[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061755 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...UPDATED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON SEP 06 2010

***** UPDATED TO CORRECT TIME *****

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURES...

TROPICAL STORM HERMINE IS CENTERED NEAR 24.1N 96.5W AT 06/1800
UTC OR ABOUT 85 MI ENE OF LA PESCA MEXICO AND ABOUT 140 MI SSE
OF BROWNSVILLE TEXAS...MOVING N AT 7 KT. THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED WIND SPEED IS 50
KT WITH GUST TO 60 KT. PLEASE SEE LATEST NHC INTERMEDIATE PUBLIC
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT5/WTNT35 KNHC AND THE
FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT5/WTNT25
KNHC FOR MORE DETAILS. SCATTERED/NUMEROUS STRONG CONVECTION
COVERS THE WESTERN HALF OF THE GULF W OF 90W. ALTHOUGH THIS
SYSTEM WILL BE INLAND OVER NORTHEASTERN MEXICO OR EXTREME
SOUTHERN TEXAS BY LATE THIS EVENING...COMPUTER MODELS
SUGGEST THE CONVECTION ASSOCIATED TO THIS SYSTEM WILL LINGER
OVER THE NW GULF THROUGH AT LEAST THURSDAY.

A 1008 MB LOW...REMNANT OF GASTON...IS ABOUT 300 NM E OF THE
NORTHERN LESSER ANTILLES NEAR 17N57W MOVING W NEAR 10 KT.
SATELLITE IMAGERY INDICATES A LOW LEVEL SWIRL REMAINS WITH A
BAND OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM OF
LINE FROM JUST W OF THE LOW NEAR 17N59W TO 22N62W. UPPER LEVEL
WINDS ARE EXPECTED TO BECOME MORE CONDUCIVE FOR DEVELOPMENT OVER
THE NEXT DAY OR SO AND THE MOISTURE SURROUNDING THE LOW SHOULD
GRADUALLY INCREASE AS IT MOVES W AT 10-15 KT. THERE IS A HIGH
CHANCE OF THIS SYSTEM BECOMING A TROPICAL CYCLONE AGAIN DURING
THE NEXT 48 HOURS. HEAVY RAINS AND GUSTY WINDS COULD BEGIN TO
AFFECT PORTIONS OF THE LEEWARD ISLANDS LATE TODAY AND TONIGHT.
INTERESTS IN THOSE ISLANDS SHOULD MONITOR THE PROGRESS OF THIS
SYSTEM.

...TROPICAL WAVES...

A TROPICAL WAVE JUST ENTERED THE FAR EASTERN ATLANTIC TROPICAL
BASIN...ANALYZED ALONG 15W S OF 16N MOVING WEST 10-15 KT.
SATELLITE DERIVED WINDS INDICATE BROAD CYCLONIC TURNING AROUND
THE WAVE AXIS. THIS WAVE IS EMBEDDED IN A SURGE OF DEEP LEVEL
MOISTURE AS NOTED ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED
MODERATE TO STRONG CONVECTION IS BETWEEN THE COAST OF WEST
AFRICA AND 23W FROM 8N TO 18N.

...ITCZ...

A MONSOONAL TROUGH EXTENDS FROM THE COASTAL WATERS OF W AFRICA
NEAR 8N17W CONTINUING WESTWARD ALONG 5N30W TO 8N40W...WHERE THE
ITCZ AXIS BEGINS AND CONTINUES WESTWARD ALONG 9N50W TO 8N60W.
SCATTERED MODERATE TO STRONG CONVECTION IS BETWEEN THE COAST OF
WEST AFRICA AND 23W FROM 8N TO 18N. THIS AREA OF CONVECTION IS
ALSO ASSOCIATED WITH A TROPICAL WAVE ALONG 15W S OF 16N. SIMILAR
CONVECTION IS WITHIN 100 NM ON EITHER SIDE OF THE MONSOONAL
TROUGH. SCATTERED WEAK TO ISOLATED MODERATE CONVECTION IS WITHIN
100 NM EITHER SIDE OF THE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
THE PRIMARY FOCUS THIS AFTERNOON FOR THE GULF OF MEXICO IS
TROPICAL STORM HERMINE PRODUCING CONVECTION TO MOST OF THE
WESTERN HALF OF THE GULF W OF 90W. SEE SPECIAL FEATURES ABOVE
FOR MORE DETAILS. A LONGWAVE UPPER LEVEL TROUGH IS EMBEDDED IN
THE RIDGE ENTERING THE NE GULF NOTED BY STRONG SUBSIDENCE ALOFT
ON WATER VAPOR IMAGERY...WHILE ANTI-CYCLONIC ROTATION ALOFT IS
OVER THE SE BASIN INDICATED BY SATELLITE DERIVED WINDS. THIS
UPPER LEVEL SCENARIO IS GENERATING DIFFLUENT FLOW ALOFT OVER THE
EASTERN GULF E OF 85W SUPPORTING SCATTERED. THIS SCENARIO IS
ENHANCING SCATTERED MODERATE TO ISOLATED HEAVY SHOWERS IN THIS
REGION. COMPUTER MODELS SUGGEST THAT THE UPPER LEVEL SCENARIO
WILL CONTINUE TO GENERATE CONVECTION IN THE EASTERN GULF S OF
27N E OF 85W OVER THE NEXT 24 HRS...INCLUDING THE FLORIDA
STRAITS.

CARIBBEAN SEA...
BROAD ELONGATED UPPER LEVEL LOW CENTERED OVER THE SOUTHERNMOST
DISTRICT OF THE BAHAMAS...GREAT INAGUA ISLAND... SUPPORTS A
RATHER WEAK SURFACE TROUGH THAT ENTERS THE DISCUSSION AREA
THROUGH HAITI ALONG 18N73W TO 17N73W WITH NO ASSOCIATED
CONVECTION AT THE MOMENT. HOWEVER...COMPUTER MODELS INDICATE THE
UPPER LEVEL LOW WILL CONTINUE TO MOVE WEST AND THE CYCLONIC FLOW
AROUND IT WILL INTERACT WITH AN LONGWAVE UPPER LEVEL TROUGH OVER
THE EASTERN SEA BOARD TO PRODUCE DIFFLUENCE ALOFT...ENHANCING
CONVECTION OVER THE NNW BASIN N OF 18N W OF 77W OVER THE NEXT 24
TO 48 HOURS. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE
OVER THE SW BASIN S OF 15N W OF 75W...ASSOCIATED WITH NEARBY
CONVERGENCE IN THE VICINITY OF THE MONSOONAL TROUGH OVER THE
FAR EASTERN PACIFIC. COMPUTER MODELS SUGGEST THIS AREA OF
CONVECTION WILL LINGER IN THIS REGION OVER THE NEXT 24 HRS.
RELATIVELY DRY/STABLE CONDITIONS IS NOTED ELSEWHERE ACROSS THE
CARIBBEAN THIS AFTERNOON. ON A SIDE NOTE...THE REMNANT LOW
PRESSURE CENTER OF GASTON WILL ENTER THE FAR EASTERN CARIBBEAN
WITH CONVECTION OVER THE NEXT 24 HOURS AFFECTING THE LESSER
ANTILLES FROM 15N TO PUERTO RICO.

ATLANTIC OCEAN...
THE 1008 MB REMNANT LOW OF GASTON REMAINS A CONCERN AS IT
CONTINUES TO MOVE TOWARD THE LEEWARD ISLANDS...SEE SPECIAL
FEATURES ABOVE FOR MORE DETAILS. BROAD ELONGATED UPPER LEVEL LOW
CENTERED OVER THE SOUTHERNMOST DISTRICT OF THE BAHAMAS...GREAT
INAGUA ISLAND...SUPPORTS A RATHER WEAK SURFACE TROUGH ANALYZED
ALONG 25N71W 21N73W 17N73W ENHANCING SCATTERED WEAK TO MODERATE
CONVECTION WITHIN 70 NM ON EITHER SIDE OF THE TROUGH N OF 20N. A
LONGWAVE UPPER LEVEL TROUGH IS MOVING OFF THE EASTERN SEABOARD
AND IT'S INTERACTING WITH THE CYCLONIC FLOW ALOFT RELATED TO THE
ELONGATED UPPER LEVEL LOW TO PRODUCE SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION TO THE FAR WESTERN ATLC W OF 76W
INCLUDING THE FLORIDA PENINSULA. THIS AREA OF CONVECTION IS
EXPECTED TO LINGER IN THIS REGION OVER THE NEXT 24 HRS. A
SURFACE TROUGH IS OVER THE EASTERN ATLC EXTENDING FROM 22N27W TO
15N30W GENERATING SCATTERED MODERATE TO ISOLATED STRONG
CONVECTION WITHIN 70 NM ON EITHER SIDE OF THE AXIS. THIS SYSTEM
WILL CONTINUE TO MOVE WEST WITH CONVECTION OVER THE NEXT 24
HOURS. ELSEWHERE ACROSS THE DISCUSSION AREA...BROAD MID/UPPER
LEVEL SUB-TROPICAL RIDGE DOMINATES THE ATLC AND SUPPORTS THE
SURFACE 1027 MB HIGH NEAR 38N40W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GARCIA





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