2013 Atlantic Hurricane Season Birdseye Discussion #46

By: NCHurricane2009 , 11:13 AM GMT on July 19, 2013

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...FRIDAY JULY 19 2013 7:15 AM EDT...
Watching tropical wave currently over Haiti expected to move into favorable upper winds over the next 48 hours. See paragraph P10 for details.

Thunderstorm activity over the Yucatan...southeast Gulf of Mexico...and Florida yesterday afternoon was associated with surface troughing mentioned in paragraph P8 interacting with upper divergence around a north-central Gulf of Mexico upper vortex mentioned in paragraph P5. As these thunderstorms have died down as of this morning...no tropical or subtropical development is expected.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jul_19_2013_0545Z_zps725e3146.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 0600Z, and the 0720Z-released WPC analysis.

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

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

...THERMODYNAMICS BIRDSEYE CHART...
 photo Jul_19_2013_0545Z_zps168c4fd9.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...MID-LATITUDES DISCUSSION...
P1...Shortwave upper trough is entering the upper-left corner of the above charts. Western convergence of the shortwave supports 1019 mb surface ridge over eastern Montana...eastern divergence of the shortwave supports broad 998 mb surface frontal depression over south-central Canada.

P2...Upper trough and associated surface 994 mb frontal cyclone continues east from eastern Canada and into the Atlantic high seas between Canada and Greenland (eastern divergence of this upper trough also supports new 1004 mb depression east of Newfoundland). Western convergence of the upper trough supports 1016 mb surface ridge between Nova Scotia and Newfoundland.

P3...Upper trough persists SSE of Greenland...with eastern divergence of the upper trough supporting a surface frontal cyclone that has moved northward and out of the picture while rounding the west side of deep-layered ridging consisting of upper ridge mentioned further down this paragraph and the western Europe portion of paragraph P6 surface ridge. Western convergence of this upper trough supports 1021 mb surface ridge currently just NW of the Azores. Warm air advection ahead of the exited frontal cyclone supports building upper ridge that has moved into the British Isles of western Europe.

P4...Cut-off upper vortex previously over New Mexico continues retrograding westward into NW Mexico and out of the picture while retrograding about the south side of a western US upper ridge. Surface troughing extending from the shores of the US mid-Atlnatic states eastward into the open central Atlantic for several hundred miles...mentioned in paragraph P3 of the previous discussion...currently persists while generally supported by split flow upper divergence between easterlies southeast of the eastern US upper ridge (pumped up by low-level warm air advection on west side of paragraph P6 surface ridge) and mainstream mid-latitude westerlies. This surface troughing wraps all the way into 1005 mb frontal depression north of the Azores supported by eastern divergence of paragraph P3 upper trough.

P5...Cut-off upper vortex previously north of the Azores is now a northeastward moving upper trough west of Portugal and Spain as it moves around the British Isles upper ridge mentioned at the end of paragraph P3. A southwest portion of this upper vorticity several days ago has evolved into what is now the upper vortex moving into the north-central Gulf of Mexico that continues retrograding westward about the eastern US upper ridge mentioned in paragraph P4.

P6...Surface ridge dominates much of the open Atlantic basin...with a current westward extension onto the US Gulf coast. The US Gulf coast and open Atlantic portion of this surface ridge is supported by southeastern convergence of paragraph P4 eastern US upper ridge and north-central Atlantic upper anticyclone mentioned in paragraph P7. This surface ridge continues to have a center that has recently moved into western Europe...supported by eastern convergence of upper ridge mentioned at the end of paragraph P3.

...TROPICAL BELT DISCUSSION...
P7...Low-latitude upper ridge axis previously over the Cape Verde Islands extending into W Africa has recently lifted northward and has expanded westward into the eastern Caribbean in the wake of the weakening and or retrograding upper vorticity features mentioned in paragraph P5. Upper outflow of Caribbean portion of low-latitude upper ridging supports t-storms over much of Central America. Upper vortex east of the Lesser Antilles has retrograded westward into the eastern Caribbean while steered by paragraph P4 eastern US upper ridge...and upper vortex south of Bermuda persists...with both of these upper vortices continuing to seperate the aforementioned low-latitude upper ridge axis from the Caribbean portion of low-latitude upper ridging. South end of all the low-latitude upper ridging in this paragraph...in conjunction with the south end of the paragraph P6 surface ridge...is also advecting dry Saharan air from Africa as seen by low-latitude brown shading in the above thermo chart. Lastly...a portion of the low-latitude upper ridging has evolved into new north-central Atlantic upper anticyclone supported by warm air advection ahead of 1004 mb depression mentioned in paragraph P2. Relatively lower pressures south of the new upper anticyclone and north of the low-latitude upper ridging supports new embedded upper vortex in the open central Atlantic.

P8...All the surface troughing mentioned in paragraph P7 of the previous discussion has consolidated into central Gulf of Mexico surface trough supported by eastern divergence of paragraph P5 north-central Gulf upper vortex...as well as a northward-extending surface trough that has moved westward from the SE US and into the Arkansas...Lousiana...Oklahoma...Texas region. This northward-extending surface trough continues to be supported by split flow upper divergence between easterlies on the north side of the paragraph P5 north-central Gulf upper vortex and southerlies on the west side of the paragraph P4 eastern US upper ridge. The central Gulf surface trough had associated t-storms from the Yucatan peninsula northeastward into Florida yesterday afternoon...but no tropical development is expected as these t-storms have recently died down. The northward-extending surface trough produced its own impressive t-storm cluster over the Arkansas yesterday afternoon as well.

P9...Tropical wave previously in the central Caribbean is moving into Central America...where its surface convergence is further agitating the Central America t-storm activity mentioned in paragraph P7 above.

P10...Tropical wave previously crossing the Lesser Antilles into the eastern Caribbean is now over Haiti this morning. In the past 24 hours...its thunderstorm activity has continued to intensify thanks to split flow upper divergence at the boundary between the paragraph P7 eastern Caribbean upper vortex and paragraph P7 upper vortex south of Bermuda. As this tropical wave continues WNW across Cuba...the Bahamas...south Florida...and into the Gulf of Mexico (while steered by SW quad of paragraph P6 surface ridge)...will be watching for development potential as this tropical wave is expected to slide under a favorable upper anticyclone shown in models to develop between the paragraph P5 north-central Gulf upper vortex and paragraph P7 upper vortex south of Bermuda. However...currently their is no computer model showing development of this tropical wave.

P11...Tropical wave previously west of the Cape Verde Islands is now midway between the Cape Verdes and Lesser Antilles. While some t-storms persist in its south half...its north half remains suppressed by dry Saharan air mentioned in paragraph P7.

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