2014 Atlantic Hurricane Season Birdseye Discussion #61

By: NCHurricane2009 , 2:32 AM GMT on August 12, 2014

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...MONDAY AUGUST 11 2014 10:33 PM EDT...
Vigorous tropical wave Invest 94-L currently southwest of the Cape Verde Islands has not become better organized but still has the potential to develop further...therefore the Lesser Antilles should monitor this system over the next few days. See special feature section below for additional details on Invest 94-L. It is quiet elsewhere in the Atlantic tropics.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Aug_11_2014_2045Z_zpsfc56a12d.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z and the 1921Z-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 Aug_11_2014_2045Z_Thermo_zps3cfac407.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 94-L...
Current prognosis...As of 1800Z the NHC TAFB has defined a 1012 mb low pressure spin centered near 11.5N-31W in association with the vigorous tropical wave currently located southwest of the Cape Verde Islands. The most organized shower and thunderstorm activity is to the southwest of the identified center...and this system has been moving faster to the west than previously forecast. Therefore my updated forecast below moves this system faster to the west...especially if this system re-generates a new center in the more organized activity southwest of the center. Have delayed forecast tropical cyclone formation to the timeframe that is 72 hours from now as this system has not become better organized in the last day.

Atmospheric Outlook for the Forecast Period...Thru the forecast period this system will be steered west around the south side of the low-level 1028 mb Atlantic subtropical ridge marked in the atmospheric features chart above. As the chart above also shows...their is a Tropical Upper Tropospheric Trough (TUTT) is forming as marked by a series of blue dashed lines and blue Ls to the north of this system. This system is increasingly finding itself in a favorable low shear/good upper outflow environment in a tropical upper ridge beginning to solidify south of the TUTT. By the end of the forecast period...the TUTT is forecast to shift south ahead of a building upper ridge in the central Atlantic. However with this system now forecast to move faster to the west than previously thought (as noted in the above current prognosis section)...it is now likely to escape the southward-shifting TUTT and slide beneath more favorable upper ridging to persist over the eastern Caribbean Sea.

Thermodynamic Outlook for the Forecast Period...As this system continues west it is beginning to encounter the swath of dry Saharan air that has recently killed off the tropical waves out ahead of this system. However animation of the above thermo chart suggests this tropical wave has so far been able to maintain its moisture field while beginning to push into the dry air. As far as sea-surface temperatures...the tropical wave will be tracking over 27 to 28 deg C early in the forecast period...increasing to 29 deg C while entering the eastern Caribbean Sea...temperatures on the favorable side for tropical development.

24 Hr Forecast (0000Z August 13)...Tropical low centered near 11.5N-39W.

48 Hr Forecast (0000Z August 14)...Tropical low centered near 11.5N-47W.

72 Hr Forecast (0000Z August 15)....35 mph max sustained wind tropical depression centered near 12N-55W.

96 Hr Forecast (0000Z August 16)...45 mph max sustained wind tropical storm centered near 12N-62W crossing the southern Lesser Antilles.

120 Hr Forecast (0000Z August 17)...50 mph max sustained wind tropical storm centered near 12.5N-69W in the southeastern Caribbean Sea.

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2. WunderAlertBot (Admin)
3:48 AM GMT on August 13, 2014
NCHurricane2009 has created a new entry.
1. GTstormChaserCaleb
3:10 AM GMT on August 12, 2014
Nice blog, so it looks like it will outrun the TUTT moving south, and I like your reference to slower air parcel lapse rate leading to higher instability. Great Analysis of the current conditions and forecast.
Member Since: June 30, 2013 Posts: 12 Comments: 8675

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