000 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