NCHurricane2009's Blog

2014 Atlantic Hurricane Season Birdseye Discussion #104

By: NCHurricane2009, 2:22 AM GMT on September 30, 2014

...MONDAY SEPTEMBER 29 2014 10:30 PM EDT...
Upper winds remain favorable in the eastern tropical Atlantic with tropical upper ridging (marked by blue H in the lower right of the atmospheric features chart below). The tropical wave which has recently emerged from western Africa however has lost shower and thunderstorm activity due to dry Saharan air seen in the lower-right of the thermodynamics chart below....and upper winds in the eastern tropical Atlantic will become less favorable after 48 hours as vorticity from the upper trough mentioned in the next paragraph arrives from the northwest and knocks out the favorable upper ridge.

What remains of the surface frontal segment offshore of the southeastern US is the surface low over Bermuda currently at 1008 mb and 1013 mb frontal depression formerly at the east end of the frontal segment which has weakened to a 1015 mb low currently midway between Bermuda and the Azores. The upper trough associated with the frontal segment has split into an upper vortex over the Bermuda low...an upper trough over the 1015 mb low...and another upper vortex over the remnant low of disturbance Invest 95-L just southwest of the Azores. The most interesting feature of these is the 1008 mb Bermuda surface low which has undergone some subtropical development below the low shear and cold de-stabilzing upper air of its overhead upper vortex such that it was upgraded to disturbance Invest 97-L on the Naval Research Laboratory (NRL) site of the US Navy. However in the next 24 hours Invest 97-L will begin to accelerate northward ahead of the 1011 mb frontal depression emerging from the SE US (supported by the upper trough currently over the eastern US) while the shear-reducing upper vortex shifts east and de-couples from 97-L...which will result in increasing shear unfavorable for additional development of 97-L.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1923Z-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 #103

By: NCHurricane2009, 2:47 AM GMT on September 29, 2014

...SUNDAY SEPTEMBER 28 2014 10:47 PM EDT...
Upper winds in the eastern tropical Atlantic are favorable with tropical upper ridging (marked by blue H in the lower right of the atmospheric features chart below). A tropical wave southwest of the Cape Verde Islands has seen an increase in showers and thunderstorms below this upper ridge...but is not expected to develop while leaving the favorable upper ridge in the next 24 hours. Another tropical wave about to emerge from western Africa will only have 72 hours to develop before the upper trough mentioned in the next paragraph arrives from the northwest and knocks out the favorable upper ridge.

A surface frontal segment offshore of the southeastern US persists. The 1013 mb frontal depression at the east end of the frontal segment and its associated upper trough continue to shift southeast while rounding the east side of the western Atlantic upper ridge (marked by blue zig-zag lines in the atmo chart below)...with the upper trough keeping upper winds unfavorable for tropical development along the frontal segment with the exception of a small area over the island of Bermuda where the upper trough has left behind an upper vortex that has become vertically stacked with a new surface 1012 mb frontal low. This 1012 mb surface low has another 24 hours to develop subtropically beneath the low shear of the upper vortex but is unlikely to do so due to dry air to the northwest associated with upper convergence behind the upper trough. After 24 hours the 1012 mb surface low will begin to accelerate northward ahead of a frontal depression emerging from the SE US supported by the upper trough currently over the central US while the shear-reducing upper vortex shifts east and de-couples from the 1012 mb surface low...which will result in increasing shear unfavorable for tropical development of the 1012 mb surface low.

...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).

2014 Atlantic Hurricane Season Birdseye Discussion #102

By: NCHurricane2009, 2:36 PM GMT on September 27, 2014

...SATURDAY SEPTEMBER 27 2014 10:36 AM EDT...
Tropical low pressure Invest 96-L midway between the Lesser Antilles and Cape Verde Islands is experiencing westerly shear from a southern fracture of a north-central Atlantic upper trough more than previously forecast (marked by blue-dashed line north of 96-L in the atmospheric features chart below). Therefore this system is no longer likely to develop and I have cancelled it as a special feature on this blog.

Even though upper winds in the eastern tropical Atlantic have become more favorable with the expansion of tropical upper ridging (marked by blue-zig-zag line and blue H in the lower right of the atmospheric features chart below)...tropical waves in the region appear not well-developed enough to take advantage of these conditions. Therefore the eastern tropical Atlantic remains quiet.

A surface frontal segment offshore of the southeastern US persists. The 1013 mb frontal depression at the northeast end of the frontal segment and its associated upper trough are beginning to shift south while rounding the east side of the western Atlantic upper ridge (marked by blue zig-zag line in the atmo chart below). As the upper trough begins shifting south...unfavorable westerly shear offshore of the southeastern US is beginning to increase and therefore time has run out for tropical development along the frontal segment.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z and 0730Z-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 #101

By: NCHurricane2009, 3:14 AM GMT on September 26, 2014

...THURSDAY SEPTEMBER 25 2014 11:15 PM EDT...
Tropical low pressure Invest 96-L midway between the Lesser Antilles and Cape Verde Islands has become stationary rather than moving west. And with the surface low likely to be quasi-stationary for another 96 hours...it will become distant from the unfavorable upper vortex moving into the Lesser Antilles and potentially tap into more favorable upper winds as tropical upper ridging expands in the wake of the upper vortex. Therefore I have upgraded it to a special feature on this blog with a high risk of tropical cyclone formation over the next few days. See special feature section below for additional details.

The western Caribbean tropical wave will encounter more favorable upper winds over the next day beneath upper ridging in the western Caribbean and western Atlantic (marked by blue H and blue-zig-zag line). However by days two and three...when this system crosses the Yucatan peninsula into the Bay of Campeche...this system will encounter less favorable westerly shear on the south side of the central US upper trough. This system is not likely to develop since it is currently not impressive on satellite and therefore is likely to not have enough time to develop with just one day left of favorable conditions.

As noted in the lower-right of the atmospheric features chart below...satellite imagery suggests a pair of suspect tropical waves. Upper winds in the eastern and central tropical Atlantic will become more favorable as the tropical upper ridging (marked by blue-zig-zag line) expands and northeastern Atlantic upper vorticity (marked by blue dashed line) contracts. Not considering either suspect tropical wave a special feature on this blog as neither wave is well organized...and moreover their is no computer model support showing either wave developing.

A surface frontal segment offshore of the southeastern US persists. The 1019 mb frontal depression at the north end of the frontal segment and eastern US upper trough will lift out to the northeast while moving around the western Atlantic upper ridge (marked by blue zig-zag line in the atmo chart below)...potentially allowing the segment of frontal boundary to develop tropically below the favorable upper ridge within the next few days. Currently not considering a special feature from this scenario as their is a lack of computer model support.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1927Z-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 LOW INVEST 96-L...
Current Prognosis...A tropical low is currently centered at 13N-44W...midway between the Lesser Antilles and Cape Verde Islands...with the shower and thunderstorm activity lopsided to the southeast half of the circulation due to westerly shear imparted by the southeast side of the upper vortex nearing the Lesser Antilles (marked by blue L northwest of 96-L in the above atmospheric features chart).

Atmospheric Outlook for the Forecast Period...For the first 72 hrs of the forecast period the surface low is likely to be quasi-stationary due to the low pressure field of ex-95L to the northeast and 1019 mb frontal depression offshore of the eastern US coming in from the northwest. By 96 to 120 hrs this system is likely to begin moving west-northwest as these low pressure features weaken and become replaced by subtropical ridging to the north. Because this system is forecast to be initially stationary...the upper vortex currently near the Lesser Antilles will move westward and away which will allow the tropical upper ridging (marked by blue-zig-zag line in the above atmo chart) to expand overhead and reduce the shear/enhance the outflow for this disturbance. The upper trough currently associated with the aforementioned 1019 mb frontal depression will be nearing this system from the northwest by 120 hrs...but the current assumption is that this system will be southeast enough of the upper trough such that this system remains under low shear.

Thermodynamic Outlook for the Forecast Period...System is expected to be over favorable 28 to 29 deg C waters thru the forecast period. The forecast below assumes the dry air to the east and west of the disturbance (seen in the above thermo chart) which has the potential to get pushed into this disturbance via vertical wind shear. However the forecast below assumes that this dry air will not be a problem for this system as the above atmospheric outlook suggests a reduction in wind shear from current levels.

24 Hr Forecast (1800Z September 26)...Tropical low centered at 13N-44W

48 Hr Forecast (1800Z September 27)...Organized tropical low centered at 13N-44W

72 Hr Forecast (1800Z September 28)...35 mph max sustained wind tropical depression centered near 14N-45W

96 Hr Forecast (1800Z September 29)...50 mph max sustained wind tropical storm centered at 15N-47.5W

120 Hr Forecast (1800Z September 30)...65 mph max sustained wind tropical storm centered at 16N-52.5W

2014 Atlantic Hurricane Season Birdseye Discussion #100

By: NCHurricane2009, 10:21 AM GMT on September 25, 2014

...THURSDAY SEPTEMBER 25 2014 6:22 AM EDT...
The tropical wave previously midway between the Lesser Antilles and Cape Verde Islands is currently nearing the Lesser Antilles and eastern Caribbean. However in the last 36 hours it has left behind a tropical low pressure in the central tropical Atlantic recently designated as Invest 96-L by the Naval Research Laboratory of the US Navy. Development of 96-L is not expected due to southwesterly vertical shear on the southeast side of the upper vortex nearing the Lesser Antilles (marked as a blue L to the northwest of 96-L in the atmospheric features chart below)

The tropical wave currently moving into the western Caribbean will encounter more favorable upper winds over the next day or two beneath upper ridging in the western Caribbean and western Atlantic (marked by blue H and blue-zig-zag line). However by day three...when this system crosses the Yucatan peninsula into the Bay of Campeche...this system will encounter less favorable westerly shear on the south side of the central US upper trough. This system is not likely to develop since it is currently not impressive on satellite and therefore is likely to not have enough time to develop with just two days of favorable conditions.

As noted in the lower-right of the atmospheric features chart below...satellite imagery suggests a tropical wave currently southwest of the Cape Verde Islands and yet another about to emerge from western Africa. The suspect tropical wave southwest of the Cape Verde Islands will encounter some unfavorable upper winds on the south side of northeastern Atlantic upper vorticity (marked by blue L)...but by 48 hours and beyond both tropical waves will encounter favorable upper winds as the tropical upper ridging (marked by blue-zig-zag line) expands and northeastern Atlantic upper vorticity contracts. Not considering either trpoical wave a special feature on this blog as the wave southwest of the Cape Verde Islands has become less organized in the last day and neither wave is well organized...and moreover their is no computer model support showing either wave developing.

As expected a cut-off upper trough over the SE US and a surface frontal segment offshore has been left behind. This SE US cut-off upper trough will lift out to the northeast while moving around the western Atlantic upper ridge (marked by blue zig-zag line in the atmo chart below)...potentially allowing the segment of frontal boundary to develop tropically below the favorable upper ridge within the next few days. Currently not considering a special feature from this scenario as their is a lack of computer model support.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0129Z-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 #99

By: NCHurricane2009, 3:42 AM GMT on September 24, 2014

...TUESDAY SEPTEMBER 23 2014 11:45 PM EDT...
The tropical wave currently midway between the Lesser Antilles and Cape Verde Islands will be arriving to the Lesser Antilles and eastern Caribbean by 48 and 72 hrs. Although it is currently under more favorable upper winds below an expanding upper ridge (marked by blue-zig-zag line in the atmospheric features chart below)...it will encounter less favorable upper winds as the cut-off upper vortex currently northeast of the Lesser Antilles (marked by blue L) will move southwest into the eastern Caribbean and Lesser Antilles by 48 and 72 hrs. Therefore this system is not expected to develop.

The tropical wave currently moving into the central Caribbean will encounter more favorable upper winds over the next two to three days as upper ridging in the central Caribbean and western Atlantic (marked by blue Hs) expands between the upper vortex northeast of the Lesser Antilles and weakening western Caribbean upper trough. However currently not considering this system a special feature on this blog with the lack of computer model support and with this system currently not showing much activity on satellite.

Satellite imagery suggests a vigorous and semi-organized tropical wave is passing south of the Cape Verde Islands...and was analyzed as a 1012 mb tropical low by the NHC TAFB as marked in the lower-right of the atmospheric features chart below. This system will be passing below favorable tropical upper ridging (marked by blue-zig-zag line in the atmospheric features chart below) over the next 24 hrs...followed by some unfavorable upper winds on the south side of northeastern Atlantic upper vorticity (marked by blue dashed line) as this tropical wave passes southwest of the islands by 48 hrs. However upper winds will be favorable again by 72 hrs and beyond as the wave enters the open central Atlantic as the tropical upper ridging expands and northeastern Atlantic upper vorticity contracts. Not considering this system a special feature on this blog while watching for persistence in organization and for computer model support.

The 968 mb frontal cyclone and associated upper trough emerging from eastern North America will leave behind a cut-off upper trough over the SE US and a surface frontal segment offshore. This SE US cut-off upper trough will lift out to the northeast while moving around the western Atlantic upper ridge (marked by blue Hs in the atmo chart below)...potentially allowing the segment of frontal boundary to develop tropically below the favorable upper ridge within the next few days. Currently not considering a special feature from this scenario as their is a lack of computer model support.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1923Z-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 #98

By: NCHurricane2009, 2:40 AM GMT on September 23, 2014

...MONDAY SEPTEMBER 22 2014 10:41 PM EDT...
The tropical wave currently midway between the Lesser Antilles and Cape Verde Islands is the same one that produced disturbance Invest 95-L in the eastern Atlantic...and will be arriving to the Lesser Antilles and eastern Caribbean by 72 and 96 hrs. Upper winds will become more favorable for this tropical wave over the next 48 hrs as the overhead upper ridge (marked by blue-zig-zag line in the atmospheric features chart below) expands...followed by unfavorable upper winds as a cut-off upper vortex (marked by blue L) moves southwest into the eastern Caribbean and Lesser Antilles by 72 and 96 hrs. Therefore this system is not likely to develop as it will only have 48 hrs of favorable upper winds.

The tropical wave currently in the eastern Caribbean will encounter more favorable upper winds over the next three to four days as upper ridging in the central Caribbean (marked by blue-zig-zag line in the atmospheric features chart below) and western Atlantic (marked by blue H) expands between the upper vortex northeast of the Lesser Antilles and weakening western Caribbean upper vortex (both upper vortices marked by blue Ls). However currently not considering this system a special feature on this blog with the lack of computer model support and with this system currently not showing much activity on satellite.

Satellite imagery suggests a vigorous and semi-organized tropical wave is emerging from western Africa as marked in the lower-right of the atmospheric features chart below. This system will be passing below favorable tropical upper ridging (marked by blue-zig-zag line in the atmospheric features chart below) over the next 48 hrs while passing south of the Cape Verde Islands...followed by some unfavorable upper winds on the south side of northeastern Atlantic upper vorticity (marked by blue Ls and blue dashed lines) as this tropical wave passes southwest of the islands by 72 hrs. However upper winds will be favorable again by 96 and 120 hrs as the wave enters the open central Atlantic as the tropical upper ridging expands and northeastern Atlantic upper vorticity contracts. Not considering this system a special feature on this blog while watching for persistence in organization and for computer model support.

The 987 mb frontal cyclone and associated upper trough emerging from eastern North America will leave behind a cut-off upper trough over the SE US and a surface frontal segment offshore. This SE US cut-off upper trough will lift out to the northeast while moving around the western Atlantic upper ridge (marked by blue H in the atmo chart below)...potentially allowing the segment of frontal boundary to develop tropically below the favorable upper ridge within the next few days. Currently not considering a special feature from this scenario as their is a lack of computer model support.

...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).

2014 Atlantic Hurricane Season Birdseye Discussion #97

By: NCHurricane2009, 8:32 PM GMT on September 21, 2014

...SUNDAY SEPTEMBER 21 2014 4:32 PM EDT...
Vigorous tropical wave Invest 95-L offshore of western Africa has left behind a 1011 mb low pressure center just southeast of the Cape Verde Islands. Even though this system is cancelled in the National Hurricane Center Tropical Weather Outlook...this low pressure center remains posted as 95-L on the Naval Research Laboratory (NRL) site of the US Navy. Tropical cyclone formation from this low pressure center is unlikely as it will track west-northwest into unfavorable upper winds associated with the amplified eastern Atlantic upper trough (marked by blue-dashed line in the atmospheric features chart below).

As expected a surface low has consolidated offshore of the southeastern United States with the support of eastern divergence of a cut-off upper trough marked by a blue-dashed line over the southeastern US in the atmospheric features chart below. This surface low is currently positioned just offshore of North Carolina. Meanwhile another upper trough/surface 998 to 999 mb frontal system coming in from the northwest has absorbed the southeastern US cut-off upper trough and will soon absorb the surface low offshore of North Carolina such that the surface low offshore of North Carolina will not be able to develop tropically. After that...the 998 to 999 mb frontal system will leave behind another cut-off upper trough over the SE US and a surface frontal segment offshore. This SE US cut-off upper trough will lift out to the northeast while moving around the western Atlantic upper ridge (marked as a blue-zig-zag line and blue H in the atmo chart below)...potentially allowing the segment of frontal boundary to develop tropically below the favorable upper ridge within the next few days. So far the CMC computer model is the only model that supports this idea.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1325Z-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 #96

By: NCHurricane2009, 6:01 PM GMT on September 20, 2014

...SATURDAY SEPTEMBER 20 2014 2:05 PM EDT...
Edouard weakens to a remnant low in the cold waters of the north Atlantic west of the Azores.

Vigorous tropical wave Invest 95-L offshore of western Africa has become less organized while encountering unfavorable upper winds associated with the amplified eastern Atlantic upper trough (shown by blue-dashed line on the right side of the atmoshperic features chart below). Tropical cyclone formation from this system is not likely.

In the next 24 hours a surface low offshore of the southeastern United States will consolidate with the support of eastern divergence of a cut-off upper trough marked by a blue-dashed line over the southeastern US in the atmospheric features chart below. Because the cut-off upper trough will be weakening during this time...the wind shear will be reducing...and coupled with warm waters the forecast surface low has a 24 hour window to gain some tropical characteristics. However by 48 hours the surface low will be accelerating rapidly northward between the 1032 mb ridge to the northeast and shortwave upper trough/surface 990 to 999 mb frontal system coming in from the northwest...and begin merging with the frontal system. Therefore not expecting this system to develop into a tropical cyclone as it will only have a 24 hour period to do so. Regardless...heavier rainfall will be developing across the east coast the United States from the coastal Carolinas...northward.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and 1328Z-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 #95

By: NCHurricane2009, 11:11 AM GMT on September 19, 2014

...FRIDAY SEPTEMBER 19 2014 7:15 AM EDT...
Edouard weakens to a tropical storm over the cool waters of the north Atlantic...and within the next 24 hours is expected to dissipate into a remnant low just west of the Azores. See special feature section below for an update on Edouard. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

Even though the vigorous tropical wave just offshore of western Africa has become a little better organized and has been upgraded to Invest 95-L on the Naval Research Laboratory (NRL) site of the US Navy...it is not likely to develop as the northeastern Atlantic upper trough (shown by blue-dashed line on the right side of the atmoshperic features chart below) is expected to be too amplified such that upper winds will be unfavorable.

In the timeframe that is 48 to 60 hrs...a surface low is expected to form offshore of the southeastern United States with the support of eastern divergence of a southern fracture of the upper trough currently over eastern North America. Because the southern fracture of the upper trough will be weakening during this time...the wind shear will be reducing...and coupled with warm waters the forecast surface low could evolve into a tropical system. However not considering the forecast surface low as a special feature at this time as this system will be accelerating northward past the Carolina shore and into cooler waters just after 60 hrs...perhaps not giving enough time for this system to become a tropical 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 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 EDOUARD...
Current Prognosis...As of the 5 AM EDT NHC advsiory...the center of Edouard was located at 39.8N-38.5W with maximum sustained winds dropping to 60 mph... classifying Edouard as a tropical storm. Compared to 24 hrs ago Edouard looks in much worse shape. Because the eastward track of the storm has slowed...it has fallen behind the upper westerly wind speed which has allowed westerly shear to blast off its thunderstorms and mid-level circulation to the east. The thunderstorms this morning have weakened as Edouard is now over water temps in the mid-20s of deg C no longer supportive of a tropical system.

Atmospheric Outlook for the Forecast Period...This system is maintaining an eastward track in response to the upper trough and associated 993 mb surface frontal cyclone to the northwest emerging from eastern North America. The eastward track has become significantly slower as a result of Edouard becoming trapped between the 1024 mb ridge strengthening to the northeast...the 1023 mb ridge to the south...and the 1026 mb ridge currently over southeastern Canada which is accelerating southeastward to the northwest of Edouard. After Edouard dissipates into a remnant low...the aforementioned ridge to the northwest will be near enough to push this system increasingly southward. The current westerly shear over Edouard is soon expected to reduce as an upper ridge wave in the vicinity amplifies due to warm air advection ahead of the aforementioned 993 mb frontal cyclone...however Edouard is going to dissipate anyway because of a prolonged period over cooler waters.

Thermodynamic Outlook for the Forecast Period...This system is currently over sea surface temps in mid 20s of deg C no longer supportive of a tropical system...with temps to decrease to low 20s of deg C as it continues to drift eastward.



Track Forecast...Edouard's current position is a bit southwest of my previous forecast track...and therefore my updated forecast track is adjusted accordingly and now is in 100% agreement with the 5 AM EDT NHC forecast track.

Intensity Forecast...The current strength of Edouard matches my previous intensity forecast...and therefore my updated forecast is the same as previous. Within the next 24 hours...it is expected Edouard will become downgraded to a cloud swirl remnant surface low void of thunderstorms while succumbing to the cooler waters. With Edouard not having any tropical support with sea surface temps too cool...and with Edouard not having any non-tropical support with the lack of upper divergence...I expect the remnant low to weaken below storm force (40+ mph) between 2 AM Sat and 2 AM Sunday in accordance with my previous intensity forecast...whereas the NHC shows the remnant low maintaining storm force thru 2 AM Sunday.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 5 AM EDT NHC tropical storm wind field along my forecast track...with narrowing of the swath throughout the forecast to reflect Edouard's forecast weakening. The swath shows dissipatioin of storm force (40+ mph) in accordance with my thoughts on forecast intensity which expects the remnant low of Edouard to weaken further to below storm force by 2 AM Sunday. However if the NHC intensity forecast is correct...then the remnant low may produce a small area of storm force winds over the westernmost Azores this weekend.

2014 Atlantic Hurricane Season Birdseye Discussion #94

By: NCHurricane2009, 11:32 AM GMT on September 18, 2014

...THURSDAY SEPTEMBER 18 2014 7:35 AM EDT...
Hurricane Edouard maintaining strength while accelerating eastward across the north Atlantic and toward the Azores islands in the northeastern Atlantic. See special feature section below for an update on Edouard. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

A vigorous tropical wave currently emerging from western Africa is not likely to develop as the northeastern Atlantic upper trough (shown by blue-dashed line on the right side of the atmoshperic features chart below) is expected to be too amplified such that upper winds will be unfavorable.

...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).

...SPECIAL FEATURE...HURRICANE EDOUARD...
Current Prognosis...As of the 5 AM EDT NHC advsiory...the center of Edouard was located at 39.6N-45.3W with maximum sustained winds holding at 85 mph...still classifying Edouard as a category 1 hurricane. Satellite presentation shows that Edouard has lost its eye and its thunderstorm core is weakening as this system is entering cooler waters no longer supportive for a tropical system.

Atmospheric Outlook for the Forecast Period...This system is accelerating eastward in response to the upper trough and associated 992 mb surface frontal cyclone to the northwest emerging from eastern North America. Between 24 and 48 hrs the eastward track is expected to be significantly slower as the 1018 mb ridge to the north is expected to strengthen to the norhteast of Edouard...with Edouard becoming trapped between that ridge...the current 1025 mb ridge to the south...and the 1023 mb ridge currently over central Canada which will be accelerating southeastward to the northwest of Edouard. By 72 hrs the ridge to the northwest will be nearing Edouard and will push this system increasingly southward and into the Azores islands. Edouard has been moving faster to the east than previously anticipated such that it has matched the speed of upper westerlies and hence the westerly shear has not been so bad for Edouard. The shear will reduce further by 36 hours as an upper ridge wave in the vicinity of Edouard amplifies due to warm air advection ahead of the aforementioned 992 mb frontal cyclone...so Edouard's dissipation is no longer expected to be due to shear and instead be due to thermodynamic conditions as outlined below.

Thermodynamic Outlook for the Forecast Period...This system is currently crossing the 26 deg C isotherm into cooler waters in the low 20s of deg C that will no longer be supportive of a tropical system. Edouard's weakening in the forecast period is expected to be due to cooler waters.



Track Forecast...Edouard has been tracking faster and a bit more south than my previous forecast track...and therefore my updated track is south and east of my previous track. Therefore my updated forecast is adjusted a bit south and further east comapred to my previous. This placed my 2 AM Friday point a bit northeast of the NHC 5 AM EDT forecast track...and therefore my 2 AM Saturday and 2 AM Sunday points are also a bit northeast of the NHC track.

Intensity Forecast...The current strength of Edouard is above my previous forecast...and therefore my updated forecast is an upward adjustment at all points and is very similar to the NHC 5 AM intensity forecast. By 72 hours...I expect Edouard will have been downgraded to a cloud swirl remnant surface low void of thunderstorms while finally succumbing to the cooler waters.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 5 AM EDT NHC tropical storm wind field along my forecast track...with narrowing of the swath throughout the forecast to reflect Edouard's forecast weakening. The adjustment in the track and intensity forecasts now causes the impact swath in the above graphic to come close to the westernmost Azores. Therefore if Edouard ends up maintanining strength for an even longer period than the above forecast shows...it is conceivable that tropical storm force winds could reach the westernmost Azores this weekend.

2014 Atlantic Hurricane Season Birdseye Discussion #93

By: NCHurricane2009, 4:14 AM GMT on September 17, 2014

...WEDNESDAY SEPTEMBER 17 2014 12:13 AM EDT...
Edouard this past afternoon was a short-lived category 3 hurricane...making it the first in the Atlantic basin since Sandy in October 2012. Edouard is currently a weakening category 1 hurricane accelerating northeastward toward the open north Atlantic. See special feature section below for an update on Edouard. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

A vigorous tropical wave currently over interior western Africa will emerge into the eastern tropical Atlantic passing south of the Cape Verde Islands by 48 to 72 hours. However computer models show the northeastern Atlantic upper trough (shown by blue-dashed line on the right side of the atmoshperic features chart below) being too amplified by that time such that I expect upper winds will be unfavorable for development of this tropical wave when it enters the Atlantic.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1934Z-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 EDOUARD...
Current Prognosis...As of the 11 PM EDT NHC advsiory...the center of Edouard was located at 33.5N-56.4W with maximum sustained winds declining to 90 mph...classifying Edouard as a category 1 hurricane. The larger and impressive eye from 24 hours ago has been contracting...and a windsat image cited in the 11 PM EDT NHC advisory suggested that another outer eye has been forming around the shrinking eye. This suggests Edouard has weakend from its category 3 peak due to an eye wall replacement cycle.

Atmospheric Outlook for the Forecast Period...This system is accelerating northeastward and eventually will accelerate eastward in response to a low-level ridge weakness coming in from the northwest associated with the surface fronts and upper trough over eastern North America. Toward the end of the forecast period the eastward track is expected to bend south as a strong low-level ridge builds in from the northwest. Edouard will soon be exiting favorable low shear characterized by upper anticyclonic flow...entering a hostile environment of westerly shear in advance of the upper trough. The shear may relax by 72 hours as an upper ridge wave in the vicinity of Edouard amplifies due to warm air advection ahead of a forecast southern Greenland frontal cyclone to be supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...This system is currently over favorable 28 deg C water...but will soon head to marginal 26 deg C waters by 24 hrs. After that time Edouard will move into waters in the low 20s of deg C that will no longer be supportive of a tropical system.



Track Forecast...Edouard is a bit northeast of my previous forecast track...and therefore my updated forecast points are adjusted a tad north and east accordingly. My 48 to 72 hr (8 PM Thu to 8 PM Fri) track is straight east while the NHC's is east-southeast. The reason I do not show an east-southeast track during this time is the extent of the low-level ridge expected to build in from the northwest is shown in models to be too far from Edouard (in my opinion) by 72 hrs to push Edouard south. However I do believe immediately after 72 hrs the low-level ridge will be near enough to begin pushing Edouard more southward.

Intensity Forecast...The current strength of Edouard is below my previous forecast...and therefore my updated forecast is a downward adjustment at all points. Edouard will be arriving to a hostile environment of cooler waters and westerly shear as outlined in the above atmospheric and thermodynamic outlook sections and therefore is expected to weaken throughout the forecast period. Even though the above atmo outlook highlights a possible reduction in shear by 72 hours...Edouard will be over waters too cold to support a tropical system and therefore I expect Edouard will have been downgraded to a cloud swirl remnant surface low void of thunderstorms by that time.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with narrowing of the swath throughout the forecast to reflect Edouard's forecast weakening. Sea swells around the hurricane are currently underway. Even though Edouard is passing well east of Bermuda...the strength of the storm will allow swells to reach the island as noted in impact statement (b). Swells are now less likely to reach the Azores at the end of the forecast period as Edouard is trending weaker than previous forecasts.

2014 Atlantic Hurricane Season Birdseye Discussion #92

By: NCHurricane2009, 5:12 AM GMT on September 16, 2014

...TUESDAY SEPTEMBER 16 2014 1:15 AM EDT...
Edouard is currently a high end category 2 hurricane in the open ocean on the verge of becoming a category 3. If Edouard makes it to category 3...it will be the first major hurricane (category 3 or greater) in the Atlantic basin since Sandy in October 2012. See special feature section below for an update on Edouard. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

Computer models forecast that the vigorous tropical wave currently over interior central Africa will emerge into the eastern tropical Atlantic southeast of the Cape Verde Islands by 96 hours. However models also show the northeastern Atlantic upper trough (shown by blue-dashed line on the right side of the atmoshperic features chart below) being too amplified by that time such that I expect upper winds will be unfavorable for development of this tropical wave when it enters the Atlantic.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and 1924Z-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 EDOUARD...
Current Prognosis...As of the 11 PM EDT NHC advsiory...the center of Edouard was located at 29.0N-56.9W with maximum sustained winds holding at 110 mph...classifying Edouard as a top end category 2 hurricane. Edouard has replaced is smaller eye from 36 hours ago with a more impressive looking larger eye and solid ring of thunderstorms around the eye. The outer cloudiness and upper outflow clouds of the hurricane are lopsided toward the northwest side of the circulation as this system is in a very light southeasterly shear environment on the west edge of an upper anticyclonic ridge (marked by blue H and blue-zig-zag line in the above atmospheric features chart).

Atmospheric Outlook for the Forecast Period...This system should is bending on a more northward track in response to a low-level ridge weakness associated with a 1009 mb frontal depression moving offshore of Newfoundland. In the next 24 hours Edouard will not be able to turn east with this frontal depression because some of what is currently the 1023 mb NE US ridge will pass north of the hurricane...therefore the track will continue to be northward. After 24 hours another weakness coming in from the northwest associated with the surface fronts and upper trough over the north-central US and central Canada (seen in the top-left of the above atmo chart) will carry Edouard northeastward and eventually eastward. Toward the end of the forecast period the eastward track is expected to bend south as a strong low-level ridge builds in from the northwest. Edouard has a little less than 24 hours left in a low shear environment characterized by upper anticyclonic flow that will allow additional strengthening...followed by the arrival of westerly shear in advance of the upper trough associated with the above-mentioned second ridge weakness. The shear may relax by 96 hours as an upper ridge wave in the vicinity of Edouard amplifies due to warm air advection ahead of a forecast southern Greenland frontal cyclone to be supported by the eastern divergence of the upper trough.

Thermodynamic Outlook for the Forecast Period...This system is currently over favorable 28 to 29 deg C water supportive of additional strengthening...with the forecast track taking this system to marginal 26 deg C waters by 48 hrs. After that time Edouard will move into waters in the low 20s of deg C that will no longer be supportive of a tropical system.



Track Forecast...Edouard is west (left) of my previous forecast track...and therefore my updated forecast is adjusted accordingly. Because satellite loops still show a slight west component to the track as it moves into 57W...and because the above atmospheric outlook concludes that Edouard will not bend east in the next 24 hours...my 24 hr forecast point (8 PM Tue) above is positioned at 57.5W. The NHC forecast point for 48 hrs (8 PM Wed) is similar to my previous forecast...and because Edouard is currently left of my previous forecast...my 48 hr point is left of the NHC. After 48 hrs...the NHC and computer models show a faster northeast and eastward track compared to yesterday...so I also show a faster track but remain a tad left of those forecasts because my 24 and 48 hr points are to the left. My 72 to 96 hr (8 PM Thu to 8 PM Fri) track is straight east while the NHC's is east-southeast. The reason I do not show an east-southeast track during this time is the extent of the low-level ridge expected to build in from the northwest is shown in models to be too far from Edouard (in my opinion) by 96 hrs to push Edouard south. However I do believe immediately after 96 hrs the low-level ridge will be near enough to begin pushing Edouard more southward.

Intensity Forecast...The current strength of Edouard lies between my less aggressive intensity forecast from discussion #91 and my more aggressive intensity forecast from discussion #91A. Therefore my updated intensity forecast for the next 24 hours is between these two forecasts but a bit leaned toward my more aggressive forecast in #91A because the core of Edouard appears very well organized and we have another 24 hours of favorable atmospheric and thermodynamic conditions as outlined in the above atmo and thermo outlook sections. Because the above track forecast shows a faster northeast and eastward track compared to the previous...Edouard is now expected to arrive to a hostile environment of cooler waters and westerly shear sooner than expected and therefore my intensity forecast for 48 hours and beyond trends toward and then slightly below my less aggressive forecast in discussion #91. Even though the above atmo outlook highlights a possible reduction in shear by 96 hours...Edouard will be over waters too cold to support a tropical system and therefore I expect Edouard will have been downgraded to a cloud swirl remnant surface low void of thunderstorms by that time. Of note...if Edouard follows either my or the NHC forecast it will be the first time we've had a category 3 in the Atlatic basin since Sandy in October 2012. In the small chance Edouard pulls a fast one in the next 24 hours and becomes a category 4...it will be the first in the Atlantic basin since Ophelia in October 2011.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 11 PM EDT NHC tropical storm wind field along my forecast track...with narrowing of the swath for the latter part of the forecast to reflect Edouard's forecast weakening. Sea swells around the hurricane are currently underway. Even though Edouard is expected to pass well east of Bermuda...the strength of the storm will allow swells to reach the island as noted in impact statement (b). Swells can be expected to reach the shores of the Azores by the end of the forecast period as well.

2014 Atlantic Hurricane Season Birdseye Discussion #91A (Special Update)

By: NCHurricane2009, 8:07 PM GMT on September 14, 2014

...SUNDAY SEPTEMBER 14 2014 4:08 PM EDT...
Edouard has already mixed out the dry air that earlier entered the south and east sides of the circulation...and this special update is to increase my intensity forecast for Hurricane Edouard. The hot tower bursts west of the eye (noted in the current prognosis of the Edouard special feature section of discussion #91) has wrapped around and we currently have the appearance of a pinhole-eye hurricane showing signs of rapid intensification. Using the satellite image below...the pinhole eye is centered at 25.2N-51.8W as of this special update. Moreover favorable conditions of 29 to 30 deg C water and upper anticyclonic outflow are expected to last for another two days. Therefore my updated intensity forecast shows rapid intensification to a category 4. If the intensity forecast below verifies...this will be the first category 3 hurricane in the Atlantic basin since Sandy in October 2012...and will be the first category 4 in the Atlantic basin since Ophelia in October 2011.

Return to full discussion #91 for an update on the rest of the Atlantic tropics. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.



8 AM Monday September 15...115 mph max sustained wind category 3 hurricane centered at 27.5N-54.5W.

8 AM Tuesday September 16...135 mph max sustained wind category 4 hurricane centered at 30.5N-55.5W

8 AM Wednesday September 17...125 mph max sustained wind category 3 hurricane centered at 34.5N-55W

8 AM Thursday September 18...90 mph max sustained wind category 1 hurricane centered at 39.5N-49W

8 AM Friday September 19...65 mph max sustained wind tropical storm centered at 41.5N-39W

2014 Atlantic Hurricane Season Birdseye Discussion #91

By: NCHurricane2009, 5:25 PM GMT on September 14, 2014

...SUNDAY SEPTEMBER 14 2014 1:25 PM EDT...
Edouard becomes the fourth hurricane of the 2014 Atlantic season...and has the potential to become a major hurricane (category 3 or greater) over the open ocean over the next couple of days. If it achieves this feat...it will be the first major hurricane in the Atlantic basin since Sandy in October 2012. See special feature section below for an update on Edouard. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

Tropical wave Invest 93-L in the eastern tropical Atlantic has weakened in the last 36 hours. As Hurricane Edouard has lifted northward...it is no longer shielding this tropical wave from the dry Saharan air to the west seen in the thermodynamics chart below. Moreover the thermodynamics chart suggests a trowal of some dry Saharan air sneaking toward 93-L from the northeast. In addition upper vorticity from the south Greenland frontal cyclone system is merging with the 999 mb deep-layered low in the northeast Atlantic...with a portion of this upper vorticity expected to dive southwest around the southeast side of upper anticyclonic flow over Edouard and toward 93-L and hit 93-L with northerly shear as it moves into the central tropical Atlantic. Therefore this system is no longer expected to become a tropical cyclone and I have dropped it as a special feature on this blog.

Satellite imagery indicates that a vigorous tropical wave has entered the tropical waters southeast of the Cape Verde Islands after emerging from western Africa. Meanwhile upper vorticity from the south Greenland frontal cyclone system is merging with the 999 mb deep-layered low in the northeast Atlantic...with a portion of this upper vorticity expected to dive southwest around the southeast side of upper anticyclonic flow over Edouard and toward the central tropical Atlantic. Therefore this tropical wave will be encountering unfavorable southwesterly shear on the east side of this upper vorticity as it moves into the central tropical Atlantic by 96 hours...and therefore is not likely to develop into a tropical cyclone.

A western fracture of the large western Atlantic upper vortex has moved into the southern Gulf of Mexico. This fracture is stronger than anticipated...keeping the favorable southeastern upper ridge at bay to the north and resulting in upper convergence between the new southern Gulf upper vortex and south side of the upper ridge such that tropical low Invest 92-L has weakened into a remnant surface trough. Therefore this system is no longer expected to become a tropical cyclone and I have dropped 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 1200Z and 1332Z-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 EDOUARD...
Current Prognosis...As of the 11 AM EDT NHC advsiory...the center of Edouard was located at 24.7N-50.7W with maximum sustained winds rising to 80 mph...classifying Edouard as the fourth category 1 hurricane of the 2014 Atalntic season. Edouard has been displaying a small eye on visible satellite with showers and thunderstorms remaining well organized around the center...albeit still a bit lopsided toward the north side of the circulation as this system is in a very light southerly shear environment between the west edge of the eastern tropical Atlantic upper ridge (marked by blue H and blue-zig-zag line in the above atmospheric features chart) and east side of a large upper vortex over the western Atlantic (marked by blue L). The northwest track of the hurricane has allowed it to pass northeast of the dry Saharan air seen in the above thermodynamics chart...and now that Edouard is just north of the dry air the light southerly shear has allowed some of this dry air to wrap into Edouard's southern circulation. The cyclonic spin of the hurricane has very recently pulled this dry air into its east side such that the cloud bands east of the eye are weaker. Meanwhile with Edouard over very favorable 30 deg C waters...their have been some hot tower bursts appearing on the west side of the eye.

Atmospheric Outlook for the Forecast Period...Because this system is strong/tall enough to feel a poleward tug on the east side of the large western Atlantic upper vortex...the upper vortex in conjunction with the 1032 mb low-level ridge to the north (makred by red H) is currently pushing this system on a northwest track. By 24 to 48 hours this system should be bending on a more north-northwest track in response to an expanding low-level ridge weakness progged to occur in the northwest Atlantic. This ridge weakness will be associated with the shortwave upper trough/1016 mb frontal depression left behind over the NE US/SE Canada by the frontal cyclonic system over southern Greenland. Between 48 and 72 hours...what is now the 1029 mb ridge over the NE US will pass Edouard to the north which will keep the track generally north around 55W longitude...followed by another weakness coming in from the northwest associated with the 1012 mb frontal depression and upper trough seen in the top-left of the above atmo chart which will carry Edouard northeastward and eventually eastward after 72 hours. Between now and 48 hours Edouard will be in a low shear environment characterized by upper anticyclonic flow that will allow additional strengthening...followed by the arrival of light southwesterly shear well in advance of the upper trough associated with the above-mentioned second ridge weakness by 72 hours. Edouard will be in a hostile westerly shear environment on the south side of the upper trough by 96 and 120 hours.

Thermodynamic Outlook for the Forecast Period...This system is currently over very favorable 29 to 30 deg C water...with the forecast track taking this system to 28 deg C waters by 72 hrs and to even less favorable 26 deg C waters by 96 hours. By the end of the forecast period Edouard will be over waters in the low 20s of deg C that will no longer be supportive of a tropical system. Humidity for Edouard should be becoming increasingly favorable thru the forecast period as the hurricane edges northward and away from the dry Saharan air to the south.



Track Forecast...Edouard is a tad north and east of my previous forecast track and therefore my updated forecast is a slight north and east adjustment from my previous and generally agrees with the NHC track forecast. The current norhtwest trajectory will gradually bend north and then east thru the forecast period due to the forecast influences discussed in detail in the above atmospheric outlook section.

Intensity Forecast...Edouard is stronger than my previous intensity forecast as the amount of favorable upper anticyclonic flow over Edouard has been trending increasingly stronger than previously forecast for the current timeframe. Therefore wind shear will now no longer be an issue for this storm until 72 hours...and therefore I show slow strengthening to a high-end category 1 (90 mph max sustained winds) by 24 hours...followed by more rapid strengthening to a high-end category 2 (110 mph max susatained winds) by 48 hours after Edouard distances itself from the dry air to the south. By 72 hours I keep the intensity flattened due to the arrival of light southwesterly shear as mentioned in the above atmo outlook section...followed by weakening as Edouard enters an environment of hostile westerly shear and cooler water temperatures. I disagree with the NHC on making Edouard evolve into a non-tropical cyclone supported by an upper trough at 120 hours as I believe the above forecast track will keep Edouard too far south of the eastern divergence zone of the upper trough its traveling with. Instead I simply believe Edouard will degenerate into a thounderstorm-free cloud swirl low northwest of the Azores just beyond the forecast period. On a final note...I maybe giving too much credence to the dry air and Edouard could strengthen more than I predicted during the next 24 hours...hence allowing Edouard to become a major hurricane (category 3 or greater with 115+ mph winds) as the 11 AM EDT NHC forecast suggested. If this happens...Edouard will be the first major hurricane in the Atlantic basin since Sandy nearly two years ago in October 2012.

Impact Forecast...Impact swath in the above forecast graphic is an extrapolation of the 11 AM EDT NHC tropical storm wind field along my forecast track...with some narrowing of the swath at the end of the forecast to reflect Edouard's forecast weakening. Sea swells around the hurricane are currently underway. Even though Edouard is expected to pass well east of Bermuda...the strength of the storm will allow swells to reach the island as noted in impact statement (b). Swells can be expected to reach the shores of the Azores by the end of the forecast period as well.

2014 Atlantic Hurricane Season Birdseye Discussion #90

By: NCHurricane2009, 12:58 PM GMT on September 13, 2014

...SATURDAY SEPTEMBER 13 2014 9:00 AM EDT...
Tropical Storm Edouard continues to gradually stregnthen over the open Atlantic and is expected to become a hurricane. See first special feature section below for an update on this system. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

The tropical wave in the eastern tropical Atlantic has passed south of the Cape Verde Islands...and has become better organized such that it has been upgraded to Invest 93-L on the Naval Research Laboratory (NRL) site of the US Navy. See third special feature section below for an update on this system.

Tropical low Invest 92-L is emerging into eastern Gulf of Mexico from the Florida peninsula this morning. This system is at risk of tropical cyclone formation over the next few days while across the Gulf of Mexico. Interests in the Gulf and western US Gulf coast should continue to monitor the progress of this system. See second special feature section below for additional details.

An upper vortex was noted over Cuba in the intro section of discussion #87 (September 9) whose western end was fracturing into a seperate upper vortex tracking westward across the southwestern Gulf of Mexico. A surface tropical wave located in the middle of the upper vortex split has been taking advantage of upper divergence and an upper ridge that has been growing between the two upper vorticity lobes over the last few days...resulting in a mass of showers and thunderstorms that have tracked across the western Caribbean...Yucatan Peninsula...and into the southwestern Gulf of Mexico since September 9. Since then the Cuba upper vortex has dissipated and the western split of the upper vortex has made landfall in Mexico...with a new tropical disturbance (desiganted as Invest 94-L) in the southwestern Gulf tracking northwestward on the east side of the Mexico upper vortex and south side of current 1031 mb ridge over the central US. Even though this system is currently more impressive than disturbance Invest 92-L in the eastern Gulf...tropical cyclone formation is not expected as this system will not have enough time over water to develop while the continued norhtwest track will cause landfall in northeastern Mexico in the next 24 hours.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...

This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and 0118Z-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 EDOUARD...
Current Prognosis...As of the 5 AM EDT NHC advsiory...the center of Tropical Storm Edouard was located at 20.7N-46.2W with maximum sustained winds rising to 50 mph. Showers and thunderstorms continue to remain well organized around the center...albeit a bit lopsided toward the north side of the circulation as this system is in a light southerly shear environment between the west edge of the eastern tropical Atlantic upper ridge (marked by blue-zig-zag line in the above atmospheric features chart) and east side of a large upper vortex over the western Atlantic (marked by blue L).

Atmospheric Outlook for the Forecast Period...Because this system is strong/tall enough to feel a poleward tug on the east side of the large western Atlantic upper vortex...the upper vortex in conjunction with the 1024 mb low-level ridge to the north (makred by red H) is currently pushing this system on a west-northwest to northwest track. By 72 to 96 hours this system should be bending on a more north-northwest track in response to an expanding low-level ridge weakness progged to occur in the northwest Atlantic. The seed for this ridge weakness will be a cut-off of the frontal boundary currently associated with the 982 mb south Greenland frontal cyclone...which will grow into a ridge weakness by 72 hours with the support of eastern divergence of an upper trough (which is about to arrive in the above atmo chart). Between 72 and 96 hours...this weakness and a small low-level ridge will pass Edouard to the north with another weakness coming in from the northwest associated with a frontal cyclone more directly associated with the upper trough. The presence of the passing low-level ridge will keep the some west component in the track between 72 and 96 hrs. Between 96 and 120 hrs Edouard should accelerate northeastward on the southeast side of the frontal cyclone and upper trough coming in from the northwest. Between now and 48 hours the southerly shear currently affecting Edouard will get stronger as Edouard nears the east side of the western Atlantic upper vortex. By 72 hours Edouard should have moved far north enough to escape the upper vortex such that shear becomes absent...followed by the arrival of light southwesterly shear well in advance of the upper trough forecast to come in from the northwest by 96 hours. As the upper trough gets closer to Edouard the southwesterly shear over Edouard will be stronger by 120 hours.

Thermodynamic Outlook for the Forecast Period...This system is currently heading to very favorable 29 to 30 deg C water...with the forecast track taking this system to 28 deg C waters by 96 hrs and to even less favorable 26 deg C waters by the end of the forecast period (120 hrs). So far Edouard's moisture field has been strong enough to handle what is left of the adjacent dry Saharan air layer seen to the west of Edouard in the above thermo chart...with the current assumption that this system will continue to have a strong enough moisture field such that this dry air is assumed to be a non-factor for Eduoard thru the forecast period.



Track Forecast...Edouard is a little north and west of my previous forecast track and therefore my updated forecast track thru 96 hrs is an up and left adjustment from my previous. My forecast position is southwest of the NHC'S at 96 hours as I believe their should be some westward component to the storm track between 72 and 96 hrs as outlined in the above atmospheric outlook section. Therefore my final 120 hr forecast point is also a bit southwest of the NHC's 120 hr point.

Intensity Forecast...Intensity of this system has been almost on par with my previous forecast...so my updated intensity forecast shown above is the same as previous thru 24 hours. Previously was anticipating Edouard to weaken a little during the timeframe that is now 24 to 48 hrs...however the latest GFS computer model shows stronger upper anticyclonic flow over Edouard and a weaker western Atlantic upper vortex such that I think the shear will be less than previously thought. Therefore my intensity forecast between 24 and 48 hrs shows Edouard maintaining strength instead of weakening...resulting in a slightly higher intensity forecast for 72 and 96 hrs. Strengthening rate is slowed at 96 hrs due to light southwesterly shear described at the end of the above atmo outlook section...followed by weakening at 120 hrs due to cooler sea-surface temps and stronger shear as the upper trough nears.

Impact Forecast...Impact swath in the above forecast graphic assumes tropical storm wind field will gradually grow in size in accordance with the above intensity forecast which calls for this system to strengthen. Impact swath follows my forecast track...and for the first 48 hours is biased to the right side of the track to reflect a system that is under southerly shear. The swath becomes more symmetric about the track at 72 hours to reflect a forecast reduction in shear...followed by the swath becoming a bit slanted to the right of the forecast track at 96 hours to reflect the development of light southwesterly shear (swath is symmetric about the forecast track at 120 hrs as the northeastward track lines up with the southwesterly shear vector). Sea swells can be expected if this system follows the above intensity forecast. Even though Edouard is expected to pass well east of Bermuda by the end of the forecast period...the storm could still be close enough to the island such that some swells reach the island as noted in impact statement (b).

...SPECIAL FEATURE...TROPICAL LOW INVEST 92-L...
Current Prognosis...A compact cloud swirl surface tropical low that is around 1011 mb in central pressure is emerging from the Florida peninsula and into the eastern Gulf of Mexico...and was centered at 26.5N-83.5W as of 0600Z early this morning. This is south and east of my previous forecast track...and therefore my updated forecast track below is adjusted accordingly. This system is under a divergent upper northeasterly flow between a large western Atlantic upper vortex (marked by blue L to the east of 92-L in the above atmo chart) and southeastern US upper ridge (marked by blue H and blue zig-zag line). The divergent nature of the upper flow is supporting showers and thunderstorms in 92-L's circulation...but the northeasterly shearing nature of the upper flow is keeping the a recent flare up of banding showers and thunderstorms biased to the southwest half of the circulation. Another batch of showers and thunderstorms continues to trail behind this circulation...currently located over the western Bahamas. Currently assuming that this is no longer part of 92-L...but instead a seperate area associated with split flow upper divergence between the western Atlatnic upper vortex and SE US upper ridge.

Atmospheric Outlook for the Forecast Period...The warm air mass south of the 982 mb south Greenland frontal cyclone will get pushed southward ahead of the frontal cyclone's cold front...with the associated SE US upper ridge shifting southward into the northern Gulf of Mexico such that the current northeasterly shear is expected to be lower when this system arrives into the central Gulf and below the upper ridge. Impressive 1031 mb ridge over the central US will steer this system westward early in the forecast period. By the middle of the forecast...eastern divergence of an upper trough (that is about to arrive in the above atmo chart) will weaken the ridge which in turn will bend the track more northward. A low-level ridge is progged to quickly build on the western convergent back side of this upper trough...but the track should continue to be west-northwest to northwest on the SW quad of this ridge. This track will cause this system to enter westerly shear on the northwest side of the northern Gulf upper ridge at the end of the forecast period...limiting strengthening of this system as it moves into the Texas Gulf coast.

Thermodynamic Outlook for the Forecast Period...This system will track over very favorable 31 deg C waters across the Gulf of Mexico. Moisture should not be an issue as Invest 94-L to the southwest has moistened the environment ahead of this system.

24 Hr Forecast (0600Z September 14)...30 mph max sustained wind tropical depression under lighter northeasterly shear in the central Gulf of Mexico at 26.5N-88W. System reaching favorable conditions while headed to the core of favorable north Gulf upper ridge and over 31 deg C waters.

48 Hr Forecast (0600Z September 15)...50 mph max sustained wind tropical storm centered in the northwestern Gulf of Mexico just south of Louisana at 27.5N-92.5W

72 Hr Forecast (0600Z September 16)...50 mph max sustained wind tropical storm under westerly shear moving west-northwest to northwest toward the Texas coast centered at 29N-95W

96 Hr Forecast (0600Z September 17)...Remnant low over central Texas centered at 31N-99W dissipating under hostile westerly shear

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE INVEST 93-L...
Current Prognosis...On cue with my previous forecast this tropical wave has organized into a tropical low pressure center. As of 0600Z the NHC TAFB evaluated it as a 1009 mb center located at 12.5N-28W. Satellite imagery concurs and shows a small round burst of showers and thunderstorms over and west of the center. This system is located a bit further north than my previous forecast and therefore the forecast track below is adjusted accordingly.

Atmospheric Outlook for the Forecast Period...This system has the potential to take advantage of low shear and enhanced outflow beneath an eastern tropical Atlantic upper ridge (marked by blue zig zag line in the lower right of the above atmo chart). A piece of upper vorticity associated with the 982 mb south Greenland frontal cyclone system is progged to rapidly dive southward on the west side of the NE Atantic deep-layered vortex...then dive southwestward on the southeast side of Edouard's upper anticyclonic outflow. The GFS computer model has trended faster with this upper vorticity such that I now forecast this system to get hit with northerly and northeasterly shear by the end of the forecast period when the upper vorticity comes into this system from the northeast. Forecasting a west to west-northwest track on the south side of the 1024 mb Atlantic subtropical ridge...followed by a more northwest track by the end of the forecast while getting caught into a large ridge weakness caused by Edouard's low pressure field and the surface non-tropical low pressure features pulling Edouard northward.

Thermodynamic Outlook for the Forecast Period...System will be over favorable 28 to 29 deg C waters thru the forecast period...arriving to 30 deg C water by the end of the period...if it follows the forecast track listed below. Edouard has moistened the enviornment ahead of this system as shown in the lower-right of the above thermodynamics chart...and therefore dry air is unlikely to be a problem for this system thru the forecast period.

24 Hr Forecast (0600Z September 14)...Organized tropical low centered at 13.5N-33.5W

48 Hr Forecast (0600Z September 15)...40 mph max sustained wind tropical storm centered at 14.5N-39W

72 Hr Forecast (0600Z September 16)...50 mph max sustained wind tropical storm centered at 16.5N-44W

96 Hr Forecast (0600Z September 17)...50 mph max sustained wind tropical storm under a burst of northerly shear centered at 19N-49W

120 Hr Forecast (0600Z September 18)...50 mph max sustained wind tropical storm under lighter northeasterly shear centered at 21.5N-54W

2014 Atlantic Hurricane Season Birdseye Discussion #89

By: NCHurricane2009, 5:55 AM GMT on September 12, 2014

...FRIDAY SEPTMEBER 12 2014 2:00 AM EDT...
Tropical wave Invest 91-L has intensified into the sixth tropical depression of the Atlantic hurricane season as expected. As of the recent 11 PM EDT National Hurricane Center advisory...the depression has become Tropical Storm Edouard. See first special feature section below for an update on this system. Visit www.nhc.noaa.gov for up to the minute latest information on Edouard.

A tropical wave has recently emerged from western Africa and is currently located south-southeast of the Cape Verde Islands. Because this tropical wave had prior computer model support (from the GFS and CMC) and because this system has become better organized in the last 24 hours...I have upgraded it to a special feature on this blog. See third special feature section below for additional details.

Tropical low Invest 92-L is moving into the Florida peninsula this evening as previously forecast. This system is at risk of tropical cyclone formation over the next few days while moving into the northern Gulf of Mexico. Interests in the northern Gulf and US Gulf coast should continue to monitor the progress of this system. See second 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 0000Z and 0121Z-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 EDOUARD...
Current Prognosis...As of the 11 PM EDT NHC advsiory...the center of newly-named Tropical Storm Edouard was located at 17.3N-39.4W. Showers and thunderstorms remain well organized around the center...albeit a bit lopsided toward the north side of the circulation as this system is in a light southerly shear environment between the west edge of the eastern tropical Atlantic upper ridge (marked by blue-zig-zag line in the above atmospheric features chart) and east side of a large upper vortex over the western Atlantic (marked by blue L and series of blue dashed lines around the blue L).

Atmospheric Outlook for the Forecast Period...Because this system is strong/tall enough to feel a poleward tug on the east side of the large western Atlantic upper vortex...the upper vortex in conjunction with the 1023 to 1026 mb low-level ridge to the north (makred by red Hs) is currently pushing this system on a west-northwest to northwest track. By 72 hours this system should be curving on a more northwest track while arrving to the east side of the upper vortex. By 96 to 120 hours this system should be bending on a more north-northwest track in response to an expanding low-level ridge weakness progged to occur in the northwest Atlantic. The seed for this ridge weakness will be a cut-off of the frontal boundary currently associated with the 986 mb east Canada frontal cyclone...which will grow into a ridge weakness by 96 hours with the support of eastern divergence of an upper trough (which has yet to arrive in the above atmo chart). Between 96 and 120 hours...this weakness and a small low-level ridge will pass Edouard to the north with another weakness coming in from the northwest associated with a frontal cyclone more directly associated with the upper trough. The presence of the passing low-level ridge will keep the track north-northwest between 96 and 120 hrs. Between now and 24 hours Edouard will remain in a light southerly shear environment as described in the above current prognosis section...with the shear by 48 hours being stronger and more southwesterly while arriving to the SE quadrant of the upper vortex. With the storm track being northwest and arriving into a southerly shear vector on east side of the upper vortex by 72 hours...the shear vector will be more aligned with the storm track such that the shear is less severe by that time. By 96 hours Edouard should have moved far north enough to escape the upper vortex such that shear becomes absent...followed by the arrival of light southwesterly shear well in advance of the upper trough forecast to come in from the northwest by 120 hours.

Thermodynamic Outlook for the Forecast Period...This system is currently over 27 deg C water...with the forecast track taking this system toward even more favorable 29 to 30 deg C water by the middle of the forecast period....then to 28 deg C water by the end of the forecast. So far this system's moisture field has been strong enough to handle the adjacent dry Saharan air layer seen to the west of this system in the above thermo chart...with the current assumption that this system will continue to have a strong enough moisture field such that this dry air is assumed to be a non-factor for Eduoard thru the forecast period.



Track Forecast...Edouard is a little north and east of my previous forecast track...and the northward slant in the track has ramped up to 2N per day instead of my previously forecasted 1N per day. Therefore I have adjusted my forecast track to the right of my previous forecast accordingly. Forecast track is a west-northwest to northwest trajectory for the first 48 hours...with a track that gradually bends north-northwest by the end of the forecast due to the influences discussed in the above atmospheric outlook section.

Intensity Forecast...Intensity of this system has been almost on par with my previous forecast...so my updated intensity forecast shown above is the same as previous thru 48 hours. Because my updated forecast track is further north than my previous...the shear vector by 72 hours is to be more aligned with the storm track and hence less severe for Edouard than previously thought as described in the above atmo outlook section. Therefore my intensity forecast by 72 hours is upped from my previous but still predicts a little weakening from the shear between 48 and 72 hours. The upped intensity forecast means I now predict Edouard to reach hurricane strength by 96 hours when he escapes shear altogether and moves across 29 to 30 deg C waters...followed by a much slower strengthening rate by 120 hours due to light southwesterly shear described at the end of the above atmo outlook section.

Impact Forecast...Impact swath in the above forecast graphic assumes tropical storm wind field will gradually grow in size in accordance with the above intensity forecast which calls for this system to strengthen. Impact swath follows my forecast track...and for the first 72 hours is biased to the right side of the track to reflect a system that is under southerly to southwesterly shear. The swath becomes more symmetric about the track at 96 hours to reflect a forecast reduction in shear...followed by the swath becoming a bit slanted to the right of the forecast track at 120 hours to reflect the development of light southwesterly shear. Sea swells can be expected if this system follows the above intensity forecast. Even though Edouard is expected to pass well east of Bermuda by the end of the forecast period...the storm could still be close enough to the island such that some swells reach the island as noted in impact statement (b).

...SPECIAL FEATURE...TROPICAL LOW INVEST 92-L...
Current Prognosis...A compact cloud swirl surface tropical low that is around 1012 mb in central pressure is making landfall on the east coast of the Florida peninsula near 27.5N-81w this evening. This remains on my previous forecast track...and therefore my updated forecast track below is a continuation of my previous. This system is under a divergent upper northerly flow between a large western Atlantic upper vortex (marked by blue L to the east of 92-L in the above atmo chart) and southeastern US upper ridge (marked by blue H and blue zig-zag line). The divergent nature of the upper flow is supporting showers and thunderstorms in 92-L's circulation...but the northerly shearing nature of the upper flow is keeping the showers and thunderstorms biased to the south side of the circulation. Radar has been showing bands of showers moving across southeastern Florida over the last several hours...with another batch of activity currently seen in satellite imagery to the east of the western Bahamas. The development of northerly shear...lack of tropical cyclone formation...and current land interaction with the Florida peninsula have caused me to delay the forecast time of tropical cyclone formation and show a weaker intensity forecast from my previous.

Atmospheric Outlook for the Forecast Period...The warm air mass south of the 986 mb east Canada frontal cyclone will get pushed southward ahead of the frontal cyclone's cold front...with the associated SE US upper ridge shifting southward into the northern Gulf of Mexico such that the current northerly shear is expected to be lower when this system arrives into the northern Gulf and below the upper ridge. The 986 mb east Canada frontal cyclone is rapidly ejecting northeastward with an impressive 1036 mb ridge building behind that will steer this system westward into and across the northern Gulf of Mexico early in the forecast period. By the middle of the forecast...eastern divergence of an upper trough (that has not yet arrived in the above atmo chart) will weaken the ridge which in turn will bend the track to the northwest. A low-level ridge is progged to quickly build on the western convergent back side of this upper trough...but the track should continue northwest on the SW quad of this ridge. The northwest track will cause this system to enter westerly shear on the north side of the northern Gulf upper ridge at the end of the forecast period...limiting strengthening of this system as it moves into the US Gulf coast.

Thermodynamic Outlook for the Forecast Period...After crossing the Florida Peninsula...this system will track over very favorable 31 deg C waters currently in the northern Gulf of Mexico.

24 Hr Forecast (0000Z September 13)...Tropical low under northerly wind shear centered in the northeastern Gulf of Mexico at 27.5N-85W.

48 Hr Forecast (0000Z September 14)...30 mph max sustained wind tropical depression under lighter northerly shear in the north-central Gulf of Mexico at 27.5N-89W. System reaching favorable conditions while headed to the core of favorable north Gulf upper ridge and over 31 deg C waters.

72 Hr Forecast (0000Z September 15)...50 mph max sustained wind tropical storm centered in the northwestern Gulf of Mexico just south of Louisana at 28N-93W

96 Hr Forecast (0000Z September 16)...50 mph max sustained wind tropical storm under westerly shear moving northwestward and making landfall at the Texas/Louisana border centered at 30N-94.5W

120 Hr Forecast (0000Z September 17)...Remnant low over eastern Texas centered at 32N-97W dissipating under hostile westerly shear

...SPECIAL FEATURE...EASTERN ATLANTIC TROPICAL WAVE...
Current Prognosis...A tropical wave in the eastern tropical Atlantic is located south-southeast of the Cape Verde Islands at longitude 22.5W as of 0000Z. The organization of the associated compact shower and thunderstorm field suggests the vorticity maximum of this tropical wave is along 11N latitude. Since the tropical wave appeared to be along the west coast of Africa around 17W as of 24 hours ago...this is a daily rate of progression of 5W to 5.5W upon which the forecast track below is based on.

Atmospheric Outlook for the Forecast Period...This system has the potential to take advantage of low shear and enhanced outflow beneath an eastern tropical Atlantic upper ridge (marked by blue zig zag line in the lower right of the above atmo chart) just like we recently saw with the formation of Tropical Storm Edouard. In fact conditions could be more favorable for this system than with Edouard because the large western Atlantic upper vortex currently shearing Edouard will be shrinking with the favorable tropical upper ridge expanding in its wake. Forecasting a west to west-northwest track on the south side of the 1023 to 1026 mb Atlantic subtropical ridge...followed by a more northwest track by the end of the forecast while getting caught into a large ridge weakness caused by Edouard's low pressure field and the surface non-tropical low pressure features pulling Edouard northward.

Thermodynamic Outlook for the Forecast Period...System will be over favorable 28 to 29 deg C waters thru the forecast period if it follows the forecast track listed below. Edouard has moistened the enviornment ahead of this system as shown in the lower-right of the above thermodynamics chart...and therefore dry air is unlikely to be a problem for this system thru the forecast period.

24 Hr Forecast (0000Z September 13)...Tropical low centered at 11.5N-28W

48 Hr Forecast (0000Z September 14)...Organized tropical low centered at 12N-33.5W

72 Hr Forecast (0000Z September 15)...40 mph max sustained wind tropical storm centered at 12.5N-39W

96 Hr Forecast (0000Z September 16)...50 mph max sustained wind tropical storm centered at 14.5N-44W

120 Hr Forecast (0000Z September 17)...65 mph max sustained wind tropical storm centered at 17N-49W

2014 Atlantic Hurricane Season Birdseye Discussion #88

By: NCHurricane2009, 3:18 AM GMT on September 11, 2014

...WEDNESDAY SEPTEMBER 10 2014 11:30 PM EDT...
Atlantic tropics heating up with three areas of interest as we are at the climatological peak of the hurricane season. In particular interests in Florida...the northern Gulf of Mexico...and US Gulf coast should pay attention to disturbance 92-L discussed in the second special feature section below.

After not developing for the last two and a half days...tropical wave Invest 91-L currently in the eastern tropical Atlantic is showing quick signs of organization over the last few hours and therefore tropical cyclone formation is possible at any time. See special feature section below for additional details on this tropical wave.

A tropical wave about to emerge from western Africa shows some signs of organization as a band of showers and thunderstorms starting east of Invest 91-L curls into the tropical wave axis. The GFS and CMC computer models over the last couple of days suggested that this system would develop in the envrionment behind 91-L. However the most recent runs of these models this evening have cancelled this idea...and therefore I have decided to not upgrade this tropical wave to a special feature on this blog.

The disturbance between a TUTT (Tropical Upper Troposhperic Trough) vortex over central Cuba and another TUTT upper vortex to the east has become much better organized and has been upgraded to Invest 92-L at a location just north of the western Bahamas. The development of this disturbance within the past 24 hours is due to the formation of a small shear-reducing/outflow-enhancing upper anticyclone that has formed in the wake of the dissipating Cuba upper vortex. In the next 24 hours...the upper vortex to the east will merge with a southern fracture of the current shortwave upper trough leaving the eastern US which will result in the formation of a large upper vortex over the western Atlantic. Previously was expecting this system to not develop while getting caught in unfavorable upper winds beneath the west side of the upper vortex...but with this system consolidated further north and west it now has the potential to develop in favorable upper winds located west of the upper vortex. Interests in Florida...the northern Gulf of Mexico...and US Gulf coast should pay careful attention to this system. See the second special feature section below for additional details.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_10_2014_2115Z_zps1bf1d1d1.png
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...
 photo Sep_10_2014_2115Z_Thermo_zps7cfca4ed.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL WAVE INVEST 91-L...
Current Prognosis...As of 1800Z the tropical wave in the eastern tropical Atlantic was producing a 1011 mb tropical low pressure spin located at 14N-34W that has become increasingly organized this past afternoon and through this evening. Even though this is 2 degrees south of my previous forecast for this timeframe...my updated forecast track below has a steeper northward incline such that it eventually re-aligns with my previous forecast track...then eventually becomes to the right (north) of my previous forecast. Justification for the more northward track mentioned in atmospheric outlook below.

Atmospheric Outlook for the Forecast Period...This system is currently forecast to take advantage of low shear and enhanced outflow beneath a tropical upper ridge...marked as a blue-zig-zag line in the lower-right of the above atmospheric features chart. 1031 mb low-level ridge to the north (makred as a red H) will push this system on a west to west-northwest track early in the forecast period. A southern fracture of the shortwave upper trough currently emerging from the eastern US (marked as a blue dashed line) will merge with a cut-off upper vortex north of the Lesser Antilles (marked as a blue L)...resulting in the formation of a large upper vortex over the western Atlantic. My previous forecast was on the left (south) side of the computer model guidance...and I have steepened the northward incline of my updated forecast track as I now understand that the computer models seem to suggest that this system will have become a tall/strong enough tropical cyclone to be tugged poleward by the east side of the forecast large upper vortex. By 96 hours my forecast shows the track going from west-northwest to northwest while arriving to east side of the upper vortex. By 120 hours I bend the track even more northward in response to an expanding low-level ridge weakness progged to occur in the northwest Atlantic. The seed for this ridge weakness will be a cut-off of the frontal boundary currently associated with the 995 mb central US frontal cyclone...which will grow into a ridge weakness by 120 hours with the support of eastern divergence of a shortwave upper trough (which has yet to arrive in the above atmo chart). My intensity forecast is upped from the previous due to the current amount of organization this system has...and also due to the more northward track allowing the vertical shear vector to be 90 degrees or less relative to the storm track on the east side of the upper vortex instead of a hostile westerly shear vector 180 degrees against the storm track on the south side of the upper vortex which is what my previous forecast track resulted in. I show re-strengthening by 120 hours as the north-northwest track by that time will allow the southerly shear vector to almost be aligned with the storm track such that the shear is reduced.

Thermodynamic Outlook for the Forecast Period...System is currently over favorable 27 to 28 deg C water...with the forecast track taking this system toward even more favorable 29 to 30 deg C water by the end of the forecast period. The fact that this system maybe near or over 30 deg C at the end of the forecast period is another reason I show re-strengthening in my 120 hour forecast below. So far this system's moisture field has been strong enough to handle the adjacent dry Saharan air layer seen to the west of this system in the above thermo chart...with the current assumption that this system will continue to have a strong enough moisture field such that it will develop into a tropical cyclone.

24 Hr Forecast (1800Z September 11)...40 mph max sustained wind tropical storm centered at 15N-39W

48 Hr Forecast (1800Z September 12)...50 mph max sustained wind tropical storm centered at 16N-44W

72 Hr Forecast (1800Z September 13)...65 mph max sustained wind tropical storm under southwesterly shear centered at 17N-49W

96 Hr Forecast (1800Z September 14)...50 mph max sustained wind tropical storm under southwesterly shear centered at 20N-52W

120 Hr Forecast (1800Z September 15)...60 mph max sustained wind tropical storm under southerly shear centered at 23.5N-54.5W

...SPECIAL FEATURE...TROPICAL LOW INVEST 92-L...
Current Prognosis...A compact cloud swirl surface tropical low has been seen in afternoon visible and nighttime infrared imagery passing just north of the western Bahamas...moving from 27N-76W as of 1800Z to 27.2N-77W as of 0000Z. That is a westward pace of 1W per 6 hours (or 4W per 24 hours) upon which the forecast track below is largely based upon. Organized showers and thunderstorms have been intermittenly flaring up on the northwest half of the cloud swirl surface low this past afternoon and through this evening.

Atmospheric Outlook for the Forecast Period...This system is currently below a small but favorable shear-reducing and outflow-enhancing upper anticyclone marked as a blue H over 92-L in the above atmospheric features chart. The warm air mass south of the 995 mb central US frontal cyclone will get pushed southward ahead of the frontal cyclone's cold front...with the associated SE US upper ridge (marked by blue H and blue-zig-zag line) shifting southward into the northern Gulf of Mexico and potentially providing more shear reduction and outflow enhancement as this system arrives into the northern Gulf. Low-level ridge weakness of 1010 mb frontal depression to the north is too weak to pull this system north such that the 1020 mb ridge currenlty over the SE US will push this system into the Florida peninsula and northeastern Gulf of Mexico. The 995 mb central US frontal cyclone will pass too far to the north to influence this system's track...resulting in this system continuing west while a rather strong low-level ridge builds across the US behind the frontal cyclone. At the end of the forecast period...eastern divergence of a shortwave upper trough (that has not yet arrived in the above atmo chart) will weaken the low-level ridging which in turn will bend the track to the northwest. The more northward track will cause this system to enter westerly shear on the north side of the northern Gulf upper ridge at the end of the forecast period...limiting strengthening of this system as it moves into the US Gulf coast.

Thermodynamic Outlook for the Forecast Period...This system will track over very favorable 30 to 31 deg C waters east of Florida and then across the northern Gulf of Mexico.

24 Hr Forecast (1800Z September 11)...35 mph max sustained wind tropical depression centered just offshore of the east coast of Florida at 27.5N-80W

48 Hr Forecast (1800Z September 12)...35 mph max sustained wind tropical depression centered in the northeastern Gulf of Mexico at 27.5N-84W recovering from earlier land interaction with the Florida peninsula.

72 Hr Forecast (1800Z September 13)...50 mph max sustained wind tropical storm centered in the north-central Gulf of Mexico at 27.5N-88W. System beginning on a brisk strengthening trend while headed to the core of favorable north Gulf upper ridge and over 31 deg C waters.

96 Hr Forecast (1800Z September 14)...70 mph max sustained wind tropical storm centered in the northwestern Gulf of Mexico at 27.5N-92W

120 Hr Forecast (1800Z September 15)...70 mph max sustained wind tropical storm under westerly shear moving northwestward into southwestern Louisiana centered at 29N-93.2W

2014 Atlantic Hurricane Season Birdseye Discussion #87

By: NCHurricane2009, 2:51 AM GMT on September 10, 2014

...TUESDAY SEPTEMBER 9 2014 10:51 PM EDT...
Tropical wave Invest 91-L currently in the eastern tropical Atlantic has not become better organized in the last two days...but remains at high risk for tropical cyclone formation as it continues across the tropical Atlantic over the next few days. See special feature section below for additional details on this tropical wave.

A surface trough over the eastern Bahamas has developed with the support of upper divergence between a TUTT (Tropical Upper Troposhperic Trough) vortex over central Cuba and another TUTT upper vortex to the east. This surface trough has become introduced into the National Hurricane Center Tropical Weather Outlook. Upper winds will become more favorable for development in the next 24 hours as the Cuba upper vortex weakens. However by 48 hours...the upper vortex to the east will merge with a southern fracture of the current shortwave upper trough over the eastern US which will result in the formation of a large upper vortex over the western Atlantic. This system should find itself in unfavorable upper winds beneath the west side of the forecast upper vortex by 48 hours and beyond and therefore tropical development from this system is not likely.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_09_2014_2215Z_zps5b25d863.png
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...
 photo Sep_09_2014_2215Z_Thermo_zpsfd76df9d.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL WAVE INVEST 91-L...
Current Prognosis...As of 1800Z the tropical wave in the eastern tropical Atlantic was analyzed by NHC TAFB to have a surface 1009 mb low pressure spin located at 14N-28W. The updated forecast track shown below is a continuation of the previous as this position is close to the previous forecast position for the current timeframe. The associated showers and thunderstorms have not become better organized in the last day and therefore the intensity forecast shown below is lowered from my previous.

Atmospheric Outlook for the Forecast Period...This system is currently forecast to take advantage of low shear and enhanced outflow beneath a tropical upper ridge...marked as a blue-zig-zag line in the lower-right of the above atmospheric features chart. The forecast track below shows the track bending more westward while escaping the deep-layered NE Atlantic vortex and becoming influenced by central Atlantic low-level subtropical ridging. Thru the forecast period...a southern fracture of the shortwave upper trough currently over the eastern US will merge with a TUTT (Tropical Upper Tropospheric Trough) vortex currently NE of the Lesser Antilles...resulting in the formation of a large upper vortex over the western Atlantic. Meanwhile the northern fracture of the eastern US shortwave will dive southward on the west side of the NE Atalntic deep-layered vortex and eventually connect with the east side of the forecast large upper vortex in the western Atlantic...resulting in an east-west TUTT whose south side is currently forecast to shear this system by the end of the forecast period if this system follows the forecast track shown below.

Thermodynamic Outlook for the Forecast Period...System is currently over favorable 28 deg C water...with the forecast track taking this system toward even more favorable 29 deg C water by the end of the forecast period. Dry saharan air to the west of this system currently seen in the above thermo chart has finished obliterating the shower and thunderstorm activity of tropical wave Invest 90-L...now leaving this system to battle the dry air on its own. So far this system's moisture field has been strong enough to handle the adjacent dry air...with the current assumption that this system will continue to have a strong enough moisture field such that it will develop into a tropical cyclone.

24 Hr Forecast (1800Z September 10)...Organized tropical low centered at 16N-34W...or west of the Cape Verde Islands

48 Hr Forecast (1800Z September 11)...35 mph max sustained wind tropical depression centered at 17N-39W

72 Hr Forecast (1800Z September 12)...50 mph max sustained wind tropical storm centered at 17.5N-44W

96 Hr Forecast (1800Z September 13)...60 mph max sustained wind tropical storm under southwesterly shear centered at 18N-49W

120 Hr Forecast (1800Z September 14)...45 mph max sustained wind tropical storm under westerly shear centered at 18.5N-54W

2014 Atlantic Hurricane Season Birdseye Discussion #86

By: NCHurricane2009, 1:14 AM GMT on September 09, 2014

...MONDAY SEPTEMBER 8 2014 9:14 PM EDT...
Tropical wave Invest 91-L currently in the eastern tropical Atlantic has not become better organized in the last 24 hours...but remains at high risk for tropical cyclone formation as it continues across the tropical Atlantic over the next few days. See special feature section below for additional details on this tropical wave.

While merging with a surface frontal boundary pusing in from the northwest...the surface low just inland of coastal Georgia has moved northeastward on an inland track into the far eastern Carolinas. This system is expected to remain on an inland track for most of its lifespan and therefore tropical development from this system is no longer possible.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_08_2014_2215Z_zps21880eda.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and the 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...
 photo Sep_08_2014_2215Z_Thermo_zpsfbc7a8e9.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL WAVE INVEST 91-L...
Current Prognosis...As of 1800Z the tropical wave in the eastern tropical Atlantic was analyzed to have a surface 1009 mb low pressure spin located at 11N-23W. This position is a bit southeast of what I previously forecast...and therefore the forecast points below are adjusted accordingly. The associated showers and thunderstorms have not become better organized in the last day and therefore I have delayed the predicted time of tropical cyclone formation a little bit compared to my previous forecast.

Atmospheric Outlook for the Forecast Period...This system is currently forecast to take advantage of low shear and enhanced outflow beneath a tropical upper ridge...marked as a blue-zig-zag line and blue H in the lower-right of the above atmospheric features chart. Meanwhile the deep-layered 1004 mb vortex in the northeastern Atlantic will become re-enforced by the upper trough that has recently emerged into the north-central Atlantic from northeastern North America. Therefore the forecast track below shows a more northwest track while influenced by the ridge weakness of the deep-layered vortex thru 48 hours...followed by a more westward track from 72 to 120 hours while escaping the deep-layered vortex and becoming influenced by central Atlantic low-level subtropical ridging.

Thermodynamic Outlook for the Forecast Period...The forecast track below will take this system across 29 deg C waters early in the forecast period...across 28 deg C waters during the middle of the forecast period....then back to 29 deg C waters by the end of the forecast period. Therefore water temps will be more than favorable for supporting development of this system. Previously have noted a tongue of dry Saharan air between this tropical wave and tropical wave 90-L. Checking in with the above thermodynamics chart suggests this dry air has weakened in the last day while the moisture field of this system and 90-L have worked together to progressively weaken the dry Saharan air over the last few days. However it is possible that the fight with the dry air maybe why this system has not become any better organized within the last day as noted in the above current prognosis section.

24 Hr Forecast (1800Z September 9)...Tropical low centered at 14N-29W...southwest of the Cape Verde Islands

48 Hr Forecast (1800Z September 10)...Organized tropical low centered at 16N-34W...or west of the Cape Verde Islands

72 Hr Forecast (1800Z September 11)...45 mph max sustained wind tropical storm centered at 17N-39W

96 Hr Forecast (1800Z September 12)...60 mph max sustained wind tropical storm centered at 17.5N-44W

120 Hr Forecast (1800Z September 13)...70 mph max sustained wind tropical storm centered at 18N-49W

2014 Atlantic Hurricane Season Birdseye Discussion #85

By: NCHurricane2009, 9:23 PM GMT on September 07, 2014

...SUNDAY SEPTEMBER 7 2014 5:30 PM EDT...
Vigorous tropical wave Invest 90-L currently west of the Cape Verde Islands has seen a reduction in showers and thunderstorms while encountering low-latitude dry Saharan air seen in the thermodynamics chart below...and therefore tropical cyclone formation from this system is not expected.

Another vigorous tropical wave with widespread showers and thunderstorms is emerging from western Africa and has been upgraded to Invest 91-L on the Naval Research Laboratory (NRL) site of the US Navy. Their is a high risk of tropical cyclone formation from this system as it moves across the eastern and central tropical Atlantic over the next few days. See special feature section below for additional details on this tropical wave.

In the next 24 hours...the surface low pressure center just inland of coastal Georgia will be merging with the frontal boundary currently associated with the 985 mb frontal cyclone that has just emerged into the far north Atlantic from eastern Canada. This merger will potentially create the seed for a tropical disturbance offshore of the southeastern US taking advantage of low shear/enhanced outflow of an upper ridge in the area (marked by blue-zig-zag line in the atmospheric features chart below). Just after conditions become favorable for development in 24 hours...a shortwave upper trough (created by some upper vorticity left behind by the frontal cyclone's upper trough) will rapidly come in from the west...with the upper convergence on the west side of the shortwave supporting a surface ridge to the northeast after it passes. Coupled with another surface frontal cyclone arriving into the central US by that time...any tropical system that does develop will move north-northeast between the surface ridge and frontal cyclone on a track passing offshore of the Carolinas and northeastern US coast...and moving into Atlantic Canada by the timeframe that is 4 days from now. This track brings some uncertainty in tropical development as it would be quickly arriving to waters below 26 deg C and unfavorable westerly shear north of the upper ridge...and it is possible such a system arriving to Atlantic Canada would be a system that has transitioned to non-tropical with the support of a shortwave upper trough in the upper-level westerlies.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_07_2014_1415Z_zpse766e63c.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and the 1336Z-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...
 photo Sep_07_2014_1415Z_Thermo_zps3663a16b.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL WAVE INVEST 91-L...
Current Prognosis...As of 1200Z a tropical wave emerging from western Africa was analyzed by the NHC TAFB to be at 17W longitude. This position is about 3W longitude further west of what I was previously forecast...and therefore the forecast points below are adjusted 2W to 3W from the previous. The organization of the associated showers and thunderstorms suggests the vorticity maximum of the tropical wave is located at approximately 10N latitude.

Atmospheric Outlook for the Forecast Period...This system is currently forecast to take advantage of low shear and enhanced outflow beneath a tropical upper ridge...marked as a blue-zig-zag line and blue H in the lower-right of the above atmospheric features chart. Meanwhile the deep-layered 1005 mb vortex in the northeastern Atlantic is becoming re-enforced by a passing north-central Atlantic upper trough...and will become further re-enforced by the upper trough currently over northeastern North America. Therefore the forecast track below shows this system bending northwest from 24 to 72 hours...and then bending more westward in track by 96 to 120 hours while escaping the deep-layered vortex and becoming influenced by central Atlantic low-level subtropical ridging.

Thermodynamic Outlook for the Forecast Period...The forecast track below will take this system across 29 deg C waters early in the forecast period...and then 27 to 28 deg C waters for the remainder of the forecast period. It was previously expected that tropical wave Invest 90-L would moisten out the low-latitude dry Saharan air such that this system would have a chance to devlep behind 90-L. Instead the above thermodynamics chart shows that a new surge of dry Saharan air has shown up between this tropical wave and 90-L. Therefore even though I have kept the time of predicted tropical cyclone formation the same as before...I have slowed the intensification rate from my previous forecast.

24 Hr Forecast (1200Z September 8)...Tropical low centered at 12N-24W...south of the Cape Verde Islands

48 Hr Forecast (1200Z September 9)...Organized tropical low centered at 15N-30W...southwest of the Cape Verde Islands

72 Hr Forecast (1200Z September 10)...35 mph max sustained wind tropical depression centered at 17N-35W...or west of the Cape Verde Islands

96 Hr Forecast (1200Z September 11)...50 mph max sustained wind tropical storm centered at 18N-40W

120 Hr Forecast (1200Z September 12)...65 mph max sustained wind tropical storm centered at 18N-45W

2014 Atlantic Hurricane Season Birdseye Discussion #84

By: NCHurricane2009, 8:27 PM GMT on September 06, 2014

...SATURDAY SEPTEMBER 6 2014 4:27 PM EDT...
Vigorous tropical wave Invest 90-L currently west-southwest of the Cape Verde Islands has seen a flare up of concentrated showers and thunderstorms on the norhwest side of its circulation as it takes advantage of a low shear and enhanced outflow environment below a tropical upper ridge (marked by blue-zig-zag line and blue H in the lower right of the atmospheric features chart). The only computer model that currently supports development of this system is the usually overagressive CMC model. Even though this system may almost become a tropical cyclone...it is not likely to do so while encountering low-latitude dry Saharan air seen in the thermodynamics chart below.

Another vigorous tropical wave with widespread showers and thunderstorms is currently located over interior western Africa at 11W longitude and will have emerged into the eastern tropical Atlantic by 48 hours. With the Euro (ECMWF)...GFS...and NAVGEM computer models supporting this system...it has stronger computer model support than Invest 90-L. And since this tropical wave remains well organized while approaching the western African coast...I have upgraded it to a special feature on this blog. See special feature section below for additional details on this system.

A surface low pressure center just inland of coastal Georgia has been introduced into the National Hurricane Center Tropical Weather Outlook. This may have originated from the decay of the frontal boundary currently over the central Atlantic (marked by a red solid line in the atmospheric features chart below)...or may have orginiated from split flow upper divergence between an upper ridge over the southeastern US (marked by blue H) and TUTT (Tropical Upper Tropospheric Trough) upper vortex to the southeast (marked by blue L). Over the next 48 hours the frontal boundary currently associated with the 990 mb eastern Canada frontal cyclone will arrive into this area...potentially creating the seed for a tropical disturbance offshore of the southeastern UStaking advantage of low shear/enhanced outflow associated with the aforementioned southeastern US upper ridge. Just after conditions become favorable for development in 48 hours...a shortwave upper trough (created by some upper vorticity left behind by the frontal cyclone's upper trough) will rapdily come in from the west...with the upper convergence on the west side of the shortwave supporting a surface ridge to the northeast after it passes. Coupled with another surface frontal cyclone arriving into the central US by that time...any tropical system that does develop will move north-northeast between the surface ridge and frontal cyclone on a track passing offshore of the Carolinas and northeastern US coast...and moving into Atlantic Canada by the timeframe that is 5 days from now. This track brings some uncertainty in tropical development as it would be quickly arriving to waters below 26 deg C and unfavorable westerly shear north of the upper ridge...and it is possible such a system arriving to Atlantic Canada would be a system that has transitioned to non-tropical with the support of a shortwave upper trough in the upper-level westerlies.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_06_2014_1215Z_zps71244a3c.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and the 1330Z-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...
 photo Sep_06_2014_1215Z_Thermo_zps08d54733.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL WAVE OVER WESTERN AFRICA...
Current Prognosis...As of 1200Z a tropical wave with widespread showers and thunderstorms was located over western Africa at 7.5W longitude. The organization of the showers and thunderstorms suggests the vorticity maximum of the tropical wave is located at approximately 10N latitude. The more recent image of the tropical wave as of 1800Z suggests the tropical wave is located at approximately 11W longitude.

Atmospheric Outlook for the Forecast Period...This system is currently forecast to take advantage of low shear and enhanced outflow beneath a tropical upper ridge...marked as a blue-zig-zag line and blue H in the lower-right of the above atmospheric features chart. Meanwhile the deep-layered trough in the northeastern Atlantic currently featuring a 1005 mb vortex will be re-enforced by the current north-central Atlantic upper trough...and then by the upper trough currently over northeastern North America...thru the forecast period. Therefore the forecast track below shows this system bending northwest from 48 to 96 hours...and then bend more westward in track by 120 hours while escaping the deep-layered trough and becoming influenced by central Atlantic low-level subtropical ridging.

Thermodynamic Outlook for the Forecast Period...The forecast track below will take this system across 29 deg C waters early in the forecast period...and then 27 to 28 deg C waters for the remainder of the forecast period. Currently expecting tropical wave Invest 90-L to moisten out the low-latitude dry Saharan air currently seen in the above thermo chart such that this system has a chance to develop behind 90-L.

24 Hr Forecast (1200Z September 7)...Tropical wave emerging from the west African coast at 14W longitude

48 Hr Forecast (1200Z September 8)...Tropical low centered at 12N-21W...southeast of the Cape Verde Islands

72 Hr Forecast (1200Z September 9)...Organized tropical low centered at 15N-27W...just southwest of the Cape Verde Islands

96 Hr Forecast (1200Z September 10)...45 mph max sustained wind tropical storm centered at 17N-32W...or west of the Cape Verde Islands

120 Hr Forecast (1200Z September 11)...60 mph max sustained wind tropical storm centered at 18.5N-38W

2014 Atlantic Hurricane Season Birdseye Discussion #83

By: NCHurricane2009, 5:57 AM GMT on September 05, 2014

...FRIDAY SEPTEMBER 5 2014 2:00 AM EDT...
Vigorous tropical wave Invest 90-L currently passing over and south of the Cape Verde Islands has some computer model support for development while it moves into a favorable and expanding tropical upper ridge (marked by blue-zig-zag line and blue H in the lower right of the atmospheric features chart) in the eastern and central tropical Atlantic over the next few days. However the tropical wave has not become any better organized in the last day...and I am currently not upgrading this tropical wave to a special feature on this blog as the previous tropical waves have not developed while encountering low-latitude dry Saharan air seen in the thermodynamics chart below. Regardless of development...the low pressure center of the tropical wave will deliver showers and thunderstorms across the Cape Verde Islands over the next few hours.

Another vigorous tropical wave with widespread showers and thunderstorms is currently located over interior western Africa at 0W longitude and will have emerged into the eastern tropical Atlantic by 96 hours. This tropical wave has stronger computer model support than Invest 90-L perhaps as 90-L will have moistened out the dry Saharan air layer by the time this system enters the Atlantic. If the tropical wave remains well organized while approaching the western African coast...and if the dry air also weakens...then I will upgrade this tropical wave to a special feature on this blog.

Showers and thunderstorms have increased across the southern Caribbean over the last day with the support of an upper ridge (marked as a blue H in the atmospheric features chart below) that is expanding between two tropical upper tropospheric trough (TUTT) upper vortices...one marked as a blue L over western Cuba and another marked as a blue L in the western Atlantic. Watching to see if a tropical wave coming in from the east...marked as a red-dashed line to the right of the thunderstorm cluster...will help enhance this area of disturbed weather further...especially since the disturbance and favorable upper ridge will be moving westward in tandem. However their is a lack of computer model support perhaps as the models track this system over Central America and southeastern Mexico over the next 72 hours. By 96 and 120 hours as this system potentially reaches the Bay of Campeche and or southwestern Gulf of Mexico...a frontal cyclone is forecast to arrive over the central US with warm air advection ahead of it amplifying upper ridging over the southeastern US which in turn will amplify the TUTT across the Gulf of Mexico. Therefore the south side of the amplified TUTT will keep westerly shear too high for development of this system as it arrives into the Bay of Campeche and or southwestern Gulf.

Over the last few days...some runs of the CMC computer model have predicted that the frontal boundary currently associated with the central US 1002 mb frontal cyclone will stall offshore of the Carolina coast and provide a seed for tropical cyclone formation for the timeframe that is currently 84 hours away. Their is some plausibility to this scenario as the upper trough associated with the frontal cyclone is too low in amplitude to knock out the upper ridge over the southeastern US (marked by blue H in the atmospheric features chart below)...which will allow the frontal boundary to potentially take advantage of low shear/enhanced outflow associated with the upper ridge as it stalls offshore of the Carolinas. Just after conditions become favorable for development in 84 hours...the GFS computer model shows a shortwave upper trough (created by some upper vorticity left behind by the frontal cyclone's upper trough) rapidly coming in from the west...with the upper convergence on the west side of the shortwave supporting a surface ridge to the northeast after it passes. Coupled with another surface frontal cyclone arriving into the central US by that time...any tropical system that does develop will move north-northeast between the surface ridge and frontal cyclone on a track passing offshore of the Carolinas and northeastern US coast...and moving into Atlantic Canada by the timeframe that is one week from now. This track brings some uncertainty in tropical development as it would be quickly arriving to waters below 26 deg C and unfavorable westerly shear north of the upper ridge...and it is possible such a system arriving to Atlantic Canada would be a system that has transitioned to non-tropical with the support of a shortwave upper trough in the upper-level westerlies.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_05_2014_0115Z_zps9cc2d2f4.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and the 0126Z-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...
 photo Sep_05_2014_0015Z_Thermo_zpsa31fc62e.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

2014 Atlantic Hurricane Season Birdseye Discussion #82

By: NCHurricane2009, 11:11 AM GMT on September 04, 2014

...THURSDAY SEPTEMBER 4 2014 7:20 AM EDT...
Dolly weakens into a diminishing remnant low over central Mexico as expected.

Elsewhere...a vigorous tropical wave emerging from western Africa has some computer model support for development while it moves into a favorable and expanding tropical upper ridge (marked by blue-zig-zag line in the lower right of the atmospheric features chart) in the eastern and central tropical Atlantic over the next few days. The tropical wave has also become better organized while producing a low pressure spin currently located east-southeast of the Cape Verde Islands that has been upgraded to Invest 90-L on the Naval Research Laboratory site of the US Navy. However not currently upgrading this tropical wave to a special feature on this blog as the previous tropical waves have not developed while encountering low-latitude dry Saharan air seen in the thermodynamics chart below.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_04_2014_0615Z_zps53e60a33.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z and the 0721Z-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...
 photo Sep_04_2014_0615Z_Thermo_zps9d67f2cf.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

2014 Atlantic Hurricane Season Birdseye Discussion #81

By: NCHurricane2009, 11:00 AM GMT on September 03, 2014

...WEDNESDAY SEPTEMBER 3 2014 7:00 AM EDT...
Tropical depression five has become Tropical Storm Dolly moving into east-central Mexico since special update #80A as expected. See special feature section below for an update on Dolly.

A vigorous tropical wave currently over western Africa has some computer model support for development while it moves into the eastern and central tropical Atlantic over the next few days...most espcially from the most recent runs of the GFS computer model. However not currently upgrading this tropical wave to a special feature as the previous tropical waves have not developed while encountering low-latitude dry Saharan air seen in the thermodynamics chart below.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_02_2014_2045Z_zpsb2a52a49.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0000Z and the 0130Z-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...
 photo Sep_03_2014_0045Z_Thermo_zps27e9fc3e.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL STORM DOLLY...
Current Prognosis...As of 4 AM CDT the center of Tropical Storm Dolly is inland over east-central Mexico at 21.8N-98.4W after landfall earlier this evening. The shower and thunderstorm activity around the center is more symmetrically distributed than it has ever been as it is directly below a Gulf of Mexico upper ridge axis (marked by blue-zig-zag line in the above atmospheric features chart) as opposed to being under northerly shear south of the upper ridge axis as it was earlier.

Atmospheric Outlook for the Forecast Period...Even though the tropical cyclone is under a favorable shear-reducing and outflow enhancing upper ridge axis...this system is on its way to dissipation due to landfall and therefore the forecast period for this system is very short.

Thermodynamic Outlook for the Forecast Period...Thermodynamic parameters (sea-surface temperatures and humidity of the air) are no longer relevant to Dolly's strength as Dolly is now an inland tropical cyclone on its way to dissipation due to landfall.

 photo Sep_03_2014_TS_Dolly_Forecast_zps1fefcfb8.png

Track Forecast...After the NHC track and computer model consensus joined my more northward forecast track in special update #80A after the system's center re-generated northward...Dolly made another center reformation to the south just before landfall earlier this past evening...and therefore my updated track forecast above is a southward adjustment from my previous. Satellite animation shows a westward progession of 1 degree W longitude per 6 hours...and therefore my 1 AM CDT forecast point is a bit further west of the NHC's forecast as this system should arrive to 100W longitude by that time at this current westward speed.

Intensity Forecast...Dolly should dissipate very soon as it continues further inland as the above forecast suggests.

Impact Forecast...Impact swath shown in the above forecast graphic is the size of the tropical storm wind field as of the 4 AM CDT NHC advisory. I did not extrapolate that wind field further inland along the forecast track as Dolly is barely a tropical storm that is about to weaken to a tropical depression and subsequently a remnant low later today. Outer rains squalls surrounding the core have the potential to deliver flash flooding rains in east-central Mexico not only within the impact swath...but also outside the swath.

2014 Atlantic Hurricane Season Birdseye Discussion #80A (Special Update)

By: NCHurricane2009, 4:14 AM GMT on September 02, 2014

...TUESDAY SEPTEMBER 2 2014 12:15 AM EDT...
Tropical low pressure Invest 99-L has intensified into the fifth tropical depression of the 2014 Atlantic Hurricane Season since full discussion #80 and tropical storm warnings are in effect for a section of the east-central Mexico coast. See the special feature section below for an update on this situation. Visit www.nhc.noaa.gov for up-to-the-minute latest information on this system...including watches and warnings.

...SPECIAL FEATURE...TROPICAL DEPRESSION FIVE...
Current Prognosis...This past afternoon aircraft reconaissance fixed the center of tropical depression five further south compared to the visible satellite fixes referenced in the current prognosis section of this system in discussion #80. Since then a ball of thunderstorms have fired over the center seen earlier in visible satellite...and the National Hurricane Center as of 11 PM EDT (10 PM CDT) has adjusted their center fix further north in alignment with the earlier visible satellite fixes...placing the center at 21N-93.9W. Aircraft reconaissance is en route to verify the center has re-generated northward toward the earlier visible satellite fixes.

Atmospheric Outlook for the Forecast Period...This system will remain on the south side of Gulf upper ridging early in the forecast period...perhaps entering more favorable conditions at the end of the forecast period while the expected west-northwest to northwest track allows the system to slide directly below the upper ridge axis. The west-northwest to northwest steering is to be produced by the southwest side of subtropical low-level ridging.

Thermodynamic Outlook for the Forecast Period...This system will be embedded in a very favorable thermodynamic environment thru the forecast period while tracking over 30 deg C waters and thru a moist airmass.

 photo Sep_01_2014_TD_Five_Forecast_CORRECTED_zps74fda2f4.png

Track Forecast...My track forecast in discussion #80 was to the right of the 5 PM EDT (4 PM CDT) forecast put out by the NHC a couple of hours after discussion #80 was written...mainly because I had fixed the center further north of where the NHC fixed the center. The NHC center fix as of 11 PM EDT (10 PM CDT) joined my more northward center fix...and the updated NHC track as of 11 PM EDT (10 PM CDT) was adjusted a bit northward as a result. However I continue to believe that the updated NHC track and model consensus remains too far south for how far north this system is currently positioned...and therefore my updated forecast track above remains to the right of the NHC and splits the difference between the NHC forecast and the forecast I put out in discussion #80.

Intensity Forecast...My updated intensity forecast shown above is a bit lower relative to discussion #80 as my track forecast is adjusted southward such that this system has less time over water to develop.

Impact Forecast...Impact swath shown in the above forecast graphic predicts that this system will develop a tight tropical storm wind core within the small circular cluster of thunderstorms that has developed over the center. Outer rains squalls surrounding the core have the potential to deliver flash flooding rains in east-central and northeastern Mexico not only within the impact swath...but also outside the swath. Ocean effects (sea swells and rip currents) are expected to be minimal since this system is not expected to have enough time over water to develop into a strong tropical cyclone.

2014 Atlantic Hurricane Season Birdseye Discussion #80

By: NCHurricane2009, 7:44 PM GMT on September 01, 2014

...MONDAY SEPTEMBER 1 2014 3:50 PM EDT...
Tropical wave Invest 99-L remains at risk for tropical cyclone formation as it moves across the Bay of Campeche and toward east-central and northeastern Mexico. See special feature section below for additional details.

The central Atlantic tropical low located between two tropical waves has dissolved while encountering the dry Saharan air layer to the north...and therefore I have cancelled this system as a special feature on this blog.

The tropical wave previously over western Africa has moved into the eastern tropical Atlantic as its showers and thunderstorms have weakened while ingesting the dry Saharan air layer to the northwest.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Sep_01_2014_1145Z_zpsb7f2cbee.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1200Z and the 1329Z-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...
 photo Sep_01_2014_1145Z_Thermo_zps7331a232.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...SPECIAL FEATURE...TROPICAL WAVE INVEST 99-L...
Current Prognosis...The tropical wave has left behind a 1009 mb low pressure spin which was located at 20N-91.5W as of 1200Z and then 20.5N-92.1W as of 1800Z according to visible satellite animation. This is a bit further northeast of where I previously predicted this system to be by this time...and therefore the updated forecast below shows this system spending more time over water and perhaps strengthening more than previously shown. This system exhibits showers...thunderstorms...and upper outflow to the south and east of the low pressure center. The activity north and west of the low pressure center is limited because it is on the south side of a Gulf of Mexico upper ridge axis (marked by blue-zig-zag line and blue H north of 99-L in the above atmospheric features chart). Each successive satellite frame shows this low pressure system is becoming better organized and aircraft reconnaissance is en route to determine if tropical cyclone fomration is occurring.

Atmospheric Outlook for the Forecast Period...This system will remain on the south side of Gulf upper ridging early in the forecast period...perhaps entering even more favorable conditions at the end of the forecast period while the expected west-northwest to northwest track allows the system to slide direclty below the upper ridge axis. Track is expected to be west-northwest curving to the northwest by the end of the forecast period on the southwest side of subtropical low-level ridging marked by a red zig-zag line to the north of Invest 99-L in the above atmospheric features chart.

Thermodynamic Outlook for the Forecast Period...As the thermodynamics chart above shows...this system will be embedded in a very favorable thermodynamic environment thru the forecast period while tracking over 31 deg C waters and thru a moist airmass.

12 Hr Forecast (0000Z September 2)...Organized tropical low over the central Bay of Campeche centered near 21N-93W

36 Hr Forecast (0000Z September 3)...45 mph max sustained wind tropical storm centered near 22N-96.5W approaching east-central Mexico

60 Hr Forecast (0000Z September 4)...60 mph max sustained wind tropical storm on the coast of northeastern Mexico centered near 24N-97.5W

84 Hr Forecast (0000Z September 5)...Remnant low centered over northeastern Mexico near 26N-99W


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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