NCHurricane2009's Blog

2014 Atlantic Hurricane Season Birdseye Discussion #129

By: NCHurricane2009, 4:50 AM GMT on October 31, 2014

...FRIDAY OCTOBER 31 2014 12:52 AM EDT...
Atlantic tropics are currently quiet. However over the next few days the upper trough associated with the eastern North America 989 mb frontal cyclone will produce a second frontal cyclone offshore of the United States. This second frontal cyclone will leave behind a frontal segment east of the Bahamas that has the potential to evolve into a tropical disturbance by day 6 in favorable upper winds between a southern fracture of the upper trough to settle in the eastern Caribbean and the rest of the upper trough as it moves away.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #128

By: NCHurricane2009, 4:44 AM GMT on October 30, 2014

...THURSDAY OCTOBER 30 2014 12:45 AM EDT...
The surface low of tropical disturbance Invest 95-L northeast of the Lesser Antilles is now moving more west and less north. On this track...this system is now moving away from lower shear associated with the central tropical Atlantic upper ridge (marked by blue zig-zag line at the bottom-center of the atmospheric features chart below) and moving toward unfavorable higher shear associated with the eastern Caribbean upper trough and upper trough associated with the 990 mb eastern North America frontal cyclone. Therefore this system is no longer likely to become a tropical cyclone and I have cancelled it as a special feature on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0125Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #127

By: NCHurricane2009, 3:38 AM GMT on October 29, 2014

...TUESDAY OCTOBER 28 2014 11:40 PM EDT...
The remnant low of Hanna has in fact re-generated northward into the western Caribbean waters just offshore of Honduras within the past 24 hours. However the circulation is approaching landfall in Belize. Land interaction after landfall and hostile wind shear from the upper trough associated with the 995 mb frontal cyclone moving into eastern North America will finally bring an end to this system...but not before it produces some locally heavy rain in Belize...northern Guatemala...and the Yucatan peninsula in southeastern Mexico.

Tropical disturbance Invest 95-L northeast of the Lesser Antilles has become better organized and appears to be generating a surface circulation further east than I had previously anticipated...while also taking a more north and less west track than previously thought. This change in position and track will over the next few days now keep this system closer to lower shear associated with the central tropical Atlantic upper ridge (marked by blue H at the bottom-center of the atmospheric features chart below) and further away from higher shear associated with the eastern Caribbean upper trough and upper trough associated with the 995 mb eastern North America frontal cyclone. Therefore I have upgraded this system into a special feature on this blog while predicting tropical cyclone formation to occur by 48 hours. See special feature section below for additoinal details. On the forecast track shown in the special feature section...the weather associated with this system will stay east of the Lesser Antilles and east of Bermuda.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1918Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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 DISTURBANCE INVEST 95-L...
Current Prognosis...At 1800Z the NHC TAFB fixed the surface low pressure center of this disturbance near 18N-60W. Using infrared satellite animation I estimate that between 1800Z and 0000Z the center has moved northwestward from 18N-60W to 18.5N-60.5W...although this estimate is a bit uncertain as this disturbance is not well organized enough at this time to identify a defenite center. In addition to warm waters of 29 deg C...this disturbance continues to feed off of supportive upper divergence between the northwest side of the upper ridge in the central tropical Atlantic (marked by blue H in the bottom-center of the above atmospheric features chart) and east side of the eastern Caribbean upper trough (marked by blue-dashed line to the left of 95-L). This upper divergent flow is also shearing in nature...pushing the thunderstorms to the northeast half of the circulation.

Atmospheric Outlook for the Forecast Period...Over the next 24 hours the dynamics across this disturbance will remain the same...with this system continuing to be channeled northwestward between the 1023 mb low-level ridge to the north and eastern Caribbean upper trough to the west. Thus the 24 hour forecast track is based on extrapolating the estimated motion in the above current prognosis section. By 48 hours the 995 mb frontal cyclone currently pushing into eastern North America will push the ridge to a location northeast of the disturbance...causing a more northward track around the west side of the ridge. By 72 hours and beyond a south fracture of the upper trough associated with the frontal cyclone is forecast to support another second frontal cyclone offshore of the eastern US...with the flow between the ridge and second frontal cyclone becoming stronger while the second frontal cyclone intensifies. This will cause this system to accelerate in forward speed and bend northeast by the end of the forecast (120 hours). Warm air advection ahead of the frontal cyclone currently over easter North America...followed by warm air advection ahead of the forecast second frontal cyclone...will de-amplify and dissipate the eastern Caribbean upper trough while amplifying the central Atlantic upper ridging northwards thru the forecast period. However because the forecast track of this system keeps it on the west side rather than under the upper ridging...this system will remain in southwesterly shear thru the forecast period. By the end of the forecast...this system is likely to transition into a non-tropical remnant low supported by upper divergence on the east side of the second frontal cyclone's upper trough...and perhaps get absorbed by the second frontal cyclone.

Thermodynamic Outlook for the Forecast Period...The forecast track listed below takes this system from current water temps in the 29 deg C range to the 26 deg C isotherm by 96 hours...then to cooler waters below 26 deg C by 120 hours which will accelerate the transition of this system to a non-tropical entity as described at the end of the above atmospheric outlook section.

24 Hr Forecast (0000Z October 30)...Sheared but organized tropical low centered at 20.5N-62.5W

48 Hr Forecast (0000Z October 31)...35 mph max sustained wind sheared tropical depression centered at 23N-63.5W

72 Hr Forecast (0000Z November 1)...45 mph max sustained wind sheared tropical storm centered at 26N-64W

96 Hr Forecast (0000Z November 2)...45 mph max sustained wind sheared tropical storm centered at 32N-62.5W

120 Hr Forecast (0000Z November 3)...45 mph max sustained wind non-tropical remnant low centered at 40N-56W

2014 Atlantic Hurricane Season Birdseye Discussion #126

By: NCHurricane2009, 3:01 AM GMT on October 28, 2014

...MONDAY OCTOBER 27 2014 11:01 PM EDT...
Tropical Storm Hanna over eastern Nicargua and eastern Honduras was downgraded to a tropical depression at the 8 PM EDT National Hurricane Center advisory and now has been downgraded to a remnant low as of the 11 PM EDT advisory. Because the small circulation does not extend into the eastern Pacific...the southern half has lost shower and thunderstorm activity which has reduced the rainfall risk in northeastern Nicaragua. Meanwhile the north half of the circulation continues to tap into western Caribbean moisture. And with the system tracking westward on the south side of a 1019 mb low-level ridge...and expected to continue west on the south side of another low-level ridge to build behind the 1000 mb frontal cyclone over central North America...the more active north half of the circulation should spread heavy rains on the north coast of Honduras and areas just inland. Now that the current center of Hanna is becoming more diffuse over land...their is a small chance in the next 24 hours that it could re-generate its center on the north coast of Honduras or even offshore within the thunderstorm activity in the north half of the circulation...which could mean Hanna re-generates yet again into a short-lived tropical cyclone that moves into the southeast coast of Belize (since this does not appear to be imminently occuring at this hour I do not have the confidence to give Hanna a special feature section on this blog right now...but keep in mind sudden regeneration could occur as we saw with this system earlier today). Regardless of re-generation...this system is likely to spread its heavy rains into Belize...northern Guatemala...and the Yucatan peninsula of southeast Mexico beyond 24 hours. Afterwards land interaction with the Yucatan and hostile wind shear from the upper trough associated with the central North America 1000 mb frontal cyclone will finally bring an end to this system.

An upper ridge has formed in the central tropical Atlantic (marked by blue-zig-zag line in the bottom-center of the atmospheric features chart below) in relatively higher pressures between a western fracture of the TUTT (Tropical Upper Troposhperic Trough) which is now an upper vortex over the eastern Caribbean (marked by blue L) and eastern fracture of the TUTT (marked as a blue-dashed line northwest of the Cape Verde Islands). Upper divergence between the eastern Caribbean upper vortex and upper ridge...in conjunction with surface convergence from the pair of tropical waves entering the eastern Caribbean...is producing a concentrated area of showers and thunderstorms just east of the Lesser Antilles that has become introduced into the National Hurricane Center Tropical Weather Outlook and has been upgraded to Invest 95-L on the Naval Research Laboratory site of the US Navy. I forecast in the next 48 hours that this system will consolidate into a tropical low tracking west-northwest while passing just north of the Lesser Antilles...Virgin Islands...and Puerto Rico. During this time it is likely the east half of the forecast low will remain active beneath the upper ridge and west half will remain suppressed due to the east Caribbean upper vortex...with the active eastern half bringing squally weather across the Lesser Antilles. Beyond 48 hours I expect that this system will then accelerate north into the ridge weakenss associated with what is now the 1000 mb frontal cyclone and its upper trough moving into central North America...with this upper trough shearing this system apart and preventing tropical cyclone formation.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1927Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #125A (Special Update)

By: NCHurricane2009, 11:33 PM GMT on October 27, 2014

...MONDAY OCTOBER 27 2014 7:33 PM EDT...
While making landfall near the Nicaragua/Honduras border late this morning...the remnants of tropical depression nine strengthened into minimal Tropical Storm Hanna. The National Hurricane Center has maintained Hanna as an inland tropical storm as of the 5 PM EDT advisory to account for possible tropical storm sustained winds along the northeast coast of Honduras. The wind however is a negligble threat as Hanna is barely a tropical storm. Rather...the main threat is heavy rain with possible flash floods and mudslides for northeastern Nicaragua and eastern Honduras. Visit www.nhc.noaa.gov for up to the minute latest information on Hanna including tropical storm warnings which are currently in effect.

At any advisory now Hanna could be declared a dissipating inland tropical cyclone. If this should occur before my next full blog update later tonight...then I will not have a special feature package for Hanna. However if it remains a tropical cyclone...I will have a special feature package for Hanna which would include a forecast.

2014 Atlantic Hurricane Season Birdseye Discussion #125

By: NCHurricane2009, 7:15 PM GMT on October 26, 2014

...SUNDAY OCTOBER 26 2014 3:15 PM EDT...
The upper trough associated with the 995 mb frontal cyclone over Nova Scotia continues to pass north of the remnants of tropical depression nine in the western Caribbean...with the western upper convergence of the upper trough producing dry sinking air. Last evening the shower and thunderstorm actvity considerably weakened while ingesting this dry air...but this morning and early afternoon this system has become consolidated and re-organized as a 1007 mb surface low offshore of Nicargaua and Honduras taking advantage of low shear and enhanced outflow beneath upper ridging (marked by blue H in the atmoshperic features chart below). Visible satellite animation suggests this system is drifting southward...and therefore it appears the southeast side of the 1019 mb low-level ridge to the northwest will drive this system south and then west into Nicaragua and Honduras...which will prevent tropical cyclone formation due to land interaction. Even if it stays over water...this system only has four days to develop after which time the favorable upper ridging will get pushed southward by a strong upper trough currently located over the western US...which will place this system in unfavorable westerly shear on the north side of the upper riding. It should be noted that the only computer model that currently suggests this system developing is the NAVGEM...however I think the NAVGEM is initialized too far northeast of where the spin is seen in visible satellite imagery which maybe why it keeps it over water and develops it.

Currently showers and thunderstorms in the central tropical Atlantic just east of the Lesser Antilles are supported by upper divergence on the southeast side of a tropical upper troposhperic trough (TUTT) marked by a blue-dashed line at the bottom-center of the atmospheric features chart below. The pair of surface tropical waves (marked by red-dashed lines) that are headed toward the Lesser Antilles are also contributing to this area of weather. The usually over-aggressive CMC computer model continues to develop this area while moving it slowly northwest into the waters north of the Lesser Antilles. If development were to occur...it would be due to the formation of favorable upper ridging in relatively higher pressures between a western fracture of the TUTT to hang over the eastern Caribbean and eastern fracture of the TUTT to become an upper vortex northwest of the Cape Verde Islands. However current runs over other models such as GFS suggest this upper ridging will be too low in amplitude to support tropical development due to the strength of the upper trough currently leaving North America and the upper trough currently over the western US as both upper troughs later move across the Atlantic. Will wait to see if other models join this idea before considering this system a special feature on this blog. If any development were to occur...it will likely track northwestward over or just east of the Lesser Antilles...and then curve northward into the open Atlantic while getting caught into the ridge weakness of the frontal cyclone of the upper trough currently over the western US while this upper trough later moves into the Atlantic.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #124

By: NCHurricane2009, 5:05 PM GMT on October 25, 2014

...SATURDAY OCTOBER 25 1:05 PM EDT...
While moving eastward into the northwest Caribbean...the remnant low of tropical depression nine has become overspread by the tail end of the surface front associated with the 992 mb frontal cyclone on the coast of Atlantic Canada. Meanwhile upper trough associated with the 998 mb frontal cyclone over eastern Canada is passing north of this system while the western upper convergence of the upper trough produces dry sinking air. So far this system is showing some signs of organization while staying south of hostile shearing winds associated with this upper trough and while taking advantage of low shear and upper divergence beneath upper ridging (marked by blue H and blue-zig-zag line in the atmoshperic features chart below). Waiting to see how well this system does against the aforementioned dry air and to see if this system...which is currently elongated due to the overspreading of the frontal zone...becomes more consolidated before considering this system a special feature with a high risk of tropical cyclone formation. If re-development were to occur this system...low-level ridging to the north will likely drive it back westward across the Yucatan and into the southwestern Gulf of Mexico. This system only has about five days to re-develop after which time the favorable upper ridging will get pushed southward by a strong upper trough currently located just offshore of the western US...which will place this system in unfavorable westerly shear on the north side of the upper riding. It should be noted that current computer model runs do not support the idea of this system re-developing.

Currently showers and thunderstorms in the central tropical Atlantic midway between the Lesser Antilles and Cape Verde Islands are supported by upper divergence on the southeast side of a tropical upper troposhperic trough (TUTT) marked by a blue-dashed line at the bottom-center of the atmospheric features chart below. The pair of surface tropical waves (marked by red-dashed lines) that are headed toward the Lesser Antilles may have also contributed to this area of weather. Over the last few days the usually over-aggressive CMC computer model has wanted to develop this area as it approaches the northern Lesser Antilles in the timeframe that is about 4 to 5 days out...but recently the NAVGEM computer model has joined this idea. If development were to occur...it would be due to the formation of favorable upper ridging in relatively higher pressures between a western fracture of the TUTT to hang over the eastern Caribbean and eastern fracture of the TUTT to become an upper vortex northwest of the Cape Verde Islands. However current runs over other models such as GFS suggest this upper ridging will be too low in amplitude to support tropical development due to the strength of the upper trough currently over eastern North America and the upper trough currently offshore of the western US as both upper troughs later move across the Atlantic. Will wait to see if other models join this idea before considering this system a special feature on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1332Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #123

By: NCHurricane2009, 7:21 AM GMT on October 24, 2014

...FRIDAY OCTOBER 24 2014 3:21 AM EDT...
The remnant low of tropical depression nine has become a little better organized over Mexico's Yucatan peninsula and Belize under less vertical shear as the upper trough associated with the 995 mb frontal cyclone offshore of the northeastern US moves away. The next upper trough...associated with the 1002 mb frontal cyclone in south-central Canada...will drag the remnant low of the tropical depression into the northwestern Caribbean. After this upper trough also moves away...upper-level winds could then become more conducive for the remnant low of the depression to re-generate into a tropical cyclone. If re-development were to occur this system...low-level ridging to the north will likely drive it back westward across the Yucatan and into the southwestern Gulf of Mexico. Currently computer models do not support the idea of this system re-generating.

Subtropical low Invest 92-L in the northeastern Atlantic has been removed from the National Hurricane Center tropical weather outlook but remains posted on the Naval Research Laboratory site of the US Navy. The parent upper vortex of 92-L has opened into an upper trough that is unfavorably shearing this system and therefore it is no longer possible for this system to become a subtropical cyclone.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0130Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #122

By: NCHurricane2009, 7:04 AM GMT on October 23, 2014

...THURSDAY OCTOBER 23 2014 3:04 AM EDT...
Satellite data on www.nhc.noaa.gov/satellite.php has stopped updating since the evening of October 21. Because this is the source for the background images used in the atmospheric and thermodynamics charts below...this outage has affected those charts. For now I have reverted to the "winds and analyses" products under "Regional Real-Time Products" at the bottom of the CIMSS website (http://tropic.ssec.wisc.edu/) as the source for the background image in the atmospheric features chart. I have cancelled the theromdyamics chart until this outage is fixed. On a final note...updated zoomed-in satellite images of individual areas of interests and storms are available by clicking on the links in the "Atlantic" section on the left pane of http://www.nrlmry.navy.mil/TC.html.

Tropical depression nine in the southwestern Gulf of Mexico has weakened to a remnant low while making landfall on the west coast of Mexico's Yucatan peninsula. Most of the thunderstorm activity from this former tropical depression has been stripped northeastward from the circulation and has become concentrated in the southeastern Gulf of Mexico and northwestern Caribbean under the support of upper divergence on the east side of the upper trough associated with the 1002 mb northeastern US frontal cyclone. Although this concentrated area of thunderstorms has been introduced as an area of interest in the National Hurricane Center tropical weather outlook...it is soon expected to transition into a less tropical feature supported by the eastern divergence of a southern fracture of another upper trough associated with a frontal cyclone moving into central Canada. This same upper trough will also drag the remnant low of the tropical depression into the northwestern Caribbean. After this upper trough moves away...upper-level winds could then become more conducive for the remnant low of the depression to re-generate into a tropical cyclone. However computer models have withdrawn support for such a solution and therefore I have cancelled this tropical depression as a special feature on this blog.

Deep-layered cyclone Invest 92-L in the northeastern Atlantic has seen a decrease in shower and thunderstorm activity...and upper-level winds will become less favorable for development as the upper vortex of this system opens into a shearing upper trough in the next 24 hours. Therefore this system no longer has the potential to become a subtropical cyclone and has been cancelled as a special feature on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z.

Features with a green "area of interest" label are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not provide an "area of interest" label if they are only included in the NHC's longer term 5-day outlook.

In light blue is upper air analysis, with the green...yellow...and blue upper-level wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the upper-level 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...
Satellite data on www.nhc.noaa.gov/satellite.php has stopped updating since the evening of October 21. Because this is the source for the background image used in this chart...this outage has affected this chart. For now I have decided to cancel this chart until this outage is fixed.

2014 Atlantic Hurricane Season Birdseye Discussion #121

By: NCHurricane2009, 4:45 AM GMT on October 22, 2014

...WEDNESDAY OCTOBER 22 2014 12:50 AM EDT...
Satellite data on www.nhc.noaa.gov/satellite.php has stopped updating since last night. Because this is the source for the background images used in the atmospheric and thermodynamics charts below...this outage has affected those charts. For now I have reverted to the "winds and analyses" products under "Regional Real-Time Products" at the bottom of the CIMSS website (http://tropic.ssec.wisc.edu/) as the source for the background image in the atmospheric features chart. I have cancelled the theromdyamics chart until this outage is fixed. On a final note...updated zoomed-in satellite images of individual areas of interests and storms are available by clicking on the links in the "Atlantic" section on the left pane of http://www.nrlmry.navy.mil/TC.html.

The broad area of surface low pressure across the southwestern Gulf of Mexico was investigated by aircraft reconaissance earlier this afternoon where a well-defined center was found. However the thunderstorm activity was poorly organized until recently when a storm burst has flared up over the center. As a result the National Hurricane Center has just upgraded this system to the ninth tropical depression of the 2014 Atlantic Hurricane Season. This depression is likely to strengthen into a tropical storm while moving into the northwestern Yucatan peninsula of southeast Mexico in the next 24 hours...and therefore tropical storm warnings have just been raised. See second special feature section below for additional details on this new tropical depression. Visit www.nhc.noaa.gov for up to the minute latest information on this depression.

The 1001 mb deep-layered cyclone in the northeastern Atlantic located south of the Azores and west of the Canary Islands has the potential to transition into a subtropical cyclone in the next 24 hours before conditions become less favorable for subtropical development by 48 hours and beyond. See first special feature section below for additional details on this system.

A tropical wave nearing the Lesser Antilles has seen an increase in thunderstorms over the last 24 hours while taking advantage of favorable low shear and enhanced outflow below a tropical upper ridge (marked by blue-zig-zag line in the atmospheric features chart below). Computer models do not forecast this system to develop further. Moreover...the upper trough in the eastern Caribbean (marked by blue-dashed line in the atmospheric features chart below) will shift east and impart unfavorable southwesterly vertical shear across this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z.

Features with a green "area of interest" label are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not provide an "area of interest" label if they are only included in the NHC's longer term 5-day outlook.

In light blue is upper air analysis, with the green...yellow...and blue upper-level wind barbs calculated by GOES satellite imagery showing the upper-level wind direction. Based on the upper-level 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...
Satellite data on www.nhc.noaa.gov/satellite.php has stopped updating since last night. Because this is the source for the background image used in this chart...this outage has affected this chart. For now I have decided to cancel this chart until this outage is fixed.

...SPECIAL FEATURE...NORTHEAST ATLANTIC SUBTROPICAL LOW INVEST 92-L...
Current Prognosis...As of 0000Z satellite imagery fixes the center of deep-layered vortex 92-L at 33.2N-28.5W. The circular area of scattered showers and thunderstorms around the center has now progressed into banding features and a small central dense overcast...indicating an even more tropical system than 24 hours ago. It should be noted that the storm activity west of the center has diminished...perhaps as dry air produced by upper-level convergence on the east side of the nearby upper ridging (marked by blue-zig-zag line to the left of 92-L in the above atmospheric features chart) has infiltrated the west side of this system.

Atmospheric Outlook for the Forecast Period...The nearby deep-layered ridge (marked by red and blue zig-zag lines northwest of 92-L in the above atmo chart) should continue pushing this system west for another 24 hrs. At 24 hrs the 1024 mb ridge currently in the northwest Atlantic will arrive from the west and block further westward progression of this system. By 48 hrs a north fragment of what is now the upper trough of the NE US 1009 mb frontal depression will merge with the parent upper vortex overhead of 92-L...resulting in the upper vortex opening into an upper trough whose west side will drag 92-L east-southeastward. Based on this outlook...92-L has another 24 hrs to develop into a subtropical cyclone in a low shear environment below its parent upper vortex. Then by 48 hrs and beyond when the upper vortex opens into an upper trough...this will increase the shear and end potential for this system to become a subtropical cyclone.

Thermodynamic Outlook for the Forecast Period...This system will be over 21 to 24 deg C waters thru the forecast period...temperatures that are normally not conducive for tropical development. However the existence of decent pockets of showers and thunderstorms in the circulation suggests the overhead upper vortex maybe cold enough to de-stabilize the atmosphere over these waters for tropical development.

24 Hr Forecast (0000Z October 23)...45 mph maximum sustained wind subtropical storm centered at 33.2N-31W

48 Hr Forecast (0000Z October 24)...Sheared remnant low centered at 32.5N-28.5W

...SPECIAL FEATURE...TROPICAL DEPRESSION NINE...
Current Prognosis...Broad tropical low pressure Invest 93-L in the southwestern Gulf of Mexico has managed to strengthen into the ninth tropical depression of the 2014 Atlantic season in what is a moderate westerly shear environment on the north side of a Central America upper ridge (marked by blue-zig-zag line in the atmoshperic feature chart above) and south side of the upper trough associated with the 1009 mb NE US frontal cyclone (marked by blue dashed line). A storm burst covers the center of the new deperssion...with plenty of bands of storms extending far northeast of the center under supportive upper divergence between the aformetioned upper trough and upper ridge. Storm activity is absent west of the center due to the aforementioned westerly shear. The 10 PM CDT National Hurricane Center advisory fixes the center of the new depression at 19.4N-92.9W

Atmospheric Outlook for the Forecast Period...Over the next 24 hrs shear will reduce and be absent by 48 hrs as the upper trough associated with the NE US frontal cyclone moves away. By 72 and 96 hrs this system is expected to interact with the southern fracture of a second upper trough associated with a frontal cyclone moving into central Canada. This second upper trough is expected to push this system further eastward into the northwestern Caribbean...with this second upper trough evolving the northern portion of this system into a less tropical feature over the SE Gulf/S Florida/NW Bahamas supported by the eastern divergence of the upper trough. Meanwhile the remaining southern portion of this system is expected to get left behind in the western Caribbean where their is some risk of this system re-generating into a strong tropical cyclone just beyond the forecast period. See intensity forecast section below for additional details on this risk.

Thermodynamic Outlook for the Forecast Period...This system will be over very favorable 30 deg C water thru the forecast period.



Track Forecast...System will be dragged eastward by the pair of upper troughs mentioned in the above atmospheric outlook section thru the forecast period. The 2W longitude per day eastward track forecast from discussion #120 has done very well and therefore I maintain that philosophy for my updated track forecast. However my updated track forecast is further south than the previous since the NHC has fixed the center at 19.4N instead of 20N. I also bend the track southeast in the late part of the forecast as the steering second upper trough is shown in model runs to gain a SW-NE tilt. Another reason the track may bend south is that the circulation center could easily re-generate further south into an area of more favorable upper winds as mentioned in the intensity forecast section below.

Intensity Forecast...Even though this system is over very warm waters...I agree with the NHC on this system only evolving into a 50 mph max sustained wind tropical storm in the next 24 hours as their will still be unfavorable wind shear during this period. Even though shear is expected to be absent by 48 hrs...this system will have arrived over the Yucatan Peninsula and therefore I expect it will have weakened to a remnant low due to land interaction. Then just like in my previous forecast I expect this system to degenerate further into a remnant and sheared elongated trough as it slides into the northwestern Caribbean during its interaction with the second upper trough. I also expect the northern part of this remnant trough to evolve into a less tropical feature over the SE Gulf/S Florida/NW Bahamas. It remains to be seen if the southern portion of the remnant trough leftover in the northwestern Caribbean later evolves into a strong tropical cyclone...a solution still shown in a few computer model runs. I am not certain about this solution since its possible for the second upper trough to be strong enough to shear this system apart. However models like the GFS have trended with a weaker version of this second upper trough relative to 24 hrs ago...and therefore my forecast above shows this system re-generating into a 35 mph max sustained wind tropical depression by day 5 in favorable upper ridging located south of the upper trough.

Impact Forecast...Biggest risk with this system over the next few days is the heavy rain mentioned in impact statement (b) in the above forecast graphic. It is possible some of this rain will be from the forecast non-tropical feature mentioned in the above atmospheric outlook section expected to form over the SE Gulf/S Florida/western Bahamas.

2014 Atlantic Hurricane Season Birdseye Discussion #120

By: NCHurricane2009, 2:27 AM GMT on October 21, 2014

...MONDAY OCTOBER 20 2014 10:27 PM EDT...
The broad area of surface low pressure across the southwestern Gulf of Mexico has become better organized such that it has been upgraded to Invest 93-L on the Naval Research Laboratory site of the US Navy and such that it has been given a high chance of tropical cyclone formation on the National Hurricane Center's latest tropical weather outlook. I have also upgraded this system to a special feature on this blog. See second special feature section below for additional details on this system. Interests in the Yucatan peninsula of southeastern Mexico should monitor the progress of this system carefully over the next few days. Regardless of development...this disturbance is likely to produce heavy rainfall over the Yucatan due to its expected slow eastward progress through the region.

The 996 mb deep-layered frontal cyclone in the northeastern Atlantic located south of the Azores and west of the Canary Islands has the potential to transition into a subtropical cyclone in the next 48 hours before conditions become less favorable for subtropical development by 72 hours and beyond. See first special feature section below for additional details on this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1925Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...NORTHEAST ATLANTIC FRONTAL LOW INVEST 92-L...
Current Prognosis...As of 0000Z satellite imagery fixes the center of deep-layered vortex 92-L at 33.5N-22.5W. The comma shaped storm mass from 24 hours ago has now transitioned into a circular area of scattered showers and thunderstorms symmetrically distributed around the center...indicating this system is less non-tropical and more subtropical. A small cluster of showers and thunderstorms also persists directly over the center.

Atmospheric Outlook for the Forecast Period...The deep-layered 1027 mb ridge west-northwest of 92-L will rapidly pass north and then northeast of 92-L in the next 24 hrs...which will drive 92-L west and west-northwest on the southwest quadrant of the deep-layered ridge. By 48 hrs...the 1020 mb ridge that has recently emerged from the eastern US will arrive to the northwest and block further west-northwest progression of this system...causing the surface center of 92-L to move west-southwest on the NW quadrant of its overhead parent upper vortex. By 72 hrs a north fragment of what is now the upper trough of the eastern Canada 1006 mb frontal depression will merge with the overhead upper vortex...resulting in the upper vortex opening into an upper trough whose west side will drag 92-L east-southeastward. Based on this outlook...92-L has 48 hrs to develop into a subtropical cyclone in a low shear environment below its parent upper vortex...but this also means this system will be gradually weakening due to a lack of divergence below the center of the upper vortex. Then by 72 hrs and beyond when the upper vortex opens into an upper trough...this will increase the shear and end potential for this system to become a subtropical cyclone.

Thermodynamic Outlook for the Forecast Period...This system will be over 21 to 24 deg C waters thru the forecast period...temperatures that are normally not conducive for tropical development. However the existence of pockets of showers and thunderstorms currently in all quadrants of the circulation suggests the overhead upper vortex maybe cold enough to de-stabilize the atmosphere over these waters for tropical development.

24 Hr Forecast (0000Z October 22)...Frontal cyclone transitioning into a subtropical low centered at 34.5N-27.5W

48 Hr Forecast (0000Z October 23)...45 mph maximum sustained wind subtropical storm centered at 33N-30W

72 Hr Forecast (0000Z October 24)...Sheared remnant low centered at 32.5N-27.5W

...SPECIAL FEATURE...BROAD TROPICAL LOW INVEST 93-L...
Current Prognosis...Wind shear over the broad tropical low in the southwestern Gulf of Mexico has reduced as a favorable upper ridge from Central America (marked as a blue-zig-zag line in the above atmospheric features chart) expands northward over this system. Visible satellite animation suggests a 12-hourly motion from 20N-96W at 1200Z to 20N-95W at 0000Z (which is 1W longitude per 12 hours or 2W longitude per 24 hours) upon which the eastward track forecast below is based on. Even though this system is better organized than 24 hours ago...this observed motion is somewhat uncertain as the center is still somewhat broad in definition.

Atmospheric Outlook for the Forecast Period...Over the next 24 hours southwesterly vertical shear over this system will increase as the amplifying upper trough associated with the 1006 mb eastern Canada frontal cyclone approaches from the northwest (which is why I do not forecast tropical cyclone formation in the next 24 hrs). Shear will reduce by 48 hrs and be absent by 72 hrs as this upper trough moves away (which is why I forecast tropical cyclone formation by 48 hrs). By 96 and 120 hrs this system is expected to interact with the southern fracture of a second upper trough associated with a frontal cyclone moving into central Canada. This second upper trough is expected to push this system further eastward into the northwestern Caribbean...with this second upper trough evolving the northern portion of this system into a less tropical feature supported by the eastern divergence of the upper trough. It remains to be seen if the southern portion of this system leftover in the northwestern Caribbean later evolves into a strong tropical cyclone...a solution shown in many of tonight's computer model runs. I am not certain about this solution since its possible for the second upper trough to be strong enough to shear this system apart.

Thermodynamic Outlook for the Forecast Period...This system will be over very favorable 30 deg C water thru the forecast period. Therefore if this system doesn't develop in the forecast period...it will either be from unfavorable atmospheric parameters such as wind shear or due to land interaction with the Yucatan peninsula.

24 Hr Forecast (0000Z October 22)...Sheared but better organized tropical low centered at 20N-93W

48 Hr Forecast (0000Z October 23)...35 mph maximum sustained wind sheared tropical depression centered at 20N-91W approaching landfall in the northwestern Yucatan peninsula.

72 Hr Forecast (0000Z October 24)...Remnant low centered over the northern Yucatan peninsula at 20N-89W

96 Hr Forecast (0000Z October 25)...Remnant elongated and sheared low entering the northwestern Caribbean from the east coast of the Yucatan at 87W longitude

120 Hr Forecast (0000Z October 26)...Remnant elongated and sheared low in the northwestern Caribbean at 85W longitude with northern portion of the elongated low evolving into a less tropical low over the Bahamas accelerating northeastward and away.

2014 Atlantic Hurricane Season Birdseye Discussion #119

By: NCHurricane2009, 4:09 AM GMT on October 20, 2014

...MONDAY OCTOBER 20 2014 12:15 AM EDT...
Gonzalo finally transitions into a strong non-tropical gale racing eastward across the north Atlantic high seas. In the next 24 hours the remnant of Gonzalo will become absorbed by a frontal cyclone northwest of Europe located at the north end of the upper trough located in the northeast Atlantic.

A broad area of surface low pressure has developed across the southwestern Gulf of Mexico and appears to be a northeastern fragment of the remnants of eastern Pacific tropical cyclone Trudy. Upper-level winds could become more favorable for tropical development in the southern Gulf of Mexico depending on how much the upper ridge over Central America (currently marked as a blue zig-zag line in the atmoshperic features chart below) expands northward into the Gulf in the wake of the upper trough that has just left the eastern US (marked by blue-dashed line). Eventually the upper trough associated with the 1004 mb frontal depression diving southeastward from western Canada will amplify and drag this disturbance eastward across the southern Gulf and into the northwestern Caribbean...but also has the potential to shear it in which case tropical development of this disturbance would become limited. Due to the broad nature of this system it is uncertain where exactly this system would consolidate...and therefore I am not upgrading this system as a special feature with a specific forecast...especially with the potential for shear that could disrupt this system's potential for development.

The 996 mb frontal cyclone in the northeastern Atlantic is evolving into a cut-off deep-layered vortex west of the Canary Islands and south of the Azores and has potential to transition into a subtropical cyclone. This system has been upgraded to Invest 92-L on the Naval Research Laboratory Site of the US Navy. See the special feature section below for additional details on this system.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1932Z-released WPC surface analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...NORTHEAST ATLANTIC FRONTAL LOW INVEST 92-L...
Current Prognosis...Within the last 24 hours the frontal cyclone that is now Invest 92-L has formed northwest of the Canary Islands under supportive divergence on the east side of a northeastern Atlantic upper trough. Meanwhile the upper trough that has recently emerged from the eastern US supports a 1004 mb frontal depression offshore of the NE US...991 mb frontal depression just SE of Greenland...and the remnant of Gonzalo. Low-level warm air advection ahead of the 1004 mb and 991 mb frontal depressions and remnant of Gonzalo has amplified upper ridging overhead of the 1027 mb Atlantic surface ridge...resulting in the formation of a deep-layered ridge to the west-northwest of 92-L. In turn this deep-layered ridge is cutting off the south part of the northeast Atlantic upper trough into an upper vortex overhead of 92-L...and as this upper vortex aligns with 92-L...92-L is evolving into a deep-layered vortex. Infrared satellite imagery as of 0000Z fixes the surface center of 92-L at 33.5N-19.7W.

Atmospheric Outlook for the Forecast Period...The deep-layered 1027 mb ridge will pass north of deep-layered vortex 92-L...which will drive 92-L westward over the next 24 hours. As the deep-layered ridge passes northeast of 92-L...the southwest quadrant of the deep-layered ridge will drive 92-L west-northwest between 24 and 48 hours. By 72 hrs...the 1025 mb ridge that is currently over the eastern US will arrive to the northwest and block further west-northwest progression of this system...causing the surface center of 92-L to move west-southwest on the NW quadrant of its overhead parent upper vortex. By 96 hrs a north fragment of what is now the upper trough of the central Canada 1004 mb frontal depression will merge with the overhead upper vortex...resulting in the upper vortex opening into an upper trough whose west side will drag 92-L east-southeastward. Based on this outlook...92-L has 72 hrs to develop into a subtropical cyclone in a low shear environment below its parent upper vortex...but this also means this system will be gradually weakening due to a lack of divergence below the center of the upper vortex. Then by 96 hrs and beyond when the upper vortex opens into an upper trough...this will increase the shear and end potential for this system to become a subtropical cyclone.

Thermodynamic Outlook for the Forecast Period...This system will be over 21 to 24 deg C waters thru the forecast period...temperatures that are normally not conducive for tropical development. However the intensity of the comma shaped storm mass associated with this system suggests the cold temperatures of the overhead upper vortex maybe cold enough to de-stabilize the atmosphere over these waters for tropical development.

24 Hr Forecast (0000Z October 21)...Frontal low centered at 33.5N-22.5W transitioning into a subtropical low

48 Hr Forecast (0000Z October 22)...50 mph maximum sustained wind subtropical storm centered at 34.5N-27.5W

72 Hr Forecast (0000Z October 23)...45 mph maximum sustained wind subtropical storm centered at 33N-30W

96 Hr Forecast (0000Z October 24)...Sheared remnant low centered at 32.5N-27.5W

2014 Atlantic Hurricane Season Birdseye Discussion #118

By: NCHurricane2009, 4:46 AM GMT on October 19, 2014

...SUNDAY OCTOBER 19 2014 12:47 AM EDT...
Tropical storm force winds to arrive in the next few hours across southeastern Newfoundland as Hurricane Gonzalo passes by. Afterwards Gonzalo is expected to transition into a strong non-tropical gale to race eastward across the far north Atlantic. See Gonzalo special feature section below for additional details on this hurricane. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

Computer models continue to suggest the potential for a broad area of surface low pressure developing across the southern Gulf of Mexico over the next few days. This disturbance appears to be the leftovers from the tail end of surface frontal boundary activity associated with the strong upper trough currently over the eastern US...perhaps in conjunction with a northeastern fragment of the remnants of tropical cyclone Trudy currently over southeastern Mexico. Upper-level winds could become more favorable for tropical development in the southern Gulf of Mexico depending on how much the upper ridge over Central America (currently marked as a blue zig-zag line in the atmoshperic features chart below) expands northward into the Gulf in the wake of the eastern US upper trough. Another upper trough associated with a clipper system diving southeastward from western Canada then has the potential to drag this disturbance eastward across the southern Gulf and into the northwestern Caribbean...but also has the potential to shear it in which case tropical development would not occur.

A new 1009 mb frontal depression in the northeastern Atlantic is expected to evolve into a cut-off deep-layered vortex west of the Canary Islands and south of the Azores in the northeastern Atlantic over the next four days. Sea-surface temperatures in this area are just below the threshold for tropical development...but it remains to be seen if the upper-layers of the deep-layered vortex will be cold enough to de-stabilize the atmosphere over these waters to support the evolution of the deep-layered vortex into a subtropical cyclone.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1928Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...HURRICANE GONZALO...
Current Prognosis...The 11 PM EDT NHC advisory has fixed the center of Gonzalo at 42.3N-57.0W. The storm canopy of the hurricane remains biased to the north of the center due to southwesterly vertical shear imparted by the upper trough that has just emerged from the eastern US. This shear has weakened Gonzalo from a category 2 to category 1 within the last 24 hours. Now that Gonzalo is over waters below 26 deg C...in the next 24 hours it will transition into a hurricane-force non-tropical gale supported by upper divergence on the east side of the upper trough.

Atmospheric Outlook for the Forecast Period...Gonzalo will continue accelerating northeastward while embedded in the strong flow between the the northwest side of the 1028 mb western Atlantic surface ridge and east side of the incoming strong eastern US upper trough and associated surface 991 mb frontal cyclone. As this upper trough moves toward Gonzalo...it will further increase the shear over Gonzalo and also transition Gonzalo into a vigorous non-tropical cyclone supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...Gonzalo has arrived to waters below 26 deg C no longer supportive of a troipcal cyclone. This will help its transition into a non-tropical cyclone.



Track Forecast...I see no reason to disagree with the NHC track forecast with the current direction of travel and speed observed.

Intensity Forecast...Gonzalo will continue to weaken while tracking toward decreasing sea-surface temps and due to southwesterly vertical shear mentioned in the above atmospheric outlook section. However the weakening rate should continue to be gradual while Gonzalo is supported by divergence on the east side of the incoming upper trough. Therefore I agree with the current NHC intensity forecast.

Impact Forecast...Impact swath in the above forecast graphic is the extrapolation of the current wind field along the forecast track. I do not shrink the swath even though Gonzalo is expected to weaken due to the fact the storm will be transitioning into a non-tropical gale supported by eastern divergence of the incoming upper trough...and such transition processes usually result in a maintainence or even expansion of the wind field despite a decline in the maximum sustained winds of the storm. The northwest edge of my impact swath suggests southeastern coastal Newfoundland (where tropical storm watches are currently posted) getting gale force winds from Gonzalo within the next few hours.

2014 Atlantic Hurricane Season Birdseye Discussion #117

By: NCHurricane2009, 4:16 AM GMT on October 18, 2014

...SATURDAY OCTOBER 18 2014 12:17 AM EDT...
The eye of Hurricane Gonzalo has made a direct and severe strike to the island of Bermuda this evening while at maximum category 2 intensity. A tropical storm watch has been raised for southeastern Newfoundalnd as Gonzalo also has the chance to bring gale force winds later this weekend. See Gonzalo special feature section below for additional details on this hurricane. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

Computer models continue to suggest the potential for a broad area of surface low pressure developing across the southern Gulf of Mexico in the timeframe that is about 3 days away. This disturbance appears to be the leftovers from the tail end of surface frontal boundary activity associated with the strong upper trough currently over the eastern US...perhaps in conjunction with a northeastern fragment of eastern Pacific Tropical Storm Trudy just offshore of southern Mexico. Upper-level winds could become more favorable for tropical development in the southern Gulf of Mexico depending on how much the upper ridge over Central America (currently marked as a blue zig-zag line in the atmoshperic features chart below) expands northward into the Gulf in the wake of the eastern US upper trough. After day 3 an upper trough associated with a clipper system diving southeastward from western Canada has the potential to drag this disturbance eastward across the southern Gulf and into the northwestern Caribbean...but also has the potential to shear it in which case tropical development would not occur.

The southern portion of the deep-layered frontal cyclone and upper trough in the northeastern Atlantic is expected to evolve into a cut-off deep-layered vortex west of the Canary Islands and south of the Azores in the northeastern Atlantic over the next five days. Sea-surface temperatures in this area are just below the threshold for tropical development...but it remains to be seen if the upper-layers of the deep-layered vortex will be cold enough to de-stabilize the atmosphere over these waters to support the evolution of the deep-layered vortex into a subtropical cyclone.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1922Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...HURRICANE GONZALO...
Current Prognosis...After the eye of Hurricane Gonzalo passed over Bermuda at 9 PM EDT earlier this evening...the 11 PM EDT NHC advisory has fixed the center center of Gonzalo just north-northeast of the island at 32.7N-64.5W. The storm canopy of the hurricane is no longer symmertic about the center and is now biased to the northeast half of the circulation due to southwesterly vertical shear imparted by the upper trough that has just emerged from the eastern US. This shear has weakened Gonzalo from a category 4 to category 2 within the last 24 hours.

Atmospheric Outlook for the Forecast Period...Gonzalo will continue north-norhteast and accelerate while becoming embedded in the strong flow between the the west side of the 1027 mb western Atlantic surface ridge and east side of the incoming strong eastern US upper trough and associated surface 989 mb frontal cyclone. As this upper trough moves toward Gonzalo...it will further increase the shear over Gonzalo and also transition Gonzalo into a vigorous non-tropical cyclone supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...On the current forecast track...Gonzalo will be over waters below 26 deg C no longer supportive of a troipcal cyclone by tomorrow night. This will help its transition into a non-tropical cyclone.



Track Forecast...Gonzalo has dead-nuts followed the previous forecast track. However the NHC has adjusted their position for 8 PM Saturday to be a little more south than previous. On the other hand since the previous forecast track has done so well...and since their are a couple of models (such as the GFS and NAVGEM) that are left of the NHC and bring the center onto southeastern Newfoundland....I prefer to not make any adjustments from the previous and therefore I am currently just a little left of the NHC.

Intensity Forecast...While weakening due to wind shear and decreasing sea surface temps...Gonzalo has dead-nuts followed my previous intensity forecast from discussion #116 and therefore I am making no changes to my intensity forecast.

Impact Forecast...Impact swath in the above forecast graphic is the extrapolation of the current wind field along the forecast track. I do not shrink the swath at the end of the forecast even though Gonzalo is expected to weaken due to the fact the storm will be transitioning into a non-tropical gale supported by eastern divergence of the incoming upper trough...and such transition processes usually result in a maintainence or even expansion of the wind field despite a decline in the maximum sustained winds of the storm. The northwest edge of my impact swath suggests southeastern coastal Newfoundland (where tropical storm watches are currently posted) getting gale force winds from the remnant low of Gonzalo by Sunday morning.

2014 Atlantic Hurricane Season Birdseye Discussion #116

By: NCHurricane2009, 4:15 AM GMT on October 17, 2014

...FRIDAY OCTOBER 17 2014 12:16 AM EDT...
Intense hurricane Gonzalo in the next 24 hours will become the worst hurricane to strike Bermuda since Fabian in 2003. All preparations should be rushed to completion on the island of Bermuda...and residents should continue to heed the advice of local officials. Gonzalo also has the chance to bring gale force winds to southeastern Newfoundland after it transitions into a strong non-tropical remnant low later this weekend. See Gonzalo special feature section below for additional details on this hurricane. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

Computer models continue to suggest the potential for a broad area of surface low pressure developing across the southern Gulf of Mexico in the timeframe that is about 3 to 4 days away. This disturbance appears to be the leftovers from the tail end of surface frontal boundary activity associated with the strong upper trough currently over the eastern US...perhaps in conjunction with a northeastern fragment of eastern Pacific tropical disturbance Invest 92-E currently just offshore of southern Mexico. Upper-level winds could become more favorable for tropical development in the southern Gulf of Mexico depending on how much the upper ridge over Central America (currently marked as a blue H in the atmoshperic features chart below) expands northward into the Gulf in the wake of the eastern US upper trough. After day 4 an upper trough associated with a clipper system diving southeastward from western Canada has the potential to drag this disturbance eastward across the southern Gulf and into the northwestern Caribbean...but also has the potential to shear it in which case tropical development would not occur.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1931Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...MAJOR HURRICANE GONZALO...
Current Prognosis...After last night's eye replacement cycle Gonzalo strengthened this past afternoon into a category 4 hurricane with 145 mph max sustained winds...making Gonzalo stronger than it has even been so far in its life. Aircraft reconaissance this evening has found that Gonzalo has weakened slightly to 140 mph maximum sustained winds. Very recent satellite frames shows that Gonzalo's pinhole eye is collapsing while a new larger outer eye is taking over...which means the hurricane is very likely to continue weakening due to another eye replacement cycle tonight. The 11 PM EDT NHC advisory fixed the center of Gonzalo at 28.0N-67.5W...with the hurricane now curving north-northeastward and taking direct aim at the island of Bermuda.

Atmospheric Outlook for the Forecast Period...Gonzalo will continue north-norhteast and accelerate while becoming embedded in the strong flow between the the west side of the 1025 mb western Atlantic surface ridge and east side of the incoming strong eastern US upper trough and associated surface 1001 mb frontal cyclone. As this upper trough moves offshore from the US and toward Gonzalo...it will increase the shear over Gonzalo and also transition Gonzalo into a vigorous non-tropical cyclone supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...The forecast track shown below will gradually take this system from waters that are currently 29 deg C to the 26 deg C isotherm by Saturday morning. By Saturday night Gonzalo will be over waters below 26 deg C no longer supportive of a tropical cyclone which will help its transition to a non-tropical cyclone.



Track Forecast...Gonzalo is a bit southeast of the previous forecast track. Adjustments in the computer models and latest NHC track reflect a southeast shift. And with models deciding not to go back to a faster track...I have now joined the NHC and computer model consensus instead of being a bit faster as I was yesterday.

Intensity Forecast...Gonzalo's strengthening to a category 4 this past afternoon...followed by maintanence of category 4 thru this evening...makes the hurricane stronger than my forecast shown in discussion #115 but 100% accurate with my forecast shown in discussion #114. Therefore tonight I have reverted back to the intensity forecast shown in discussion #114...which shows Gonzalo will now begin to weaken due to increasing shear as the upper trough approaches from the US (as reflected in the above atmo outlook section) and due to decreasing sea-surface temps (as reflected in the above thermo outlook). In addition...the observations of a new eye replacement in the above current prognosis section also supports the idea of Gonzalo weakening. However do not let the forecast weakening be deceiving...because Bermuda will still get a direct strike from a top-end category 2...or possibly a category 3 hurricane...still making this of the caliber of Fabian in 2003 which brought severe damage to the island.

Impact Forecast...Impact swath in the above forecast graphic is the extrapolation of the current wind field along the forecast track. I do not shrink the swath at the end of the forecast even though Gonzalo is expected to weaken due to the fact the storm will be transitioning into a non-tropical gale supported by eastern divergence of the incoming central US upper trough...and such transition processes usually result in a maintainence or even expansion of the wind field despite a decline in the maximum sustained winds of the storm. The impact swath suggests Bermuda will receive tropical storm conditions by Friday afternoon...and extremely severe hurricane conditions by Friday night. The southeast shift in the forecast track has lessened the risk to southeastern Newfoundland...with my current impact swath now suggesting only southeastern coastal Newfoundland getting gale force winds from the remnant low of Gonzalo by Sunday morning.

2014 Atlantic Hurricane Season Birdseye Discussion #115

By: NCHurricane2009, 4:29 AM GMT on October 16, 2014

...THURSDAY OCTOBER 16 2014 12:30 AM EDT...
Gonzalo this past afternoon became the Atlantic Ocean's first category 4 hurricane since Ophelia in October 2011. Shortly thereafter it weakened back to a category 3 hurricane due to internal structural changes. In the next 24 hours Gonzalo will remain a very intense hurricane with additional fluctuations in intensity. Shortly thereafter Gonzalo is expected to become the worst hurricane to hit the island of Bermuda since Fabian in 2003 by Friday morning...afterwards striking Newfoundland as a hurricane-force non-tropical remnant gale this upcoming weekend. See Gonzalo special feature section below for additional details on this hurricane. The hurricane watch in Bermuda has been upgraded to a hurricane warning and preparations in Bermuda should be rushed to completion in the next 24 hours. Residents of Bermuda should continue to heed the advice of local officials. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

In the last couple of days multiple computer models have hinted at a disturbance forming across the southern Gulf of Mexico in the timeframe that is about 4 days away. This disturbance appears to be the leftovers from the tail end of surface frontal boundary activity associated with the strong upper trough currently over the eastern US...perhaps in conjunction with a northeastern fragment of eastern Pacific tropical disturbance Invest 92-E currently just offshore of southern Mexico. Upper-level winds could become more favorable for tropical development in the southern Gulf of Mexico depending on how much the upper ridge over Central America (currently marked as a blue-zig-zag line in the atmoshperic features chart below) expands northward into the Gulf in the wake of the eastern US upper trough. After day 4 an upper trough associated with a clipper system diving southeastward from western Canada has the potential to drag this disturbance eastward across the southern Gulf...but also has the potential to shear it in which case tropical development would not occur.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...MAJOR HURRICANE GONZALO...
Current Prognosis...This past afternoon Gonzalo became a category 4 hurricane with 130 mph maximum sustained winds while having the satellite appearance of a classic...compact...and symmetrical hurricane with a pinhole eye. The eye then disappeared from satellite this early evening as aicraft reconaissance confirmed an eye wall replacement cycle which caused a weakening to category 3. Very recently a pinhole eye has reappeared...but aircraft reconaissance has found that Gonzalo has further weakened to 120 mph maximum sustained winds (however this is still a category 3). However observations from aicraft reconaissance and the reapperance of a pinhole eye on satellite concur that Gonzalo has just finished the eye wall replacement cycle and therefore is very likely to re-strengthen very shortly. The 11 PM EDT NHC advisory fixed the pinhole eye at 24.6N-68.7W.

Atmospheric Outlook for the Forecast Period...Gonzalo is curving northward and will eventually be accelerating north-northeastward while channeled into the strong flow between the the west side of the 1026 mb western Atlantic surface ridge and east side of the incoming strong eastern US upper trough and associated surface 1005 mb frontal cyclone. As this upper trough moves offshore from the US and toward Gonzalo...it will increase the shear over Gonzalo and also transition Gonzalo into a vigorous non-tropical cyclone supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...The forecast track shown below will gradually take this system from waters that are currently 29 deg C to the 26 deg C isotherm by Friday night. By Saturday Gonzalo will be over waters below 26 deg C no longer supportive of a tropical cyclone which will help its transition to a non-tropical cyclone.



Track Forecast...The previous track forecast has held up very well within the past 24 hours...and therefore I have made no changes to the 24 hr (8 PM Thursday) forecast point which places me just a bit ahead of the most recent NHC forecast for that time. For the timeframe that is 48 and 72 hrs...the computer models have shifted to a slower northward track (and accordingly the NHC has adjusted their track to be slower)...this after the models last night were shifting to a faster track. Therefore my updated forecast points for 48 and 72 hrs (8 PM Fri and 8 PM Sat) are what the NHC was showing 24 hrs ago in case the models decide to switch back to a faster track.

Intensity Forecast...My updated intensity forecast shown above predicts Gonzalo will re-strengthen into a minimal category 4 of 130 mph max sustained winds based on the observation of Gonzalo completing its eye wall replacement cycle as noted in the above current prognosis section. This is higher than the latest NHC intensity forecast which doesn't predict a re-strengthening. Since my intensity forecast point for 8 PM Thursday is a bit lower than my previous...I have adjusted my intensity forecast for 8 PM Friday and 8 PM Saturday to also be a bit lower.

Impact Forecast...Impact swath in the above forecast graphic is the extrapolation of the current wind field along the forecast track. I do not shrink the swath at the end of the forecast even though Gonzalo is expected to weaken due to the fact the storm will be transitioning into a non-tropical gale supported by eastern divergence of the incoming central US upper trough...and such transition processes usually result in a maintainence or even expansion of the wind field despite a decline in the maximum sustained winds of the storm. The impact swath suggests Bermuda will receive tropical storm conditions by Friday morning and that Newfoundland will receive tropical storm conditions by late Saturday night (Gonzalo's remant low could be strong enough to bring hurricane conditions to parts of Newfoundland). It is extermely likely...perhaps imminent...that hurricane conditions will directly strike Bermuda since forecasts have consistently been passing the center of the hurricane over or very close to Bermuda. If the above forecast verifies...this could be the worst hurricane to strike Bermuda since Fabian struck the island as a category 3 in 2003.

2014 Atlantic Hurricane Season Birdseye Discussion #114

By: NCHurricane2009, 4:13 AM GMT on October 15, 2014

...WEDNESDAY OCTOBER 15 2014 12:13 AM EDT...
Gonzalo as expected has become a major hurricane (category 3 or greater)...the second of the 2014 Atlantic season after Edouard. A hurricane watch has just been issued for Bermuda where preparations should begin for a possible direct strike from Gonzalo which has a high chance of still being a major hurricane when it arrives. If so...this will be the worst hurricane to strike Bermuda since Fabian in 2003 which hit Bermuda directly as a category 3. Interests in Newfoundland should also watch Gonzalo as this system has the potential to transition into a hurricane-force non-tropical gale that could move in this weekend. See Gonzalo special feature section below for additional details on this hurricane. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

Broad tropical surface low Invest 91-L midway between the Cape Verde Islands and Lesser Antilles remains quasi-stationary in a col between a western fracture of the eastern Atlantic upper trough located to the west and the remainder of this upper trough located to the north. This system remains stationary due to the ridge weakness associated with the remnant low of Fay and intense northeastern Atlantic gale...and should drift north-northwestward toward this weakness. This track will move 91-L toward hostile westerly shear on the south side of the upper trough to the north...and such hositle shear will be re-enforced as the western fracture of this upper trough gets pulled eastward toward this system by the upper trough associated with the intense northastern Atlantic gale. Therefore I continue to expect no development from 91-L.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...MAJOR HURRICANE GONZALO...
Current Prognosis...As of the 11 PM EDT NHC advisory Hurricane Gonzalo was centered at 22.2N-66.6W and curving northwestward away from the northeastern Caribbean Islands and toward the island of Bermuda. Gonzalo currently appears as a classic compact intense hurricane with a central dense overcast (CDO) featuring a pinhole eye...with a spiral band extending north and east of the CDO.

Atmospheric Outlook for the Forecast Period...Gonzalo continues on a northwest track while simultaneously steered by the east side of the western Atlantic upper vortex (marked by pair of blue Ls to the left of Gonzalo in the above atmospheric features chart) and south side of the 1030 mb western Atlantic surface ridge. Over the next 24 hours the strength of Gonzalo's latent heat release should punch out the northern lobe of this upper vortex....allowing Gonzalo to maintain a shear-reducing/outflow enhancing upper anticyclone over itself in between the southern lobe of the upper vortex (which will be over the eastern Caribbean) and out ahead of the strong upper trough currently moving into the eastern US. Gonzalo will curve and accelerate north-northwestward...northward...and eventually north-northeastward as it becomes channeled into the strong flow between the the west side of the western Atlantic surface ridge and out ahead of the incoming strong US upper trough and associated surface frontal cyclone by the end of the forecast period. As this upper trough moves offshore from the US and toward Gonzalo...it will increase the shear over Gonzalo and also transition Gonzalo into a vigorous non-tropical cyclone supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...The forecast track shown below will gradually take this system from waters that are currently 30 deg C to the 26 deg C isotherm by Friday night. By Saturday Gonzalo will be over waters below 26 deg C no longer supportive of a tropical cyclone which will help its transition to a non-tropical cyclone.



Track Forecast...Instead of tracking a bit to the right of the NHC track as thought in discussion #113...Gonzalo has been following the NHC forecast and therefore I have adjusted my forecast to follow the NHC's forecast track line. The NHC forecast track (and tracks shown in computer models) have not changed in the last day for the first 48 hours. After that time the models are showing a faster and further left track to which the late part of the NHC forecast has adjusted toward (as models move the eastern US upper trough faster toward Gonzalo...and the leftward adjustment is due to models forecasting the upper trough to be more amplified when it approaches Gonzalo). The GFS continues to be the fastest with moving Gonzalo northward....and the once-slower NAVGEM and Euro (ECMWF) have been catching up toward the GFS solution which currently brings Gonzalo into Newfoundland by 96 hrs (8 PM Saturday). This is why my above forecast track points beyond 48 hours are ahead (faster) than the NHC's. Meanwhile the CMC remains far slower with Gonzalo's northward progression I think due to it forecasting Invest 91-L becoming a strong tropical cyclone to the southeast whose low pressure field would keep Gonzalo tugged toward the south. However discarding the CMC solution with 91-L not likely to develop.

Intensity Forecast...Gonzalo being at 125 mph maximum sustained winds as of 11 PM EDT makes him a category 3 and nearly on par with my intensity forecast from discussion #113. As the above atmospheric outlook describes...Gonzalo should punch out the northern lobe of the western Atlantic upper vortex in the next 24 hrs...and with Gonzalo expected to be over very favorable 29 deg C waters by that time I expect a high potential that Gonzalo becomes a category 4 hurricane by 8 PM Wednesday. By 8 PM Thursday the incoming upper trough is still too far away to shear Gonzalo and he will be over waters of 28 deg C...therefore I am forecasting Gonzalo to maintain category 4 through that time. Afterwards wind shear will increase as the upper trough nears...which will begin the weakening process of Gonzalo...especially as it tracks toward cooler waters as well. My above intensity forecast is identical to the one I showed in discussion #113 and is slightly above the latest NHC intensity forecast. If my above and NHC current intensity forecasts verify...this will be the first category 4 in the Atlantic basin since Ophelia in 2011.

Impact Forecast...Impact swath in the above forecast graphic is the extrapolation of the current wind field along the forecast track. I do not shrink the swath at the end of the forecast even though Gonzalo is expected to weaken due to the fact the storm will be transitioning into a non-tropical gale supported by eastern divergence of the incoming central US upper trough...and such transition processes usually result in a maintainence or even expansion of the wind field despite a decline in the maximum sustained winds of the storm. The impact swath suggests Bermuda will receive tropical storm conditions by Friday morning and that Newfoundland will receive tropical storm conditions by Saturday night. It is likely hurricane conditions directly strike Bermuda since forecasts have consistently been passing the center of the hurricane over or very close to Bermuda. A hurricane watch has been issued for Bermuda where preparations for this storm should begin. If the above forecast verifies...this could be the worst hurricane to strike Bermuda since Fabian struck the island as a category 3 in 2003.

2014 Atlantic Hurricane Season Birdseye Discussion #113A (Special Update)

By: NCHurricane2009, 7:00 AM GMT on October 14, 2014

...TUESDAY OCTOBER 14 2014 3:00 AM EDT...
Aircraft reconaissance finds Gonzalo is undergoing rapid intensification with maximum winds rising from 85 mph to 105 mph in the matter of about three hours (between 11 O'clock PM and 2 O'clock AM). This now makes Gonzalo a category 2 hurricane. Gonzalo has the apperance of a compact hurricane capable of extremely rapid intensification. Therefore I have upped my intensity forecast as shown below and now predict Gonzalo to become a category 5 hurricane. If the intensity forecast below verifies...this will be the first category 4 in the Atlantic basin since Ophelia in 2011 and first category 5 in the Atlantic basin since Felix in 2007. Interests in Bermuda should pay very strong attention to Gonzalo over the next few days.

Return to full discussion #113 for an update on the rest of the Atlantic tropics. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

8 PM Tuesday October 14...140 mph max sustained wind category 4 hurricane centered at 21.5N-65.5W.

8 PM Wednesday October 15...160 mph max sustained wind category 5 hurricane centered at 24.5N-67W

8 PM Thursday October 16...145 mph max sustained wind category 4 hurricane centered at 27.5N-67W

8 PM Friday October 17...120 mph max sustained wind category 3 hurricane centered at 32.5N-64W with the eye passing just east of Bermuda

8 PM Saturday October 18...100 mph max sustained wind category 2 hurricane centered at 38.5N-57.5W

2014 Atlantic Hurricane Season Birdseye Discussion #113

By: NCHurricane2009, 6:17 AM GMT on October 14, 2014

...TUESDAY OCTOBER 14 2014 2:17 AM EDT...
Fay has transitioned into a frontal non-tropical cyclone in the open ocean well east of Bermuda....and will merge with the intense frontal cyclone to the north which will result in an impressive non-tropical gale event in the northeastern Atlantic over the next few days.

Gonzalo is expected to become a category 3 or greater intense hurricane while lifting northward from the northern Lesser Antilles within the next 24 hours. Interests in Bermuda should carefully monitor the progress of Gonzalo as the hurricane could make a close or direct pass over the island by Friday. Interests in coastal Newfoundland should also watch Gonzalo as this system has the potential to transition into a strong non-tropical gale that could pass over or nearby by this weekend. See Gonzalo speical feature section below for additional details on this hurricane. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

Tropical wave Invest 91-L midway between the Cape Verde Islands and Lesser Antilles has left behind a broad 1010 mb tropical low pressure spin that has become a little better organized in a col of favorable upper winds between a western fracture of the eastern Atlantic upper trough located to the west and the remainder of this upper trough located to the north. This broad tropical low appeared quasi-stationary during this past afternoon's visible satellite animation...suggesting that the ridge weakness associated with the remnant low of Fay and intense northeastern Atlantic gale is largely affecting the track of this system. Therefore this tropical low is expected to drift north-northwestward while pulled toward this ridge weakness. The northward shift in expected track for 91-L means that it will soon arrive into hostile westerly shear on the south side of the upper trough to the north...which will be re-enforced as the western fracture of this upper trough gets pulled eastward toward this system by the upper trough associated with the intense northastern Atlantic gale. Therefore I am no longer expecting 91-L to become a tropical cyclone and have cancelled it as a special feature on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...HURRICANE GONZALO...
Current Prognosis...As of the 11 PM EDT NHC advisory Hurricane Gonzalo was centered at 18.7N-63.4W and is exiting the northern Lesser Antilles after striking them with a direct blow as a category 1 hurricane. Gonzalo currently appears as a classic compact hurricane with a central dense overcast (CDO) and spiral band extending north and east of the CDO. In the midst of the CDO an eye became briefly visible on satellite this past afternoon as Gonzalo became a hurricane...but since then storm bursts have obscured the eye.

Atmospheric Outlook for the Forecast Period...As mentioned in special update #112B Hurricane Gonzalo has made a turn to the north much earlier than previous forecasts while becoming a strong/tall tropical cyclone steered by the east side of the western Atlantic upper vortex (marked by pair of blue Ls to the left of Gonzalo in the above atmospheric features chart). The strength of Gonzalo's latent heat release should punch out the northern lobe of this upper vortex....allowing Gonzalo to maintain a shear-reducing/outflow enhancing upper anticyclone over itself in between the southern lobe of the upper vortex (which will be over the eastern Caribbean) and out ahead of the strong upper trough currently over the central US. Gonzalo will curve north-northwestward...northward...and eventually north-northeastward as it becomes steered between the western Atlantic upper vortex and 1029 mb western Atlantic surface ridge in the short term...then in between the west side of the surface ridge and out ahead of the central US upper trough and associated surface frontal cyclone by the end of the forecast period. As the central US upper trough moves offshore and toward Gonzalo...it will increase the shear over Gonzalo but also transition Gonzalo into a vigorous non-tropical cyclone supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...The forecast track shown below will gradually take this system from waters that are currently 30 deg C to waters that will be 26 deg C by the end of the forecast period. Once Gonzalo crosses into waters below 26 deg C just beyond the forecast period this will help Gonzalo in its transition to a non-tropical cyclone.



Track Forecast...The NHC has been continuously adjusting their forecast track to the right in the last day...and latest satellite animation suggests to me that Gonzalo may be tracking still a bit to the right of the latest NHC forecast. This is why my forecast above is to the right of the NHC. Computer models agree on the forecast track scenario outlined in the above atmospheric outlook section...but have a strong disagreement on the forward speed of this system in the later part of the forecast. The GFS pulls Gonzalo rapidly northward through the strong flow on the east side of the incoming central US upper trough/surface frontal cyclone and west side of the western Atlantic low-level ridge...taking Gonzalo toward southeastern Newfoundland by 120 hrs. Meanwhile the Euro (ECMWF)...CMC...and NAVGEM models have Gonzalo near or southeast of Bermuda by 120 hrs while having Gonzalo stay south of this strong flow. My and the NHC forecast above split the difference between these models...but I am faster than the NHC since I believe the GFS is more likely to be correct since Gonzalo's track has been trending more north and less west than previous expectations...with its more northerly position making it more likely to get pulled into the strong flow.

Intensity Forecast...Between 1200Z (8 AM EDT) Oct 13 and 0000Z (8 PM EDT) we have seen Gonzalo's max sustained winds go up by 20 mph in the matter of 12 hours. Therefore my intensity forecast for 8 PM tomorrow night is up another 20 mph from 8 PM tonight...which puts Gonzalo as a category 3 of 120 mph maximum sustained winds...which is higher than the NHC forecast. As the above atmospheric outlook describes...Gonzalo should punch out the northern lobe of the western Atlantic upper vortex...and with Gonzalo expected to be over very favorable 29 deg C waters by that time I expect a high potential that Gonzalo become a category 4 hurricane by 48 hours (8 PM Wed). By 8 PM Thursday the incoming central US upper trough is still too far away to shear Gonzalo and he will be over waters of 28 deg C...therefore I am forecasting Gonzalo to maintain category 4 through that time. Afterwards wind shear will increase as the upper trough nears...which will begin the weakening process of Gonzalo...especially as it tracks toward cooler waters as well. If my above intensity forecast verifies...this will be the first category 4 in the Atlantic basin since Ophelia in 2011.

Impact Forecast...Impact swath in the above forecast graphic shows additional growth in the wind field for the next 24 hours as Gonzalo becomes a major hurricane...afterwards a maintenance in the wind field size. I do not shrink the swath at the end of the forecast even though Gonzalo is expected to weaken due to the fact the storm will be transitioning into a non-tropical gale supported by eastern divergence of the incoming central US upper trough...and such transition processes usually result in a maintenance or even expansion of the wind field despite a decline in the maximum sustained winds of the storm. The impact swath suggests Bermuda will receive tropical storm conditions on Friday. It is possible hurricane conditions directly strike Bermuda if the center tracks over the island. Needless to say...Bermuda should pay very careful attention to Gonzalo this week.

2014 Atlantic Hurricane Season Birdseye Discussion #112B (Special Update)

By: NCHurricane2009, 10:47 PM GMT on October 13, 2014

...MONDAY OCTOBER 13 2014 6:45 PM EDT...
Gonzalo has strengthened faster than previously anticipated and as a result has made a direct strike on the northern Lesser Antilles as a category 1 hurricane this afternoon. Instead of Gonzalo's latent heat release punching out the western Atlantic upper vortex to the west...the upper vortex remains intact and Gonzalo is now a strong/tall enough tropical cyclone to be steered more northward by the east side of the upper vortex. This interaction with the upper vortex perhaps explains the rightward shift in the computer models between October 11 and 12...and therefore my more westward track forecast shown in discussion #112 is no longer valid. In fact the rightward shift in the models on the 12th may have not been rightward enough as the current northwestward track seen in visible satellite will now cause the worst of Gonzalo to pass east of the Virgin Islands and Puerto Rico...contrary to earlier track forecasts. The more rightward shift in track means Gonzalo will have a longer time before interacting with unfavorble upper winds from a strong upper trough expected to emerge from the United States. Moreover...with Gonzalo already strengthening faster than expected and very recently developing some hot tower bursts over the once-visible eye...Gonzalo is very likely to rapidly intensify to a major hurricane (category 3 or greater) in the western Atlantic waters north of the Lesser Antilles and south of Bermuda over the next day or so. Continue to visit www.nhc.noaa.gov for up to the minute latest information of Hurricane Gonzalo. My next full blog update will be late tonight which will include an updated track and intensity forecast on Gonzalo.

2014 Atlantic Hurricane Season Birdseye Discussion #112A (Special Update)

By: NCHurricane2009, 1:08 AM GMT on October 13, 2014

...SUNDAY OCTOBER 12 2014 9:10 PM EDT...
Tropical Storm Fay became better organized at a location northeast of Bermuda after the 11 AM EDT National Hurricane Center advisory such that it was upgraded to a minimal category 1 hurricane of 75 mph maximum sustained winds as of the 5 PM EDT advisory. This makes Fay the fifth hurricane of the 2014 Atlantic season. Fay's satellite organization has been detereorating just before...during...and after the 5 PM update such that it is likely no longer a hurricane and will likely be downgraded to a tropical storm in the upcoming 11 PM EDT advisory. Fay is still expected to transition into a non-tropical frontal cyclone within the next 24 hours. Visit www.nhc.noaa.gov for up to the minute latest information on Fay.

Elsewhere...Tropical Storm Gonzalo continues to approach the northern Lesser Antilles and will be crossing those islands by tomorrow morning. As of 5 PM EDT aircraft reconaissance reported additional intensification to 45 mph maximum sustained winds and the potential for rapid strengthening of Gonzalo due to warm waters...low shear...and the compact structure including an eye-type feature which was reported by aircraft reconaissance. Tropical storm advisories remain for the northern Lesser Antilles...Virgin Islands...and Puerto Rico where Gonzalo has an imminent chance of delivering tropical storm conditions in the next 48 hours. Puerto Rico was also placed under a hurricane watch due to the potential for rapid development of Gonzalo. As of the 8 PM EDT update Gonzalo has not become better organized nor has strengthened futher..and therefore I believe that Gonzalo is not rapidly developing at the moment and therefore I am making no changes to my intensity forecast shown in full discussion #112. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

Return to full discussion #112 for more information on Fay...Gonzalo...and the rest of the Atlantic tropics.

2014 Atlantic Hurricane Season Birdseye Discussion #112

By: NCHurricane2009, 8:39 PM GMT on October 12, 2014

...SUNDAY OCTOBER 12 2014 4:40 PM EDT...
After battering Bermuda overnight with strong tropical storm conditions...Fay is accelerating east-northeastward away from the island. Tropical Storm Fay is expected to transition into a frontal non-tropical cyclone in the next 24 hours...then merge with a rapidly intensifying frontal cyclone to the north which will result in an impressive non-tropical gale in the northeastern Atlantic over the next few days. See Fay special feature section below for additional details.

Aircraft reconaissance has found that tropical disturbance Invest 90-L has strengthened into Tropical Storm Gonzalo which poses a growing threat to the northern Lesser Antilles....Virgin Islands...Puerto Rico...Hispaniola (Haiti and the Dominican Republic)...and the eastern Bahamas. Tropical storm advisories are in effect for the northern Lesser Antilles...Virgin Islands...and Puerto Rico where Gonzalo will immeninently hit these areas with tropical storm conditions in the next 48 hours. See Gonzalo speical feature section below for additional details on this developing situation. Visit www.nhc.noaa.gov for up to the minute latest information on Gonzalo.

The tropical wave previously west-southwest of the Cape Verde Islands is now midway between the Cape Verde Islands and Lesser Antilles while seeing a further expansion in the size of its thunderstorm field within the last 36 hours. This tropical wave has been upgraded to Invest 91-L on the Naval Research Laboratory site of the US Navy. This system may find more favorable upper winds within the next 72 hours before upper winds become less favorable for development after that time...and therfore I am maintaining this tropical wave as a special feature on this blog. See third special feature section below for an update on this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1335Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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 FAY...
Current Prognosis...As of the 11 AM EDT NHC advisory Fay was centered at 34.0N-62.8W while its track accelerates east-northeastward away from Bermuda. The center of Fay is below a strong thunderstorm canopy which is becoming increasingly stretched as Fay begins to deal with disrutpion from the rapidly developing frontal cyclone to the north and its associated shortwave upper trough which has just emerged from the northeastern United States. Sky conditions over Bermuda are improving this afternoon as the southwest extent of its thunderstorm canopy has cleared the island.

Atmopsheric Outlook for the Forecast Period...A shortwave upper trough which has just emerged from the northastern United States (marked by blue-dashed line in the above atmospheric features chart) is supporting a rapidly developing 1002 mb frontal cyclone to the north with its eastern divergence...with the frontal cyclone rapidly accelerating Fay east-northeastward. By 24 hours Fay will have transitioned into a non-tropical cyclone along the frontal cyclone's front...and over the next few days merge with with frontal cyclone which will result in an impressive non-tropical gale in the northeastern Atlantic.

Thermodynamic Outlook for the Forecast...Since Fay will soon transition into a nont-tropical frontal cyclone supported by divergence ahead of the shortwave upper trough mentioned in the above atmospheric outlook...thermodynamic parameters such as humidity and sea-surface temps are becoming irrelevant to the strength of this system.



Track Forecast...Fay has been tracking left of the previous forecast shown in discussion #111 which caused the center to pass closer to Bermuda last night. Therefore I have adjusted my 8 PM Sunday forecast point to the left based on the size of this error...which places my updated point the right of the NHC's 8 PM Sunday point. Therefore my 8 AM Monday point is also to the right of the NHC's. I agree with placing my updated points on the NHC's track line as Fay's current trajectory on satellite animation is in agreement. This track line shows a more east and less north track for the end of Fay's forecast compared to the previous. This makes sense since Fay will be aligning with the flow on the southwest edge of the frontal cyclone instead of its southern or southeastern edges due to the more leftward track that Fay has taken.

Intensity Forecast...The updated intensity forecast shown above is higher than the previous forecast shown in discussion #111 since Fay has strengthened more than expected as noted in special update #111A. The weakening rate of this system (due to shear from the northeastern US shortwave upper trough) should be gradual instead of rapid as this system will take some advantage of eastern upper-level divergence provided by the upper trough.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 11 AM EDT tropical storm wind field along the forecast track.

...SPECIAL FEATURE...TROPICAL STORM GONZALO...
Current Prognosis...Aircraft reconaissance as of 1:30 PM EDT found that tropical low Invest 90-L has a tightly defined center at 16.4N-58.4w with maximum sustained winds of 40 mph. Therefore 90-L has been upgraded to Tropical Storm Gonzalo. Gonzalo is a well-organized and compact tropical storm with spiral bands in all quadrants of the circulation.

Atmospheric Outlook for the Forecast Period...Because Gonzalo is tracking almost perfectly due west it is clear the low-level ridge weakness associated with Fay is not affecting Gonzalo...and therefore my updated forecast track shown below is adjusted south of my previous forecast for this system shown in discussion #111. The mostly west track will continue for another 48 hours as a strong low-level ridge (currently marked at 1027 mb over the NE US in the above atmo chart) builds behind Fay. By 72 hrs this system will be curving more northward on the southwest quadrant of the low-level ridge...followed by a north and north-northeast track by 96 and 120 hrs while influenced by a strong upper trough and surface frontal system emerging from the United States. Upper-level winds will be initially favorable for development as this system takes advantage of low shear on the southwestern quadrant of the central Atlantic upper anticyclone (marked by blue H in the atmospheric features chart above). I suspect that the western Atlantic upper vortex (marked by blue L) will weaken more than shown in this morning's 06Z GFS model run (which did not show Gonzalo develop as fast as this system is actually doing) as Gonzalo develops into a formidable tropical cyclone with vigorous thunderstorm latent heat release that punches out the upper vortex. Therefore I don't expect Gonzalo to have problems from shear from upper vorticity until the strong upper trough emerges from the United States by 96 and 120 hrs.

Thermodynamic Outlook for the Forecast Period...The forecast track shown below will take this system over 29 to 30 deg C waters rather favorable for tropical development through the forecast period.



Track Forecast...My forecast track for Gonzalo is clearly west of the NHC's as I believe the strong low-level ridge to build behind Fay will be strong enough to propel Gonzalo as far west as I have shown above.

Intensity Forecast...My intensity forecast for Gonzalo is higher than what I showed for this system in discussion #111 due to Gonzalo becoming a tropical storm earlier than what I showed in that discussion. However my intensity forecast is not as high as the NHC's as my more south and west track causes more land interaction with the landmasses of Puerto Rico and Hispaniola during the middle of the forecast...followed by a closer position to the unfavorable upper trough emerging from the United States by the end of the forecast.

Impact Forecast...Impact swath in the above forecast graphic shows gradual growth of the tropical storm wind field along my forecast track...but the growth of the wind field is rather small as I believe Gonzalo will retain its compact structure thru the forecast period. I also bias the swath to the right of my forecast track at the end of the forecast due to southwesterly shear imparted by the upper trough expected to emerge from the United States by then.

...SPECIAL FEATURE...TROPICAL WAVE INVEST 91-L...
Current Prognosis...Since the previous update the shower and thunderstorm activity of this tropical wave has further increased in size while moving into the waters midway between the Cape Verde Islands and Lesser Antilles. The tropical low at the northeast end of the tropical wave (located at 15N-30W 36 hours ago) has diminished due to unfavorable westerly shear on the southeast side of the eastern Atlantic upper trough (marked by blue-dashed line in the above atmospheric features chart). However this tropical wave has developed a new large and broad tropical low located further southwest at 12.5N-39W as of 1200Z.

Atmospheric Outlook for the Forecast Period...Forecasting a continued west track for another 24 hours while while steered by the 1024 mb ridge to the north...followed by a northward bend in the track by 48 hours while the low-level ridging to the north weakens with the arrival of the remnants of Fay and strong frontal cyclone absorbing Fay. The track is then expected to bend more westward after 48 hours as a strong low-level ridge builds behind the frontal cyclone...but their will be some northward component in the westward track as this ridge will be narrow while squeezed between the frontal cyclone and frontal system emerging from the US expected to turn Gonzalo northward. I expect this system to land in a col of favorable upper winds in the next 48 hours as the shearing eastern Atlantic upper trough (mentioned in the above current prognosis) is beginning to split into a residual upper trough to the northeast and cut-off upper vortex retrograding westward and away. By 72 hrs and beyond...the upper vorticity marked as a blue-dashed line southwest of Gonzalo (formerly the parent upper vortex that produced Fay days ago) and the aforementioned cut-off upper vortex will merge into a low-latitude upper trough dragged eastward toward this system by the upper trough that has recently emerged from the NE US. The arrival of this low-latitude upper trough from the west will subsequenlty kill off any chances of tropical development as noted in the forecast shown below.

Thermodynamic Outlook for the Forecast Period...Forecast track shown below keeps this system over favorable waters in the 28 to 29 deg C range. Therefore lack of development will be due to the arrival of the low-latitude upper trough mentioned at the end of the above atmospheric outlook.

24 Hr Forecast (1200Z October 13)...Large and broad tropical low centered near 12.5N-44W

48 Hr Forecast (1200Z October 14)...Organizing and large tropical low centered near 14N-49W

72 Hr Forecast (1200Z October 15)...35 mph large tropical depression under unfavorable wind shear on the east side of a low-latitude upper trough

96 Hr Forecast (1200Z October 16)...Broad remnant surface low suppressed below low-latitude upper trough

2014 Atlantic Hurricane Season Birdseye Discussion #111A (Special Update)

By: NCHurricane2009, 4:53 PM GMT on October 11, 2014

...SATURDAY OCTOBER 11 2014 12:53 PM EDT...
As expected the center of Fay has moved northward into the thunderstorm burst previously northwest of its center which has caused its transition into a tropical storm. The latent heat release of the thunderstorm burst has amplified upper ridging over the storm (which in turn has amplified the western Atlantic upper trough to its west into an upper vortex)...and therefore with the western Atlantic upper trough unable to shear this system the arrival of wind shear is now delayed until the shortwave upper trough from the northeastern US reaches this system. Aircraft reconaissance has also found Fay has strengthened a bit more than the previous itensity forecast shown in discussion #111. Therefore Fay has a high chance of becoming a category 1 hurricane while passing just southeast of Bermuda later today. Tropical storm conditions are expected to reach Bermuda by tonight.

Visit www.nhc.noaa.gov for up to the minute latest information on Fay.

2014 Atlantic Hurricane Season Birdseye Discussion #111

By: NCHurricane2009, 5:55 AM GMT on October 11, 2014

...SATURDAY OCTOBER 11 2014 1:55 AM EDT...
Subtropical disturbance Invest 99-L passing north of the Lesser Antilles and curving toward Bermuda has intensified into subtropical depression seven and then into subtropical storm Fay within the last 24 hours. Tropical storm advisories are in effect for Bermuda. See Fay special feature section below for additional details. Meanwhile weather associated with the tropical wave southeast of Fay has produced a second organizing disturbance now seperate from Fay which has been upgraded to Invest 90-L on the Naval Research Laboratory site of the US Navy. Interests in the northern Lesser Antilles...Puerto Rico...and eastern Bahamas should carefully monitor the progress of this new disturbance as multiple computer models as of 1800Z have latched onto a solution showing tropical cyclone formation from Invest 90-L. See second special feature section below for additional details on Invest 90-L.

The tropical wave currently west-southwest of the Cape Verde Islands continues to track more northward than previously forecasted...therefore exposing it to less favorable westerly shear on the south side of the eastern Atlantic upper trough (marked by blue-dashed line in the atmospheric featuers chart below). However this system has seen a tremendous increase in showers and thunderstorms within the last 24 hours...which has finally caused its introduction into the National Hurricane Center Tropical Weather Outlook. And with potential for this system finding more favorable upper winds after a few days...I am maintaining this tropical wave as a special feature on this blog. See third special feature section below for an update on this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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...SUBTROPICAL STORM FAY...
Current Prognosis...As of the 11 PM EDT NHC advisory Fay was centered at 25.9N-64.5W while its track bends northward toward Bermuda. Fay has the classic structure of a subtropical cyclone supported by upper divergence on the northeastern quadrant of its parent upper vortex covering the southwest half of the system. As would be expected in a subtropical cyclone such as this the upper vortex is keeping thunderstorms suppressed southwest of the center while a comma-shaped thunderstorm mass covers the north and east half of the system. The head of the comma is just northwest of the center which featuers an impressive thunderstorm burst on current infrared satellite imagery.

Atmopsheric Outlook for the Forecast Period...A southwestern lobe of the of the upper vortex currently over eastern Canada is about to emerge from the northeastern US as a shortwave upper trough in the next 24 hours...with eastern divergence of this shortwave beginning to weaken the low-level subtropical ridge north of Fay and replacing the ridge with a surface frontal cyclone by 24 hours. The weakening of the subtropical ridge and formation of this frontal cyclone...in conjunction with the parent upper vortex southwest of Fay and the western Atlantic upper trough just west of Fay are all causing the track of this system to bend northward. By 48 hours the rapidly developing frontal cyclone will pull Fay northeastward into its southwestern quadrant and absorb Fay.

Thermodynamic Outlook for the Forecast...Between now and forecast absorption time...Fay will be tracking from waters currently at 29 deg C to waters of 27 deg C. These waters will be sufficiently warm for some additional strengthening of this system and a transition into a fully tropical cyclone.



Track Forecast...Computer models are in tight agreement with the NHC forecast track shown above...and with the way Fay is tracking on satellite animation I see no reason to deviate from the NHC. Therefore my forecast track is in agreement with the NHC's.

Intensity Forecast...The northward track means Fay will be tracking away from its parent upper vortex and into the thunderstorm burst just northwest of the center...which should support its transition into a fully tropical system and allow for some additional strengthening before southerly and southwesterly shear increases from the encroaching western Atlantic upper trough and shortwave upper trough emerging from the northeastern US. The weakening rate of this system (due to shear) between 24 and 48 hrs should be gradual instead of rapid as this system will take some advantage of eastern upper-level divergence provided by the upper trough emerging from the northeastern US. My intensity forecast is in agreement with the NHC's.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 11 PM EDT tropical storm wind field along the forecast track. This swath suggests the arrival of tropical storm conditions at Bermuda by Saturday (tomorrow) night.

...SPECIAL FEATURE...TROPICAL LOW INVEST 90-L...
Current Prognosis...Within the last 24 hours the tropical wave southeast of Subtropical Storm Fay has left behind a tropical low pressure spin becoming increasingly seperate from Fay's cloudiness prior to the tropical wave moving into the Lesser Antilles. As of 0000Z...satellite animation suggests this new tropical low was centered at 15N-51W while elongated east-to-west.

Atmospheric Outlook for the Forecast Period...The west-northwest track of this system will initially have a steeper northward component while influenced by the low-level ridge weakness of Fay and the frontal cyclone expected to absorb Fay. Afterwards a strong low-level ridge building behind the frontal cyclone is expected to bend the track more westward between 48 and 72 hrs. The by 96 and 120 hrs...a strong upper trough and surface frontal system emerging from the United States is expected to curve this system northwestward and then northward by the end of the forecast period. Upper-level winds will be initially favorable for development as this system takes advantage of low shear on the southwestern quadrant of the central Atlantic upper anticyclone (marked by blue H in the atmospheric features chart above). Later in the forecast period the western Atlantic upper trough (marked by blue dashed line) will have weakened such that this system will continue to feature favorable upper anticyclonic outflow overhead.

Thermodynamic Outlook for the Forecast Period...The forecast track shown below will take this system over 29 to 30 deg C waters rather favorable for tropical development through the forecast period.

24 Hr Forecast (0000Z October 12)...Organized tropical low centered at 16.5N-32.5W located below southwestern quadrant of central Atlantic upper anticyclone

48 Hr Forecast (0000Z October 13)...35 mph max sustained wind tropical depression centered at 18N-61W over the northern Lesser Antilles and below southwestern quadrant of central Atlantic upper anticyclone

72 Hr Forecast (0000Z October 14)...45 mph max sustained wind tropical storm centered at 19N-66W just north of Puerto Rico.

96 Hr Forecast (0000Z October 15)...60 mph max sustained wind tropical storm centered at 21N-71W just east of the eastern Bahamas intensifying more rapidly as western Atlantic upper trough diminshes which allows this system to develop more symmetric anticyclonic outflow

120 Hr Forecast (0000Z October 16)...75 mph max sustained hurricane lifting northward from the eastern Bahamas centered at 24N-73W. This hurricane maybe comma shaped as light southwesterly shear in advance of the upper trough emerging from the United States reaches this system.

...SPECIAL FEATURE...TROPICAL WAVE WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS...
Current Prognosis...Since the previous update the shower and thunderstorm activity of this system has further increased in intensity while expanding in size..and moreover the spiral banding features have become better organized. Based on the spiral banding this tropical wave features a surface tropical low centered at 15N-30W as of 0000Z. This system continues to track more northward than I previously forecast perhaps while becoming pulled by the southeast side of the eastern Atlantic upper trough (marked by blue-dashed line in the above atmospheric features chart). Even though the spiral banding looks better than it did 24 hours ago...this system is still sheared by this upper trough as evidenced by the fanning of upper outflow clouds to the north and east while outflow is restricted on the south and west sides of this system.

Atmospheric Outlook for the Forecast Period...Forecasting a continued more north and less west track for another 24 hours while continuing to be pulled by the eastern Atlantic upper trough. Then for 48 to 72 hours I forecast the track to bend more westward as the majority of the upper trough breaks off into a cut-off upper vortex that retrogrades westward and away. After 72 hrs I forecast the track to bend more northward as the frontal cyclone that absorbs Fay weakens the low-level subtropical ridging due north of this system. Warm air advection ahead of this frontal cyclone will amplify the central Atlantic upper anticyclone (marked by blue H in the above atmo chart) such that a portion of the eastern Atlantic upper trough is pushed southward toward this system and significantly shears it by 24 and 48 hrs. Then by 72 and 96 hrs this system will escape the eastern Atlantic upper trough and reach more favorable upper winds on the south side of the central Atlantic upper anticyclone. By the end of the forecast period (120 hrs)...shear is likely to increase again as the above-mentioened retorgrading cut-off upper vortex gets pulled back toward this system by the upper trough associated with the frontal cyclone.

Thermodynamic Outlook for the Forecast Period...Updated forecast track shown below takes this system over favorable waters in the 27 to 29 deg C range.

24 Hr Forecast (0000Z October 12)...Sheared tropical low centered at 17N-33W

48 Hr Forecast (0000Z October 13)...Very sheared tropical low centered at 18N-37W

72 Hr Forecast (0000Z October 14)...Tropical low centered at 19N-41.5W

96 Hr Forecast (0000Z October 15)...Organized tropical low centered at 21N-45.5W

120 Hr Forecast (0000Z October 16)...Sheared 35 mph max sustained wind tropical depression centered at 23N-49.5W

2014 Atlantic Hurricane Season Birdseye Discussion #110A (Special Update)

By: NCHurricane2009, 9:56 PM GMT on October 10, 2014

...FRIDAY OCTOBER 10 2014 5:56 PM EDT...
Tropical storm warnings are in effect for Bermuda as subtropical disturbance Invest 99-L passing north of the Lesser Antilles has developed into subtropical depression seven and then subtropical storm Fay within the last few hours. The thunderstorm field of this system has expanded such that the associated latent heat release has amplified upper ridging overhead which in turn is amplifying the incoming upper trough to the west...which will result in less vertical shear from the upper trough than previously anticipated. Therefore Fay is likely to have an impact on Bermuda later this weekend. Visit www.nhc.noaa.gov for up to the minute latest information on Fay. My next full blog update later tonight will feature Fay as a special feature complete with a forecast.

2014 Atlantic Hurricane Season Birdseye Discussion #110

By: NCHurricane2009, 3:59 AM GMT on October 10, 2014

...FRIDAY OCTOBER 10 2014 12:00 AM EDT...
The southern Caribbean upper ridge (marked by blue H in the atmospheric features chart below) continues to support a broad tropical disturbance covering Central America and the adjacent eastern Pacific. Below the core of the upper ridge is a rotating area of concentrated thunderstorms over Nicaragua...eastern Honduras...and Caribbean waters just offshore of these areas. A surface tropical wave approaching from the east may enhance this thunderstorm cluster in the next 24 hours. However the continued lack of computer model support for Atlantic development from this system suggests that whatever develops from this thunderstorm cluster is not likely to develop due to land interaction with Central America.

The surface trough passing just north of the the Lesser Antilles has deepened into a quickly organizing 1005 mb surface subtropical low supported by divergence on the northeastern quadrant a cut-off upper vortex. As a result within the last day the National Hurricane Center has increased its odds of subtropical or tropical cyclone formation to high levels and this system has been upgraded to Invest 99-L on the Naval Research Laboratory site of the US Navy. Meanwhile a fragment of the Gulf of Mexico cut-off upper trough has fractured into an unfavorable western Atlantic upper trough heading eastward toward Invest 99-L. As this upper trough nears in 24 to 48 hours...unfavorable southerly and southwesterly vertical shear will increase and therefore I forecast 99-L will degenerate into an elongated surface trough south-southeast of Bermuda by this time. Therefore not upgrading this system to a special feature on this blog. However I may need to issue special updates between now and my next full blog update in case this system becomes a subtropical or tropical cyclone in the short term prior to the arrival of unfavorable conditions in 24 to 48 hours.

The tropical wave currently southwest of the Cape Verde Islands has tracked a little more northward than I previously forecasted...therefore exposing it to less favorable westerly shear on the south side of the eastern Atlantic upper trough (marked by blue-dashed line in the atmoshperic features chart below). However with the forecast upper winds becoming more favorable in the latest computer model runs...I am maintaining this tropical wave as a special feature on this blog. See special feature section below for an update on this tropical wave.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1930Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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 WAVE SOUTHWEST OF THE CAPE VERDE ISLANDS...
Current Prognosis...Since the previous update the shower and thunderstorm activity of this system has increased...but the spiral banding features of the associated surface low pressure spin (currently estimated to be at 12N-28W) have recently become less defined as this system becomes less organized while tracking a bit northward into less favorable westerly shearing upper winds on the south side of the eastern Atlantic upper trough (marked by blue-dashed line in the atmoshperic features chart above).

Atmospheric Outlook for the Forecast Period...Surface subtropical ridging to the north will steer this system wes-northwest through the forecast. Later in the forecast period a southwestern lobe of the upper vortex currently over eastern Canada (marked by blue L) will emerge from the northeastern US as a shortwave upper trough...with this shortwave producing a rapidly developing frontal cyclone crossing the north Atlantic. In turn warm air advection ahead of the forecast frontal cyclone will amplify the upper anticyclone over the central Atlantic (marked by blue H). It was previously shown in computer models that the amplified upper anticyclone would push the eastern Atlantic upper trough southward toward this system which would make conditions even less favorable. Now models show the upper anticyclone splitting off the western portion of the upper trough into a small upper vortex that retrogrades westward and away from this system such that this system finds itself in favorable upper winds on the south side of the upper anticyclone later in the forecast period.

Thermodynamic Outlook for the Forecast Period...Upper divergence on the southeast side of the eastern Atlantic upper trough has resulted in a regime of expansive showers and thunderstorms in the environment ahead of this system. Therefore dry air is not expected to be an issue for this system's development. Forecast track shown below takes this system over favorable waters in the 29 deg C range.

24 Hr Forecast (0000Z October 11)...Sheared tropical low centered at 13.5N-32.5W

48 Hr Forecast (0000Z October 12)...Sheared tropical low centered at 14.5N-37W

72 Hr Forecast (0000Z October 13)...Tropical low under reduced shear on the south side of upper anticyclone. Tropical low centered at 15.5N-41.5W

96 Hr Forecast (0000Z October 14)...35 mph max sustained wind tropical depression centered at 16.5N-46W

120 Hr Forecast (0000Z October 15)....45 mph max sustained wind tropical storm centered at 17.5N-50.5W

2014 Atlantic Hurricane Season Birdseye Discussion #109

By: NCHurricane2009, 3:50 AM GMT on October 09, 2014

...WEDNESDAY OCTOBER 8 2014 11:50 PM EDT...
The southern Caribbean upper ridge (marked by blue H in the atmospheric features chart below) continues to expand between the weakening cut-off upper trough over the Gulf of Mexico and cut-off upper vortex northeast of the Lesser Antilles mentioned in the next paragraph. The associated southern Caribbean disturbance taking advantage of the low shear and upper outflow provided by the upper ridge...featuring showers and thunderstorms rotating around a broad 1009 mb low pressure center...is no longer expected to develop on the Atlantic side while interacting with land over Central America or alterantively developing into an eastern Pacific tropical cyclone.

The 1013 mb surface low northeast of the Lesser Antilles supported by eastern divergence of a cut-off upper vortex has been downgraded to a surface trough. In the next 48 hours I am forecasting the tropical wave currently between the Cape Verde Islands and Lesser Antilles to join this surface trough from the southeast. By 72 hours the cut-off upper vortex will have merged with some of the vorticity from the Gulf of Mexico cut-off upper trough...resulting in a western Atlantic upper trough whose eastern divergence will be supporting the surface trough which I am expecting will be a rather elongated feature south-southeast of Bermuda by this time. After the upper trough weakens by 96 hrs and beyond their maybe opportunity for development along this surface trough. Even though this system has been introduced into the National Hurricane Center Tropical Weather Outlook...not considering this system a special feature on this blog until I see how well this system survives the strong western Atlantic upper trough expected to develop by 72 hours.

The tropical wave southeast of the Cape Verde Islands continues to show signs of organization and therefore I have upgraded it to a special feature on this blog. See special feature section below for additional details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1918Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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 WAVE SOUTHEAST OF THE CAPE VERDE ISLANDS...
Current Prognosis...Between 0600Z and 1800Z on October 8 this system was well organized on satellite imagery while showing a circular cluster of thunderstorms featuring some spiral banding features. As of the current time (0000Z October 9) the thunderstorms have weakened but the spiral banding features remain. Based on the spiral banding...estimating a surface low pressure spin centered at 10N-23.5W. Satellite animation over the last day suggests a 24-hourly motion just below 5W longitude per day upon which the forecast below is based on.

Atmospheric Outlook for the Forecast Period...Surface subtropical ridging to the north will steer this system west through the forecast. Upper-level winds will be initially favorable with the eastern Atlantic upper trough (marked by blue-dashed line in the above atmospheric features chart) remaining at bay to the north...with this system taking advantage of low shear and enhanced outflow below tropical upper ridging south of the upper trough (marked by blue-zig-zag line). Later in the forecast period a southwestern lobe of the upper vortex currently over eastern Canada (marked by blue L) will emerge from the northeastern US as a shortwave upper trough...with this shortwave producing a rapidly developing frontal cyclone in the NW Atlantic. In turn warm air advection ahead of the forecast frontal cyclone will amplify the upper anticyclone over the central Atlantic (marked by blue H)...and the amplified upper anticyclone will push the eastern Atlantic upper trough southward toward this system. Therefore currently forecasting this system to encounter unfavorable northwesterly shear on the southwest side of the eastern Atlantic upper trough by the end of the forecast period.

Thermodynamic Outlook for the Forecast Period...The tropical wave to the west of this system has been interacting with upper divergence on the southeast side of the eastern Atlantic upper trough which has resulted in a very expansive area of moisture...showers...and thunderstorms in the environment ahead of this system. Therefore dry air is not expected to be an issue for this system's development. Forecast track shown below takes this system over favorable waters in the 29 deg C range.

24 Hr Forecast (0000Z October 10)...Organized tropical low centered at 11N-28W

48 Hr Forecast (0000Z October 11)...40 mph max sustained wind tropical storm centered at 12N-32.5W

72 Hr Forecast (0000Z October 12)...60 mph max sustained wind tropical storm centered at 13N-37W

96 Hr Forecast (0000Z October 13)...65 mph max sustained wind tropical storm under westerly shear centered at 14N-41.5W

120 Hr Forecast (0000Z October 14)...50 mph max sustained wind tropical storm under northwesterly shear centered at 15N-46W

2014 Atlantic Hurricane Season Birdseye Discussion #108

By: NCHurricane2009, 11:19 AM GMT on October 08, 2014

...WEDNESDAY OCTOBER 8 2014 7:15 AM EDT...
A southern Caribbean upper ridge (marked by blue-zig-zag line in the atmospheric features chart below) continues to expand in the wake of diminishing upper vorticity that had been keeping Caribbean weather suppressed over the last several days. The southern part of the longwave upper trough over the eastern US has left behind a cut-off upper trough over the Gulf of Mexico that will be gradually weakening. The current southern Caribbean upper ridge will therefore continue to expand in relatively higher pressures between the diminishing Gulf cut-off upper trough and eastern Atlantic upper vorticity mentioned in the next paragraph. A surface tropical wave has moved into Central America in the last day...but has initialzed a tropical disturbance in the southern Caribbean currently analyzed as a 1008 mb low just east of Nicaragua while the wave interacted with the favorable outflow of the expanding upper ridge to produce showers and thunderstorms. The surface tropical wave currently entering the eastern Caribbean could also add to this southern Caribbean disturbed weather over the next few days. Computer models have recently become less aggressive with their solutions on a southern Caribbean disturbance while suggesting that such a disturbance would suffer land interaction while moving west-northwest across Central America.

The eastern Atlantic upper vortex as expected has recently split into an upper vortex northeast of the Lesser Antilles (marked by blue L in the atmospheric features chart below) and an upper trough over the eastern Atlantic (marked by blue dashed line). Upper divergence on the east side of the upper vortex NE of the Lesser Antilles has produced a 1013 mb surface low (it is also possible this surface low is a northern fracture of the tropical wave currently entering the eastern Caribbean). Meanwhile upper divergence on the southeast side of the eastern Atlantic upper trough has increased the showers and thunderstorms of the tropical wave currently midway between the Lesser Antilles and Cape Verde Islands. A col of favorable upper winds will be developing between the eastern Atlantic upper trough and upper vortex NE of the Antilles. It is possible that the 1013 mb surface low develops in these favorable upper winds...the tropical wave midway between the Lesser Antilles and Cape Verde Islands develops in these favorable upper winds...or the 1013 mb low and tropical wave merge into a disturbance that develops.

A tropical wave that has recently emerged from western Africa has rapidly become better organized southeast of the Cape Verde Islands this morning below a favorable upper ridge (marked by blue-zig-zag line) located southeast of the eastern Atlantic upper trough. It is possible this tropical wave continues to stay south of the unfavorable upper trough and develop into a tropical cyclone while moving across the Atlantic tropics over the next few days...a solution only supported by the usually aggressive CMC computer model. However if current organization trends continue...I will consider upgrading this tropical wave to a special feature on this blog.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0123Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #107

By: NCHurricane2009, 3:10 AM GMT on October 07, 2014

...MONDAY OCTOBER 6 2014 11:10 PM EDT...
Re-starting daily updates on the Atlantic tropics on this blog in lieu of consistent computer model support for two potential tropical disturbances predicted to develop by 120 hours (5 days).

A southern Caribbean upper ridge (marked by blue-zig-zag line in the atmospheric features chart below) is expanding in the wake of diminishing upper vorticity that had been keeping Caribbean weather suppressed over the last several days. The southern part of the longwave upper trough over the eastern US will soon fracture over the Gulf of Mexico...after which time it will gradually weaken while becoming cut-off. The current southern Caribbean upper ridge will therefore continue to expand in relatively higher pressures between the diminishing Gulf cut-off upper trough and eastern Atlantic upper vortex. A surface tropical wave is already interacting with the favorable outflow of the expanding upper ridge to produce showers and thunderstorms over the southern Caribbean...and the surface tropical wave currently east of the Lesser Antilles will likely add to this weather over the next few days. Therefore the formation of a southern Caribbean tropical disturbance is likely by 120 hours (5 days).

The eastern Atlantic upper vortex (marked by blue L in the atmospheric features chart below) is expected to split into two upper vortices within the next few days. Computer model runs support the idea of a tropical disturbance forming at the north end of the tropical wave that is currently west-southwest of the Cape Verde Islands in a col of favorable upper winds between the two upper vortices at a location southeast of Bermuda and northeast of the Lesser Antilles by 120 hours (5 days).

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1922Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #106A (Special Update)

By: NCHurricane2009, 10:42 AM GMT on October 03, 2014

...FRIDAY OCTOBER 3 2014 6:50 AM EDT...
All subtropical disturbances in the mid-latitudes of the Atlantic are not expected to develop. The slow pace of the 2014 Atlantic Hurricane Season continues with no tropical cyclones expected over the next few days. Therefore I have ceased daily blog updates on the season until the threat of tropical development returns to the Atlantic.

2014 Atlantic Hurricane Season Birdseye Discussion #106

By: NCHurricane2009, 11:07 AM GMT on October 02, 2014

...THURSDAY OCTOBER 2 2014 7:10 AM EDT...
Four subtropical disturbances are present across the mid-latitudes of the Atlantic Ocean as follows...

The remnant surface low of disturbance Invest 97-L and 1008 mb frontal depression to the south-southwest are trapped to the south of the 1025 mb ridge emerging from southeastern Canada...and therefore both are cyclonically orbiting each other while they merge over the western Atlantic. Even though the remnant low of 97-L saw an increase in thunderstorms yesterday afternoon (which caused its re-introduction into the NHC tropical weather outlook and re-initialization on the Navy NRL site)...this was due to the upper divergence on the east side of the upper trough of the 1008 mb frontal depression. Wind shear is too high on the east side of the upper trough and the remnant low of 97-L is now over waters too cool to support subtropical cyclone development...and therefore is not expected to become a subtropical cyclone.

The upper trough formerly over disturbance 97-L is currently southeast of 97-L and its eastern divergence has produced another subtropical disturbance over 26 deg C water designated as Invest 98-L. Invest 98-L is expected to drift northward into cooler waters less favorable for additional development while becoming pulled by the east sides of the 1008 mb frontal depression and remnant low of 97-L mentioned in the previous pargraph...and therefore subtropical cyclone development from 98-L is unlikely.

The 1018 mb low midway between Bermuda and the Azores has seen an increase in unfavorable wind shear as expected as its overhead upper trough has moved southeastward and away while becoming absorbed into the deep-layered vortex mentioned in the next paragraph. Moreover this surface low is expected to drift northward into cooler waters less favorable for additional development while becoming pulled by the east sides of the 1008 mb frontal depression and remnant low of 97-L mentioned two pargraphs ago.

The remnant low of disturbance Invest 95-L remains a deep-layered vortex presently south-southeast of the Azores and is moving southwestward around the southeast side of the 1033 mb Atlantic subtropical ridge and into more favorable waters at or above 26 deg C. However due to the strength of this subtropical ridge surface pressures are on the high side for subtropical cyclone development and no current computer model suggests subtropical cyclone development from this feature.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0131Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).

2014 Atlantic Hurricane Season Birdseye Discussion #105

By: NCHurricane2009, 6:24 AM GMT on October 01, 2014

...WEDNESDAY OCTOBER 1 2014 2:26 AM EDT...
Three subtropical disturbances remain present across the mid-latitudes of the Atlantic Ocean as follows...

The remnant surface low of disturbance Invest 97-L has moved northward away from Bermuda ahead of the 1006 mb frontal depression that has emerged from the SE US (supported by the upper trough currently emerging from the eastern US). Meanwhile the disturbance's former overhead upper vortex has shifted east as an upper trough while its eastern divergence produces showers and thunderstorms north-northeast of the Lesser Antilles...but their is no surface feature associated with this activity at this time. Because the remnant surface low of 97-L is now de-coupled from its overhead upper vortex it is now in a hostile shear environment. The 1022 mb ridge currently emerging from southeastern Canada will pass north of the remnant low of 97-L and 1006 mb frontal depression...blocking the northward progresison of both features and causing both to cyclonically orbit each other while they merge over the western Atlantic.

The 1015 mb low midway between Bermuda and the Azores has weakened further to 1020 mb. However the overhead upper trough has amplified such that wind shear had reduced and this system has become better organized as a subtropical disturbance over 26 deg C water. However the surface low is expected to drift northward into cooler waters less favorable for additional development while becoming pulled by the east sides of the 1006 mb frontal depression and remnant low of 97-L mentioned in the previous paragraph. Moreover unfavorable wind shear will increase when the overhead upper trough de-couples while shifting southeastward as it merges with the deep-layered vortex mentioned in the next paragraph.

The remnant low of disturbance Invest 95-L remains a deep-layered vortex presently south-southeast of the Azores and is expected to move southwestward around the southeast side of the 1030 mb Atlantic subtropical ridge and into more favorable waters at or above 26 deg C. However due to the strength of this subtropical ridge surface pressures are on the high side for subtropical cyclone development and no current computer model suggests subtropical cyclone development from this feature.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0135Z-released WPC analysis.

Features boxed in green...if any...are mentioned in the National Hurricane Center (NHC) traditional 48-hour outlook and or are considered an "Invest" on the Naval Research Laboratory site of the US Navy at the time the chart was generated. I do not box features in green if they are only included in the NHC's longer term 5-day outlook.

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...

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).


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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