[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 031752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON SEP 03 2012

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

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

...SPECIAL FEATURES...

TROPICAL STORM LESLIE IS CENTERED NEAR 24.4N 63.1W AT 03/1500
UTC. THIS LOCATION IS ABOUT 510 MI...825 KM N OF THE LEEWARD
ISLANDS AND ABOUT 555 MI...895 KM S OF BERMUDA. LESLIE IS MOVING
NNW AT 7 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 MB...
WITH MAXIMUM SUSTAINED WIND SPEEDS OF 50 KT GUSTING TO 60 KT.
SCATTERED TO NUMEROUS MODERATE AND SCATTERED STRONG CONVECTION
IS FROM 20N-25N BETWEEN 58W-65W. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE
DETAILS.

AN ELONGATED UPPER LEVEL LOW IS NOTED ON WATER VAPOR IMAGERY
CENTERED NEAR 25N42W...SUPPORTING ITS CO-LOCATED SURFACE 1015 MB
LOW REFLECTION AND ASSOCIATED SURFACE TROUGH ANALYZED FROM
32N40W ALONG THE LOW LEVEL CENTER TO 20N42W. THIS SYSTEM IS
GENERATING SCATTERED WEAK SHOWERS CONCENTRATED WITHIN 100 NM
OVER THE NE QUADRANT OF THE SURFACE LOW. ISOLATED SHOWERS ARE
ALSO WITHIN 100 NM E OF THE SURFACE TROUGH N OF THE LOW CENTER.
ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR DEVELOPMENT...AND
THIS LOW COULD BECOME A TROPICAL DEPRESSION DURING THE NEXT DAY
OR SO. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

THE TROPICAL WAVE MOVING ACROSS THE CENTRAL TROPICAL ATLC
CONTINUES TO BE DIFFICULT TO PIN DOWN. AS OF 1200 UTC...THE WAVE
AXIS IS ANALYZED FROM 18N35W TO 12N37W. HOWEVER...MODEL GUIDANCE
AND LIMITED OBSERVATIONS NEAR THIS SYSTEM INDICATED NO CYCLONIC
CURVATURE NEAR THE WAVE AXIS...NOR AT 700 MB LEVEL WHERE
CYCLONIC CURVATURE SHOULD BE BEST PRONOUNCED. IT IS LIKELY THAT
THIS WAVE BECAME EMBEDDED IN THE MONSOONAL GYRE DESCRIBED BELOW
...AS SEVERAL EARLIER SCATTEROMETER PASSES ONLY INDICATED
SURFACE TURNING ASSOCIATED TO THE MONSOON TROUGH AXIS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE WEST AFRICAN COASTAL CITY OF
DAKAR SENEGAL ALONG 15N22W 14N30W 13N30W TO 12N40W...WHERE THE
ITCZ AXIS CONTINUES ALONG 11N51W TO NEAR THE COASTAL WATERS OF
TRINIDAD AND TOBAGO GUYANA AROUND 10N61W. SCATTERED MODERATE TO
ISOLATED STRONG CONVECTION IS FROM 10N-15N BETWEEN 18W-37W.

...DISCUSSION...

GULF OF MEXICO...
NE FLOW ALOFT CONTINUES TO BRING DRY AIR ACROSS THE UPPER LEVELS
OF THE GULF BASIN...AROUND A BROAD UPPER LEVEL RIDGE LOCATED
OVER THE CENTRAL PLAINS OF THE CONUS. THIS UPPER LEVEL
ENVIRONMENT IS SUPPORTIVE OF A SURFACE RIDGE ANCHORED BY A 1019
MB HIGH CENTERED OVER THE NE GULF NEAR 28N87W...PROVIDING FAIR
WEATHER CONDITIONS ACROSS THE AREA WITH ONLY A FEW ISOLATED
SHOWERS DOTTING THE SE AND NE REGIONS OF THE GULF. OTHERWISE...
MARINE OBSERVATIONS ACROSS THE GULF SHOW LIGHT TO GENTLE
ANTICYCLONIC FLOW AROUND THE SURFACE HIGH CENTER. AN UPPER LOW
LOCATED IN THE WRN ATLC SPINNING JUST A FEW MILES OFF THE SE
FLORIDA PENINSULA WILL BRING A CHANCE FOR SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE STRAITS OF FLORIDA AND FAR
ERN GULF DURING THE NEXT 24 HOURS. AN UPPER LEVEL SHORTWAVE
MOVING ACROSS THE SE CONUS WILL BRING SIMILAR ACTIVITY TO THE
COASTAL WATERS NEAR THE FLORIDA PANHANDLE AND ALABAMA DURING THE
FORECAST PERIOD.

CARIBBEAN SEA...
WATER VAPOR IMAGERY INDICATES A FAIR AMOUNT OF DRY AIR ALOFT
ACROSS MOST OF THE CARIBBEAN BASIN THIS AFTERNOON. MIDDLE TO
UPPER LEVEL MOISTURE INCREASES OVER THE FAR SW BASIN...S OF 12N
W OF 76W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN THIS
REGION...IN CLOSE PROXIMITY WITH THE ERN PACIFIC MONSOON TROUGH
ANALYZED ACROSS INLAND PORTIONS OF COSTA RICA...PANAMA TO NRN
COLOMBIA. THE SURFACE FLOW OVER FAR ENE CARIBBEAN CONTINUES TO
UNDER THE INFLUENCE OF THE LARGE CYCLONIC WIND FIELD ASSOCIATED
TO TROPICAL STORM LESLIE LOCATED NNE OF THE NORTHERN LEEWARD
ISLANDS. OTHERWISE...GENTLE TO MODERATE EASTERLY TRADE WIND FLOW
IS ELSEWHERE ACROSS THE DISCUSSION AREA...INCREASING TO 20 KT
OVER THE COASTAL WATERS OF NRN COLOMBIA. GLOBAL MODELS SUGGEST
THE CONVECTION OVER NEAR THE MONSOON TROUGH CONTINUING DURING
THE NEXT 24-36 HOURS...WITH NO OTHER CHANGES ELSEWHERE ACROSS
THE DISCUSSION AREA.

ATLANTIC OCEAN...
WATER VAPOR IMAGERY SHOWS A NEARLY STATIONARY UPPER LOW LOCATED
IN THE WRN ATLC BETWEEN THE NW BAHAMAS AND THE SE FLORIDA
PENINSULA NEAR 25N79W. THIS FEATURE APPEARS TO BE EMBEDDED IN
DRY AIR ALOFT. HOWEVER...SURFACE CONVERGENCE AND MIDDLE TO UPPER
LIFTING GENERATED BY THE UPPER LOW IS PRODUCING AN AREA OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 23N-27N
BETWEEN 77W AND THE FLORIDA COAST. THIS AREA OF SHOWERS WILL
CONTINUE TO MOVE WESTWARDS ACROSS THE SRN FLORIDA PENINSULA AND
FAR ERN GULF OF MEXICO DURING THE NEXT 24 HOURS...AS THE UPPER
LOW BEGINS TO DRIFT WEST LATER THIS AFTERNOON. FARTHER EAST...
TROPICAL STORM LESLIE CONTINUES TO TRACK NNW...STEERED BY A
WEAKNESS IN THE MIDDLE TO UPPER LEVEL SUBTROPICAL RIDGE. SEE
SPECIAL FEATURES SECTION ABOVE FOR MORE DETAILS. THE NEXT SYSTEM
TO THE EAST IS ALSO DESCRIBED IN THE SAME SECTION...LEAVING THE
REMAINDER OF THE ATLC BASIN UNDER FAIR WEATHER CONDITIONS...
PROVIDED BY A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE CENTERED
NEAR 22N25W..COMBINED WITH DRY SAHARAN DUST ALOFT NOTED ON
METEOSAT-9 IMAGERY.

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

$$

GARCIA




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