000 AXNT20 KNHC 240001 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SUN SEP 23 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...SPECIAL FEATURES... TROPICAL STORM NADINE WAS LOCATED NEAR 31.0N 26.1W AT 23/2100 UTC. THIS POSITION IS LOCATED ABOUT 485 MI...785 KM S OF THE AZORES...MOVING WNW AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 986 MN. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUST TO 60 KT. PLEASE SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 28N-34W BETWEEN 22W-30W. ...TROPICAL WAVES... TROPICAL WAVE IS E OF THE LESSER ANTILLES EXTENDING FROM 14N54W TO 11N58W MOVING W 15-20 KT. SCATTERED HEAVY SHOWERS AND THUNDERSTORMS ARE FROM 10N-17N BETWEEN 5W-60W. AN UPPER LEVEL LOW MOVING ACROSS THE ERN CARIBBEAN IS PROVIDING A DIFFLUENT ENVIRONMENT ABOVE THE WAVE...ENHANCING THE CONVECTION NEAR THE WAVE AXIS AND OVER THE ERN CARIBBEAN. THE CONVECTION NEAR THE WAVE SEEMS TO BE MORE RELATED TO THE UPPER LOW THAN THE WAVE ITSELF. TROPICAL WAVE MOVES ACROSS THE WRN BAY OF CAMPECHE AND INLAND PORTIONS OF SRN MEXICO EXTENDING FROM 21N95W TO 15N96W. THIS WAVE IS INTERACTING WITH A SURFACE TROUGH ANALYZED OVER THE WRN GULF OF MEXICO GENERATING SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS S OF 26N W OF 92W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM A 1010 MB LOW OFF THE COAST OF MAURITANIA NEAR 18N16W ALONG 11N20W TO 8N30W...WHERE THE ITCZ CONTINUES ALONG 7N33W 8N40W 10N50W TO E OF THE TROPICAL WAVE NEAR 11N56W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 7N-13N E OF 26W...WITHIN 130 NM S OF THE ITCZ BETWEEN 26W-44W...AND WITHIN 90 NM N OF THE ITCZ W OF 44W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH CONTINUES TO SLOWLY MOVE OFF THE ERN CONUS SEABOARD THIS EVENING PROVIDING A STRONG WESTERLY FLOW ALOFT ACROSS THE ENTIRE BASIN. THIS PATTERN IS BRINGING DRY AIR AND STRONG SUBSIDENCE ALOFT OVER THE NRN HALF OF THE GULF N OF 25N. DESPITE THE ENVIRONMENTAL CONDITIONS ALOFT AROUND THE UPPER TROUGH...THIS FEATURE SUPPORTS A COLD FRONT EXTENDING ACROSS THE NRN FLORIDA PENINSULA INTO THE GULF ALONG 28N82W TO NEAR THE COAST OF ALABAMA BASED ON DEW POINT OBSERVATIONS. THIS FRONT IS NOT CAUSING ANY SIGNIFICANT WEATHER...EXPECTED TO MOVE ACROSS THE N GULF THIS EVENING THEN BECOME STATIONARY ACROSS THE CENTRAL GULF LATER TONIGHT. THE FRONT WILL GRADUALLY WASH OUT THROUGH WED AS HIGH PRESSURE NE OF THE AREA GRADUALLY WEAKENS. AN AREA OF STRONG DIFFLUENCE ASSOCIATED WITH THE UPPER TROUGH COVERS THE SRN HALF OF THE BASIN S OF 25N SUPPORTING A SURFACE TROUGH ANALYZED ACROSS SRN FLORIDA ALONG 26N81W TO NEAR THE NRN COAST OF THE YUCATAN PENINSULA NEAR 22N88W. SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE OVER THIS REGION S OF 26N E OF 87W...AS WELL AS INLAND PORTIONS OF CENTRAL AND SOUTH FLORIDA PENINSULA. THE NRN PORTION OF A TROPICAL WAVE MOVES ACROSS THE WRN BAY OF CAMPECHE AND IS INTERACTING WITH A SURFACE TROUGH ANALYZED FROM 25N97W TO 19N96W GENERATING SIMILAR CONVECTION S OF 26N W OF 92W. FAIR WEATHER WITH A FEW ISOLATED WEAK SHOWERS ARE ACROSS THE REMAINDER OF THE GULF SUPPRESSED BY THE DRY/SUBSIDENT AIR ALOFT. THE WEATHER WILL REMAIN UNSETTLED ACROSS THE SRN HALF OF THE GULF DURING THE NEXT 24 HOURS. CARIBBEAN SEA... DIFFLUENCE FLOW ALOFT CONTINUES OVER THE NW CARIBBEAN SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 17N W OF 82W. SHORT RANGE COMPUTER MODELS SUGGEST THIS PATTERN WILL BE SLOW TO DISSIPATE DURING THE NEXT 24 HOURS. SIMILAR ACTIVITY IS NOTED ACROSS THE SW BASIN S OF 14N W OF 78W ASSOCIATED TO THE ERN PACIFIC MONSOON TROUGH EXTENDING ACROSS CENTRAL AMERICA OVER COSTA RICA TO NRN COLOMBIA. AN UPPER LEVEL LOW MOVES ACROSS THE ERN BASIN PROVIDING AN AREA OF DIFFLUENCE OVER THE LESSER ANTILLES AND SE CARIBBEAN. WITH PLENTY OF LOW LEVEL MOISTURE IN THIS REGION NOTED ON TPW IMAGERY...THIS UPPER FEATURE IS GENERATING SCATTERED HEAVY SHOWERS AND ISOLATED THUNDERSTORMS S OF 17N E OF 69W. THIS AREA OF CONVECTION WILL CONTINUE TO AFFECT THE SE CARIBBEAN AND SRN LESSER ANTILLES DURING THE NEXT 24 HOURS. FAIR WEATHER WITH A FEW ISOLATED SHOWERS ARE NOTED ACROSS THE REMAINDER OF THE BASIN. TRADEWIND FLOW OF 15-20 KT IS PRESENT ACROSS MUCH OF THE BASIN. ATLANTIC OCEAN... A BROAD UPPER LEVEL TROUGH CONTINUES TO SLOWLY MOVE OFF THE ERN CONUS SEABOARD THIS EVENING SUPPORTING A COLD FRONT EXTENDING ACROSS THE SEABOARD TO NRN FLORIDA. WHILE THIS FRONT CURRENTLY LACKS OF CONVECTION...A SURFACE TROUGH IS ANALYZED AHEAD OF IT ALONG 32N74W TO TO A WEAK 1016 MB LOW NEAR 29N77W PRODUCING AN AREA OF SCATTERED MODERATE TO STRONG CONVECTION WITHIN 150 NM SE OF THE SURFACE TROUGH AXIS INCLUDING THE NW BAHAMAS. THIS SYSTEM IS EXPECTED TO SLOWLY DRIFT EASTWARD WITH CONVECTION DURING THE NEXT 24 HOURS. AN ELONGATED UPPER LEVEL LOW IS CENTERED NEAR 28N57W PRODUCING AN AREA OF SHOWERS AND ISOLATED THUNDERSTORMS FROM 23N-27N BETWEEN 58W-64W. A STRONG/BROAD SURFACE RIDGE DOMINATES THE REMAINDER OF THE CENTRAL AND ERN ATLC ANCHORED BY A 1032 MB HIGH NEAR 43N41W. HOWEVER...TROPICAL STORM NADINE NOW DOMINATES A SMALL SECTION OF THE ERN ATLC...SEE SPECIAL FEATURES ABOVE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA