[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 091759
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 09 2009

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
1715 UTC.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 24W S OF 15N MOVING W NEAR 18 KT.
ALTHOUGH LACKING A DEFINED SATELLITE PRESENTATION DUE TO A LARGE
AREA OF SAHARAN DUST ACROSS THE ERN TROPICAL ATLC...THIS WAVE
TRACKED W OF DAKAR AROUND 07/1800 UTC...BASED ON THE UPPER AIR
TIME SECTION ANALYSES THE PAST FEW DAYS FROM DAKAR SENEGAL. ALSO
AN EARLIER SCATTEROMETER PASS AROUND 0800 UTC CONFIRMED THE WAVE
REMAINS AT LOW-LATITUDE AND LARGELY EMBEDDED WITHIN THE ITCZ.
SCATTERED MODERATE CONVECTION IS FROM 5N-13N BETWEEN 18W-22W AND
FROM 5N-9N BETWEEN 22W-27W.

A TROPICAL WAVE IS ALONG 52W S OF 20N MOVING W NEAR 15 KT. A
LARGE AREA OF SAHARAN DUST SURROUNDS THE WAVE AND IS LIMITING
ANY DEEP CONVECTION TO S OF 12N. AN EARLIER QUIKSCAT PASS AROUND
0930 UTC DEPICTED VERY BROAD CYCLONIC WIND FLOW IN THE VICINITY
OF THE WAVE AXIS. CONFINED MOSTLY ALONG THE ITCZ
AXIS...SCATTERED MODERATE CONVECTION IS FROM 8N-12N BETWEEN
51W-59W.

A TROPICAL WAVE EXTENDS FROM THE CENTRAL BAY OF CAMPECHE NEAR
22N92W ACROSS THE ISTHMUS OF TEHUANTEPEC INTO THE E PACIFIC
MOVING W NEAR 15 KT. THIS WAVE COINCIDES WITH AN AREA OF
INCREASED PRECIPITABLE WATER ACROSS THE S/CENTRAL GULF OF
MEXICO...YUCATAN PENINSULA AND A LARGE PORTION OF CENTRAL
AMERICA. WHILE ONLY SCATTERED SHOWERS ARE FOUND IN THE BAY OF
CAMPECHE NEAR THE WAVE AXIS...LOW-LEVEL SURFACE WIND CONVERGENCE
AND OROGRAPHIC EFFECTS ACROSS THE HIGHER TERRAIN OF CENTRAL
AMERICA ARE ENHANCING SCATTERED MODERATE/ISOLATED STRONG
CONVECTION FROM 13N-21N BETWEEN 84W-90W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 12N16W 9N22W 7N26W 6N37W 9N51W
10N55W ACROSS NRN TRINIDAD TO 10N66W. SCATTERED MODERATE
CONVECTION IS FROM 5N-13N BETWEEN 18W-22W AND FROM 5N-9N BETWEEN
22W-27W ASSOCIATED WITH THE TROPICAL WAVE ALONG 24W. SIMILAR
CONVECTION IS W OF THE TROPICAL WAVE ALONG 52W FROM 8N-12N
BETWEEN 51W-59W.

...DISCUSSION...

GULF OF MEXICO...
MOSTLY SE TO S SURFACE WINDS ARE OBSERVED ACROSS THE GULF OF
MEXICO S OF 26N AS A RIDGE OF HIGH PRESSURE EXTENDS FROM THE W
ATLC OVER SRN FLORIDA AND ALONG 25N TO 98W. N OF 26N...LOW-LEVEL
CONVERGENCE IS CONCENTRATED ALONG A SURFACE TROUGH THAT EXTENDS
FROM THE WRN FLORIDA PANHANDLE TO 29N90W  IN THE N/CENTRAL GULF
AND IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 26N-30N E OF
92W OVER THE NE GULF AND ACROSS THE CENTRAL FLORIDA PENINSULA.
AN UPPER LEVEL TROUGH IS PROGRESSING SLOWLY EWD ACROSS THE SE
CONUS AND NE GULF WHICH IS ALSO ENHANCING THIS ACTIVITY.
ELSEWHERE ACROSS THE REMAINDER OF THE GULF S OF 26N...MOSTLY
FAIR SKIES PREVAIL...HOWEVER...A TROPICAL WAVE IS MOVING ACROSS
THE BAY OF CAMPECHE AND SW GULF BRINGING INCREASED CLOUDINESS
AND MOISTURE IN THE FORM OF ISOLATED SHOWERS S OF 21N. OTHER
SCATTERED SHOWERS AND TSTMS ARE OCCURRING OVER THE YUCATAN
PENINSULA BUT REMAINING MOSTLY OVER INTERIOR LOCATIONS.

CARIBBEAN SEA...
THE WWD EXTENT OF NELY FLOW ALOFT ON THE BACK SIDE OF AN UPPER
LOW OVER THE CENTRAL CARIBBEAN CENTERED NEAR 16N75W IS
GENERATING SCATTERED SHOWERS AND TSTMS ACROSS THE GULF OF
HONDURAS...PORTIONS OF CENTRAL AMERICA N OF 14N AND THE YUCATAN
PENINSULA. THE NELY FLOW ALOFT IS PROVIDING MOST OF THE NW AND
CENTRAL CARIBBEAN WITH MODERATE TO STRONG SUBSIDENCE AND FAIR
WEATHER CONDITIONS. HOWEVER...SCATTERED SHOWERS AND TSTMS ARE
ACROSS THE SW CARIBBEAN AND ADJACENT COASTAL AREAS OF CENTRAL
AMERICA FROM 8N-13N W OF 73W. SURFACE CONVERGENCE DUE TO THE
PROXIMITY OF THE E PACIFIC ITCZ ALONG 8N IS ENHANCING THIS
ACTIVITY. ACROSS THE ERN CARIBBEAN...A SURFACE TROUGH IS MOVING
WESTWARD N OF PUERTO RICO OVER THE SW NORTH ATLC AND IS
PROVIDING A FEW ISOLATED SHOWERS OVER THE ERN GREATER ANTILLES.
ELSEWHERE OVER THE SE CARIBBEAN...AS THE TROPICAL WAVE ALONG 52W
TRACKS CLOSER TO THE LESSER ANTILLES...INCREASED MOISTURE AND
INSTABILITY IS NOTED ON SATELLITE IMAGERY AS SCATTERED SHOWERS
AND ISOLATED TSTMS ARE OVER THE WINDWARD ISLANDS S OF 14N E OF
63W. FRESH TO STRONG ELY TRADE WIND FLOW CONTINUES ACROSS THE
BASIN AND IS FORECAST TO PERSIST THROUGH THE WEEKEND.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND ISOLATED TSTMS ARE ACROSS THE SW NORTH
ATLC NW OF A LINE FROM MELBOURNE FLORIDA TO 32N73W. THIS
ACTIVITY IS DRIVEN BY LOW-LEVEL CONVERGENCE ALONG AND S OF A
FRONTAL BOUNDARY THAT IS POSITIONED NORTH OF THE AREA ALONG
32N/33N AND FOCUSED NEAR A 1013 MB LOW CENTERED NEAR 32N79W.
THIS ACTIVITY IS FURTHER ENHANCED BY UPPER LEVEL DIFFLUENCE
BETWEEN AN UPPER LEVEL RIDGE OVER THE WRN AND CENTRAL ATLC
CENTERED NEAR 32N56W AND AN UPPER LEVEL TROUGH OVER THE SE CONUS
AND FLORIDA PENINSULA. A 1026 MB SURFACE HIGH IS OVER THE
CENTRAL ATLC NEAR 30N45W AND EXTENDS A RIDGE ACROSS THE
REMAINDER OF THE SW NORTH ATLC...INCLUDING THE BAHAMAS...
PROVIDING GENERALLY CLEAR SKIES AND FAIR WEATHER. HOWEVER...A
WEAKNESS IN THE SURFACE RIDGE IS ANALYZED AS A SURFACE TROUGH
THAT EXTENDS FROM 26N53W TO N OF PUERTO RICO NEAR 19N67W.
SCATTERED SHOWERS ARE WITHIN 120 NM EITHER SIDE OF THE SURFACE
TROUGH IN MODERATE ELY TRADES.

$$
HUFFMAN





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