000 AXNT20 KNHC 222358 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT SEP 22 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... POST-TROPICAL CYCLONE NADINE IS CENTERED OVER THE NORTHEASTERN ATLC ANALYZED AS A 987 MB SURFACE LOW NEAR 30N26W MOVING SE AT 5-10 KT. ISOLATED MODERATE CONVECTION IS NEAR THE LOW CENTER AND TO THE NE FROM 30N-32N BETWEEN 24W-26W. CONDITIONS ARE EXPECTED TO BE MARGINALLY FAVORABLE FOR REGENERATION OF THIS SYSTEM INTO A TROPICAL OR SUBTROPICAL CYCLONE AS IT MOVES OVER SLIGHTLY WARMER WATERS DURING THE NEXT DAY OR TWO. THIS SYSTEM HAS A MEDIUM CHANCE OF BECOMING A TROPICAL OR SUBTROPICAL CYCLONE AGAIN DURING THE NEXT 48 HOURS. ADDITIONAL INFORMATION ON POST-TROPICAL CYCLONE NADINE CAN BE FOUND IN HIGH SEAS FORECASTS ISSUED BY METEO FRANCE. ...TROPICAL WAVES... TROPICAL WAVE MOVES ACROSS THE CENTRAL TROPICAL ATLC WITH AXIS FROM 15N45W TO 10N50W MOVING W AT ABOUT 15-20 KT. THE WAVE LIES WITHIN A HORIZONTALLY ELONGATED AREA OF DEEP LAYER MOISTURE. A WEAK LOW LEVEL CIRCULATION AROUND THE WAVE AXIS IS NOTED ON INFRA-RED IMAGERY. SCATTERED MODERATE CONVECTION IS FROM 12N-15N BETWEEN 45W-48W. TROPICAL WAVE EXTENDS FROM THE ERN BAY OF CAMPECHE OVER THE GULF OF MEXICO AT 21N90W TO THE ERN PACIFIC NEAR 11N94W...ENHANCING INLAND LOCAL PRECIPITATION ACROSS THE YUCATAN PENINSULA. OVER THE NEXT 24 HOURS...THE NORTHERN HALF OF THE WAVE AXIS WILL LIKELY DISSIPATE OVER THE ERN SIERRA MADRE MOUNTAINS AS THE SOUTHERN PORTION CONTINUES IN THE E PACIFIC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO A 1008 MB SURFACE LOW ALONG THE COAST OF SENEGAL AT 16N15W AND CONTINUES OVER ATLC WATERS ALONG 10N23W 6N34W. THE ITCZ BEGINS AT 6N34W AND CONTINUES ALONG 7N38W 8N47W 7N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-8N BETWEEN 16W-28W. NO OTHER DEEP CONVECTION IS NOTED. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH CONTINUES TO SLOWLY MOVE ACROSS THE ERN CONUS THIS EVENING PROVIDING SOUTHWESTERLY FLOW ACROSS THE ENTIRE BASIN. THIS PATTERN IS BRINGING DRY AIR AND STRONG SUBSIDENCE ALOFT OVER THE NW AND MOST OF THE CENTRAL PORTION OF THE GULF. HOWEVER...AN AREA OF STRONG DIFFLUENCE ASSOCIATED WITH THE UPPER TROUGH EXTENDS INTO THE SE GULF SUPPORTING A SURFACE TROUGH ANALYZED FROM 27N83W TO THE YUCATAN CHANNEL NEAR 21N86W. SCATTERED MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE OVER THIS REGION S OF 26N E OF 86W...AS WELL AS INLAND PORTIONS OF CENTRAL AND SOUTH FLORIDA PENINSULA. A WEAK TROPICAL WAVE IS ENTERING THE ERN BAY OF CAMPECHE...ENHANCING INLAND LOCAL PRECIPITATION ACROSS THE YUCATAN PENINSULA. SEE TROPICAL WAVE SECTION FOR MORE DETAILS. TO THE W OF THIS TROPICAL WAVE...A SURFACE TROUGH IS ANALYZED FROM 24N96W TO 20N94W GENERATING SIMILAR CONVECTION S OF 25N W OF 93W. FAIR WEATHER WITH A FEW ISOLATED WEAK SHOWERS ARE ACROSS THE REMAINDER OF THE GULF SUPPRESSED BY THE DRY/SUBSIDENT AIR ALOFT AND A SURFACE RIDGE ANCHORED INLAND OVER SW LOUISIANA. THE WEATHER WILL REMAIN UNSETTLED ACROSS THE SRN HALF OF THE GULF DURING THE NEXT 24 HOURS. CARIBBEAN SEA... THE SAME DIFFLUENT PATTERN ALOFT ACROSS THE S-ERN GULF OF MEXICO EXTENDS INTO THE NW CARIBBEAN SUPPORTING A SURFACE TROUGH THAT EXTENDS OVER THE SE GULF TO THE YUCATAN CHANNEL NEAR 21N86W. SCATTERED SHOWERS AND THUNDERSTORMS ARE NOTED ACROSS THIS AREA N OF 17N W OF 80W. THIS PATTERN WILL SLOWLY LIFT N ALLOWING FOR DRYER WEATHER TO TAKE PLACE. SIMILAR ACTIVITY IS NOTED ACROSS THE SW BASIN S OF 12N W OF 75W ASSOCIATED TO THE ERN PACIFIC MONSOON TROUGH EXTENDING ACROSS CENTRAL AMERICA OVER COSTA RICA TO NRN COLOMBIA. FAIR WEATHER WITH A FEW ISOLATED SHOWERS ARE NOTED ACROSS THE REMAINDER OF THE BASIN DUE TO DRY AIR ALOFT BETWEEN A WEAK UPPER LEVEL RIDGE OVER THE NW CARIBBEAN AND A DRY ELONGATED UPPER LEVEL LOW MOVING ACROSS THE EASTERN CARIBBEAN NEAR 14N63W. TRADEWIND FLOW OF 15-20 KT IS PRESENT ACROSS MUCH OF THE BASIN. EXPECT MOIST CONDITIONS TO REMAIN ACROSS THE SW CARIBBEAN FOR THE NEXT 24 HOURS. ATLANTIC OCEAN... THE UPPER LEVEL TROUGH OVER THE EASTERN CONUS IS GENERATING AN AREA CONVECTION OFF THE SE CONUS COAST. A SURFACE TROUGH IS ANALYZED FROM 33N72W TO 27N78W ENHANCING THE AREA OF CONVECTION N OF 24N W OF 74W...INCLUDING THE NW BAHAMAS. THE ENVIRONMENT IS EXPECTED TO REMAIN FAVORABLE FOR THE DEVELOPMENT OF CONVECTION DURING THE NEXT 24 HOURS AS IT DRIFTS EASTWARD. AN UPPER LEVEL RIDGE IS TO THE E OF THIS AREA OF CONVECTION OVER THE WRN ATLANTIC PROVIDING FAIR CONDITIONS W OF 60W. OVER THE PAST 6 HOURS THE UPPER LEVEL LOW NEAR 32N59W HAS BEEN SHOWING SIGNS OF ELONGATION AND THE ASSOCIATED CONVECTION HAS DETACHED SIGNIFICANTLY. SHOWERS AND ISOLATED THUNDERSTORMS ARE LOCATED N OF 26N AND BETWEEN 52W-60W. ANOTHER AREA OF SCATTERED SHOWERS/THUNDERSTORMS IS LOCATED FARTHER SOUTH FROM 22N-26N BETWEEN 55W-58W. UPPER LEVEL RIDGING DOMINATES THE CENTRAL ATLC CENTERED NEAR 33N40W. POST-TROPICAL STORM NADINE IS LOCATED OVER THE EASTERN ATLANTIC ATTACHED TO AN UPPER LEVEL TROUGH PRODUCING SOME SHOWER ACTIVITY TO THE E AND NE OF THE CENTER AS WELL AS GALE FORCE WINDS IN THE NW QUADRANT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA/DELGADO