[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 110553
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI SEP 11 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

HURRICANE FRED IS CENTERED NEAR 17.4N 35.1W AT 11/0300 UTC OR
ABOUT 640 NM WEST OF THE CAPE VERDE ISLANDS MOVING N AT 3 KT.
ESTIMATED CENTRAL PRESSURE IS 980 MB. MAXIMUM SUSTAINED WIND
SPEED IS 75 KT WITH GUSTS TO 90 KT. SCATTERED MODERATE/STRONG
CONVECTION IS FROM 16N-21N BETWEEN 32W-36W. WIDELY SCATTERED
MODERATE CONVECTION COVERS THE REMAINDER OF THE AREA FROM
15N-22N BETWEEN 30W-37W. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 76W S OF 19N MOVING W NEAR 15 KT. CIMSS
WAVETRAK MODEL GUIDANCE INDICATES THE WAVE COINCIDES WITH A 700
MB VORTICITY MAXIMUM NEAR 14N76W AND WEAK 700 MB TROUGH MOVING
ACROSS THE WRN CARIBBEAN. HOWEVER...ALOFT THE WAVE CONTINUES
MOVING BENEATH THE BASE OF AN UPPER TROUGH EXTENDING FROM PUERTO
RICO SW ACROSS THE CENTRAL CARIBBEAN TO 15N77W. ONLY MID TO HIGH
LEVEL CLOUDINESS IS NOTED ON SATELLITE IMAGERY...THUS NO SHOWERS
OR DEEP CONVECTION ARE ASSOCIATED WITH THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 9N13W 8N21W 13N30W 12N38W 12N47W
12N52W 11N62W. CLUSTERS OF WIDELY SCATTERED MODERATE CONVECTION
ARE FROM 4N-16N BETWEEN 18W-25W. THIS ACTIVITY MAY BE ASSOCIATED
WITH THE NEXT TROPICAL WAVE EMERGING OFF THE W AFRICAN COAST.
THE DAKAR SENEGAL UPPER AIR TIME SECTION ANALYSIS INDICATES A
SURFACE TO 850 MB CYCLONIC WIND SHIFT OCCURRED SHORTLY BEFORE
11/0000 UTC. ELSEWHERE...SCATTERED MODERATE CONVECTION IS FROM
8N-12N BETWEEN 37W-58W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0300 UTC...A WEAK UPPER-LEVEL SHORTWAVE AND ASSOCIATED
LOBE OF MID-LEVEL VORTICITY IS SUPPORTING A 1014 MB SURFACE LOW
CENTERED NEAR HOUSTON TEXAS WITH A COLD FRONT DRAPED TO THE SW
ALONG THE TEXAS GULF COAST TO THE RIO GRANDE RIVER NEAR 29N100W.
LOW-LEVEL CONVERGENCE E OF THE FRONT ACROSS THE NW GULF AND
UPPER LEVEL DIFFLUENCE FROM UPPER LEVEL RIDGING ACROSS THE WRN
GULF ARE GENERATING SCATTERED SHOWERS N OF 23N W OF 90W. MORE
ISOLATED ACTIVITY EXTENDS ALONG THE MEXICAN GULF COAST AND OVER
PORTIONS OF INTERIOR E/CENTRAL MEXICO W OF 96W. ACROSS THE ERN
GULF...A LINGERING SURFACE TROUGH IS OVER THE SE GULF EXTENDING
FROM THE YUCATAN PENINSULA NEAR 21N89W NE ALONG 25N85W AND OVER
THE FLORIDA PENINSULA NEAR PORT CHARLOTTE. SERVING AS A FOCUS
FOR LOW-LEVEL CONVERGENCE...THE SURFACE TROUGH ALONG WITH UPPER
LEVEL RIDGING AND A DIFFLUENT ATMOSPHERE OVER THE SE GULF ARE
PRODUCING SCATTERED SHOWERS AND TSTMS S OF 27N E OF 87W...
INCLUDING THE FLORIDA KEYS AND STRAITS OF FLORIDA.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH COVERS THE SW CARIBBEAN EXTENDING NE
ACROSS THE CENTRAL CARIBBEAN TO PUERTO RICO. N OF THIS TROUGHING
ACROSS THE NW CARIBBEAN...ANTICYCLONIC FLOW AND AN UPPER LEVEL
DIFFLUENT ATMOSPHERE ARE GENERATING SCATTERED SHOWERS AND
ISOLATED TSTMS OVER CUBA AND THE NEARBY CARIBBEAN WATERS FROM
18N-23N BETWEEN 80W-86W. FARTHER S...AN AREA OF SCATTERED
SHOWERS ARE OVER THE SW CARIBBEAN FROM 11N-15N BETWEEN 80W-85W.
ACROSS THE ERN CARIBBEAN E OF 67W...FAIRLY ZONAL WESTERLY FLOW
ALOFT AND MODERATELY DRY AIR IS NOTED ON WATER VAPOR IMAGERY
WITH ONLY A FEW ISOLATED SHOWERS MOVING SW ACROSS THE NRN
LEEWARD ISLANDS AND US/UK VIRGIN ISLANDS.

ATLANTIC OCEAN...
AS OF 0300 UTC...A SURFACE TROUGH EXTENDS THROUGH 32N73W SW TO
THE FLORIDA PENINSULA NEAR VERO BEACH AND INTO THE GULF OF
MEXICO NEAR PORT CHARLOTTE. AN UPPER LEVEL TROUGH SUPPORTS THE
SURFACE TROUGH AND COVERS MUCH OF THE W ATLC N OF 23N W OF 70W.
ALSO...A NARROW UPPER RIDGE EXTENDS FROM THE SE BAHAMAS NE TO
BERMUDA. LOW-LEVEL CONVERGENCE ALONG AND SE OF THE SURFACE
TROUGH ALONG WITH DIFFLUENCE ALOFT DUE TO THE UPPER RIDGING IS
GENERATING A BROAD AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS
FROM 23N-32N BETWEEN THE SURFACE TROUGH BOUNDARY AND 69W. A WEAK
1015 MB SURFACE LOW IS N OF PUERTO RICO NEAR 22N67W. THE LOW IS
SUPPORTED BY AN UPPER LEVEL LOW CENTERED NEAR 25N65W. A WEAK
SURFACE RIDGE COVERS THE REMAINDER OF THE W ATLC ANCHORED ON A
1022 MB HIGH CENTERED NEAR 29N59W. FARTHER E OVER THE CENTRAL
ATLC...AN UPPER LEVEL TROUGH ENTERS THE BASIN NEAR 32N32W TO AN
ELONGATED UPPER LOW NEAR 22N47W. THIS UPPER TROUGH SUPPORTS A
SURFACE TROUGH EXTENDING FROM 32N43W TO 25N52W WITH ISOLATED
SHOWERS WITHIN 60 NM EITHER SIDE OF THE BOUNDARY. THIS UPPER LOW
IS ALSO SUPPORTING A SECOND SURFACE TROUGH THAT EXTENDS FROM
24N47W S TO 13N49W WITH POSSIBLE ISOLATED SHOWERS WITHIN 90 NM
EITHER SIDE OF THE SURFACE TROUGH. A SURFACE RIDGE IS OVER THE
ERN ATLC EXTENDING N OF 25N E OF 40W.

$$
HUFFMAN




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