2013 Atlantic Hurricane Season Birdseye Discussion #55

By: NCHurricane2009 , 1:04 AM GMT on July 30, 2013

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...MONDAY JULY 29 2013 9:05 PM EDT...
See paragraph P8 for update on remnant tropical wave of Tropical Storm Dorian. It is quiet elsewhere in the Atlantic tropics.

...ATMOSPHERIC FEATURES BIRDSEYE CHART...
 photo Jul_29_2013_2215Z_zps6cc10611.png
This chart is generated based on surface analysis from the National Hurricane Center TAFB at 1800Z, and the 1928Z-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_29_2013_2215Z_zps15c5922d.png
This chart is generated using GOES water vapor satellite imagery. Brown indicates dry air. White, blue, and purple indicates moist air. An increase in moisture indicates slower air parcel lapse rates with elevation and hence an increase toward instability.

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

...MID-LATITUDES DISCUSSION...
P1...Upper vortex previously over the Michigan lower peninsula is now an upper trough over the NE US and eastern Canada. Center of associated surface frontal cyclone...currently at 1011 mb...has moved from southeastern Ontario and into west-central Quebec while supported by eastern divergence of the upper trough. Western convergence of the upper trough supports 1023 mb surface ridge over the central and southeastern US. Low-level warm air southwest of the frontal cyclone supports SW US upper ridge mentioned in paragraph P2 of the previous discussion...and low-level warm air southeast of the frontal cyclone supports western of two north Atlantic upper anticyclones also mentioned in paragraph P2 of the previous discussion.

P2...Upper trough previously over the Nw Atlantic has moved into the north-central Atlantic...with its eastern divergence supporting a 1006 mb surface frontal low that has tracked from the waters just east of Newfoundland and into the waters NW of the Azores in the last 24 hrs...and with its western convergence supporting a 1025 mb surface ridge along the east coast of Canada. Low-level warmer air ahead of the 1006 mb frontal low supported eastern of two north Atlantic upper anticyclones mentioned at the end of paragraph P2 of the previous discussion...but now this upper anticyclone has merged with upper anticyclone north of the Cape Verde Islands mentioned in paragraph P6 below.

P3...Large NE Atlantic upper trough has finally moved into Europe (and exited the upper-right corner of the above charts) while knocking out deep-layered ridge over Europe associated with prior heat wave. Surface trough previously SW of the Canary Islands and NW of the Cape Verde Islands is now midway between the Lesser Antilles and Cape Verde Islands while retrograding westward around the south side of the paragraph P4 surface ridge. This surface trough was fracture from surface low previously supported by the exited NE Atlantic upper trough...and because of its current location I will move it to the tropical belt section in the next discussion if it still around by that time.

P4...Surface ridge dominates much of the open Atlantic basin...with a current westward 1020 mb extension into the Gulf of Mexico. The westward extension is supported by SE convergence of paragraph P1 SW US upper ridge. A 1025 mb center over Bermuda is supported by convergence between western of two North Atlantic upper anticyclones (mentioned in paragraph P1) and upper anticyclone over the remnants of Dorian. A 1022 mb center just west of Portugal is supported by western convergence of paragraph P3 upper trough.

P5...Upper vortex south of Bermuda is retrograding westward into the Bahamas while steered by western of the two north Atlantic upper anticyclones mentioned at the end of paragraph P1. At any time...the upper vortex will begin stalling over the Bahamas as further westward progression blocked by SW US upper ridge mentioned in paragraph P1.

...TROPICAL BELT DISCUSSION...
P6...Broad and retrograding upper vortex previously west of the Cape Verde Islands has arrived into the waters midway between the Lesser Antilles and Cape Verde Islands...and along with the paragraph P5 upper vortex south of Bermuda...has split low-latitude upper ridging into one upper anticyclone over Central America...a second upper anticyclone in the vicinity of the NE Caribbean Islands and over the remnants of Dorian...and a third upper anticyclone of the Cape Verde Islands and into western Africa. South end of aforementioned upper anticyclone in the vicinity of the NE Caribbean Islands...in conjunction with the south end of the paragraph P4 surface ridge and south end of paragraph P1 and P2 north Atlantic upper anticyclones...is advecting dry Saharan air from Africa as seen by low-latitude brown shading in the above thermo chart.

P7...Latent heat release of persistent central America thunderstorms has intensified paragraph P6 Central America upper anticyclone in the last 24 hrs...and in turn the increased outflow of the upper anticyclone has been re-enforcing the thunderstorms.

P8...Remnant tropical wave of Dorian earlier today continued to show signs of attempting to regenerate into a tropical storm due north of the Caribbean Islands while taking advantage of outflow of overhead upper anticyclone mentioned in paragrpah P6. While satellite imagery showed the thunderstorms become highly organized around a mid-level center and while reconnaissance aircraft indicated that this system continues to produce tropical storm force winds of about 40 mph...a closed surface circulation still could not be spotted and the lowest surface pressures are not collocated with the mid-level spin and therefore technically Dorian could not be re-classified as a tropical storm. As the remnant tropical wave moves toward the Bahamas during the next day or so...expect its activity and intensity to reduce while becoming suppressed by paragraph P5 upper vortex also settling into the Bahamas.

P9...Tropical wave west and southwest of the Cape Verde Islands continues proceeding westward while phased with suppressing retrograding upper vortex and Saharan dry air mentioned in paragraph P6.

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