as this tropical wave is moving into hostile SW vertical shear ahead of the Bermuda-Lesser Antilles upper vortex.

P10...Tropical wave south of the Cape Verde Islands in the previous discussion is now SW of the islands. This tropical wave is located below favorable eastern lobe of low-latitude upper ridging which currently has an anticyclonic center NNW of the Cape Verde Islands...and for the next two days models show the paragraph P5 upper vortex and pararagph P8 Leser Antilles-Bermuda upper vortex weakening enough to allow this eastern lobe of low-latitude upper ridge to expand westward into the open central Atlantic as this tropical wave arrives their. Despite forecast favorable upper winds...as expected this tropical wave has moved westward into an unfavorable batch of dry Saharan air (seen by brown shading in lower-right of above thermo chart) apparently advected from Saharan Africa by south side of paragraph P6 1036 mb ridge center and re-enforced by eastern convergence of the paragraph P6 upper ridge wave and eastern convergence of anticyclonic center NNW of the Cape Verde Islands mentioned in this paragraph.

P11...Metoesat-9 satellite imagery previously showed an impressive tropical wave over interior western Africa with a curved t-storm band NW of the axis. This tropical wave is currently marked in the lower-right corner of the above atmo chart as it is about to roll off the west African coast. Despite its early impressivenes...currently their is no computer model support for devleopment...and it could easily cough on dry air that lies ahead in its path much like the tropical wave mentioned in paragraph P10 above.

2013 Atlantic Hurricane Season Birdseye Discussion #27

By: NCHurricane2009, 3:40 AM GMT on June 28, 2013

...THURSDAY JUNE 27 2013 11:41 PM EDT...
Atlantic tropics are quiet at this hour...

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_27_2013_2045Z_zpsac8e65ee.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 2228Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_27_2013_2045Z_zps08b92942.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Large frontal cyclone and upper trough is parked offshore of the west US coast...with warm air advection ahead of it producing a building upper ridge over the SW US. Upper vorticity has ejected eastward from this system...which is currently an upper trough over the Great Lakes. Eastern divergence of this upper trough supported a 1002 mb frontal cyclone over south-central Canada during the previous discussion which has now weakened to 1004 mb while the non-divergent axis of the upper trough settles overhead of it. Eastern divergence of this upper trough now supports a 1004 mb frontal depression over the NE US. Spit flow divergence between westerlies across this upper trough and easterlies south of the SW US upper ridge supports 1010 mb frontal depression over north-central Kansas...while western convergence of this upper trough supports a surface ridge building to the north of that frontal depression.

P2...An upper trough and surface frontal cyclone is entering the upper left corner of the above atmo chart from Canada's Husdon Bay at a location NE of the paragraph P1 weather system.

P3...Upper trough near the east Canada coast during the previous discussion has now crossed southern Greenland and continues east into the Atlantic high seas...and so has the attendant surface frontal cyclone. Western convergence of this upper trough supports surface ridge that has moved from Hudson Bay and into the waters SW of Greenland while strengthening to 1023 mb. Not far behind this system...another upper trough that was over eastern Canada/NE US in the previous discussion is now moving into the far NW Atlantic...with its eastern divergence supporting a 1006 mb frontal depression currently over SE Newfoundland. Warm air advection ahead of this 1006 mb depression formerly supported NW Atlantic upper ridge currently centered over Bermuda...but this upper ridge is now supported by warm air advection ahead of the NE US 1004 mb depression mentioned in paragraph P1.

P4...Surface troughing persists SSE of Newfoundland.

P5...Large upper vortex persists in the open central Atlantic.

P6...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1038 mb...is NE of the Azores and remains generally deep-layered in nature. The 1038 mb surface center is supported by upper convergence NE of its upper-level center. This upper-level center has been anticyclonic in nature until today...when the center opened into an upper ridge wave while merging with the eastern lobe of tropical upper ridging to the south described in paragraphs P9 and P10 below. This surface ridge continues to have a westward extension currently located across the W Atlantic...Florida...and Gulf of Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraphs P1 and P3...including east side of NW Atlantic upper ridge and east side of SW US upper ridge.

...TROPICAL BELT DISCUSSION...
P7...Pair of tropical waves continue westward across the Caribbean Sea (see above atmo chart for precise locations of both waves as of this writing). Meanwhile low-latitude upper ridging persists across much of the Atlantic tropics...but a large section of this upper ridge remains de-amplified by the paragraph P8 Bahamas-Bermuda upper vortex and paragraph P5 central Atlantic upper vortex. However...western lobe of this upper ridge is not so de-amplified such that its enhanced poleward outflow supports a flare up of t-storms over Panama and Costa Rica to the south of these tropical waves.

P8...Upper vortex remains quasi-stationary between Bermuda and the Bahamas...with its eastern divergence supporting t-storms and a surface trough just north of the Lesser Antilles (this surface trough may be a northern fracture of the eastern of the two tropical waves mentioned in paragraph P7 above). Upper vortex persists over the Bay of Campeche.

P9...Tropical wave midway between the Lesser Antilles and Cape Verde Islands remains suppressed by the westerly vertical shear on the north side of the de-amplified portion of low-latitude upper ridging mentioned in paragraph P7 above. However as paragraph P10 below explains...the eastern lobe of this upper ridging is begining to expand....with favorable upper outflow of this eastern lobe supporting a recent and sprawling increase in t-storms to the east of the wave axis.

P10...Tropical wave rolling off of Africa in the previous discussion has been added to NHC TAFB maps in the last 24 hrs...and is currently located south of the Cape Verde Islands. After previously featuring an impressive t-storm cluster...it now only continues to have weak cloudiness. This tropical wave is located below favorable eastern lobe of low-latitude upper ridging...and for the next three days models show the paragraph P5 upper vortex and pararagph P8 Bahamas-Bermuda upper vortex weakening enough to allow this eastern lobe of low-latitude upper ridge to expand westward into the open central Atlantic as this tropical wave arrives there. Despite forecast favorable upper winds...their is a batch of dry Saharan air due west of the tropical wave (seen by brown shading in above thermo chart) apparently advected from Saharan Africa by south side of paragraph P6 1039 mb ridge center. Moreover their is no computer model support showing development from this wave in the next 3 days...and beyond 3 days this wave may get sheared by south side of the Bahamas-Bermuda upper vortex.

2013 Atlantic Hurricane Season Birdseye Discussion #26

By: NCHurricane2009, 9:31 AM GMT on June 27, 2013

...THURSDAY JUNE 27 2013 5:30 AM EDT...
I have discontinued the pair of Caribbean tropical waves as a special feature on this blog due to the loss of thunderstorms in the south-central Caribbean Sea in addition to computer models trending toward less favorable upper winds. See paragraph P6 in the tropical belt section below for more information.

Vigorous tropical wave appears to be rolling off of Africa...and within the next 4 days will track toward favorable upper winds to develop in the open central Atlantic. However a batch of Saharan dry air detected to the west and lack of computer model support suggests no development. See paragraph P9 in the tropical belt section for more information.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_26_2013_2345Z_CORRECTED_zps1ac1e7a5.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 2228Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_26_2013_2345Z_zps28bfc408.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Large frontal cyclone and upper trough is parked offshore of the west US coast...with warm air advection ahead of it producing a building upper ridge over the SW US. A slowly-developing upper trough has ejected eastward from this system and is supporting another frontal cyclone currently at 1002 mb over south-central Canada.

P2...Upper trough persists near the east Canada coast. Attendant surface frontal cyclone currently over southern Greenland has weakened from 980 to 996 mb in the last 24 hrs while the non-divergent upper trough axis shifts overhead of it (western convergence of this upper trough also supports 1018 mb ridge over Hudson Bay). Elsewhere over North America...central US upper trough has moved into eastern Canada/NE US with its eastern divergence supporting a 1005 mb frontal depression that has been quasi-stationary near the US/Canada border. Warm air advection ahead of the 1005 mb depression supports a NW Atlantic upper ridge currently centered over Bermuda.

P3...Surface troughing persists SSE of Newfoundland.

P4...Large upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1039 mb...is NE of the Azores and remains generally deep-layered in nature. The 1039 mb surface center is supported by upper convergence NE of its upper-level center. This surface ridge continues to have a westward extension currently located across the W Atlantic...SE United States...and Gulf of Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraphs P1 and P2...including east side of NW Atlantic upper ridge and east side of SW US upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Pair of tropical waves continue westward across the Caribbean Sea (see above atmo chart for precise locations of both waves as of this writing). Meanwhile low-latitude upper ridging persists across much of the Atlantic tropics...but a large section of this upper ridge remains de-amplified by the paragraph P7 Bahamas-Bermuda upper vortex and paragraph P4 central Atlantic upper vortex. Upper winds over the western Caribbean Sea continue to become more favorable as the not-so-deamplified western lobe of this upper ridge merges with Florida-area upper ridge mentioned in paragraph P7...and the pinnacle of these favorable upper winds will be between now and 72 hrs...after which time the computer models have been increasingly aggressive with the paragraph P1 weather system's amplitude to the degree that they now forecast the associated upper trough to come in from the NW as squeeze out the favorable upper winds. Event the enthusiastic CMC computer model is no longer enthusiastic about developing the pair of Caribbean Sea tropical waves...and therefore these waves are no longer special features on this blog.

P7...Upper vortex remains quasi-stationary between Bermuda and the Bahamas. Upper vortex that recently migrated into the Gulf of Mexico (while orbiting around Florida-area upper ridge) is currently centered over the Bay of Campeche.

P8...Tropical wave WSW of the Cape Verde Islands in the previous discussion is now midway between the Lesser Antilles and Cape Verde Islands. It remains suppressed by the westerly vertical shear on the north side of the de-amplified portion of low-latitude upper ridging mentioned in paragraph P6 above.

P9...Satellite animation shows a supsect tropical wave along the west coast of Africa as marked in the lower-right of the above atmo chart. The wave featured an impressive t-storm cluster...and even though the t-storm cluster has fizzled for now...the shape of the remaining debris clouds suggest cyclonic turning about the wave axis. This suspect tropical wave is located below favorable eastern lobe of low-latitude upper ridging...and for the next four days models show the paragraph P4 upper vortex and pararagph P7 Bahamas-Bermuda upper vortex weakening enough to allow this low-latitude upper ridge to recover northward in the open central Atlantic as this tropical wave arrives there. Despite forecast favorable upper winds...their is a batch of dry Saharan air due west of the tropical wave (seen by brown shading in above thermo chart) apparently advected from Saharan Africa by south side of paragraph P9 1039 mb deep-layered ridge center. Moreover their is no computer model support showing development from this wave in the next 4 days...and beyond 4 days this wave may get sheared by south side of the Bahamas-Bermuda upper vortex.

2013 Atlantic Hurricane Season Birdseye Discussion #25

By: NCHurricane2009, 4:33 AM GMT on June 26, 2013

...WEDNESDAY JUNE 26 2013 12:30 AM EDT...
Pair of tropical waves continues to head to favorable upper winds developing in the western Caribbean Sea. Based on current observations and the forecast shown in computer model runs...this situation appears rather similar to the formation of last week's Tropical Storm Barry...and therefore I continue to have the pair of tropical waves as a special feature. See special feature section below on potential tropical cyclone development in the western Caribbean region within the next 4 days.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_25_2013_2345Z_zps7885c1fe.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 2230Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_25_2013_2345Z_zps36fa64b3.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPEICAL FEATURE...TROPICAL WAVE PAIR CROSSING THE CARIBBEAN SEA...
Low-latitude upper ridge persists across much of the Atlantic tropics. Pair of tropical waves has continued westward across the Lesser Antilles...with both wave axes now in the Caribbean Sea (see above atmo chart on precise location of both wave axes as of this writing). NW Atlantic upper ridge (paragraph P2) had recently pushed the paragraph P6 and P4 upper vorticity southward such that much of the low-latitude upper ridging remains de-amplified. The de-amplified portion of the low-latitude upper ridge previously suppressed these tropical waves with hostile westerly vertical shear.

Meanwhile the western lobe of the low-latitude upper ridge is not quiet as de-amplified such that its anticyclonic outflow continues enhancing an area of t-storms over the south-central Caribbean Sea. Coupled with tropical wave activity sliding toward such a t-storm cluster...this pattern is quiet similar to the pattern in paragraph P8 of discussion #15 just before last week's pre-Barry disturbance became a special feature on this blog. Therefore I continue to have this tropical wave pair as a special feature...especially considering that computer models insist on expanding the paragraph P6 Florida-area upper ridge into the W Caribbean in between the two paragraph P6 upper vortices (and I think some of this favorable W Caribbean upper ridging will also be a manifestation of the anticyclonic outflow presently over the south-central Caribbean t-storms).

Regarding computer model support...CMC continues to be the most aggressive in showing development (now by 144 hrs) while GFS support continues to be lax if their is any support at all. However with models also showing the W Caribbean upper winds becoming quiet favorable between now and 96 hours...I think gradual tropical cyclone development in the W Caribbean could occur within the next 96 hours (4 days). Apparenty as the paragraph P1 weather system has become better sampled over land (as opposed to its more sparse sampling when it was over the Pacific)...their is more vorticity associated with the developing shortwave upper trough such that in the last 24 hrs models have increasingly depicted the paragraph P1 weather system becoming more amplified than previously shown. This means the paragraph P1 weather system could erode the west extent of the paragraph P5 ridge moreso than previously thought to the degree that this system could end up getting pulled more northward into the Gulf of Mexico. For instance the CMC computer model shows a strong tropical cyclone developing out of this system that turns northward into the eastern Gulf of Mexico. This early on its hard to make any defintive forecasts from any one model run...so stay tuned over the next days....

...MID-LATITUDES DISCUSSION...
P1...Large frontal cyclone and upper trough is parked offshore of the west US coast. In the next days...a slowly-developing shortwave upper trough will soon eject eastward from this system while supporting another frontal cyclone. The early phases of this are beginning in the upper-left corner of the above chart with a 1001 mb surface frontal depression over the Dakotas.

P2...Upper trough persists near the east Canada coast...with its eastern divergence supporting a 980 mb frontal cyclone that has drifted eastward into southern Greenland...and with its western convergence supporting a 1020 mb surface ridge over Hudson Bay. Elsewhere over North America...central US upper trough's eastern divergence supports a 1002 mb frontal depression that has migrated eastward from south-central Canada to the Maine/Canada border in the last 24 hrs. Warm air advection ahead of the 1002 mb depression supports a NW Atlantic upper ridge.

P3...1020 mb frontal depression SSE of Newfoundland mentioned in paragraph P3 of the previous discussion has weakened into mere surface troughs as the south extent of the supporting paragraph P2 east Canada coast upper trough has lifted north-northeastward from the region.

P4...Large upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1037 mb...is NE of the Azores and remains generally deep-layered in nature. The 1037 mb surface center is supported by upper convergence NE of its upper-level center. This surface ridge continues to have a westward extension currently located across the W Atlantic...SE United States...and Gulf of Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraph P2...including east side of NW Atlantic upper ridge...west side of upper trough along east coast of Canada...and west side of central US upper trough.

...TROPICAL BELT DISCUSSION...
P6... Central Bahamas upper vortex has shifted a bit NE into the waters midway between the Bahamas and Bermuda. Upper vortex that recently migrated into the Gulf of Mexico (while orbiting around Florida-area upper ridge) is currently centered over the SW Yucatan peninsula of Mexico.

P7...Suspect tropical wave south of the Cape Verde Islands...mentioned in paragraph P8 of the previous discussion...has been added to NHC TAFB maps in the last 24 hrs and is currently located well to the WSW of the Cape Verde Islands. As expected in the previous discussion...it has left behind the favorable eastern lobe of low-latitude upper ridging while moving into the hostile westerly vertical shear environment mentioned in the above special feature section. Therefore I continue to expect no development here in the short-term.

2013 Atlantic Hurricane Season Birdseye Discussion #24

By: NCHurricane2009, 3:57 AM GMT on June 25, 2013

...MONDAY JUNE 24 2013 11:55 PM EDT...
Pair of tropical waves moving across the Lesser Antilles is heading toward favorable upper winds developing in the western Caribbean Sea. Based on current observations and the forecast shown in computer model runs...this situation appears rather similar to the formation of last week's Tropical Stom Barry...and therefore I have upgraded the pair of tropical waves to a special feature. See special feature section below on potential tropical cyclone development in the western Caribbean region within the next 5 days.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_24_2013_2345Z_zps51342180.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0739Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_24_2013_2345Z_zps3dd4db27.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPEICAL FEATURE...TROPICAL WAVE PAIR ENTERING THE CARIBBEAN SEA...
Low-latitude upper ridge persists across much of the Atlantic tropics. Pair of tropical waves has continued westward across the Lesser Antilles...with the western of the two now in the eastern Caribbean. Upper ridge that has moved into the NW Atlantic (paragraph P2) has pushed the paragraph P7 and P4 upper vorticity southward such that much of the low-latitude upper ridging has de-amplified. The de-amplified portion of the low-latitude upper ridge is providing westerly shear across the tropical wave pair...and coupled with dry Saharan air advected westward by the 1034 mb center in paragraph P5 (see brown shading in lower-right of above thermo chart)...current development of this tropical wave pair is suppressed.

Meanwhile the western lobe of the low-latitude upper ridge is not quiet as de-amplified such that its anticyclonic outflow is enhancing an area of t-storms over the south-central Caribbean Sea. Coupled with tropical wave activity sliding toward such a t-storm cluster...this pattern is quiet similar to the pattern in paragraph P8 of discussion #15 just before last week's pre-Barry disturbance became a special feature on this blog. Therefore I have decided to upgrade this tropical wave pair to a special feature as well...especially considering that computer models insist on expanding the paragraph P7 Florida-area upper ridge into the W Caribbean in between the two paragraph P7 upper vortices (and I think some of this favorable W Caribbean upper ridging will also be a manifestation of the anticyclonic outflow presently over the south-central Caribbean t-storms).

CMC and GFS computer models support some kind of development in the W Caribbean...Yucatan...Bay of Campeche area by 180 hours. But with the models also showing the W Caribbean upper winds becoming quiet favorable between now and 120 hours...I think gradual tropical cyclone development in the W Caribbean could occur within the next 120 hours (5 days). Currently the paragraph P1 weather system is expected to have enough amplitude as to weaken the west extent of the paragraph P5 ridge...so it is possible this system gets pulled northward towards the Gulf of Mexico region in the coming days before turning west due to the ridge that builds behind the paragraph P1 weather system.

...MID-LATITUDES DISCUSSION...
P1...Large frontal cyclone and upper trough is parked offshore of the west US coast. In the next days...a slowly-developing shortwave upper trough will soon eject eastward from this system while supporting another frontal cyclone. The early phases of this are beginning in the upper-left corner of the above chart with a 997 mb surface frontal depression over the Wyoming/Montana border.

P2...Upper trough persists near the east Canada coast and NW Atlantic...with its eastern divergence supporting a 998 mb frontal cyclone between Canada and Greenland...and with its western convergence supporting a 1021 mb surface ridge moving into Hudson Bay. Elsewhere over North America...western US upper trough is moving into the central US while its eastern divergence supports a 1000 mb frontal depression that has migrated NE from the Colorado/Kansas and into south-central Canada in the last 36 hrs. SE US upper vortex mentioned in the previous discussion has weakened into a shortwave upper trough becoming absorbed by aformentioned upper trough moving into central US. Warm air advection ahead of the 1000 mb south-central Canada frontal depression supports an upper ridge that has moved from the central US into the NW Atlantic in the last 36 hrs.

P3...Although an upper trough and associated surface frontal cyclone exited the picture from the NE Atlantic (paragraph P2 of the previous discussion)...the long frontal zone stretching several hundred miles to the southwest left some features behind including a 1013 mb frontal depression east of Newfoundland supported by the eastern divergence of the east Canada coast/NW Atlantic upper trough mentioned in paragraph P2 above. Since then....this 1013 mb depression has also exited the picture from the NE Atlantic...but its front leaves behind a 1020 mb depression SSE of Newfoundland now supported by the eastern divergence of the east Canada coast/NW Atlantic upper trough.

P4...Cut-off upper vortex N of the Cape Verde Islands (paragraph P3 of the previous discussion) and cut-off upper vortex in the open central Atlantic (paragraph P4 of the previous discussion) have merged into one large upper vortex in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is NE of the Azores and remains generally deep-layered in nature. The 1034 mb surface center is supported by upper convergence NE of its upper-level center. This surface ridge continues to have a westward extension currently located across the W Atlantic...SE United States...Gulf of Mexico..and into east-central Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraph P2...including west side of the SE US upper shortwave trough...east side of upper ridge that has moved into the NW Atlantic...and west side of upper trough along east coast of Canada/NW Atlantic.

...TROPICAL BELT DISCUSSION...
P6...South fragment of tropical wave moving across Central America (mentioned in paragraphs P6 and P7 of the previous discussion) has moved into the eastern Pacific and therefore will no longer be mentioned on this blog. North fragment of tropical wave moving into the east Florida coast (mentioned in paragraph P7 of the previous discussion) has dissipated.

P7...Cut-off upper vorticity over the eastern Bahamas has during the past two discussions split into two upper vortices. One upper vortex has migrated southward from the waters S of Bermuda and into the central Bahamas while pushed by the paragraph P2 upper ridge moving into the NW Atlantic. Second upper vortex has retrograded across the Caribbean and into the Gulf of Mexico while orbiting around the persistent Florida-area upper ridge.

P8...See above special feature section for update on pair of tropical waves and overhead low-latitude tropical upper ridging mentioned in paragraph P8 of the previous discussion. Based on Meteosat-9 satellite animation over the last couple of days...it appears a tropical wave with on-off t-storm clustering has recently rolled off Africa and is currently south of the Cape Verde Islands as marked in the lower-right of the above atmo chart. Although it currently has a t-storm cluster below a favorable eastern lobe of low-latitude upper ridging...it appears to be headed into the dry air/westerly vertical shear environment mentioned in the above special feature section...I expect no development here in the short-term...

2013 Atlantic Hurricane Season Birdseye Discussion #23

By: NCHurricane2009, 3:25 PM GMT on June 23, 2013

...SUNDAY JUNE 23 2013 11:25 AM EDT...
Pair of tropical waves moving toward the southern Lesser Antilles are currently suppressed by Saharan dry air and increasing westerly vertical shear. However these tropical waves may reach favorable upper winds in the western Caribbean Sea by 5 to 7 days. See paragraph P8 for details on current prognosis and future outlook on these tropical waves.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_23_2013_0815Z_zpsccb1d038.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0739Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_23_2013_0815Z_zpsc72f32b3.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Upper trough persists near the east Canada coast and NW Atlantic...with its eastern divergence supporting a 995 mb frontal cyclone between Canada and Greenland...and with its western convergence supporting a 1020 mb surface ridge just SE of Hudson Bay. Elsewhere over North America...western US upper trough persists while its eastern divergence supports a 1001 mb frontal depression currently over the Colorado/Kansas border. A fragment of this western US upper trough tracked into the south-central US as a shortwave during the previous discussion...and has merged with the SE US upper vortex...thus re-enforcing that upper vortex. Warm air advection ahead of the 1001 mb frontal depression supports a central US upper ridge.

P2...Upper trough and associated surface frontal cyclone moving across the NE Atlantic during the previous discussion has exited the picture from the upper-right corner of the above charts...but the front extending from that cyclone still leaves behind features several-hundred miles to the southwest that are still in the picture. For instance a frontal depression east of Newfoundland has intensified from 1022 mb to 1013 mb in the last 24 hrs while moving NE in the supportive divergent SW flow ahead of the east Canada coast/NW Atlantic upper trough mentioned in paragraph P1. There is also leftover frontal activity along the SE US coast detailed more in paragraph P7 below.

P3...Cut-off upper vortex N of the Cape Verde Islands persists.

P4...Cut-off upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...has moved NE from the Azores but remains generally deep-layered in nature. The NE migration appears to be the surface center re-building below upper convergence NE of its upper-level center and SW of the exiting NE Atlantic upper trough mentioned in paragraph P2. This surface ridge continues to have a westward extension currently located across the W Atlantic...SE United States...Gulf of Mexico..and into east-central Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraph P1...including west side of the SE US upper vortex...east side of the central US upper ridge...and west side of upper trough along east coast of Canada/NW Atlantic.

...TROPICAL BELT DISCUSSION...
P6...Upper-level anticyclonic ridge over parts of Mexico...Central America...and Bay of Campeche has made a westward migration into the eastern Pacific (due to westward retrograding of upper vorticity mentioned in paragraph P7)...where it supports the recent upheaval in eastern Pacific tropical cyclone activity (see www.nhc.noaa.gov for info on eastern Pacific activity as this is not the scope of this blog). Northerly flow east of this upper ridge splits with westerly flow on the south side of the paragraph P7 upper vorticity...producing upper-level divergence supporting cloudiness and t-storms across Central America and south-central Caribbean (this Central America t-storm activity may also be enhanced by the south fragment of the tropical wave mentioned in paragraph P7).

P7...Cut-off upper vorticity over the eastern Bahamas has split into one vortex south of Bermuda and another vortex retrograding SW across the Caribbean around the Florida-area upper ridge. Surface tropical wave in the area remains split into two fragments...the south fragment moving into central America (as mentioned at the end of paragraph P6 above)...and a north fragment moving toward east Florida coast as an inverted surface trough steered westward by the south side of the western extension of the paragraph P5 surface ridge. Surface frontal zone over the SE US coast...leftover from paragraph P2 weather system...has become concentrated around a 1018 mb depression which has weakend to 1020 mb in the last 24 hrs. Despite being on the south side of the W extent of the paragraph P5 surface ridge (where it would get steered westward)...this depression has instead tracked northward thru eastern North Carolina (thru the paragaraph P5 ridge)...and it now resides on the NC/VA border. Perhaps the northward track was because the surface depression got attracted to surface pressure drops associated with the split flow upper divergence maximum between the north side of the Florida-area upper ridge and east side of the paragraph P1 SE US upper vortex.

P8...Low-latitude upper ridge persist in the central and eastern tropical Atlantic. Pair of troipcal waves continue westward toward the southern Lesser Antilles...with the eastern of the two continuing to have a t-storm cluster in its south half...while its north half has recently choked on a well-defined westward expansion of dry Saharan air seen in the above thermo chart. This dry air appears to be advected westward from Africa by the easterly flow on the south side of the deep-layered 1034 mb ridge center mentioned in paragraph P5. Central US upper ridge in paragraph P1 will soon move into the NW Atlantic...and tremendous upper ridging will be developing over much of the US behind that (due to warm air advection of ahead of a frontal cyclone stalling offsore of the western US). All this upper ridging is already beginning to push the paragraph P3 upper vortex...paragraph P4 upper vortex...and paragraph P7 upper vorticity southward such that the low-latitude upper ridging mentioned in this paragraph is de-amplifying. With the de-amplifying upper ridge overhead of the tropical waves increasing the westerly shear and with the Saharan dry air...no development is expected in the near term. However by the end of the week...computer models suggest that the paragraph P7 Florida-area upper ridge will have expanded into the W Caribbean in between the two paragraph P7 upper vortices...and so by late in the week we may have to watch the western Caribbean as these two tropical waves reach this area. At this time...no computer models (other than CMC) show development from either tropical wave. The CMC solution is interesting...showing the north end of the eastern tropical wave spinning up a tropical cyclone in the Hispaniola/Bahamas area around 120 hrs in the northeast extent of the forecast favorable W Caribbean upper ridging. The CMC (like all the other models) then shows a shortwave upper trough ejecting from a frontal cyclone parked offshore of the western US that supports another frontal cyclone over east Canada strong enough to break the paragraph P5 surface ridge and pull the CMC's forecast tropical cyclone northward and parallel to the SE US coast after 120 hrs. Taking CMC superficially at this time with no other models showing any development.

2013 Atlantic Hurricane Season Birdseye Discussion #22

By: NCHurricane2009, 5:38 PM GMT on June 22, 2013

...SATURDAY JUNE 22 2013 1:39 PM EDT...
Still watching the north end of a tropical wave interacting with favorable upper winds of a Florida-area upper ridge as mentioned in paragraph P7. A leftover front (delivered by weather system mentioned in paragraph P2) along the southeastern United States coast has also interacted with these favorable upper winds where the National Hurricane Center has briefly mentioned this area in their Tropical Weather Outlook. However any development appears unlikely as surface pressures in the region remain high due to the dominance of the west extension of the surface ridge mentioned in paragraph P5.

Atlhough their are a pair of tropical waves sliding below a favorable central Atlantic low-latitude upper ridge as mentioned in paragraph P8...lack of computer model support...Saharan Dry air...and a forecast de-amplification of this upper ridge will prevent tropical development in the near term. However over the course of the next week...the Florida-area upper ridge is expected to persist...so perhaps one week out as these tropical waves arrive into the upper ridge's region from the western Caribbean we may have something to watch.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_22_2013_1215Z_zpsb2aa3d06.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1328Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_22_2013_1215Z_zpsf8add0f3.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Upper trough that has recently crossed Canada's Hudson Bay is currently over the east Canada coast and NW Atlantic...with its eastern divergence supporting a broad area of surface rotation and frontal boundaries across Hudson Bay...eastern Canada...and southern Greenland...and with its western convergence supporting a 1022 mb surface ridge just SW of Hudson Bay. Elsewhere over North America...western US upper trough persists while its associated surface frontal cyclone has dissipated below its non-divergent axis...but the eastern divergence of this upper trough is supporting a new 1003 mb frontal depression currently over the Colorado/Kansas border. A fragment of this western US upper trough has tracked into the SE US as a shortwave where we now have a SE US cut-off upper vortex...and yet another fragment has recently moved into the south-central US also as a shortwave. Warm air advection ahead of 1003 mb frontal depression supports a central US upper ridge...albeit this upper ridge has been recently split by aforementioend south-central US shortwave.

P2...Upper trough moving into the NW Atlantic in the previous discussion is now in the NE Atlantic. Eastern divergence supports a surface frontal cyclone that has moved from the Atlantic high seas and into the northern British Isles in the last 36 hours. Low-level warm air advection ahead of the frontal cyclone formerly supported an upper ridge that was building across the north Atlantic...and now this upper ridge has become vertically stacked with the paragraph P5 surface ridge to produce a deep-layered ridge centered in the vicinity of the Azores. The frontal cyclone also leaves behind a long front stretching several-hundred miles to the southwest...where we have a new 1022 mb frontal depression SE of Newfoundland supported by the eastern divergence of the east Canada coast/NW Atlantic upper trough mentioned in paragraph P1...and where we have activity along the SE US coast detailed more in paragraph P7 below.

P3...Cut-off upper vortex N of the Cape Verde Islands persists.

P4...Cut-off upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is located in the vicinity of the Azores and deep-layered in nature as mentioned in paragraph P2 above. This surface ridge continues to have a westward extension currently located across the NW Atlantic (while the 1027 mb center offshore of Nova Scotia mentioned in paragraph P2 of the previous discussion joins this ridge)...eastern US...and into eastern Mexico. This western extension is supported by upper convergence from a variety of upper features mentioned in paragraph P1...including west side of the paragraph P1 SE US upper vortex...east side of the central US upper ridge...west side of south-central US shortwave...and west side of upper trough along east coast of Canada/NW Atlantic.

...TROPICAL BELT DISCUSSION...
P6...Parts of Mexico...Central America...and Bay of Campeche continue to be dominated by upper-level anticyclonic ridge. Northerly flow east of this upper ridge splits with westerly flow on the south side of the E Bahamas upper vortex mentioned in paragraph P7...producing upper-level divergence supporting cloudiness and t-storms across Central America (this Central America t-storm activity may also be enhanced by the south fragment of the tropical wave mentioned in paragraph P7).

P7...Cut-off upper vortex persists over the eastern Bahamas. As expected...a Florida-area upper ridge has formed in relatively higher pressures between this upper vortex and SE US upper vortex mentioned in paragraph P1...with the E Bahamas upper vortex beginning to retrograde SW into the Caribbean around the Florida-area upper ridge. Surface tropical Wave over the central Caribbean in the previous discussion has split into two fragments...with the south fragment moving into central America (as mentioned at the end of paragraph P6 above)...and with the north fragment over the western Bahamas while producing weak cloudiness and cyclonic rotation noted in visible satellite animation. Atlhough the north fragment of the tropical wave is sliding below the favorable upper divergence and low shear below the Florida-area upper ridge...it shows no signs of significant activity perhaps while overwhelmed by high surface pressures of the west extent of the paragraph P5 surface ridge. Surface frontal zone over the SE US coast...leftover from paragraph P2 weather system...also has been interacting with the favorable Florida-area upper ridge and as a result was introduced in the NHC tropical weather outlook within the last 24 hrs (the activity of this SE US coastal front may have also been enhanced by upper divergence between the Florida-area upper ridge and paragraph P1 SE US upper vortex). With the W Bahamas tropical wave fragment and SE US surface front structured as inverted troughs steered along the south side of the paragrah P5 surface ridge...expect an area of scattered showers and t-storms (over the W Bahamas...Florida...eastern Georgia...and eastern Carolinas) moving slowly westward while showing cyclonic rotation about these surface features on Doppler Radar.

P8...Low-latitude upper ridge persist in the central tropical Atlantic. Tropical wave midway between the Cape Verde Islands and Lesser Antilles in the previous discussion is now east of the southern Lesser Antilles. Tropical wave passing south of the Cape Verde Islands in the previous discussion is now SW of the Cape Verde Islands and still has an associated t-storm cluster in its south half...while its north half has recently choked on a well-defined westward expansion of dry Saharan air seen in the above thermo chart. This dry air appears to be advected westward from Africa by the easterly flow on the south side of the deep-layered Azores ridge center mentioned in paragraph P5. Even though both tropical waves mentioned in this paragraph are moving into the favorable upper winds of the central Atlnatic low-latitude upper ridge...this Saharan dry air should suppress them. Moreover...computer models show the current paragraph P1 central US upper ridge moving into the NW Alantic...with tremendous upper ridging developing over much of the US behind that (due to warm air advection of ahead of a frontal cyclone stalling offsore of the western US). All this upper ridging will push the paragraph P3 and P4 cut-off upper vortices southward...which will de-amplify the central Atlantic low-latitude upper ridge...introducing hostile westerly vertical shear across these tropical waves. Computer models also show the paragraph P7 Florida-area upper ridge persisting thru the next week...so perhaps one week out as these tropical waves arrive into the upper ridge's region from the western Caribbean we may have something to watch.

2013 Atlantic Hurricane Season Birdseye Discussion #21

By: NCHurricane2009, 7:23 AM GMT on June 21, 2013

...FRIDAY JUNE 21 2013 3:24 AM EDT...
Barry dissipates into a remnant low over east-central Mexico.

Elsewhere...an upper ridge is expected in the vicinity of Florida as detailed in paragraph P7 below...and their is a slight possibility the north end of the Caribbean tropical wave (also mentioned in paragraph P7) could interact with the favorable upper winds of this upper ridge in the next 72 hours. However...their is no computer model support for tropical development in this area at this time...and surface pressures in the region are forecast to be high due to upper convergence on the east side of a central United States upper ridge mentioned in paragraph P1.

Upper winds will also be favorable below the central Atlantic low-latitude upper ridge mentioned in paragraph P8. However computer models show no tropical development with any tropical waves to pass below the upper ridge...and Saharan dry air in the region also makes conditions unfavorable.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_20_2013_2345Z_zps78bbb978.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0130Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_20_2013_2345Z_zpse6c80208.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...A couple of new mid-latitude features have entered the scope of this discussion from the upper-left corner of the above charts in the last 48 hours. First is an upper trough and attendant 999 mb surface frontal cyclone from northern Canada that has recently crossed Hudson Bay (with western convergence of this upper trough also supporting a 1026 mb surface ridge over southern Hudson Bay). Second is a western US upper trough with attendant surface frontal cyclone...with an upper ridge over the central US developing due to warm air advection ahead of the frontal cyclone. A fragment of this western US upper trough has tracked into the SE US as a shortwave.

P2...Upper trough over eastern US and eastern Canada is moving into the NW Atlantic. Eastern divergence supports a surface frontal cyclone that has moved from Newfoundland to the Atlantic high seas in the last 24 hrs while it has deepened to 984 mb. Western convergence of this upper trough supports 1027 mb surface ridge that has moved from the Great Lakes to the waters offshore of Nova Scotia. Low-level warm air advection ahead of the 984 mb frontal cyclone supports upper ridge that has built into the north Atlantic from the W Atlantic in the last 24 hrs.

P3...Cut-off upper vortex N of the Cape Verde Islands persists.

P4...Cut-off upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is located in the vicinity of the Azores while currently supported by upper convergence between easterlies south of the N Atlantic upper ridge in paragraph P2 and southerlies east of the paragraph P4 upper vortex. This surface ridge continues to have a westward extension into the Gulf of Mexico (with a current 1019 mb center) while supported by convergent upper NW flow west of the paragraph P1 SE US shortwave...and convergent NW flow east of the paragraph P1 central US upper ridge (this upper convergence may be also enhanced by the robust outflow on the north side of Barry adding resistance against the convergent upper NW flow). In the low-levels (700 to 850 mb)...CIMSS still shows that the west extent of the surface ridge goes all the way into Mexico...with the Mexico portion of the ridge steering Barry westward further into Mexico.

...TROPICAL BELT DISCUSSION...
P6...Central America and parts of Mexico continue to be dominated by upper-level anticyclonic ridge in part associated with the outflow structure of former tropical cyclone Barry. As mentioned in paragraph P5...the weakening remnant low of Barry is being steered further west into Mexico by the west extent of the low-level ridge discussed in that paragraph.

P7...Cut-off upper vortex persists over the eastern Bahamas. Tropical Wave over Puerto Rico/E Caribbean in the previous discussion is currently located over Hispaniola and the central Caribbean...with surface convergence from the tropical wave and eastern upper divergence of the upper vortex supporting occasional t-storm clouds over Hispaniola...E Bahamas...and nearby W Atlantic waters. As mentioned in paragraph P1...a shortwave upper trough has arrived into the SE US...with a new Florida upper ridge expected to form in relatively higher pressures between the SE US shortwave and the eastern Bahamas upper vortex. In turn...a fragment of the upper vortex will retrograde SW around the Florida upper ridge. Because of this...the south half of the tropical wave will become suppressed by the retrograding upper vortex...but watching the north end of this tropical wave to see if it interacts with the more favorable upper winds beneath the expected Florida upper ridge. However...their is no computer model support for tropical development in this area at this time...and surface pressures in the region are forecast to be high due to the west extent of the paragraph P5 surface ridge.

P8...Low-latitude upper ridge persist in the central tropical Atlantic. Tropical wave SW of the Cape Verde Islands in the previous discussion is currently below this low-latitude upper ridge in the waters midway between the Cape Verdes and Lesser Antilles. Tropical wave rolling off Africa in the previous discussion is now passing south of the Cape Verde Islands and still has an associated t-storm cluster. Meanwhile...westward expansion of dry air continues in the lower-right of the above thermo chart...perhaps advection of Sahara Desert air via the south side of the paragraph P5 ridge. Even though the first of the two above-mentioned tropical waves is currently below the favorable upper winds of the central Atlantic low-latitude upper ridge...this dry air is suppressing this tropical wave...so perhaps the second of the two tropical waves south of the Cape Verde Islands will eventually lose its t-storm cluster to this dry air. Currently...no computer models suggest development from either of these two tropical waves as they slide beneath the central Atlantic low-latitude upper ridge.

2013 Atlantic Hurricane Season Birdseye Discussion #20

By: NCHurricane2009, 5:29 AM GMT on June 20, 2013

...THURSDAY JUNE 20 2013 1:30 AM EDT...
Tropical depression two has strengthened to Tropical Storm Barry while moving across the Bay of Campeche in the last 24 hours...and will be making landfall in east-central Mexico later this morning where tropical storm warnings are in effect. Biggest threat from Barry will be heavy rainfall with flash flooding along coastal and also inland areas. See special feature section below for additional details on Tropical Storm Barry.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_19_2013_2345Z_zps813696b3.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0132Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_19_2013_2345Z_zps5df294dd.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM BARRY...
My previous forecast for this tropical cyclone called for a westward turn across the Bay of Campeche with the expectation that a low-level ridge would build over Mexico under the same supportive upper convergence mechanisms described in the latter part of paragraph P5 below. Although isboars in surface maps currently do not reflect a Mexican low-level ridge...the CIMSS site shows a low-level ridge has indeed built over northern Mexico at least in the 700 to 850 mb layer of the atmosphere as shown in Figure 2. My previous intensity forecast called for development into a moderate tropical storm over warm Bay of Campeche waters and under favorable upper winds provided by the paragraph P6 upper ridge...especially with southerly shear reducing thanks to the upper ridge core moving westward and closer to the tropical cyclone (the mechanisms pushing the upper ridge west are explained in paragraph P7 below). Both my previous track and intensity forecasts have performed exceedingly well...and so my updated forecast in Figure 1 below is almost a copy-paste of my previous. The only difference is I moved my 10 AM Thu forecast point further inland to account for the fact Barry has tracked a little faster to the west than I prevoiusly predicted. Simulteanously I am NOT inclined to shift my 10 PM Thu forecast point further inland because the forward motion of the storm is slowing as reported in each new NHC public advisory. In all...I am currently forecasting Barry to move into Mexico a bit faster than the recent 10 PM CDT NHC forecast...and so my intensity forecast is a bit lower than the 10 PM CDT NHC because I carry Barry away from water and into land sooner than the NHC shows.

 photo Jun_19_2013_TS_Barry_Forecast_zpse37ebf16.png
Figure 1: Forecast for Tropical Storm Barry

 photo Jun_19_2013_TS_Barry_Steering_zps8765df89.png
Figure 2: Left-to-right shows that a low-level ridge has built in the 700 to 850 mb atmospheric layer and across northern Mexico in the last 24 hours (ridge location in each frame is marked with red-zig-zag line). This ridge is what has caused Barry's track to recently bend westward.

Impact swath in Figure 1 is initialized based on a circular core of t-storms over the center as well as t-storm banding north and east of that core currently seen in color-enhanced infrared satellite...and extrapolating that structure along the forecast track. This structure has been more or less consistent with Barry in the last infrared satellite frames...and that is where I believe the highest rainfall and flash flooding potential with this storm exists. Meanwhile...infrared satellite loops also show respectable t-storm complexes that have been pulsing on and off well to the southwest and southeast of my above impact swath...which is why I wrote statement (b) in Figure 1 (I believe these complexes are developing due to the upper divergence provided by the large-sized paragraph P6 upper ridge in the region).

...MID-LATITUDES DISCUSSION...
P1...A couple of new mid-latitude features have entered the scope of this discusison from the upper-left corner of the above charts. First is an upper trough and attendant 1004 mb surface frontal cyclone from northern Canada currently crossing the Hudson Bay. Second is a western US upper trough with attendant 992 mb surface frontal cyclone. A fragment of this western US upper trough is currently racing eastward as a shortwave soon to enter the SE US in the next 24 hours.

P2...Upper trough over central US in the previous discussion has moved into the eastern US and eastern Canada. Eastern divergence supports a surface frontal cyclone that has moved from North Carolina to Newfoundland in the last 24 hrs while it has deepened to 1007 mb. Western convergence of this upper trough supports 1022 mb surface ridge near the Great Lakes area. To the southeast of the upper trough...W Atlantic upper ridge is building rapidly into the north Atlantic while supported by low-level warm air advection ahead of the 1007 mb frontal cyclone. Meanwhile...a fragment of this upper trough dove past the upper ridge 7 days ago...where we now have a north-central Atlantic upper trough with attendant less-than-1004 mb frontal cyclone currently located east of Greenland that is supported by the eastern divergnce of this north-central Atlantic upper trough.

P3...Upper vortex N of the Cape Verde Islands has been pushed southward due to the upper ridge building in the north Atlantic mentioned in paragraph P2 above.

P4...Cut-off upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is located in the vicinity of the Azores while currently supported by southeastern convergence of paragraph P2 upper ridge building into the north Atlantic. This surface ridge continues to have a westward extension into the Gulf of Mexico (with a current 1017 mb center) while supported by SW convergence of paragraph P2 upper trough...and soon to be supported by convergent NW flow west of the paragraph P1 shortwave headed into the SE US...and convergent NW flow to develop east of an upper ridge ahead of paragraph P1 western US upper trough (this upper convergence may be also enhanced by the robust outflow on the north side of Barry adding resistance against the convergent upper NW flow).

...TROPICAL BELT DISCUSSION...
P6...Central America and parts of the western Caribbean continue to be dominated by upper-level anticyclonic ridge in part associated with the outflow structure of Tropical Storm Barry.

P7...Cut-off upper vortex south of Bermuda in the previous discussion is now over the eastern Bahamas and continues enhancing thunderstorms over the Lesser Antilles and adjacent areas with divergence at its southeastern quadrant. In the next 24 hrs...a shortwave upper trough will eject into the SE US (as mentioned in paragraph P1 above)...with a new Florida upper ridge forming in relatively higher pressures between the SE US shortwave and upper vortex south of Bermuda. In turn...a fragment of the upper vortex will retrograde SW around the Florida upper ridge...which in turn will continue pushing the paragraph P6 upper ridge westward. At the surface...tropical over NW Venezuela in the previous discussion was re-analyzed to a more northeastward position over Puerto Rico/E Caribbean as of 0600Z June 19 by the NHC TAFB...and from this position its surface convergence appears to be also helping out with the aforementioned Lesser Antilles thunderstorms. Because a fragment of the aforementioned east Bahamas upper vortex will be retrograding SW...this tropical wave will become suppressed as it continues west.

P8...Low-latitude upper ridge formerly in the eastern tropical Atlantic has been displaced westward into the central tropical Atlantic (thanks to southward push of paragraph P3 upper vortex). Tropical wave SSW of the Cape Verde Islands in the previous discussion is currently SW of the Cape Verde Islands. Yet another tropical wave appears to be rolling off of Africa with a distinct t-storm cluster this evening based on satellite imagery (as marked in the lower-right of the above atmo chart). Meanwhile...westward expansion of dry air continues in the lower-right of the above thermo chart...perhaps advection of Sahara Desert air via the south side of the paragraph P5 ridge. It remains to be seen if either of the two tropical waves mentioned in this paragraph will be suppressed by this dry air...or become enhanced while sliding beneath the favorable upper winds of the central tropical Atlantic low-latitude upper ridge later on. Currently...no computer models suggest development from either of these two tropical waves.

2013 Atlantic Hurricane Season Birdseye Discussion #19

By: NCHurricane2009, 6:12 AM GMT on June 19, 2013

...WEDNESDAY JUNE 19 2013 2:10 AM EDT...
Tropical depression two has moved across Belize...northern Guatemala...southeastern Mexico...and into the Bay of Campeche on a more northerly than expected trajectory. As a result...it will now track moreso over the warm open waters of the Bay of Campeche and has what I now forecast a high risk of becoming a tropical storm before making landfall in east-central Mexico on Thursday morning. Visit www.nhc.noaa.gov for latest info on this tropical cyclone and associated tropical storm advisories currently in effect for east-central Mexico. See special feature section below for additional details on tropical depression two.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_18_2013_2345Z_zps31e8056e.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0129Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_18_2013_2345Z_zps8052d00e.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL DEPRESSION TWO...
As mentioned in the intro statement of this discussion and as shown by the NHC recorded storm track in Figure 1...tropical depression two has tracked more northward than expected...and as a result its center has just recently entered the Bay of Campeche. During my previous special feature section on tropical depression two...it was assessed the depression was under some southerly shear west of the paragraph P6 Caribbean upper ridge center and east of the paragraph P5 upper vortex. Perhaps with the thunderstorms being biased a bit to the north side under the shear...maybe we saw a northward regeneration of the circulation below those thunderstorms. Or perhaps the east side of the paragraph P5 upper vortex was low enough in the atmosphere to impart a northward drag on this shallow tropical depression's track. If its to be believed the northward motion was caused by center reformation below thunderstorms...it now appears the center is basically collocated with a small t-storm cluster over open water such that no more northward motion should occur. If its to be believed the northward motion was cuased by the east side of the paragraph P5 upper vortex...the depression is now north of the upper vortex such that no more northward motion should occur.

With it assessed that the forces pulling the depression more northward coming to a close...in the next 12 hrs I gradually expect it to return to the WNW track it had at birth...a track parallel to the isobars of the west extension of the paragraph P4 low-level ridge and 1021 mb Great Lakes/Hudson Bay ridge mentioned in paragraph P1. As mentioned in my previous discussion of tropical depression two...computer model runs such as GFS insist on building a blocking low-level ridge over Mexico and due west of the tropical depression. By again studying the GFS models today...I now believe this low-level ridge will form in the next 24 hours due to upper-level convergence at the SW end of the paragraph P1 central US upper trough...due to upper-level convergence west of the forecast SE US shortwave upper trough mentioned in paragraph P7...and due to upper-level convergence east of an upper ridge ahead of the next mid-lat upper trough about to enter the above charts (this upper convergence may be enhanced if the strengthening of TD 2 results in a strong upper anticyclone over TD 2 that clashes with that upper ridge). However unlike the GFS...I don't think the forecast Mexico low-level ridge will be due west of the system as to slow/stall its forward speed...but rather due northwest of the depression such that it tracks straight west with its current speed after 24 hrs. Basically my forecast track in Figure 1 below agrees with the NHC expect that I show a bit of a northward bias to account for the fact that the most recent segment of the NHC recorded storm track has not yet shown a bend back to a WNW track.

Even though the depression is under some southerly shear west of the paragraph P6 upper ridge and east of the paragraph P5 upper vortex...the upper winds directly over the depression are anticyclonic and divergent such that the southerly shear is not strong and such that upper winds are rather favorable for development over the warm 30 deg C Bay of Campeche waters. In fact by looking at the very latest satellite-derived upper wind barbs...it seems like TD 2 could soon develop its own mini-anticyclone above itself and within the larger-scale paragraph P6 upper ridge...which would reduce the shear even further (even if this is not the case...paragraph P7 explains that the core of the upper ridge is headed westward toward TD 2 which will also reduce the shear further). With very warm waters...favorable upper winds...and a t-storm burst near the center...I am making my intensity forecast higher than the 10 PM CDT NHC forecast...predicting intensification to a 45 mph max wind tropical storm by tonight.

 photo Jun_18_2013_TD_2_Forecast_zpsa3ab3bd2.png
Figure 1: Forecast for Tropical Depression Two

Current colorized infrared satellite shows t-storm burst near the center and a mass of t-storms to the southeast...so I intialized my impact swath in Figure 1 based on that structure. I predict that as TD 2 strengthens and consolidates over the Bay of Campeche...the central t-storm burst will grow in size whereas the t-storm mass southeast of center gets pulled into the central t-storm burst...and so the evolution of my impact swath is based on this prediction while moving the system along my forecast track. Impact statement (b) is added due to the propsect of this system strengthening into a tropical storm.

...MID-LATITUDES DISCUSSION...
P1...Upper trough originating from western Canada is now a major feature across the central US extending into eastern Canada. Within the last 12 hours...eastern divergence of this upper trough has supported surface frontal cyclogenesis over the Ohio/Tennesse Valleys...and since then the frontal cyclone has tracked eastward where it now has a 1009 mb center over North Carolina. Western convergence of this upper trough supports 1021 mb surface ridge near Hudson Bay and the Great Lakes that is building rapidly behind the 1009 mb center. To the southeast of the upper trough...former United States upper ridge is reduced to a Florida/W Atlantic upper ridge supported by low-level warm air advection ahead of the 1009 mb center. Meanwhile...a fragment of this upper trough dove past the upper ridge 6 days ago...where we now have an upper trough that has moved from the west Atlantic into the north-central Atlantic with attendant less-than-984 mb frontal cyclone currently located SE of Greenland that is supported by the eastern divergnce of this north-central Atlantic upper trough. Meanwhile western convergence if this north-central Atlantic upper trough supports new 1015 mb surface ridge just offshore of the east Canada coast.

P2...Relatively new upper vortex N of the Cape Verde Islands...mentioned in paragraph P2 of the previous discussion....persists in relatively lower pressures between upper anticyclone mentioned in paragraph P4 and eastern Atlantic low-latitude upper ridge mentioned in paragraph P8.

P3...Cut-off upper vortex persists in the open central Atlantic.

P4...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is now stacked with upper anticyclone near the Azores...effectively creating a deep-layered anitcyclone over the Azores at the moment. This upper anticyclone is a result of warm air advection ahead of the less-than-984 mb frontal cyclone mentioned in paragraph P1 above. This surface ridge has had a westward extension into the Gulf of Mexico over the past days due to what is now southeastern convergence of what is now the Florida/W Atlantic upper ridge mentioned in paragraph P1.

...TROPICAL BELT DISCUSSION...
P5...Cut-off Upper trough over SE Mexico and the Bay of Campeche in the previous discussion has continued to be pushed westward thanks to the warming provided by tropical depression two's t-storm latent heat release. As a result of its continued westward track...this upper trough has now moved out of the scope of the above charts and into the eastern Pacific as an upper vortex.

P6...Western half of the Caribbean Sea continues to be dominated by upper-level anticyclonic ridge in part associated with the outflow structure of Tropical Depression Two.

P7...Tropical wave crossing the southern Lesser Antilles mentioned in paragraph P6 of the previous discussion is now over NW Venezuela. Cut-off upper vortex left south of Bermuda by what is now the paragraph P1 north-central Atlantic upper trough (mentioned in paragraphs P1 and P6 of previous discussion #18) is suppressing activity associated with this tropical wave...but is simultaneously enhancing thunderstorms over the Lesser Antilles with divergence at its southeastern quadrant. In the next 48 hrs...a shortwave upper trough will eject into the SE US (originating from next mid-lat upper trough not yet in the scope of the above charts)...with a new Florida upper ridge forming in relatively higher pressures between the SE US shortwave and upper vortex south of Bermuda. In turn...a fragment of that upper vortex will retrograde SW around the Florida upper ridge...which in turn will push the paragraph P6 upper ridge westward.

P8...Low-latitude upper ridge remains in the eastern tropical Atlantic. Although a tropical wave that has recently rolled off of Africa is currently SSW of the Cape Verde Islands and below this favorable upper ridge...the eastern tropical Atlatnic remains quiet under a recent westward expansion of dry air seen in the lower-right of the above thermo chart. It appears this expansion of dry air is a plume of Sahara Desert air advected westward by the deep-layered Azores anticyclone mentioned in paragraph P4.

2013 Atlantic Hurricane Season Birdseye Discussion #18

By: NCHurricane2009, 1:43 AM GMT on June 18, 2013

...MONDAY JUNE 17 2013 9:45 PM EDT...
Caribbean tropical wave Invest 93-L has intensified into tropical depression two within the last 24 hours while moving into the western Caribbean Sea. The center has made landfall in southern Belize this past afternoon. See special feature section below for additional information on tropical depression two.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_17_2013_2045Z_zpsfef9cf3b.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1930Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_17_2013_2045Z_zpsb56fb701.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL DEPRESSION TWO...
Tropical depression two has formed in the western Caribbean sea from tropical disturbance Invest 93-L...and has made landfall in southern Belize as of this past afternoon. See Figure 1 below for my forecast versus the NHC's as of this past afternoon/early evening. Visit www.nhc.noaa.gov for latest NHC forecasts and info on tropical depression two.

As the 12-hourly NHC recorded storm track in Figure 1 below shows...newly formed tropical depression two has taken a WNW track which is parallel to the isobars of the western extension of the paragraph P4 low-level ridge. Through the forecast period...computer models maintain low-level ridging with the same isboaric structure as a low-latitude upper ridge is expected to quickly build behind an Ohio/Tennesse Valley frontal cyclone as mentioned in paragraph P1. Therefore my track forecast philosophy is to simply maintain the current speed and heading of the current WNW track...which makes me a bit south of the NHC forecast track but generally keeping up with the forward pace in the NHC forecast track. Albeit...my forecast track beyond 48 hours is a bit faster than shown by NHC...perhaps due to the fact that computer models such as GFS build a blocking low-level ridge over Mexico and due west of the tropical depression (but while studying the simultaneous GFS upper wind forecast I see no source of upper convergence to support such a blocking low-level ridge...and therefore that is why I do not slow my forecast track beyond 48 hours). Note that midway in my forecast track I kink the circulation a bit more northward as I now believe their is a high probability that t-storms in the north half of the circulation will intensify over the Bay of Campeche when the system arrives there...with the circulation regenerating northward toward those t-storms. Previously I thought this system was going to track straight west and not emerge over the Bay of Campeche...but obviously now I have changed my mind given that the current track is more WNW rather than straight west.

The 12Z GFS model run from yesterday (shown in Figure 1b of my previous discussion) has done a good job of predicting the evolution of the Caribbean upper ridge...correctly predicting that the Honduras anitcyclonic center above this system would dissipate in the face of the paragraph P5 upper trough while also predicting that the dominate anticyclonic center would retrograde from northern South America to the waters south of Jamaica (indeed the blue H south of Jamaica in the above atmo chart confirms this). This has placed the tropical depression in southerly shear west of the Jamaica anticyclonic center and east of the paragraph P5 upper trough as evidenced by the thickest clouds being north of center. I was previously concerned the GFS model did not give enough credence to this system's t-storm latent heat release by dissipating the Honduras upper anticyclonic center...but by animating yesterday's 12Z GFS...the most recent GFS model run...and comparing to how well the runs match the current state of the upper atmosphere...I now trust the GFS has a good handle on what should happen. The GFS shows that the paragraph P5 upper trough should continue to get shoved off to the west perhaps due to warming provided by TD 2's t-storm latent heat release...but also due to the upper anticyclonic center south of Jamaica also getting displaced westward. The GFS shows a shortwave upper trough ejecting into the SE US by 72 hrs (originating from next mid-lat upper trough not yet in the scope of the above charts)...with a new Florida upper ridge forming in relatively higher pressures between the SE US shortwave and paragraph P1 upper vortex south of Bermuda. In turn...a fragment of that upper vortex retrogrades SW around the Florida upper ridge...which in turn is what pushes the upper anticyclone south of Jamaica to the west.

Therefore with the paragraph P5 upper trough moving westward and away from TD 2...and with the upper anticyclone south of Jamaica rapidly advacing westward over TD 2 thru the forecast period...low shear and enhanced upper outflow from the upper anticyclone keep TD 2's conditions favorable for development. Therefore the only inhibiting factor against strengthening will be land interaction. My intensity forecast in Figure 1 below assumes TD 2 will soon weaken to a remnant low as it advances further inland...and is below the NHC forecast which predicts re-development to a minimal tropical storm when it emerges over the Bay of Campeche (I prefer to keep it below tropical storm force (below 40 mph winds) as my more southerly forecast track has less exposure to Bay of Campeche water than the NHC's forecast track does). TD 2 will then make landfall again in the heart of Mexico...when it then ultimately dissipates.

 photo Jun_17_2013_TD_2_Forecast_zpsb3239c4f.png
Figure 1: Forecast for Tropical Depression Two

Current colorized infrared satellite shows a ball of convection a bit sheared northward from the center with an outer rain band along the west coast of the Yucatan peninsula. I predict that the ball will be generally persistent with TD 2 thru the forecast....and so my impact swath in Figure 1 is based on extrapolating that ball along my forecast track. It is entirely possible we will see outer rain bands fling outward from the ball and outside my impact swath region...but with the rainfall to be heaviest in the ball....I believe the most significant impacts with this sytem will be where my impact swath region is drawn.

...MID-LATITUDES DISCUSSION...
P1...East-west trowal of upper vorticity originating from western Canada is gaining a more SW-NE tilt as shown by blue-dashed line in upper-left corner of above atmo chart. The trowal is expected to soon swing east with its eastern divergence to soon support surface frontal cyclogenesis over the Ohio/Tennesse Valleys within the next 12 to 24 hours (in fact the 1012 mb surface low over NE Oklahoma in the above atmo chart appears to be the early phases of this cyclogenesis). Western convergence of this upper trowal supports 1022 mb surface ridge (also marked in upper-left corner of above atmo chart) that will be building rapidly behind the forecast Ohio/Tennessee valley surface frontal cyclogenesis. To the south of the trowal...former United States upper ridge has been reduced to a Texas upper ridge due to the swining in of this trowal. Meanwhile...a fragment of the upper trowal that dove around the upper ridge 10 days ago is now an upper trough and associated 1005 mb surface frontal cyclone zooming across the northeastern Atlantic and currently moving into western Europe. 5 days ago...yet another fragment of the upper trowal had dove around the upper ridge...where we now have an upper trough in the western Atlantic that has recently broken into an upper vortex south of Bermuda...a shortwave upper trough and attendant 1022 mb surface frontal depression SE of Newfoundland...and north-central Atlantic upper trough and attendant 982 mb surface frontal cyclone that has weakened to 992 mb as it has settled (like all mature frontal cyclones) directly below the upper trough axis where their is a lack of divergence.

P2...Upper anticyclone NW of the Cape Verde Islands...mentioned in paragraph P2 of the previous discussion...has reversed into a brand new upper vortex N of the Cape Verde Islands due to relatively lower pressures between upper anticyclone mentioned in paragraph P4 and eastern Atlantic low-latitude upper ridge mentioned in paragraph P6. Some of this new upper vortex's vorticity maybe a cut-off of the NE Atlantic upper trough mentioned in paragraph P1.

P3...Cut-off upper vortex persists in the open central Atlantic.

P4...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is now supported by eastern upper-level convergence of a north-central Atlantic upper anticyclone moving into the Azores. This upper anticyclone is a result of warm air advection ahead of the 992 mb frontal cyclone mentioned in paragraph P1 above. This surface ridge has had a westward extension into the Gulf of Mexico over the past days due to what is now southeastern convergence of what is now the Texas upper ridge mentioned in paragraph P1.

...TROPICAL BELT DISCUSSION...
P5...Cut-off Upper trough over the Yucatan peninsula in the previous discusison has been pushed west into SE Mexico and the Bay of Campeche thanks to the warming provided by tropical depression two's latent heat release. As the above special feature section discusses in detail...expect this upper trough to continue to get pushed westward.

P6...Elsewhere in the Atlantic tropics...Caribbean Sea continues to be dominated by upper-level anticyclonic ridge in part associated with the outflow structure of Tropical Depression Two. Low-latitude tropical upper ridging meanwhile remains in the eastern Atlantic. Tropical wave east of the southern Lesser Antilles in the previous discussion is now crossing the southern Lesser Antilles into the southeastern Caribbean Sea tonight. It appears the tropical wave's t-storms have recently been enhanced by divergent northwesterly upper flow at the boundary between the Caribbean upper ridge (mentioned earlier in this paragraph) and relatively new upper vortex located south of Bermuda (mentioned in paragraph P1). As the above special feature section discussed in detail...expect a portion of the upper vortex south of Bermuda to have a southern fracture that will retrograde west across the Caribbean....and as a result this tropical wave will soon become suppressed as it tracks through the Caribbean.

2013 Atlantic Hurricane Season Birdseye Discussion #17

By: NCHurricane2009, 1:30 AM GMT on June 17, 2013

...SUNDAY JUNE 16 2013 9:30 PM EDT...
Southern Caribbean tropical disturbance has become better organized and as a result has been upgraded to Invest 93-L. However...the consolidation of the disturbance's upper-level anticyclonic outflow and low-level cyclonic spin has occured at a location further southwest than I previously anticipated...and as a result is interacting with the Central American landmass moreso than I previously thought it would. Therefore I now believe it has a lower chance of developing into a tropical cyclone before crossing the Yucatan...and has a very low probability of having its circulation emerge over the Bay of Campeche as its newly-formed circulation should track straight west from its current position over Honduras. The only reason I am currently keeping Invest 93-L a special feature is that despite the circulation being over Honduras that the NHC may find a closed surface circulation and sufficiently strong winds in the offshore rainbands to declare this a tropical cyclone within the next 24 hours. Another possibility is that strong enough t-storms develops in one of the offshore rain bands with enough latent heat release to slightly relocate the upper-level anticyclonic outflow just offshore...with surface pressure drops below a relocated outflow causing the low-level circulation to regenerate offshore within the next 24 hours. Regardless of further development...heavy rainfall with flooding potential is expected over Honduras...Belize...Guatemala...southeastern Mexico...and the Yucatan Peninsula of Mexico. See special feature section below for details on Invest 93-L. Visit www.nhc.noaa.gov in the event 93-L becomes a tropical cyclone with associated warnings during the next 24 hours.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_16_2013_2015Z_zps864c5e7f.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1942Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_16_2013_2015Z_zps6fee2a99.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CARIBBEAN TROPICAL WAVE INVEST 93-L...
1009 mb surface low near the coast of Costa Rica mentioned previously in this special feature section has dissipated...leaving the thunderstorms to consolidate with the more northerly positoned tropical wave axis that is currently marching into the western Caribbean Sea and Honduras. Despite the northward shift of the thunderstorms...they have remained focused at locations further south and further west than I previously anticipated they would be at this point. As a result...the latent heat release of these t-storms has generated an upper-level anticyclonic center in the Caribbean upper ridge further SW than I thought as shown by the black "X" over eastern Honduras in Figure 1b and by the blue H near eastern Honduras in the above atmo chart. Visible satellite imagery this past afternoon confirms a low-level low pressure circulation is spinning up over eastern Honduras as a result of surface pressure drops due to the outflow of the relatively new upper-level anticyclonic center.

Despite the circulation consolidating over land and hence reducing development potential...see the intro statement of this discussion as to why I am maintaining this as a special feature on this blog. I previously used the June 14 18Z GFS upper-level wind forecast shown in Figure 1a to upgrade this system to a special feature...predicting that on 1200Z Monday the thunderstorms and low-level spin would be focused near or below the black "X" west of Jamaica and over open water as that "X" represented where GFS showed the anticyclonic center of the Caribbean upper ridge consolidate. Instead as shown by today's GFS model initialization in Figure 1b the Caribbean upper ridge now has two anticylonic centers (shown by two black "X" marks)...one over northern south America...and the other near eastern Honduras. With this initialization...as Figure 1b also shows...today's GFS model now predicts that on 1200Z Monday that the anticyclonic center over eastern Honduras dissiapted in the face of the paragraph P5 Yucatan upper trough while the one over northern south America gets displaced westward (to the south of Jamaica) thanks to the amplifying upper trough of the 983 mb cyclone mentioned in paragraph P1. By dissipating the upper anticyclone currently over eastern Honduras by 1200Z Monday...the GFS model run in Figure 1b I think is not giving enough credence to the tremendous t-storm latent heat release backing that upper anticyclone...and in fact I think their is a chance this upper anticyclone could completely displace the paragraph P5 Yucatan upper trough (but if GFS in Figure 1b is correct that the Yucatan upper trough instead wins out...this would reduce the rainfall potential over the Yucatan and southeastern Mexico).

As the caption of Figure 1 concludes...the circulation of this disturbance has formed further southwest than I previously thought. Now with the circulation formed...it should track straight west thanks to deep-layered ridge axis in northern Gulf of Mexico mentioned in paragraph P4...and thanks to another surface ridge to develop behind forecast Ohio Valley frontal cyclone mentioned in paragraph P1. With the westward track beginning at a location further south than previously thought...it should now track over mainland southeast Mexico later on rather than the Bay of Campeche waters...so I currently believe tropical cyclogenesis potential over the Bay of Campeche from this system later on (if it doesn't develop in the next 24 hours) has gone out the window.

 photo Jun_16_2013_300mb_GFS_for_Invest_93L_zpsb5aaa4ba.png
Figure 1: The image with label (a) is the upper-level 18Z GFS computer model run from June 14. The images with label (b) is the upper-level 12Z GFS computer model run from today. All black Xs represent an anticyclonic center of the Caribbean Sea upper ridge. I previously predicted using image (a) that the circulation of this disturbance would develop near or below the black X west of Jamaica and over open water by 1200Z Monday. Instead as shown by the top-right image (b)...on 1200Z Sunday (today) we have an anticyclonic center much further southwest and near eastern Honduras where the circulation of this disturbance has in reality developed (easterly wind barb over Honduras in the top-right image (b) is how I spotted the anticyclonic center over eastern Honduras). The loss of Honduras easterly wind barbs in the bottom-right image (b) shows that this particular model run loses the eastern Honduras upper anticyclone by 1200Z Monday.

...MID-LATITUDES DISCUSSION...
P1...Main component of upper trough and surface frontal system originating from western Canada is currently about to leave the east Canada coast with a deep-layered 995 mb center. As anticipated during the last few discussions...the bulk of the upper vorticity of this system has become an east-west trowal (see east-west blue-dashed line in upper-left corner of above atmo chart). The trowal is expected to soon swing east...but the associated surface frontal cyclogenesis that was expected to occur over the central US by now has been delayed in models for another 48 hours and is now expected to occur over the Ohio Valley. Regardless...southeastern divergence of the upper-level trowal supports central US frontal activity...with low-level warm air advection ahead of this frontal activity continuing to support United States upper ridge (albeit this upper ridge has recently been pushed south into the southern states and northern Gulf of Mexico as the aforementioned east-west trowal has pushed in). Meanwhile...a fragment of the upper vorticity that is now this east-west trowal dove SE around the crest of this upper ridge 9 days ago...where we now have an upper trough and associated 1000 mb surface frontal cyclone zooming across the northeastern Atlantic NNE of the Azores and toward western Europe. 4 days ago...yet another fragment of the upper vorticity also dove SE around the crest of the upper ridge...where we now have an upper trough moving across the W Atlnatic whose western convergence supports 1023 mb ridge that recently moved offshore from the eastern US...and whose eastern divergence supports a relatively new 1014 mb frontal depression NE of Bermuda and an intensifying 982 mb frontal cyclone that recently crossed Newfoundland and into the Atlantic high seas SW of Greenland (this frontal cyclone will shortly absorb the 995 mb frontal depression mentioned in the early part of this paragraph).

P2...NE Atlantic upper anticyclone has been pushed further south to a location NW of the Cape Verde Islands thanks to amplificaiton of northeastern Atlantic upper trough mentioned in paragraph P1 above.

P3...Cut-off upper vortex persists in the open central Atlantic.

P4...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1031 mb...is now supported by upper-level convergence between easterlies streaming south of a north-central Atlantic upper anticyclone and southerlies steraming east of the paragraph P3 upper vortex. The north-central Atlantic upper anticyclone is a result of warm air advection ahead of the 983 mb frontal cyclone mentioned in paragraph P1 above. This surface ridge has had a westward extension into the Gulf of Mexico over the past days (and currently this extension has a 1019 mb center). This extension was due to southeastern upper convergence of the paragraph P1 United States upper ridge...and because the upper ridge has recently shifted southward and stacked with the extension...we now effectively have a deep-layered ridge axis in the northern Gulf of Mexico tonight. Furthermore...the 1023 mb center offshore of the eastern US also mentioned in paragraph P1 has recently joined this extension. This extension remains a bit split off from the aforementioned main 1031 mb center due to southward-digging cold front extending from the 983 mb frontal cyclone.

...TROPICAL BELT DISCUSSION...
P5...Cut-off Upper trough over the western Caribbean in the previous discussion is now over the Yucatan Peninsula. With the United States upper ridge in paragraph P1 acting as a blockade against any injections from mid-latitude upper troughs...this cut-off upper trough over the next days will gradually diminish (as all cut-offs without injections do) while becoming squeezed between the United States upper ridge and the upper ridge of tropical disturbance Invest 93-L.

P6...Elsewhere in the Atlantic tropics...the Caribbean Sea is dominated by the low-level low pressure circulation of tropical disturbance Invest 93-L and upper-level anticyclonic ridge supported by the latent heat release of the immense thunderstorms of the disturbance. Low-latitude tropical upper ridging meanwhile remains in the eastern Atlantic. As of 1800Z this evening...the NHC TAFB added a weakly-defined tropical wave east of the southern Lesser Antilles as marked in the bottom-center of the above atmo chart. Not sure if this tropical wave is the same one I suspected existed in paragraph P11 of discussion #13 which I subsequently removed by discussion #15 because of the lack of its existence in prior TAFB maps. This weakly-defined tropical wave is inactive while currently in unfavorable upper winds in the gap between the aformentioned Caribbean Sea upper-level ridge and aforementioned low-latitude eastern Atlantic upper ridge.

2013 Atlantic Hurricane Season Birdseye Discussion #16

By: NCHurricane2009, 6:01 AM GMT on June 16, 2013

...SUNDAY JUNE 16 2013 2:00 AM EDT...
A tropical disturbance has developed this past afternoon in the southern Caribbean below a favorable western fracture of low-latitude upper ridging. Because of the forecast evolution of the upper ridge fracture...I am now expecting a high probability of tropical cyclone formation either in the western Caribbean Sea as early as late Monday...or potentially later in the week after this system crosses the Yucatan into the Bay of Campeche. Interests in Central America should monitor this system in case it does not develop further north and instead goes west into their area with plenty of rainfall potential. Interests in the Yucatan...Bay of Campeche...and east-central Mexico should monitor this situation for possible tropical depression or tropical storm development. See special feature section below for additional details on this situation.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_15_2013_2045Z_zps3d39e378.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1924Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_15_2013_2045Z_zps3ed2545d.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...CARIBBEAN SEA TROPICAL WAVE...
As paragraph P8 in the previous discussion mentioned...upper outflow at the west end of the current Caribbean Sea upper ridge continues to enhance t-storms over parts of Central America and the south-central Caribbean Sea where we now have a 1009 mb surface low near the coast of Costa Rica. Tropical wave also mentioned in paragraph P8 of the previous discussion is arriving into the central Caribbean and with its surface convergence it appears to have enhanced this area of t-storms to the degree that the National Hurricane Center introduced this system into their Tropical Weather Outlook this evening. The strongest computer model support continues to be with the GFS which shows eventual development later on when this tropical wave moves into the Bay of Campeche. The CMC and Euro are also suggestive of some development...but on the weakish side while only showing a weaker Bay of Campeche low pressure area while they favor a more eastern Pacific solution.

While studying the June 14 18Z GFS model run during the previous discussion...I claimed that I believed the model was initialzied with too amplified of a Caribbean upper ridge while citing a SSW upper wind vector over the central Bahamas when my 00Z atmo chart at the time was showing more of a SW upper wind vector over the central Bahamas. The problem with that comparison was I was comparing an 18Z initialization to 00Z wind vectors...and indeed scrolling that 18Z GFS model 6 hours ahead (to 00Z) showed it accurately matching that 00Z atmo chart nearly spot-on. In fact...that June 14 18Z GFS model run 24 hours out is still proving quiet accurate when comparing it to the above upper-level wind barbs in the above 18Z atmo chart. Therefore I am relying on the GFS upper-level wind model to give a prognosis on what could happen with this disturbance. As such the following is my outlook on this disturbance...

One scenario is that the thunderstorms simply consolidate around the aforementioned 1009 mb surface low such that the latent heat release causes the anticyclonic core of the Caribbean upper ridge to consolidate at a more southward location. In such a scenario...the disturbance would then spend little time over water...move into Central America...and then move into the eastern Pacific perhaps realizing the CMC and Euro suggestions of eastern Pacific activity. By studying the GFS upper-level wind forecast...the GFS suggests that by 1200Z Monday that the anticyclonic core of the Caribbean upper ridge will instead shift west and north such that it lands in the open western Caribbean Sea to the east of the Yucatan Peninsula. It appears the west shift of the upper ridge would be due to the dissipation of the paragraph P5 upper trough and due to the southward digging of the upper trough associated with the amplifying 996 mb frontal cyclone in paragraph P1. It appears the north shift of the upper ridge would be due any latent heat release of t-storms along the more northerly positioned tropical wave axis...and due to warm air advection ahead of the forecast central US frontal cyclone mentioned at the very end of paragraph P1. Moreover...the GFS's forecast western Caribbean upper anticyclone is made more impressive by an enhanced eastern outflow channel into a new cut-off upper vortex to develop from the 996 mb frontal cyclone's upper trough. Therefore I see it highly likely that this disturbance by 1200Z Monday will have consolidated northwestward and below the impressive western Caribbean upper anticyclone...with possible surface tropical cyclone formation just east of the Yucatan as early as very late on Monday. After Monday...models show a strong surface ridge developing behind the forecast central US frontal cyclone...and such a ridge would steer this west across the Yucatan...across the Bay of Campeche...and into east-central Mexico. GFS suggests that the favorable upper ridge core moves west with the disturbance through that time as the upper ridge becomes directly related with the t-storm latent heat release of this system.

...MID-LATITUDES DISCUSSION...
P1...Main component of upper trough and surface frontal system originating from western Canada is currently over eastern Canada with a 1001 mb surface frontal depression...with western convergence of the upper trough supporting a surface ridge over Hudson Bay. However...the bulk of the upper vorticity of this system remains behind over western Canada/western US where its eastern divergence supports surface front and associated thunderstorms pushing into the central US. Low-level warm air advection ahead of this central US front supports United States upper ridge. Meanwhile...a fragment of the aforementioned western Canada/western US upper vorticity dove SE around the crest of this upper ridge 8 days ago...where we now have an upper trough and associated 1002 mb surface frontal cyclone zooming across the northeastern Atlantic to the north of the Azores and toward western Europe (western convergence of this upper trough now supports surface ridge near the S tip of Greenland mentioned in paragraph P3 of the previous discussion...which is currently 1023 mb). 3 days ago...yet another fragment of the western Canada/western US upper vorticity also dove SE around the crest of the upper ridge...where we now have an upper trough moving into the W Atlnatic whose western convergence supports 1020 mb ridge that moved from the Great Lakes to the eastern US...and whose eastern divergence supports a brand new 1008 mb frontal depression just north of Bermuda and an intensifying 996 mb frontal cyclone that has moved across Newfoundland and toward southern Greenland in the last day (this frontal cyclone will shortly absorb the 1001 mb frontal depression mentioned in the early part of this paragraph). In the next 24 hours...the bulk of the upper vorticity over western Canada/western US will evolve into an east-west trowal to the north of the upper ridge...and then the trowal will swing east while supporting yet another frontal cyclone that will eject eastward from the central US.

P2...NE Atlantic upper anticyclone persits south of the Azores and west of the Canary Islands while pushed southward by northeastern Atlantic upper trough mentioned in paragraph P1 above.

P3...Cut-off upper vortex persists in the open central Atlantic.

P4...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1027 mb...is now supported by convergence at the SE quad of a relatively new NW Atlantic upper anticyclone. This upper anticyclone has developed thanks to warm air advection ahead of the 996 mb frontal cyclone mentioned in paragraph P1 above. This surface ridge had a westward extension into the Gulf of Mexico over the past days (and currently this extension has a 1018 mb center). This extension is due to southeastern upper convergence of the paragraph P1 United States upper ridge...however this extension has recently been split off from this ridge due to southward-digging cold front extending from the 996 mb frontal cyclone.

...TROPICAL BELT DISCUSSION...
P5...Cut-off Upper trough over the Florida Straits in the previous discussion is now in the western Caribbean. With the United States upper ridge in paragraph P1 acting as a blockade against any injections from mid-latitude upper troughs...this cut-off upper trough over the next days will gradually diminish (as all cut-offs without injections do) while becoming squeezed between the United States upper ridge and the upper ridge of the tropical disturbance mentioned in the above special feature section.

P6...Elsewhere in the Atlantic tropics...low-latitude upper ridging has been covering the eastern tropical Atlantic over the last several days...with the west end of this upper ridge fracturing into the Caribbean Sea while now associated with the tropical disturbance discussed in the above special feature section.

2013 Atlantic Hurricane Season Birdseye Discussion #15

By: NCHurricane2009, 5:28 AM GMT on June 15, 2013

...SATURDAY JUNE 15 2013 1:28 AM EDT...
As paragraph P1 in the mid-latitudes discussion below describes...an upper ridge persists over the United States...which has been promoting shearing upper vorticity features (such as the upper trough mentioned in paragraph P7) over June's climatologically favored Caribbean and Gulf of Mexico areas thanks to the relatively lower pressures southeast of the upper ridge. However as computer models have been predicting...this shearing upper vorticity is becoming replaced by a western fracture of low-latitude upper ridging. See paragraph P8 below for info on potential Bay of Campeche tropical development below this favorable fracture of the upper ridge during the next week.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_14_2013_2345Z_UPDATED_zps6db05a01.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0116Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_14_2013_2345Z_zpsa7c99869.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Main component of upper trough and surface frontal system originating from western Canada is currently over eastern Canada with a 1007 mb surface frontal depression...with western convergence of the upper trough supporting surface ridging over Hudson Bay. However...the bulk of the upper vorticity of this system remains behind over western Canada/western US where its eastern divergence supports surface western US front and associated Great Plains t-storm activity. Prior low-level warm air advection ahead of this system promoted an upper ridge over the United States...but based on looking at the lastest US drought monitor and surface temp map I would say this upper ridge currently appears bolstered by the hot and dry air mass associated with a drought over the interior US. Meanwhile...a fragment of the aforementioned western Canada/western US upper vorticity dove SE around the crest of this upper ridge 7 days ago...where we now have an upper trough and associated 1001 mb surface frontal cyclone zooming across the north-central Atlantic. 2 days ago...yet another fragment of the western Canada/western US upper vorticity also dove SE around the crest of the upper ridge...where we now have an eastern US upper trough supporting a 1020 mb ridge over the Great Lakes with its western convergence...and with its eastern divergence supporting an intensifying 999 mb frontal cyclone that has moved from the NE US into the NW Atlantic during the last day. In the next 48 hours...the bulk of the upper vorticity over western Canada/western US will evolve into an east-west trowal to the north of the upper ridge...and then the trowal will swing east while supporting yet another frontal cyclone that will eject eastward from the central US.

P2...NE Atlantic upper anticyclone persits midway between the Canary Islands and Azores while supported by low-level warm air advection ahead of the east-moving 1001 mb frontal cyclone in the north-central Atlantic mentioned in paragraph P1 above.

P3...Upper trough shifting eastward across the far NE Atlantic during the previous discussion is making landfall in western Europe. Attendant frontal cyclone is moving into the British Isles...and has deepened from 1004 mb to 997 mb while once again tapping into eastern divergence of the upper trough. Western convergence of this upper trough supports surface 1020 mb ridge in the far north Atlnatic near the south tip of Greenland.

P4...Cut-off upper vortex persists in the open central Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1028 mb...is now supported by convergence at the SE quad of a brand new NW Atlnatic upper anticyclone. This upper anticyclone has developed thanks to warm air advection ahead of the 999 mb NW Atlc frontal cyclone mentioned in paragraph P1 above. This surface ridge continues to have a westward extension across the northern Gulf of Mexico and onto the Texas coast (with 1014 mb center) thanks to southeastern upper convergence of the paragraph P1 United States upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical upper ridge moving into northern Mexico in the previous discussion has now merged with the prominent upper ridge over the United States mentioned in paragrpah P1.

P7...Upper vortex over the Florida Straits has opened up into an upper trough while temporarily trying to link with the mid-latitude eastern US upper trough mentioned in paragraph P1 above. The mid-latitude eastern US upper trough will soon bypass this upper trough...rendering this upper trough cut-off to the southeast of the strong United States upper ridge (also mentioned in paragraph P1). With the United States upper ridge acting as a blockade against any other injections from mid-latitude upper troughs...this cut-off upper trough over the next days will gradually diminish (as all cut-offs without injections do) while becoming squeezed between the United States upper ridge and tropical upper ridge mentioned in paragraph P8 below.

P8...Low-latitude upper ridging has been covering the eastern tropical Atlantic over the last several days...with the west end of this upper ridge fracturing into the Caribbean Sea in the wake of the gradually weakening paragraph P7 upper trough. As paragraph P8 of the previous discussion mentioned...thunderstorms continue to be enhanced over the south-central Caribbean and parts of Central America due to upper outflow at the west end of this Caribbean upper ridge fracture. Tropical wave crossing the Lesser Antilles into the eastern Caribbean Sea mentioned in paragraph P9 of the previous discussion is currently positioned from Hispaniola...thru the open Caribbean waters...and into NW Venezuela. This tropical wave is tracking toward the aforementioned south-central Caribbean thunderstorms. Coupled with the fact that computer models insist on shifting the favorable Caribbean upper ridge fracture westward into the Bay of Campeche (BOC) as this tropical wave also tracks toward that area...perhaps their is potential for BOC tropical cyclone development next week as suggested by the 18Z cycle of GFS...CMC...and Euro models. Things that will cause the Caribbean upper ridge fracture to shift west into the BOC include the gradual dissipation of the cut-off upper trough mentioned in paragraph P7 coupled with a southward-digging upper trough associated with amplifying 999 mb frontal cyclone mentioned in paragraph P1. However I am a bit skeptical of this potential BOC tropical development at the moment as the above atmo chart suggests the tropical wave is about to enter shearing upper southwesterlies ahead of the paragraph P7 upper trough. I also beleive the 18Z cycle of the GFS model was initialized with too amplified of a favorable Caribbean upper ridge fracture (for instance the 18Z upper-level wind field showed SSW vector over the central Bahamas whereas the above atmo chart's upper-level wind barbs show the vectors over the central Bahamas more from the SW). As I wrote this...the more recent 00Z cycles of models appear better initialized...but those model runs were not yet complete to see whether or not they now downplay the BOC development potential as a result of being initialized with a less amplified Caribbean upper ridge fracture.

2013 Atlantic Hurricane Season Birdseye Discussion #14

By: NCHurricane2009, 1:24 AM GMT on June 14, 2013

...THURSDAY JUNE 13 2013 9:25 PM EDT...
As paragraph P1 in the mid-latitudes discussion below describes...an upper ridge persists over the United States...which has been promoting shearing upper vorticity features (such as the upper vortex mentioned in paragraph P7) over June's climatologically favored Caribbean and Gulf of Mexico areas thanks to the relatively lower pressures southeast of the upper ridge. However as computer models have been predicting...this shearing upper vorticity is becoming replaced by a western fracture of low-latitude upper ridging...see paragraphs P8 and P9 below for details. Other than tonight's 18Z GFS computer model which shows tropical cyclone formation in the western Caribbean and Bay of Campeche by 180 hours...computer model runs are otherwise not showing tropical cyclone development below the forecast western fracture of the upper ridge. Given that the GFS model has recently hinted at potential...given that the Caribbean is the climatological spot for Atlantic tropical cyclones in June...and given that we have tropical wave activity sliding underneath the favorable western fracture of the upper ridge (as discussed in paragraph P9)...will be watching the Caribbean area over the next days.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_13_2013_2045Z_zps1fcba742.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1930Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_13_2013_2045Z_zps5b9d82c1.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Main component of upper trough and surface frontal system originating from western Canada is currently over Hudson Bay and eastern Canada with a 1005 mb surface frontal depression...with western convergence of the upper trough supporting 1026 mb surface ridge just SW of Hudson Bay. However...the bulk of the upper vorticity of this sytem remains behind over western Canada/western US where its eastern divergence supports surface western US front and t-storm activity. Prior low-level warm air advection ahead of this system promoted an upper ridge over the United States...but based on looking at the lastest US drought monitor and surface temp map I would say this upper ridge now appears bolstered by the hot and dry air mass associated with a drought over the interior US. Meanwhile...a fragment of the aforementioned western Canada/western US upper vorticity dove SE around the crest of this upper ridge 6 days ago...where we now have a NW Atlantic upper trough and associated 1000 mb deep-layered frontal cyclone. 24 hrs ago...yet another fragment of the western Canada/western US upper vorticity also dove SE around the crest of the upper ridge...which is supporting a severe-weather-producing 1000 mb surface frontal cyclone that has moved from Minnesota to the NE US in last day. In the next 72 hours...the bulk of the upper vorticity over western Canada/western US will evolve into an east-west trowal to the north of the upper ridge...and then the trowal will swing east while supporting yet another frontal cyclone that will eject eastward either from the Great Lakes or from the central US area.

P2...Central Atlantic upper anticyclone is shifting eastward into the NE Atlantic while supported by low-level warm air advection ahead of the east-moving 1000 mb deep-layered frontal cyclone in the NW Atlantic mentioned in paragraph P1 above.

P3...Upper trough regime over the north-central Atlantic is finally shifting eastward across the far NE Atlantic and toward Europe. Attendant 994 mb frontal cyclone near the south tip of Greenland has likewise shifted east into the far NE Atlantic while weakening to around 1004 mb while it remains directly below the non-divergent environment of the upper trough regime. Western convergence of this upper trough regime supports surface 1017 to 1020 mb ridge that has lifed off the east Canada coast into the far north Atlantic.

P4...Cut-off upper vortex far SE of Bermuda has shifted ENE into the open central Atlantic while accelerating in SW flow ahead of the larger-sized NW Atlantic upper trough mentioned in paragraph P1.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1028 mb...is now supported by convergence at the SW quad of the paragraph P4 upper vortex. It continues to have a westward extension across the northern Gulf of Mexico and into eastern Texas (with 1019 mb center) thanks to upper convergence on the southeast quad of the paragraph P1 United States upper ridge.

...TROPICAL BELT DISCUSSION...
P6...As the paragraph P7 upper vortex shifts westward...tropical upper ridge in the western Gulf of Mexico area is being pushed westward into northern Mexico.

P7...Upper trough over the Bahamas in paragraph P7 of the previous discussion has evolved into a westward-moving upper vortex over the Florida Straits as it gets steered around the much larger United States upper ridge mentioned in paragraph P1 above.

P8...Tropical wave moving across the south-central Caribbean Sea in the previous discussion is currently moving across Central America. As mentioned in this tropical wave's previous discussion (paragraph P9 of discussion #13)...because the paragaraph P7 upper vortex has lifted northward and now westward out of the way...this has allowed the west end of the tropical upper ridge (referred to in paragraph P9 below) to expand westward toward this tropical wave. Enhanced upper outflow of this upper ridge's west end continues to enhance t-storms in the eastern part of this tropical wave...which currently extend across parts of Central America and into the south-central Caribbean.

P9...Tropical wave mentioned in paragraph P10 of discussion #13 is currently crossing the Lesser Antilles into the eastern Caribbean Sea. Possible tropical wave mentioned in paragraph P11 of discussion #13 I estimate is currently midway between the Cape Verde Islands and Lesser Antilles based on continuity since then...but I may simply drop this tropical wave from future discussions if the NHC TAFB continues to not add it to their TAFB surface maps. Low-latitude upper ridging has been covering the eastern tropical Atlantic over the last several days...and as paragraph P8 above mentions....the west end of this upper ridge is building over the Caribbean Sea in the wake of departing paragraph P7 upper vortex. An upper anticyclonic core just east of the Lesser Antilles appears to be associated with this westward expansion of the upper ridge...with the upper outflow of this core appearing to enhance thunderstorms in the vicinity of the two tropical waves mentioned in this paragraph.

2013 Atlantic Hurricane Season Birdseye Discussion #13

By: NCHurricane2009, 2:54 AM GMT on June 13, 2013

...WEDNESDAY JUNE 12 2013 11:00 PM EDT...
As paragraph P1 in the mid-latitudes discussion below describes...an upper ridge persists over the United States...which will over the next 48 hours promote shearing upper vorticity features (such as the upper trough mentioned in paragraph P7) over June's climatologically favored Caribbean and Gulf of Mexico areas thanks to the relatively lower pressures southeast of the upper ridge. Therefore...the Atlantic tropics should be quiet over the next 48 hours. By 72 hours and beyond...models insist that the shearing upper vorticity features will then be replaced by a western fracture of the low-latitude upper ridge mentioned in paragraphs P10 and P11. However their are no computer model runs showing Caribbean tropical cyclone development below the forecast western fracture of the upper ridge.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_12_2013_2045Z_zps3da7f430.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1926Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_12_2013_2045Z_zpsef84a64a.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Upper trough and and surface frontal cyclonic system from western Canada has entered the upper-left corner of the above atmo chart with a 1007 mb deep-layered cyclonic center currently over Hudson Bay...although the bulk of the upper vorticity of this sytem remains behind over western Canada. Prior low-level warm air advection ahead of this system has been promoting an upper ridge over the United States which is still present. Meanwhile...a fragment of the upper vorticity dove SE around the crest of this upper ridge 120 hours ago...where we now have an upper trough moving into the NW Atlantic from the eastern US and associated 998 mb deep-layered frontal cyclone just offshore of Maine. Yet another upper trough fragment...which is supporting a 1005 mb surface frontal cyclone over southern Minnesota...has dove southeast (around the crest of the upper ridge) into the central US. In the next 100 hours...the bulk of the upper vorticity over western Canada will evolve into an east-west trowal to the north of the upper ridge...and then the trowal will swing east while supporting yet another frontal cyclone that will eject eastward from the central US.

P2...Western Atlantic upper anticyclone is shifting eastward into the central Atlantic while supported by low-level warm air advection ahead of the east-moving 998 mb frontal cyclone mentioned in paragraph P1 above.

P3...Upper trough regime persists over the north-central Atlantic. Eastern divergence of this regime supported new 1000 mb frontal depression north of the Azores during the previous discussion. This depression has evolved into a full-fledged less-than-1000 mb gale moving rapidly northeast into the British Isles while cool air advection behind the gale has amplified a fragment of the upper trough southward into the NE Altlantic to the east of the paragraph P2 upper anticyclone. 994 mb frontal cyclone near the south tip of Greenland has weakened to 996 mb as it remains directly below the non-divergent environment of the upper trough regime. Western convergence of this upper trough regime meanwhile supports surface 1013 mb ridge on the east Canada coast...and western convergence of the aforementioned NE Atlantic upper trough fragment supports 1025 mb ridge over the Azores.

P4...Cut-off upper vortex persists at a location well SE of Bermuda and well ENE of the Lesser Antilles.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1028 mb...is supported by southeastern convergence of the upper anticyclone mentioned in paragrpah P2 above. It has undergone a recent westward expansion across the northern Gulf of Mexico and into eastern Texas (with 1021 mb center) thanks to upper convergence west of the paragraph P1 NW Atlnatic upper trough and east of the paragraph P1 United States upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical upper ridge persists in the western Gulf of Mexico area...with its upper outflow supporting persistent t-storms in the west Gulf area.

P7...Upper trough over the Caribbean Sea has lifted a bit northward into the Bahamas over the last 24 hours while pulled toward the NW Atlantic upper trough fragment mentioned in paragraph P1. Eastern divergence of this upper trough supports a comma shaped weak area of cloudiness south of Bermuda.

P8...Tropical wave previously moving across the Florida Straits in the previous discussion...formerly tropical disturbance Invest 92-L...has dissipated and has been removed from NHC TAFB surface maps in the last 24 hours.

P9...Tropical wave moving across the south-central Caribbean Sea is producing t-storms in the area as it interacts with split flow upper divergence between westerlies flowing into the paragraph P7 upper trough and easterlies flowing across the south side of the paragraph P6 upper ridge. Moreover...because the paragaraph P7 upper trough has lifted northward...this has allowed the west end of the tropical upper ridge in paragraphs P10 and P11 to expand westward toward this tropical wave...and perhaps upper outflow of this upper ridge's west end is also enhancing some of this tropical wave's eastern t-storms.

P10...Tropical wave midway between the Lesser Antilles and Cape Verde Islands in the previous discussion is nearing the Lesser Antilles. Still no signs of this tropical wave being enhanced by outflow low-latitude upper ridging covering the eastern tropical Atlantic.

P11...Meteosat-9 satellite animation suggests a tropical wave has recently rolled off of Africa in the last 48 hours...and by tracking that storm cluster I estimate the possible wave is now SW of the Cape Verde Islands as marked in the lower-right of the above atmo chart. I estimate the possible tropical wave is just east of the associated t-storm cluster while surmising that the t-storm cluster is sheared off to the west of the wave axis thanks to the wave being positioned amongst upper easterlies on the south side of low-latitude upper ridging in the eastern tropical Atlantic.

2013 Atlantic Hurricane Season Birdseye Discussion #12

By: NCHurricane2009, 2:32 AM GMT on June 12, 2013

...TUESDAY JUNE 11 2013 10:32 PM EDT...
As paragraph P1 in the mid-latitudes discussion below describes...an upper ridge has built over the United States...which will over the next 72 hours promote shearing upper vorticity features over June's climatologically favored Caribbean and Gulf of Mexico areas thanks to the relatively lower pressures southeast of the upper ridge. Therefore...the Atlantic tropics should be quiet over the next 72 hours. By 96 hours and beyond...models insist that the shearing upper vorticity features will then be replaced by a western fracture of the low-latitude upper ridge mentioned in paragraphs P10 and P11. However their are no computer model runs showing Caribbean tropical cyclone development below the forecast western fracture of the upper ridge.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_11_2013_1945Z_zpsfd357494.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1929Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_11_2013_1945Z_zps173789ef.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Upper trough and and surface frontal cyclonic system over western Canada has finally entered the upper-left corner of the above atmo chart with a 1007 mb center. Low-level warm air advection ahead of this system has been promoting a building upper ridge over the United States thanks to low-level warm air advection ahead of it. Meanwhile...a fragment of this upper trough and surface cyclonic system dove SE around the crest of this upper ridge 94 hours ago...where we now have an eastern US upper trough and associated NE US 1002 mb frontal cyclone. Over the next 24 hours...yet another upper trough fragment and surface cyclonic system will dive southeast (around the crest of the upper ridge) into the central US from western Canada.

P2...Western Atlantic upper anticyclone persists while supported by warm air advection ahead of 1002 mb cyclone mentioned in paragraph P1 above.

P3...Major upper trough persists over the north-central Atlantic. Eastern divergence of this upper trough supports the remnant low of Andrea currently zooming northeastward toward NW France and the SE British Isles as marked in the upper-right corner of the above atmo chart. Eastern divergence of this upper trough also supports new 1000 mb frontal depression that has formed north of the Azores. 991 mb frontal cyclone near the south tip of Greenland in the previous discussion has weakened to 994 mb as expected due to the fact that the axis of the major upper trough has now settled over the cyclone where it is now suppressing it. Western convergence of this upper trough meanwhile supports surface 1022 mb ridge in the NW Atlantic which extends along the east coast of Canada.

P4...Cut-off upper vortex persists at a location well SSE of Bermuda and well ENE of the Lesser Antilles.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1028 mb...is supported by southeastern convergence of the W Atlantic upper anticyclone mentioned in paragraph P2 above. It has undergone a recent westward expansion across the northern Gulf of Mexico and into eastern Texas (with 1020 mb center) thanks to upper convergence west of the paragraph P1 eastern US upper trough and east of the paragraph P1 United States upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical upper ridge persists in the Gulf of Mexico area. Western divergence of the tropical upper ridge...coupled with the fact that westerlies flowing across this upper ridge are in heavy divergence with respect to easterlies on the south side of the United States upper ridge in paragraph P1...is supporting thunderstorms across the western Gulf of Mexico.

P7...Upper trough over the Caribbean Sea persists. Eastern divergence of this upper trough supports cloudiness in the eastern Caribbean Sea extending across Puerto Rico...the Virgin Islands...and into parts of the W Atlantic.

P8...Tropical wave previously moving by the islands of the Bahamas and Cuba...formerly tropical disturbance Invest 92-L...is currently moving across the Florida Straits into the eastern Gulf of Mexico. This tropical wave is in a signifcantly weaker state than days prior after suffering suppression beneath the paragraph P7 upper trough as it journeyed beneath it over the last couple of days.

P9...Tropical wave moving across Venezuela in the previous discussion is now over the south-central Caribbean. Although it is intereacting with divergence at the SE end of the paragraph P7 upper trough to produce a t-storm flare up on the NW Colombian coast...westerly shear across the south end of the paragraph P7 upper trough is preventing any sort of tropical development here.

P10...Tropical wave SW of the Cape Verde Islands in the previous discussion is now midway between the Lesser Antilles and Cape Verde Islands. Still no signs of this tropical wave being enhanced by outflow low-latitude upper ridging covering the eastern tropical Atlantic.

P11...Meteosat-9 satellite animation suggests a tropical wave has recently rolled off of Africa in the last 24 hours...and by tracking that storm cluster I estimate the possible wave is now south of the Cape Verde Islands as marked in the lower-right of the above atmo chart. It appears the t-storm cluster is a bit sheared off to the west of the wave axis thanks to the wave being positioned amongst upper easterlies on the south side of low-latitude upper ridging in the eastern tropical Atlantic.

2013 Atlantic Hurricane Season Birdseye Discussion #11

By: NCHurricane2009, 12:23 AM GMT on June 11, 2013

...MONDAY JUNE 10 2013 8:23 PM EDT...
As paragraph P1 in the mid-latitudes discussion below describes...an upper ridge will be building over the United States over the course of the next week...promoting shearing upper vorticity features over June's climatologically favored Caribbean and Gulf of Mexcio areas thanks to the relatively lower pressures southeast of the forecast upper ridge. Therefore...the Atlantic tropics should be quiet over the course of the next week.

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_10_2013_1815Z_zps6fd385ac.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1330Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_10_2013_1815Z_zps7fd11ee0.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Upper trough and and surface frontal cyclonic system offshore of the west Canada coast has moved into western Canada but is still mainly outside the scope of the above charts. Low-level warm air advection ahead of this system has been promoting a building upper ridge over the SW US thanks to low-level warm air advection ahead of it. This upper ridge will be building northeastward and dominate the upper air pattern over the United States. Meanwhile...a fragment of this upper trough and surface cyclonic system dove SE around the crest of the building upper ridge 60 hours ago...where we now have a central US upper trough and associated 1007 mb frontal cyclone currently moving into the Great Lakes and eastern US. Western convergence of this upper trough fragment supports central US 1012 mb surface ridge. Over the next 48 hours...yet another upper trough fragment and surface cyclonic system will dive southeast (around the crest of the upper ridge) into the central US from western Canada.

P2...Western Atlantic upper anticyclone supported by warm air advection ahead of non-tropical Andrea...mentioned in paragraph P6 of the previous discussion...is now supported by warm air advection ahead of 1007 mb cyclone mentioned in paragraph P1 above. However...westerly advection of the warm air beneath the anticyclone...caused by the south side of non-tropical Andrea's circulation...has extended this W Atlantic upper anticyclone eastward into the open central Atlantic.

P3...Eastern Canada upper trough in paragraph P2 of the previous discussion has merged with north-central Atlantic upper vortex in paragraph P3 of the previous discussion...resulting in a major upper trough currently over the north-central Atlantic. Eastern divergence of this major upper trough supports the remnant low of Andrea currently zooming eastward at a location north of the Azores. 1000 mb frontal cyclone that was passing by the south tip of Greenland...mentioned in paragraph P3 of the previous discussion...has intensified to 991 mb. This was probably due to the fact that the suppressing upper vortex over the cyclone was absorbed by the east Canada upper trough...with eastern divergence of the east Canada upper trough re-invigoraitng the surface cyclone. This surface cyclone will once again begin a decay phase as the upper trough axis settles directly overhead and begins suppressing it like the prior upper vortex did. The new 1009 mb frontal depression just north of the Azores...mentioned in paragraph P3 of the previous discussion...has become lost amongst the low pressure fields of ex-Andrea and teh 991 mb frontal cyclone. Lastly...western convergence of the major north-central Atlantic upper trough supports surface 1024 mb ridge over the northeastern United States and 1016 mb just offshore of the east Canada coast.

P4...Pair of cut-off upper vortices persists far to the south of the Azores. The western of the two is more prominent at a location well SE of Bermuda and well NE of the Lesser Antilles.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1027 mb...is supported by southeastern convergence of the W Atlantic upper anticyclone mentioned in paragraph P2 above. It has undergone a recent westward expansion across the northern Gulf of Mexico and into eastern Texas thanks to upper convergence west of the paragraph P1 Great Lakes upper trough and east of the paragraph P1 SW US upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical upper ridge persists in the Gulf of Mexico area. Western divergence of the tropical upper ridge...coupled with the fact that westerlies flowing across this upper ridge are in heavy divergence with respect to easterlies on the south side of the SW US upper ridge in paragraph P1...is supporting thunderstorms across the western Gulf of Mexico.

P7...Sprawling upper vortex over the Caribbean Sea persists. Eastern divergence of this upper vortex supports cloudiness in the eastern Caribbean Sea.

P8...Tropical wave previously moving by the island of Hispaniola...formerly tropical disturbance Invest 92-L...is currently moving by the islands of the Bahamas and Cuba. This tropical wave is currently inactive while suppressed beneath the upper vortex mentioned in paragraph P7 above.

P9...Tropical wave making landfall in northeastern South America in the previous discussion is currently moving across Venezuela.

P10...Tropical wave south of the Cape Verde Islands in the previous discussion is now SW of the islands. So far no signs of this tropical wave being enhanced by outflow low-latitude upper ridging covering the eastern tropical Atlantic.

2013 Atlantic Hurricane Season Birdseye Discussion #10

By: NCHurricane2009, 4:15 PM GMT on June 09, 2013

...SUNDAY JUNE 9 2013 12:15 PM EDT...
After an active start...this is the first day of the hurricane season where the Atlantic tropics are quiet. As paragraph P1 describes...an upper ridge will be building over the United States over the course of the next week...promoting shearing upper vorticity features over June's climatologically favored Caribbean and Gulf of Mexcio areas thanks to the relatively lower pressures southeast of the forecast upper ridge. Therefore...the Atlantic tropics should be quiet over the course of the next week.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_9_2013_1245Z_zps8ca92489.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z, and the 1348Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_9_2013_1245Z_zpsf65020f2.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Over the last days...upper trough and surface frontal cyclonic system offshore of the west Canada coast has been promoting a building upper ridge over the SW US thanks to low-level warm air advection ahead of it. This upper ridge will be building northeastward and dominate the upper air pattern over the United States. Meanwhile...a fragment of this upper trough and surface cyclonic system has dove SE around the crest of the building upper ridge in last 36 hours...where we now have a central US upper trough and associated 1002 mb frontal cyclone marked in the upper-left of the above atmo chart. Over the next 72 hours...while the current central US upper trough exits stage right into the Atlantic...yet another upper trough fragment and surface cyclonic system will dive southeast (around the crest of the upper ridge) into the central US from western Canada.

P2...Central US upper trough in paragraph P1 of the previous discussion (not to be confused with the brand new central US upper trough mentioned in paragraph P1 above) has moved into eastern Canada over the last 36 hours. As this upper trough has lifted northeastward away from the Gulf of Mexico...the Yucatan and southern Gulf surface trough it used to support with its SE divergence has now dissipated as of 0600Z TAFB this morning...but not before it was briefly an area of interest in the NHC tropical weather outlook between 8 AM and 2 PM EDT yesterday due to a circular storm burst that was associated with the surface trough. Meanwhile...the eastern divergence of this upper trough continues to support the remnant low of Andrea currenly centered just south of Newfoundland. Expect the remnant of Andrea to zoom eastward on the north side of the paragraph P5 surface ridge and into the paragraph P3 weather system where it will subsequently get abosrbed. Lastly...western convergence of this upper trough supports surface 1025 mb ridge over the northeastern United States.

P3...North-central Atlantic upper vortex persists SSE of Greenland. East Canada coast frontal cyclone formerly supported by eastern divergence of this upper disturbance has moved eastward and passed by the south tip of Greenland...and remains in a position beneath the upper disturbance itself where divergence is zero..and as a result it remains generally weak at 1000 mb. A new 1009 mb depression north of the Azores...located along the front of the 1000 mb cyclone...has developed due to upper divergence at the SE edge of the upper vortex. Western convergence of the upper vortex supports 1018 mb ridge that has moved offshore of the east Canada coast.

P4...Pair of cut-off upper vortices south of the Azores...mentioned in paragraph P4 of the previous discussion...continue to persist. The western of the two appears to have zoomed westward around the W Atlantic upper anticyclone mentioned in paragraph P6 while perhaps merging with a fragment of the paragraph P7 upper vorticity...resulting in a prominent upper vortex centered well ESE of Bermuda and well NE of the Lesser Antilles.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1032 mb...is supported by southeastern convergence of the W Atlnatic upper anticyclone mentioned in paragraph P6.

...TROPICAL BELT DISCUSSION...
P6...Tropical upper ridge persists in the NW Caribbean and eatern Gulf area...while its lengthy NE extension into the W Atlantic waters...supported by warm air advection ahead of non-tropical Andrea...has split off into a W Atlantic upper anticyclone.

P7...Southern stream upper trough has evolved into sprawling upper vortex over the Caribbean Sea.

P8...Tropical moving into the Lesser Antilles and eastern Caribbean in the previous discussion...formerly tropical disturbance Invest 92-L...is currently moving by the island of Hispaniola (Haiti and the Dominican Republic). Eastern divergence of the paragraph P7 upper vortex supports some stray cloudiness in the eastern Caribbean in the vicinity of this tropical wave...but this cloudiness is under high southwesterly vertical shear such that no tropical cyclone development is possible. Expect further cloud activity of this tropical wave to be rather suppressed as it moves westward directly beneath the upper vortex over the next several hours.

P9...Tropical wave located ESE of the paragraph P8 tropical wave is making landfall in northeastern South America while it appears its thunderstorm activity is enhanced by the outflow of persistent low-latitude upper ridging covering the eastern tropical Atlantic.

P10...Tropical wave has recently rolled off the west Africa coast and is currently south of the Cape Verde Islands. So far no signs of this tropical wave being enhanced by outflow low-latitude upper ridging covering the eastern tropical Atlantic.

2013 Atlantic Hurricane Season Birdseye Discussion #9

By: NCHurricane2009, 12:10 PM GMT on June 08, 2013

...SATURDAY JUNE 8 2013 1:00 AM EDT...
Andrea racing north-northeast up the United States east coast and has become non-tropical as of last afternoon. During the next 48 hours....non-tropical Andrea will bring gusty winds and potentially heavy rain across the northeastern United States...southern Nova Scotia...and Newfoundland. Please visit www.nws.noaa.gov and or www.nhc.noaa.gov for latest info on Andrea and associated watches and warnings that maybe in your area. See paragraph P1 for statement on the remnant on Andrea.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_7_2013_2345Z_UPDATED_zps3f109080.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0122Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_7_2013_2345Z_zps9e6f6da8.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Central US upper trough persists and has merged with Gulf cut-off upper trough mentioned in paragraph P6 of the previous discussion. As a result...divergence on the SE end of this major upper trough now supports surface trough over Yucatan and southern Gulf also mentioned in paragraph P6 of the previous discussion. Its eastern divergence is now fully supporting Andrea...which is why she has been downgraded to a non-tropical gale. However....Andrea is still capable of gusty winds...surf and rip currents...and heavy rain as she will rapidly track NNE....NE...and eventually east across the NE US...Nova Scotia...and Newfoundland over the next 48 hours while she rounds the NW quad of paragraph P5 surface ridge. Lastly...western convergence of this upper trough supports surface 1016 mb ridge over the central US marked over Minnesota in the upper-left corner of the above atmo chart.

P2...North-central Atlantic upper trough has tightened into an upper vortex south of Greenland. East Canada coast frontal cyclone formerly supported by eastern divergence of this upper disturbance remains in a position beneath the upper disturbance itself where divergence is zero..and as a result it has weakened from 993 mb to 1004 mb since the previous discussion. Western convergence of the upper vortex supports 1032 mb ridge center ESE of Newfoundland and 1023 mb center near the east Canada coast.

P3...Warm air advection ahead of paragraph P2 surface frontal cyclone continues supporting NE Atlantic upper ridge.

P4...NE Atlantic upper trough has broken up into a multiplicity of upper vortices marked with blue Ls in the upper-right of the above atmo chart. One upper vortex is over NW Spain while the other two have become cut-off to the SE of the of the amplfiying paragraph P3 upper ridge at a location south of the Azores. Split flow divergence between the two cut-off upper vortices supports weak surface trough south of the Azores.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1034 mb...is supported by southeastern convergence of paragraph P6 tropical upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical upper ridge persists in the NW Caribbean and eatern Gulf area...and has a lengthy NE extension into the W Atlantic waters thanks to warm air advection ahead of non-tropical Andrea.

P7...Southern stream upper trough remains cut-off in the Caribbean region at a location SE of the paragraph P6 upper ridge.

P8...Tropical midway between the Lesser Antilles and Cape Verde Islands in the previous discussion...formerly tropical disturbance Invest 92-L...is no longer impressive while moving into the Lesser Antilles as it has become thrashed by westerly vertical shear on the north side of the low-latitude upper ridging and in advance of paragraph P7 upper trough. With computer models forecasting the paragraph P7 upper trough to evolve into a sizeable Caribbean upper vortex...I do not expect this tropical wave to develop on the Atlantic side of things as it gets suppressed below such an upper vortex.

P9...Finally...a tropical wave that I was suspecting had rolled off of Africa days ago...located ESE of the paragraph P8 tropical wave...has been added to NHC TAFB maps at a location midway between the Lesser Antilles and Cape Verde Islands.

2013 Atlantic Hurricane Season Birdseye Discussion #8A (Special Update)

By: NCHurricane2009, 3:28 PM GMT on June 07, 2013

...FRIDAY JUNE 7 2013 11:30 AM EDT...
Since previous discussion #8 was written this early morning...Tropical Storm Andrea has undergone changes in track. It appears northerly flow on the west side of her larege circulation is advecting cooler air southward beneath the upper trough mentioned in paragraph P1 of discussion #8. As a result...the upper trough has become more amplified...with the steering flow ahead of the upper trough both stronger and more southerly than anticipated. Therefore...Andrea has taken a more leftward and also faster track keeping her further inland than shown by all forecasts in Figure 1 of discussion #8.

The faster track means impacts to arrive into the northeastern United States and Nova Scotia sooner...and the more leftward track (coupled with the latest radar presentation) suggests the north and west end of my impact swath should now include central Pennsylvania...central New York...all of Vermont and New Hampshire...all of Maine...and a greater chunk of southern Nova Scotia. See Figure 1 of discussion #8 for other areas also in the impact swath. Hazards in the swath mainly include the slight risk for tornadoes...heavy rainfall with flooding potential...and gusty winds closer to the storm center as well as along the coast and offshore waters where rain bands are not as limited by land friction. As impact statment (b) of Figure 1 mentioned...also watch out for continuing surf and rip currents along the east US coast and southeast Canada coast thru this weekend. Please visit www.nws.noaa.gov and www.nhc.noaa.gov for latest info on Andrea and associated watches and warnings that maybe in your area.

2013 Atlantic Hurricane Season Birdseye Discussion #8

By: NCHurricane2009, 4:42 AM GMT on June 07, 2013

...FRIDAY JUNE 7 2013 12:42 AM EDT...
Tropical Storm Andrea has made landfall across northern Florida...and will bring significant rainfall potential and gusty winds to the southeastern United States and coastal northeastern United States. If you have interests here...please visit www.nws.noaa.gov and or www.nhc.noaa.gov for latest info on Andrea and associated watches and warnings that maybe in your area. See special feature section below for additional details on Andrea.

Tropical wave midway between the Lesser Antilles and the Cape Verde Islands...mentioned in paragraph P8 below...has become better organized and was upgraded to Invest 92-L despite tracking toward westerly vertical shear. However...tropical cyclone development is not expected with the system tracking into those shearing upper winds.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_6_2013_1815Z_zps6d940b8c.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1920Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_6_2013_1815Z_zpsf1a67a8e.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM ANDREA...
My forecast for Andrea versus the NHC's is summarized in the graphic in Figure 1 below.

The tropical storm reached a peak of 65 mph maximum winds just before landfall yesterday afternoon...higher than my predicted peak strength of 50 mph max winds in the previous discussion. This appears to be due to the fact that the storm center yesterday morning regenrated eastward directly below a t-storm burst noted in the previous discussion...taking full advantage of the burst. The storm has weakened to 45 mph max winds since landfall...and I agree with the NHC forecast of 45 mph max winds thru the next 24 hours due to supportive divergence ahead of the paragraph P1 upper trough as we see with a non-tropical system. I agree with NHC's transition to non-tropical by 11 PM Fri (24 hours)...as this is about when the 18Z GFS model run showed Andrea losing touch with warm core upper anticyclonic outflow of the tropical upper ridging (this is shown as the incoming paragraph P1 upper trough shoving off the anticyclonic outflow to the east...embedding Andrea beneath its more linear eastern flow).

Warm air advection ahead of Andrea and paragraph P1 frontal system is building up the paragraph P6 tropical upper ridging into a vast W Atlantic upper ridge...with SE convergence of the upper ridge supporting the paragraph P5 surface ridging. In the model runs...the vast ridging appears to lock the paragraph P1 upper trough into the eastern US for quiet a long period...and so the models show a long-lasting period of curving and deep-layered flow east of the upper trough and west of the vast ridging. Therefore forecast track philosophy is to simply show Andrea following this curving steady-state flow....and so like the previous discussion I show Andrea later on curving eastward and passing just offshore of Nova Scotia (based on the shape of the curving flow in the models I think the NHC has adjsuted their forecast track too far north into Nova Scotia). And based on the track seen on radar in Figure 2...I show a rightward lean in track relative to NHC for the shorter-term as well. Based on the 7-hourly motion between the two radar fixes marked in Figure 2...I think the NHC forecast track is a bit too fast as well...so my forecast track is a bit behind the NHC's forward pace.

 photo Jun_6_2013_TSAndrea_Forecast_zps16dfe48e.png
Figure 1: Tropical Storm Andrea Forecast

 photo Jun_6_2012_TS_Andrea_Radar_zps6a2bcfd8.png
Figure 2: Structure of Tropical Storm Andrea on Doppler Radar earlier this evening

Impact swath in Figure 1 is initialized based on Andrea's radar presentation in Figure 2. This swath includes a much greater area on the storm's west side than my previous impact swath in discussion #7....as Andrea wrapped around her central storm burst into her NW side before she made landfall. The expansion of the rain into her NW half may also be associated with the eastern divergence of the paragraph P1 upper trough. The impact swath is extrapolated along my forecast track with the assumption Andrea continues to maintain her structure shown in Figure 2.

...MID-LATITUDES DISCUSSION...
P1...Central US upper trough is working its way into the Ohio Valley and eastern US...and will soon merge with Gulf cut-off upper trough mentioned in paragraph P6. Its eastern divergence supports a frontal cyclone which has moved from Minnesota to the Ohio Valley while deepening from 1014 to 1008 mb since the previous discussion. Western convergence of this upper trough supports surface 1019 mb ridge over the central US marked over Nebraska in the upper-left corner of the above atmo chart.

P2...Eastern north America upper trough has shifted into the north-central Atlantic. East Canada coast frontal cyclone formerly supported by eastern divergence of this upper trough has whirled into a position beneath the upper trough axis itself where divergence is less..and as a result wit has weakened from 986 to 993 mb since the previous discussion. Western convergence of the upper trough supports surface ridge which has moved from the Massachusetts coast to waters offshore of Nova Scotia and is currently at 1027 mb. This surface ridge extends to 1023 mb center over southern Hudson Bay.

P3...Warm air advection ahead of paragraph P2 surface frontal cyclone supports upper ridge which is shifting into the open northeastern Atlantic.

P4...NE Atlantic upper trough is shifting eastward out of the picture into western Europe.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1030 mb...will soon be supported by southeastern convergence of paragraph P6 tropical upper ridge...as mentioned in the Andrea special feature section. It also has a northeastward extension to a 1029 mb lobe (marked in upper-right corner of above atmo chart) supported by western convergence of paragraph P4 upper trough.

...TROPICAL BELT DISCUSSION...
P6...Tropical Storm Andrea has made landfall in northern Florida...and intensified to a peak of 65 mph max sustained winds while supported by outflow of tropical upper ridge in the region. Gulf of Mexico upper trough (that cut-off from paragraph P2 upper trough three days ago) is supporting a surface trough extending south from Andrea with its eastern divergence. The tropical upper ridge continues to have a NE extension into the W Atlantic waters thanks to warm air advection ahead of paragraph P1 frontal cyclone.

P7...Southern stream upper trough remains cut-off in the eastern Caribbean region.

P8...Tropical midway between the Lesser Antilles and Cape Verde Islands still seems to be enhanced by low-latitude eastern Atlantic upper ridging...and as a result it developed an impressive thunderstorm cluster with 1012 mb surface vortex. It has been upgraded to tropical disturbance Invest 92-L...and the 8 PM EDT NHC tropical weather outlook from earlier this evening suggested this system almost became a tropical storm. However...as evidenced by the fact the thunderstorm cluster is biased east of the vortex center...it will be entering a jet of shearing upper westerlies on the north side of the low-latitude upper ridging and in advance of paragraph P7 upper trough.

P9...As marked in the lower-right corner of the above atmo chart...satellite animation over the last days suggests a tropical wave maybe currently SW of the Cape Verde Islands and ESE of Invest 92-L. However the NHC TAFB analyses have so far not acknowledged this tropical wave. If this continues...I may soon cancel this suspect tropical wave from subsequent atmo charts.

2013 Atlantic Hurricane Season Birdseye Discussion #7A (Special Update)

By: NCHurricane2009, 4:06 PM GMT on June 06, 2013

...THURSDAY JUNE 6 2013..12:07 PM EDT...
Since full discussion #7 was written early this morning...Troipcal Storm Andrea has undergone changes in track and intensity.

Initially Andrea was following my NNE track forecast which was slightly left of NHC...then the center during the daylight hours of this morning regenerated to the east beneath the storm burst mentioned in the special feature section of discussion #7. This eastward regeneration of the center puts Andrea moreso in deep-layered southerly flow on the west side of the tropical upper ridging and surface ridging mentioned in paragraphs P5 and P2 of discussion #7...so I would imagine the center would soon have to turn more northward and re-join earlier forecast tracks. This is probably why the NHC forecast track remains essentially the same (except for the latter portion of the forecasted non-tropical phase of Andrea where the NHC has adjusted toward my discussion #7 forecast track and even a bit left of that such that the center of non-tropical Andrea would be closer to Massachusetts by this weekend).

In addition...my discussion #7 intensity forecast predicted strenghtening to 50 mph max winds (higher than what NHC showed at the time)...but Andrea has gone further to 60 mph max winds. No additional strengthening is likely as she is now traversing relatively cooler/shallower NE Gulf waters and as she interacts more with land...and Andrea is still forecast to maintain 45 mph max winds well after landfall due to supportive eastern divergence of upper trough mentioned in paragraph P1 of discussion #7.

Andrea has also gone an improvement in structure...wrapping around the adjacent storm burst such that she now has decent rainfall activity in part of her NW half she did not previously have. Therefore...my impact swath shown in Figure 1 of discussion #7 needs a leftward adjustment. Areas that should now be included in my impact swath that were not previously included are more inland areas of eastern Georgia...more inland areas in eastern South Carolina...more inland areas in eastern North Carolina...the southeast corner of Virginia...southeastern Maryland...all of Delaware...southern New Jersey...Long Island New York...eastern Connecticut...Rhode Island...eastern Massachusetts...and southern Nova Scotia...

2013 Atlantic Hurricane Season Birdseye Discussion #7

By: NCHurricane2009, 6:02 AM GMT on June 06, 2013

...THURSDAY JUNE 6 2013..2:01 AM EDT...
Tropical disturbance Invest 91-L has become Tropical Storm Andrea in the eastern half of the Gulf of Mexico within the last 24 hours....and appears poised to bring tropical storm conditions to parts of the Florida peninsula...as well as coastal Georgia and coastal Carolinas. If you have interests here...please visit www.nws.noaa.gov and or www.nhc.noaa.gov for latest info on Andrea and associated watches and warnings that maybe in your area. See special feature section below for additional details on Andrea.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_5_2013_2045Z_zpsd2e8b048.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1925Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_5_2013_2045Z_zpsba83d587.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...TROPICAL STORM ANDREA...
My forecast for Andrea versus the NHC's is summarized in the graphic in Figure 1 below.

Strong tropical upper ridge covering the east half of this storm remains robust...due to warm air advection ahead of the paragraph P1 frontal cyclone and perhaps mainly due to latent heat release of persistent t-storms in the east half of the storm. The upper flow over Andrea is southerly on the west flank of this upper ridge and east flank of Gulf cut-off upper trough...the low-level flow is also southerly on the west flanks of paragraph P2 and P5 surface ridging...and with 18Z GFS showing this pattern persisting thru 12 hours (thru 10 AM Thu) it seems Andrea should be tracking straight north. But instead she has leaned more NNE while the broad center appears to be regenerating toward an adjacent t-storm burst near the center seen in Figure 2. Therefore I extrapolate the current NNE motion thru this 12 hour time assuming this regeneration process continues...and because the current NNE track is a bit left of the NHC forecast...this makes me go slighly left of NHC initially. I also forecast the storm to strengthen to 50 mph max winds (a bit higher than NHC forecast) by Thursday afternoon due to the storm burst...then predict weakening to 45 mph max winds for landfall as Andrea traverses relatively cooler/shallower NE Gulf waters and interacts more with land. Between 12 and 24 hrs (10 AM Thu and 10 PM Thu)...GFS shows lower and upper flow becoming more southwesterly in advance of paragraph P1 upper trough and frontal cyclone pushing into the Ohio Valley...so I bend the track rightward and re-align with NHC as a result by 10 PM Thu.

After 10 PM Thu...models show warm air advection ahead of Andrea and paragraph P1 frontal system building up the tropical upper ridging into a vast W Atlantic upper ridge...with SE convergence of the upper ridge supporting the paragraph P5 surface ridging. The vast ridging appears to lock the paragraph P1 upper trough into the eastern US for quiet a long period...and so the models show a long period of curving and deep-layered flow east of the upper trough and west of the vast ridging. Therefore...forecast track philosophy after 10 PM Thu is to simply show Andrea following this curving steady-state flow...and with the NHC track in parallel with that forecast flow between 10 PM Thu and 10 PM Friday I see no reason to disagree with that segment of NHC's track. After 10 PM Friday...I think the NHC track doesn't quiet follow the forecast curving flow...so my red line in Figure 1 is a bit different than NHC's black line during that timeframe. I agree with NHC showing Andrea maintaining 45 mph max winds after landfall...due to supportive divergence ahead of the paragraph P1 upper trough as we see with a non-tropical system. I agree with NHC's transition to non-tropical by 10 PM Fri (48 hours)...as this is precisely when the 18Z GFS model run showed Andrea losing touch with warm core upper anticyclonic outflow of the tropical upper ridging (this is shown as the incoming paragraph P1 upper trough shoving off the anticyclonic outflow to the east...embedding Andrea beneath its more linear eastern flow).

 photo Jun_5_2013_TSAndrea_Forecast_zps2ecbcc43.png
Figure 1: Tropical Storm Andrea Forecast

 photo Jun_5_2013_TSAndrea_Structure_zpsd478be59.png
Figure 2: Structure of Tropical Storm Andrea earlier this evening

Impact swath in Figure 1 is initialized based on the coldest (orange and red) cloud tops shown on the colorized infrared in Figure 2...which seems to correspond well with where Doppler radar also shows the heaviest rain bands of Andrea. This swath also corresponds with where Andrea's low-level southerly winds are in directional shear with the tropical upper ridge's westerly winds....with such directional shear enhancing the tornado risk (which is why I mention that risk in the impact statements of Figure 1). Because Andrea will be under westerly shear for her entire life...that is why the swath is shown to be biased to the right of my forecast storm track. Due to t-storm complexes firing up over the southeast US well to the northwest of Andrea's rain shield...associated with the tail end of the paragraph P2 front and paragraph P1 front...I decided to write impact statement (b) in Figure 1. I expect these t-storm complexes to produce more transient flash flooding risk...while the flooding risk wihtin the impact swath itself (mentioned in impact statement (a)) could be more significant than a trasient flash flood event.

...MID-LATITUDES DISCUSSION...
P1...Central US upper trough will be working its way into the eastern US. Its eastern divergence supports a 1014 mb frontal cyclone which has moved from the eastern Dakotas to Minnesota since the previous discussion. Western convergence of this upper trough supports surface 1024 mb ridge over the NW US marked in the upper-left corner of the above atmo chart.

P2...Eastern north America upper trough continues shifting eastward...with its south extent now reaching into the NW Atlantic. Eastern divergence of the upper trough supports east Canada coast frontal cyclone which has intensified from 990 to 986 mb since the previous discussion. Western convergence of the upper trough supports surface ridge which has moved from the North Carolina coast to the Massachusetts coast and is currently 1023 mb. This surface ridge is re-enforced by 1028 mb center over southern Hudson Bay also supported by western convergence of the upper trough.

P3...Warm air advection ahead of paragraph P2 surface frontal cyclone supports upper ridge currently extending from southern Greenland and into the open central Atlantic.

P4...NE Atlantic upper trough continues shifting eastward. Long surface front still extends southward into the open eastern Atlantic and is decaying into a surface trough according to latest TAFB maps.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1028 mb...continues shifting eastward as it transitions to being supported by eastern convergence of paragraph P3 upper ridge. It also has a northeastward extension to a 1025 mb lobe (marked in upper-right corner of above atmo chart) supported by western convergence of paragraph P4 upper trough.

...TROPICAL BELT DISCUSSION...
P6...Tropical disturbance across the eastern Gulf of Mexico...supported by outflow of tropical upper ridge in the region...and supported by eastern divergence ofGulf upper trough (that cut-off from paragraph P2 upper trough two days ago)...has intensified into Tropical Storm Andrea and is discussed in greater detail in the above special feature section. The tropical upper ridge continues to have a NE extension into the W Atlantic waters thanks to warm air advection ahead of paragraph P2 frontal cyclone.

P7...Southern stream upper trough remains in the W Atlantic extending southward into the Lesser Antilles and E Caribbean.

P8...Eastern Caribbean tropical wave has been dropped from NHC TAFB maps while it moved over Hispaniola as of 1800Z earlier this evening.

P9...Tropical midway between the Lesser Antilles and Cape Verde Islands still seems to be enhanced by low-latitude eastern Atlantic upper ridging. However it will be entering a jet of shearing upper westerlies on the north side of the low-latitude upper ridging and in advance of paragraph P7 upper trough.

P10...Satellite animation suggests yet another tropical wave maybe currently south of the Cape Verde Islands as marked in the lower-right corner of the above atmo chart. This tropical wave will likely suffer the same fate as the paragraph P9 tropical wave.

2013 Atlantic Hurricane Season Birdseye Discussion #6A (Special Update)

By: NCHurricane2009, 12:56 AM GMT on June 06, 2013

...WEDNESDAY JUNE 5 2013...9:00 PM EDT...
As forecast during discussion #6...Invest 91-L has strengthened into a tropical cyclone based on observations of a sufficiently strong closed surface circulation made by aircraft reconnaissance this afternoon. Invest 91-L is now Tropical Storm Andrea...centered in the eastern Gulf of Mexico....and tropical storm warnings are in effect along the west Florida coast...with tropical storm watches along the northeast Florida coast and southeast US coast up through North Carolina as it appears Andrea could maintain strength after her Florida panhandle landfall due to a near-coastal track and due to supportive divergence on the east side of an upper trough (paragraph P1 feature of discussion #6). Please visit www.nhc.noaa.gov and www.nws.noaa.gov for up to date info on Andrea and associated watches and or warnings for your local area.

Late this evening...I will be releasing my next full birdseye discussion with a forecast for Tropical Storm Andrea. Return to discussion #6 for an assessment on the rest of the Atlantic tropics.

2013 Atlantic Hurricane Season Birdseye Discussion #6

By: NCHurricane2009, 11:05 AM GMT on June 05, 2013

...WEDNESDAY JUNE 5 2013...7:05 AM EDT...
Tropical disturbance Invest 91-L continues to organize across the eastern half of the Gulf of Mexico....and I am now predicting tropical cyclone formation later today or tonight. See special feature section for forecast on Invest 91-L. If you have interests in the eastern Gulf of Mexico...the Florida peninsula...the Florida Keys...and Florida panhandle...and southern Georgia...please keep abreast of this developing situation. Visit www.nhc.noaa.gov and or www.nws.noaa.gov to check on tropical cyclone formation and any associated warnings that could become issued later today as a result.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_5_2013_0615Z_zpsc1bd249e.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0729Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_5_2013_0615Z_zpse7aac06a.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...GULF OF MEXICO DISTURBANCE INVEST 91-L...
Computer models have accurately predicted how strong the tropical upper ridge covering the east half of this disturbance was going to build...due to warm air advection ahead of the paragraph P1 frontal cyclone and perhaps mainly due to latent heat release of persistent t-storms in the east half of the disturbance. Because of the inflation of the upper ridge...this has pushed the unfavorable shearing cut-off upper trough westward...and moreover the cut-off upper trough is more amplified as a result of the adjacent amplification of the tropical upper ridge. The more amplified nature of the cut-off upper trough also has reduced the westerly shear over the disturbance. Based on the NHC TAFB declaring a 1008 mb low pressure center along the surface trough (as of 0600Z)...based on thunderstorms building closer to that center...and based on the improving quality of the curving cloud bands in the east half of the disturbance....I expect tropical cyclone formation later today or tonight.

The system has been quasi-stationary while trapped between paragraph P5 surface ridge to the east and and paragraph P2 surface ridging to the north. Now that the paragraph P2 surface ridging is shifting east in advance of the paragraph P1 frontal cyclone...both the paragraph P5 and P2 surface ridges will stack north-to-south such that the low-level flow will be southerly in the next 24 hours. Meanwhile the upper flow will switch from southerly to more southwesterly by the end of 24 hours as the paragraph P1 upper trough and cut-off upper trough begin to combine and push into this system from the west. So with the deep-layer flow being southerly for the next 24 hours (perhaps with some upper southwesterly influence by the end of 24 hours)...I expect the center of this system to track mainly north with a bit of a north-northeast bend toward the western Florida panhandle coast by tomorrow (Thursday) morning. Both the upper and lower-level flow will become southwesterly between 24 and 48 hours in advance of the paragraph P1 upper trough and paragraph P1 surface frontal cyclone pushing in from the northwest...so I then expect the track to bend northeast for a western Florida panhandle landfall by 36 hours (late Thursday night...early Friday)...followed by arrival into southwestern Georgia as disspating tropical cyclone by 48 hours (Friday morning).

In the next 48 hours...hazards across all of Florida and southern Georgia will include the overspreading of the eastern rain bands of the system...which will bring gusty winds (especially toward the center of circulation)...heavy rain with possible flash flooding...and isolated tornadoes (directional vertical shear for tornadoes could be enhanced as low-level southerlies in the east half of the surface circulation conflict with upper westerlies across the tropical upper ridge).

...MID-LATITUDES DISCUSSION...
P1...Western US upper trough is currently working its way into the central US. Its eastern divergence supports a 1013 mb frontal cyclone which has moved from SE Montana to the eastern Dakotas in last 24 hours. Western convergence of this upper trough supports surface ridge building into the upper-left corner of the above atmo chart from western Canada.

P2...Eastern north America upper trough continues shifting eastward...and in the last 24 hours was re-enforced by high-latitude upper trough digging in from Hudson Bay as remarked in paragraph P2 of the previous discussion. Eastern divergence of re-enforced upper trough supports SE Canada frontal cyclone which has intensified from 1002 to 990 mb while the cyclone has shifted onto the east Canada coast. Western convergence of the upper trough supports surface ridge which has moved from Michigan to the North Carolina coast and is currently 1021 mb. This surface ridge is re-enforced by 1028 mb center over SW Hudson Bay...and this 1028 mb center was delivered by western convergence of the aforementioned high-latitude upper trough.

P3...Warm air advection ahead of paragraph P2 surface frontal cyclone supports upper ridge currently extending from southern Greenland and into the open central Atlantic.

P4...NE Atlantic upper trough continues shifting eastward. The decaying 992 mb frontal cyclone directly below the upper trough...positioned SE of Greenland in the previous discussion...has now exited the scope of this discussion from the upper-right corner of the above atmo chart while weakening to 1010 mb. However...the long front extending south of the 1010 mb center remains well in the scope of this discussion while reaching into the open eastern Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. Its main center...currently 1026 mb...continues shifting eastward as it transitions to being supported by eastern convergence of paragraph P3 upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Tropical disturbance across the eastern Gulf of Mexcio...supported by outflow of tropical upper ridge in the region...and supported by eastern divergence of W Gulf upper trough (that cut-off from paragraph P2 upper trough since yesterday)...is described in greater detail in the above special feature section. The tropical upper ridge continues to have a NE extension into the W Atlantic waters thanks to warm air advection ahead of paragraph P2 frontal cyclone.

P7...Southern stream upper trough remains in the W Atlantic extending southward into the Lesser Antilles.

P8...Eastern Caribbean tropical wave is currently making its way into the central Caribbean. As forecast in paragraph P9 of the previous discussion... the wave is becoming suppressed in a patch of unfavorable sinking south-central Caribbean dry air (seen in above thermo chart) generated by southeastern upper convergence of paragraph P6 upper ridge.

P9...Tropical midway between the Lesser Antilles and Cape Verde Islands seems to have become enhanced a bit in the last 24 hours by low-latitude eastern Atlantic upper ridging. However it will be entering a jet of shearing upper westerlies on the north side of the low-latitude upper ridging and in advance of paragraph P7 upper trough.

P10...Satellite animation suggests yet another tropical wave maybe currently south of the Cape Verde Islands as marked in the lower-right corner of the above atmo chart. This tropical wave will likely suffer the same fate as the paragraph P9 tropical wave.

2013 Atlantic Hurricane Season Birdseye Discussion #5

By: NCHurricane2009, 6:45 AM GMT on June 04, 2013

...TUESDAY JUNE 4 2013...2:45 AM EDT...
Tropical disturbance Invest 91-L has become a little more organized across the eastern half of the Gulf of Mexico in the last 24 hours. I expect a high likelihood of tropical cyclone formation around 48 hours from now...and as such Invest 91-L has a special feature section below. If you have interests in the eastern Gulf of Mexico...western Cuba...the Florida Keys...the Florida peninsula...and the western Bahamas...see special feature section below.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_4_2013_0315Z_zps01c20a98.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0129Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_4_2013_0315Z_zps948fa34f.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...GULF OF MEXICO DISTURBANCE INVEST 91-L...
Previously I had predicted the Yucatan and SE Gulf surface trough would regenerate southeastward into the NW Caribbean as the tropical upper ridge in paragraph P7 got pushed southeast ahead of paragraph P2 upper trough. I expected that such a regeneration process would be tropical in nature (i.e. concentrated NW Caribbean thunderstorms would develop below outflow of upper ridge...in turn the upper ridge strengthening from t-storm latent heat release such that surface pressures drop below upper ridge where the surface trough would regenerate). Instead during the last 24 hours...the forcing has been more like what we would see with a mid-latitude non-tropical feature...with the south end of the paragraph P2 upper trough cutting-off...with eastern divergence of the cut-off upper trough strengthening the Yucatan-SE Gulf surface trough. Looking back at yesterday's and today's model runs...this cut-off upper trough is something the models have been showing all along...but I failed to interpret the surface trough would stay parked in the Yucatan/SE-Gulf area while supported by this cut-off upper trough (and indeed the models over the last days kept on showing surface trough/surface low development right here instead of my NW Caribbean prediction made yesterday). With the Yucatan-SE Gulf surface trough now tighlty defined...its chances for any eastward regeneration into the upper ridge (through the above-described tropical processes) is much lower.

The Yucatan-SE Gulf position of the surface trough positions it under less favorable and westerly shearing upper winds rather than the lower shear/better upper outflow had it regenerated into the NW Caribbean. In addition...western convergence of the cut-off upper trough supports dry air seen in the above thermo chart choking the west half of this disturbance's t-storms. However during the next 48 hours...as the paragraph P2 upper trough exits stage right into the Atlantic...the GFS computer model continues to insist that the upper ridge will strongly build over Cuba and over the east half of this disturbance...due to warm air advection ahead of the paragraph P1 frontal cyclone and perhaps due to latent heat release of persistent t-storms in the east half of the disturbance. If the upper ridge indeed inflates like this...this will push the unfavorable shearing cut-off upper trough westward and away such that tropical cyclone formation will still be possible by 48 hours. Another reason the cut-off upper trough could retrograde westward would be due to attraction toward incoming paragraph P1 upper trough. By 72 through 96 hours...this disturbance will then be swept northeastward by paragraph P1 weather system across the Florida peninsula into the W Atlantic...where it will either become a remnant non-tropical frontal low or get absorbed by the paragraph P1 weather system.

Currently this system is quasi-stationary while trapped between paragraph P6 surface ridge and paragraph P2 central US surface ridge. Therefore regardless of tropical cyclone formation or not...this system will bring lots of rain and potential flooding to western Cuba...western Bahamas...the Florida Keys...and the Florida peninsula.

...MID-LATITUDES DISCUSSION...
P1...Upper trough continues entering the upper-left corner of the above charts from the western US. Its eastern divergence supports a frontal cyclone which has moved from NW Wyoming to SE Montana in last 24 hours...and this frontal cyclone is currently at 1006 mb.

P2...Central US upper trough has moved into eastern North America. Eastern divergence of upper trough supports SE Canada frontal cyclone...but this cyclone has weakened from 996 to 1002 mb in last 24 hours while whirling cyclonically to a position beneath the upper trough axis itself where upper divergence is less. Western convergence of the upper trough supports central US surface ridge...marked with 1018 mb center over Michigan. A high-latitude upper trough from Canada's Hudson Bay is entering the above atmo chart from the upper-left...and this high-latitude upper feature is bringing in another surface ridge and surface cold front supported by its western convergence and eastern divergence...repsectively. As the energy of this high-latitude weather system merges with our eastern North America upper trough...expect the 1002 mb frontal cyclone and 1018 mb ridge to be re-enforced.

P3...Warm air advection ahead of paragraph P2 surface frontal cyclone supports upper ridge currently over the east coast of Canada extending into the open central Atlantic.

P4...Central Atlantic upper trough has moved into the NE Atlantic. Mature 983 mb frontal cyclone south of Greenland in the previous discussion has decayed to 992 mb while weakening below the non-divergent axis of the upper trough. This cyclone is now just SE of Greenland as it has whirled cyclonically beneath its upper trough axis.

P5...NE Atlantic upper ridge axis in the previous discussion...supported by Warm air advection ahead of the paragraph P4 frontal cyclone...has exited the picture from the upper-right of the above atmo chart while shifting into NW Europe.

P6...Surface ridge dominates much of the open Atlantic basin. 1027 mb center NE of the Lesser Antilles in the previous discussion is now 1029 mb while shifting eastward as it transitions to being supported by eastern convergence of paragraph P3 upper ridge. The greater-than-1032 mb center offshore of Europe has shifted onto mainland NW Europe (and out of the scope of this discussion) as the eastern convergence of its supporting upper ridge (paragraph P5) has shifted to this location.

...TROPICAL BELT DISCUSSION...
P7...Tropical disturbance across the eastern Gulf of Mexcio...supported by outflow of tropical upper ridge in the region...and supported by eastern divergence of W Gulf upper trough (that has cut-off from paragraph P2 upper trough)...is described in greater detail in the above special feature section. The tropical upper ridge has gained a NE extension across SE Florida...into the waters offshore of the Carolinas...thanks to warm air advection ahead of paragraph P2 frontal cyclone.

P8...Southern stream upper trough remains in the W Atlantic in the vicinity of Bermuda. South end of this upper trough remains fractured off at a location over the Lesser Antilles while pushed SE ahead of the strong tropical upper ridge highlighted in paragraph P7.

P9...Tropical wave is currently crossing the Lesser Antilles into the eastern Caribbean. It remains under unfavorable southwesterly vertical shear ahead of the paragraph P8 upper trough...and will be later entering a patch of unfavorable sinking south-central Caribbean dry air (seen in above thermo chart) generated by southeastern upper convergence of paragraph P7 upper ridge.

P10...Tropical wave SW of the Cape Verde Islands in the previous discussion is now entering the waters midway between the Lesser Antilles and Cape Verde Islands. It is entering a jet of shearing upper westerlies on the north side of low-latitude eastern Atlantic upper ridge and in advance of paragraph P8 upper trough.

P11...Satellite animation suggests yet another tropical wave maybe just off the west African coast as marked in the lower-right corner of the above atmo chart. This tropical wave will likely suffer the same fate as the paragraph P9 and P10 tropical waves.

2013 Atlantic Hurricane Season Birdseye Discussion #4

By: NCHurricane2009, 5:52 AM GMT on June 03, 2013

...MONDAY JUNE 3 2013...2:00 AM EDT...
The northwestern Caribbean portion of disturbed weather highlighted in the National Hurricane Center tropical weather outlook in the last 24 hours (as noted in paragraph P6 of the previous discussion) has become slightly better organized and has been upgraded to Invest 91-L by the Naval Research Laboratory of the United States Navy. I am now forecasting tropical cyclone development from this system within the next 5 days...and as such I have given Invest 91-L a special feature section below. If you have interests in the western Caribbean...western Cuba...the Florida Keys...south Florida...and the western Bahamas...see special feature section below.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_3_2013_0315Z_CORRECTED_zps46c0c6be.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0116Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_3_2013_0315Z_zps0bb7b528.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...SPECIAL FEATURE...NORTHWESTERN CARIBBEAN DISTURBANCE INVEST 91-L...
Tropical upper ridge continues supporting broad surface pressures across southeast Mexico and the northwestern Caribbean at this hour...and 0000Z TAFB analysis shows a surface trough across the Yucatan and SE Gulf of Mexico which seemed to correspond with some cyclonic rotation seen in earlier visible satellite animation during last afternoon's sunset. Over the next 24 hours as the south end of the central US (paragraph P2) upper trough pushes into the Gulf...westerly shear will increase across the Yucatan with the upper trough also pushing the core of the upper ridge into the NW Caribbean. That is why in the next 24 hours..I forecast the surface trough will relocate southeastward into the NW Caribbean while redeveloping beneath the core of the outflow-enhancing upper ridge.

Once the central US (paragraph P2) upper trough exits stage right into the Atlantic...GFS computer model continues to show the upper ridge re-gaining ground and building impressively over the NW Caribbean and Cuba area in advance of the paragraph P1 upper trough. Meanwhile I forecast this system to remain quasi-stationary in the NW Caribbean between 24 and 96 hours while trapped between paragraph P6 surface ridge and paragraph P2 central US ridge while it slowly organizes into a tropical cyclone beneath the upper ridge. During this quasi-stationary period...I expect this system will bring lots of rain and potential flooding to western Cuba...western Bahamas...the Florida Keys...and south Florida.

Between 96 and 120 hrs...I expect the paragraph P1 weather system will then pick up and accelerate this system northeast across western Cuba...south Florida...the NW Bahamas...and into the W Atlantic where it then transitions into a remnant frontal low or becomes absorbed by the paragraph P1 weather system.

...MID-LATITUDES DISCUSSION...
P1...Next upper trough and surface frontal system (with 1000 mb frontal depression center in Nw Wyoming) is entering the upper-left corner of the above charts.

P2...Central US upper trough will be translating eastward into eastern North America in next 24 hours. Eastern divergence of upper trough is supporting a surface frontal cyclone that has moved into SE Canada from the Great Lakes while it has deepened from 1003 mb to 996 mb since my previous discussion. Western convergence of the upper trough supports surface ridge entering central Canada and central US...marked with 1018 and 1023 mb centers in the upper-left corner of the above atmo chart.

P3...Warm air advection ahead of paragraph P2 surface frontal cyclone supports upper ridge over eastern Canada and NW Atlantic.

P4...Upper trough is present over the central Atlantic. Mature 978 mb frontal cyclone south of Greenland has decayed to 983 mb while weakening below the non-divergent axis of the upper trough.

P5...Warm air advection ahead of the paragraph P4 frontal cyclone supports upper ridge axis in the NE Atlantic.

P6...Surface ridge dominates much of the open Atlantic basin. It features a 1027 mb center ESE of Bermuda and NE of the Lesser Antilles once supported by western convergence of paragraph P4 upper trough and now will become supported by western convergence of southern fracture of paragraph P8 upper trough. It also features a greater-than-1032 mb center offshore of Europe supported by eastern convergence of pargraph P5 upper ridge.

...TROPICAL BELT DISCUSSION...
P7...Tropical disturbance across southeast Mexico and western Caribbean...supported by outflow of tropical upper ridge in the region...has been moved to special feature section above.

P8...Southern stream upper trough remains in the W Atlantic in the vicinity of Bermuda. South end of this upper trough has fractured off at a location over the Lesser Antilles while pushed SE ahead of the strong tropical upper ridge highlighted in paragraph P7. Upper divergence east of the Bermuda-area upper trough axis supports continued cloudiness over and east of the Bahamas...where a new but weak surface trough has been marked as of 0000Z TAFB.

P9...Tropical wave continues approaching the Lesser Antilles. It remains under unfavorable southwesterly vertical shear ahead of the paragraph P4 and P8 upper troughs.

P10...Tropical wave SSW of the Cape Verde Islands in the previous discussion is now SW of the Cape Verde Islands. Although it is under a shear-reducing and outflow enhancing low-latitude upper ridge in the eastern Atlantic tropics...climatology and an eventual westward track toward the shearing paragraph P4 and paragraph P8 upper troughs suggest that tropical cyclone development here is not expected.

P11...Satellite animation suggests yet another tropical wave is about to roll off the African coast as marked in the lower-right corner of the above atmo chart. This tropical wave will likely suffer the same fate as the paragraph P9 and P10 tropical waves.

2013 Atlantic Hurricane Season Birdseye Discussion #3

By: NCHurricane2009, 2:57 PM GMT on June 02, 2013

...SUNDAY JUNE 2 2013...10:57 AM EDT...
Watching western Caribbean...Bay of Campeche...and southeastern Mexico activity as noted in paragraph P6...mainly for flooding concerns. Still no signs of imminent tropical cyclone development from this area at this time.

An outage persist with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_2_2013_0615Z_zps98e0f7ac.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0725Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_2_2013_0615Z_zpsb52e2f2c.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Central US deep-layered vortex has translated eastward....with the upper-layer now opening into a large upper trough and surface layer currently a 1003 to 1002 mb frontal cyclone over the Great Lakes and SE Canada supported by the eastern divergence of the upper trough. Western convergence of the upper trough supports surface ridge entering central Canada and central US...marked with 1022 and 1023 mb centers in the upper-left corner of the above atmo chart.

P2...Warm air advection ahead of paragraph P1 surface frontal cyclone supports upper ridge over eastern Canada and NW Atlantic.

P3...Upper trough is present over the central Atlantic with an upper vortex at its south end. The 998 mb frontal depression midway between Greenland and Canada in paragraph P3 of the previous discussion has intensified rapidly to a 978 mb cyclone while diving SE to a position south of Greenland...thanks to supportive eastern divergence of the upper trough. Now that the cyclone is below the non-divergent upper trough axis...decay of the cyclone should begin.

P4...Warm air advection ahead of the paragraph P3 frontal cyclone supports upper ridge axis in the NE Atlantic.

P5...Surface ridge dominates much of the open Atlantic basin. It features a 1025 mb center ESE of Bermuda and NE of the Lesser Antilles supported by western convergence of paragraph P3 upper trough and 1033 mb center offshore of Europe supported by eastern convergence of pargraph P4 upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Surface pressures remain generally low across southeast Mexico...Bay of Campeche...and western Caribbean...where impressive pop-up thunderstorm complexes persist thanks to supportive outflow of tropical upper ridge in the region. Even though their is a 1008 mb center in the Bay of Campeche...the Naval Reaserch Laboratory has ceased classifying the Bay of Campeche portion of this weather as Invest 90-L...all while the NHC has highlighted a NW Caribbean portion of the weather while stating a 10% chance of tropical cyclone formation in the next 48 hours. Due to the broadness of the low surface pressures...any Bay of Campeche or western Caribbean tropical cyclone development will be slow to occur. Computer models still show a transient surface low pulling northward into the Gulf of Mexico (between 72 and 120 hrs from now) and getting ripped apart by wind shear on the north side of the tropical upper ridge...with the exception of the CMC model which shows the development of a strong tropical cyclone in the Gulf (but such development will not be possible with vast westerly shear north of the tropical upper ridge...so CMC appears to be an incorrect solution). With the GFS at 120 hrs showing the tropical upper ridge impressively building over Cuba (in advance of the next upper trough which has yet to enter the above atmo chart)...still a little wary of development potential...but no models show development below the forecast Cuba upper ridge perhaps as that upper ridge will be too far northeast of where our lowest surface pressures have been parked. Regardless of development...concerned about flooding potential over SE Mexico due to recent saturation from last week's Hurricane Barbara coupled with some fairly impressive t-storm complexes that have been firing up in last 24 hours.

P7...Southern stream upper trough remains in the W Atlantic with a Bermuda-area upper vortex. South end of this upper trough has fractured off at a location over the Lesser Antilles while retorgrading SE ahead of the strong tropical upper ridge highlighted in paragraph P6. As predicted previously in special update #1B...westerly upper flow south of the Bermuda-area upper vortex is still diverging with northerly flow E of the paragraph P6 upper ridge...resulting in cloudiness over and east of the Bahamas.

P8...Tropical wave midway between the Lesser Antilles and Cape Verde Islands in the previous discusison is approaching the Lesser Antilles. It remains under unfavorable southwesterly vertical shear ahead of the paragraph P3 and P7 upper troughs.

P9...Impressive tropical wave rolling off of Africa in the previous discussion is not so impressive this morning while SSW of the Cape Verde Islands. Although it is under a shear-reducing and outflow enhancing low-latitude upper ridge in the eastern Atlantic tropics...climatology...lack of computer model support (as of 06Z)...and an eventual westward track toward the shearing paragraph P3 and paragraph P7 upper troughs suggest that tropical cyclone development here is not expected.

2013 Atlantic Hurricane Season Birdseye Discussion #2A (Special Update)

By: NCHurricane2009, 6:29 AM GMT on June 01, 2013

...SATURDAY JUNE 1 2013...2:30 AM EDT...
The area of disturbed weather in the Bay of Campeche...Central America...southeastern Mexico...and western Caribbean Sea...described in paragraph P6 of discussion #2...was upgraded to disturbance Invest 90-L on the Naval Reasearch Laboratory of the United States Navy since yesterday afternoon. As such...I have updated the atmospheric features birdseye chart as shown below to reflect this. The National Hurricane Center has just given 90-L a 10% chance of tropical cyclone genesis in the next 48 hours.

See paragraph P6 of discussion #2 for details on Invest 90-L. Return to discussion #2 for a current assessment on the rest of the Atlantic tropics.

...UPDATED ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_1_2013_0315Z_UPDATED_zpsf01a8563.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0128Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

2013 Atlantic Hurricane Season Birdseye Discussion #2

By: NCHurricane2009, 5:44 AM GMT on June 01, 2013

...SATURDAY JUNE 1 2013...1:48 AM EDT...
Welcome to the official start of the 2013 Atlantic Hurricane Season! This means I am now resuming my daily to near-daily full birdseye discussions from now through November. As the season starts...watching western Caribbean...Bay of Campeche...Central America...and southeastern Mexico activity as noted in paragraph P6. Also noting an impressive tropical wave rolling off of Africa as mentioned in paragraph P9. However...none of these areas are showing any imminent signs of tropical cyclone development at this time.

Concept of my birdseye discussions is to analyze the entire Atlantic basin from two maps that provide a "birdseye" view of the region as can be seen below. In 2012 I released a total of 169 such discussions on a daily to near-daily basis during the hurricane season.

An outage developed with GOES-E satellite imagery during the last few days. GOES-W has been extended to cover much of the view in the two birdseye charts below. However...the east edge of the temporary GOES-W scan has a bias for showing cold cloud tops that are not actually present. Therefore...I have patched the east side of the atmospheric birdseye chart with Meteosat-9 grafts. The east side of the thermodynamics birdseye chart is left unrepaired...so be mindful that the moisture content on the east side of this chart has a positive bias due to the false illusion of cold cloud tops

As promised in my final 2012 hurricane season birdseye discussion...I have begun to release post-storm reports for the 2012 Atlantic Hurricane Season which includes evaluations of how my storm forecasts (issued on these birdseye discussions) compared with that of the official forecasts from the National Hurricane Center. As these post-storm reports come out...they can be viewed on my other blog thread at www.wunderground.com/blog/MIHurricane2009.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jun_1_2013_0315Z_zps6c5815e3.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z, and the 0128Z-released WPC analysis.

In light blue is upper air analysis, with 200 mb wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the 200 mb wind barbs, blue-dashed lines are locations of upper troughs, blue-zig-zag lines are locations of upper ridges. Blue Ls are locations of upper lows, blue Hs are locations of upper ridges.

In red is surface analysis, with solid lines indicating locations of surface fronts, dashed lines indicating locations of surface troughs, and zig-zag lines indicating surface ridge axes. Ls indicate surface lows, Hs indicate surface highs.

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jun_1_2013_0315Z_zps06ea00c5.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

Sea-surface temperatures are overlaid with light blue isotherms. The 26 deg C isotherm is highlighted in red. Waters at and south of the 26 deg C isotherm indicate low-level warmth and hence faster environmental lapse rates with elevation (more instability). Waters north of the 26 deg C isotherm indicate slower environmental lapse rates with elevation (less instability).

...MID-LATITUDES DISCUSSION...
P1...Central US deep-layered vortex with 995 mb surface center over the eastern Dakotas is currently present. Eastern divergence of the upper-layer of the vortex supports 998 mb surface frontal depression in western Oklahoma. Warm moist low-level southerly flow ahead of the 998 mb depression coupled with cold upper-level westerly flow on the south half of the deep-layered vortex is creating instability and directional wind shear favoring severe weather and torandoes across the central US. Please visit www.nws.noaa.gov and www.spc.noaa.gov to get up-to-the-minute forecasts...watches...and warnings that may be present in your community if you live in the central US.

P2...Warm air advection ahead of paragraph P1 deep-layered vortex supports upper ridge over the eastern US and southeast Canada.

P3...Upper trough is present over the central Atlantic. Beneath the axis of the upper trough are 1006 mb (just ESE of Newfoundland) and 998 mb (midway between Greenland and Canada) mature frontal depressions that will no longer strengthen as they are direclty beneath the non-divergent axis of the upper trough. Eastern divergence of the upper trough supports greater-than-1024 mb surface frontal depression in the open Atlantic WNW of the Azores.

P4...Warm air advection ahead of the paragraph P3 frontal features supports eastern Atlantic upper ridge.

P5...Surface ridge dominates much of the open Atlantic basin. It features a 1026 mb center just E of Bermuda supported by western convergence of paragraph P3 upper trough and 1036 mb center supported by eastern convergence of pargraph P4 upper ridge.

...TROPICAL BELT DISCUSSION...
P6...Even though the remnant surface trough of former eastern Pacific Hurricane Barbara has dissipated in the Bay of Campeche...surface pressures remain generally low and pop-up thunderstorm complexes persist in her wake thanks to supportive outflow of tropical upper ridge featuring anticyclonic center over the NE Yucatan. Due to the broadness of the low surface pressures...any Bay of Campeche or western Caribbean tropical cyclone development will be slow to occur. Currently their is no computer model support for development other than GFS and NAM 18Z models showing a transient surface low pulling northward into the Gulf of Mexico and getting ripped apart by wind shear on the north side of the tropical upper ridge. Regardless of development...any persistent thunderstorm complexes over SE Mexico and Central America could cause risk of floods and mudslides...especially SE Mexico areas recently saturated by Barbara.

P7...Southern stream upper trough...referred to as "Area #2" in previous special updates #1B through #1D...is currently in the W Atlantic (with a Bermuda-area upper vortex) and in the eastern Caribbean. As predicted previously in special update #1B...westerly upper flow south of the Bermuda-area upper vortex is diverging with northerly flow E of the paragraph P6 upper ridge...resulting in thick clouds and t-storms over the eastern Bahamas. This upper divergence occasionally has also been supporting fire-ups of t-storms in the southern and western Caribbean. A weak surface trough is presently E of Bermuda...and given that a warm shortwave upper ridge (located just east of our southern stream upper trough) is over the surface trough it seems this may be a warm core (but weak) surface trough that developed from the concentrated latent heat release of the t-storms described previously in the Area #2 section of special updates #1C and #1D. I don't expect any tropical cyclone development here due to high surface pressures of the paragraph P5 surface ridge.

P8...Tropical wave midway between the Lesser Antilles and Cape Verde Islands is inactive while under hostile southwesterly vertical shear ahead of the paragraph P3 upper trough.

P9...A tropical wave rather impressive for the month of June is rolling off of Africa with a 1010 mb low pressure spin and organzied t-storms. Based on the symmetry of cirrus outflow streaks in all quadrants of the t-storm activity...I would say their is a supportive outflow enhancing and shear reducing upper ridge directly overhead that could seemingly aid in this tropical wave's development. However...climatology...lack of computer model support (as of 18Z)...and an eventual westward track toward the shearing paragraph P3 upper trough suggest that tropical cyclone development here is not likely at this time.


The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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