[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 111050
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

HURRICANE FRED IS CENTERED NEAR 17.7N 35.1W AT 11/0900 UTC OR
ABOUT 645 NM WEST OF THE CAPE VERDE ISLANDS MOVING N AT 3 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 980 MB. MAXIMUM SUSTAINED
WIND SPEED IS 75 KT WITH GUSTS TO 90 KT. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 17N-22N BETWEEN 32W-36W.
WIDELY SCATTERED MODERATE CONVECTION COVERS THE REMAINDER OF THE
AREA FROM 12N-24N BETWEEN 31W-38W. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE
DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 19W S OF 19N MOVING W NEAR 15 KT. A 1010
MB LOW IS ALONG THE WAVE AXIS NEAR 13N. FIRST VISIBLE METEOSAT-9
SATELLITE IMAGES CONFIRM THAT THE WAVE HAS EMERGED OFF THE W
AFRICA COAST AS THE DAKAR SENEGAL UPPER AIR TIME SECTION
ANALYSES INDICATED WITH A STRONG SURFACE TO 600 MB ANOMALOUS
WIND SIGNATURE. A 11/0650 UTC QUIKSCAT PASS ALSO CONFIRMS A
LOW-LEVEL CIRCULATION CENTER EVIDENT. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 11N-17N BETWEEN 18W-22W.

TROPICAL WAVE IS ALONG 78W S OF 19N MOVING W NEAR 15 KT. CIMSS
WAVETRAK MODEL GUIDANCE INDICATES THE WAVE COINCIDES WITH A 700
MB VORTICITY MAXIMUM NEAR 14N78W 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 AN UPPER LOW CENTERED
OVER COSTA RICA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS FROM 10N-16N BETWEEN 78W-83W AND MAY BE MORE ASSOCIATED WITH
ATMOSPHERIC LIFT DUE TO THE UPPER LOW AND TROUGHING.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 8N19W 10N29W 11N51W 9N61W AND
ACROSS NRN VENEZUELA ALONG 9N. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 4N-10N BETWEEN 19W-28W. ELSEWHERE...
WIDELY SCATTERED MODERATE CONVECTION IS FROM 8N-12N BETWEEN
40W-49W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 0900 UTC...A WEAK UPPER-LEVEL SHORTWAVE AND ASSOCIATED
LOBE OF MID-LEVEL VORTICITY IS SUPPORTING A 1013 MB SURFACE LOW
CENTERED NEAR HOUSTON TEXAS WITH A STATIONARY FRONT DRAPED ALONG
THE TEXAS GULF COAST TO THE RIO GRANDE RIVER NEAR 28N100W.
LOW-LEVEL CONVERGENCE SE OF THE FRONT ACROSS THE NW GULF AND
UPPER LEVEL DIFFLUENCE FROM UPPER LEVEL RIDGING ACROSS THE WRN
GULF ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS N OF
26N W OF 87W. MORE ACTIVITY EXTENDS ALONG THE MEXICAN GULF
COAST..SW GULF AND OVER PORTIONS OF INTERIOR E/CENTRAL MEXICO W
OF 93W. ACROSS THE ERN GULF...A LINGERING SURFACE TROUGH IS OVER
THE SE GULF EXTENDING FROM THE WRN YUCATAN PENINSULA NEAR 21N90W
NE ALONG 25N87W AND OVER THE FLORIDA PENINSULA NEAR SARASOTA.
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
26N E OF 87W...INCLUDING THE FLORIDA KEYS AND STRAITS OF FLORIDA.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS CENTERED OVER COSTA RICA AND COVERS THE SW
CARIBBEAN WITH TROUGHING THAT EXTENDS 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 WRN CUBA AND THE NEARBY CARIBBEAN WATERS N OF 19N BETWEEN
78W-86W. FARTHER S...AN AREA OF SCATTERED SHOWERS AND TSTMS ARE
OVER THE SW CARIBBEAN FROM 10N-16N BETWEEN 78W-83W. ACROSS THE
ERN CARIBBEAN E OF 68W...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 LEEWARD ISLANDS...
US/UK VIRGIN ISLANDS AND ERN PUERTO RICO.

ATLANTIC OCEAN...
AS OF 0900 UTC...A SURFACE TROUGH EXTENDS THROUGH 32N74W SW TO
THE FLORIDA PENINSULA NEAR MELBOURNE AND INTO THE GULF OF MEXICO
NEAR SARASOTA. AN UPPER LEVEL TROUGH LOCATED OVER THE ERN U.S.
SEABOARD 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 68W. A WEAK 1016 MB SURFACE LOW IS N-NW OF PUERTO
RICO NEAR 22N67W. THE LOW IS SUPPORTED BY AN UPPER LEVEL LOW
CENTERED NEAR 25N65W. ISOLATED SHOWERS ARE WITHIN 60 NM OF A
LINE FROM 23N68W SE TO 18N64W. A WEAK SURFACE RIDGE COVERS THE
REMAINDER OF THE W ATLC ANCHORED ON A 1021 MB HIGH CENTERED NEAR
29N62W. FARTHER NE OVER THE CENTRAL ATLC...A VIGOROUS N ATLC
UPPER LEVEL TROUGH SUPPORTS A COLD FRONT THAT ENTERS THE
DISCUSSION AREA NEAR 32N48W AND CONTINUES WWD TO 32N56W.
SCATTERED SHOWERS AND TSTMS ARE WITHIN 90 NM S OF THE FRONT. A
PRE-FRONTAL TROUGH IS ANALYZED SE OF THE COLD FRONT FROM 32N44W
TO 25N51W. POSSIBLE SCATTERED SHOWERS ARE WITHIN 60 NM EITHER
SIDE OF THE SURFACE TROUGH. AN UPPER LEVEL TROUGH ENTERS THE
BASIN NEAR 32N30W TO AN ELONGATED UPPER LOW NEAR 22N45W. THIS
UPPER TROUGH SUPPORTS A SURFACE TROUGH EXTENDING FROM 23N49W S
TO 15N49W WITH POSSIBLE ISOLATED SHOWERS WITHIN 90 NM EITHER
SIDE OF THE SURFACE TROUGH. A SURFACE RIDGE IS OVER THE NE ATLC
PORTION OF THE DISCUSSION AREA EXTENDING N OF 25N E OF 40W.

$$
HUFFMAN



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