000 AXNT20 KNHC 250003 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT SAT SEP 24 2011 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 OPHELIA IS CENTERED NEAR 17.9N 57.4W AT 24/2100 UTC OR ABOUT 295 MI...475 KM E OF THE LESSER ANTILLES MOVING WNW AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 15N-21N BETWEEN 51W-59W. SHEAR IS EXPECTED TO GRADUALLY INCREASE OVER THE NEXT 72 HOURS...WHICH SHOULD INDUCE GRADUAL WEAKENING. TROPICAL DEPRESSION SEVENTEEN BECAME T.S. PHILIPPE AT 24/2100 UTC CENTERED NEAR 11.2N 27.9W...OR ABOUT 345 MI...550 KM SW OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING WNW AT ABOUT 12 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. SCATTERED MODERATE/STRONG CONVECTION IS AROUND THE S-WRN SEMI-CIRCLE FROM 8N-12N BETWEEN 27W-31W. PHILIPPE IS EXPECTED TO MOVE WEST-NORTHWESTWARD AROUND THE SOUTHERN PERIPHERY OF A STRONG SUBTROPICAL RIDGE LOCATED TO THE NORTH OF THE CYCLONE. ...TROPICAL WAVES... TROPICAL WAVE IS IN THE CENTRAL ATLC ANALYZED FROM 18N39W TO 11N40W MOVING W 10-15 KT. LOW LEVEL SATELLITE DERIVED WINDS INDICATE WEAK CYCLONIC TURNING AROUND THE WAVE AXIS. THE WAVE IS BETTER DEPICTED ON TOTAL PRECIPITABLE WATER IMAGERY SHOWING A SURGE OF DEEP LAYER MOISTURE IN THE VICINITY OF THE WAVE AXIS. CURRENTLY NO DEEP CONVECTION ACCOMPANIES THE WAVE. ...ITCZ/MONSOON TROUGH... DUE TO THE LARGE SCALE CIRCULATION OF NEWLY FORMED T.S. PHILIPPE ...THE CENTRAL ATLC TROPICAL WAVE AND T.S. OPHELIA...THE OCEANIC MONSOON TROUGH AND THE ITCZ ARE NOT PRESENT. AS PHILIPPE MOVES TOWARDS THE WNW...THE MONSOON TROUGH WILL SLOWLY BUILD BACK IN BEHIND IT. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY SHOWS A BROAD UPPER TROUGH/CUT-OFF LOW CENTERED OVER THE STATE OF ILLINOIS. THE CYCLONIC FLOW ASSOCIATED TO THIS FEATURE COVERS MOST OF THE ERN CONUS AND PUSHES A LONGWAVE THAT SWINGS OVER THE NE GULF...SUPPORTING A WEAK STATIONARY FRONT EXTENDING ACROSS THE NRN GULF FROM 30N83W TO 28N91W. THIS FRONT RELATES VERY WELL WITH FAIRLY DRY DEW POINTS TO THE N OF ITS AXIS...WITH NO SIGNIFICANT CONVECTION OCCURRING IN ITS VICINITY. THE SAME UPPER LEVEL CONDITIONS APPLY TO A WEAK SURFACE TROUGH ANALYZED FROM 26N85W TO 23N90W. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE DEVELOPING WITHIN 30-90 NM ON EITHER SIDE OF THE TROUGH AXIS. FAIR WEATHER CONDITIONS ARE OBSERVED ELSEWHERE ACROSS THE BASIN THIS EVENING. EXPECT THE STATIONARY FRONT CONTINUE TO WEAKEN OVER THE NEXT 12-24 HOURS. THE UPPER LEVEL TROUGH WILL ALSO REMAIN SOMEWHAT STATIONARY ACROSS THE ERN CONUS KEEPING DRY AIR ACROSS THE NW GULF WHICH WILL FURTHER SUPPORT FAIR CONDITIONS. CARIBBEAN SEA... MOSTLY FAIR WEATHER CONDITIONS WITH 15-20 KT ELY TRADEWIND FLOW ARE OBSERVED OVER MOST OF THE CARIBBEAN SEA THIS EVENING AS A DRY AIRMASS MOVES ACROSS THE ERN AND CENTRAL CARIBBEAN. THE ONLY AREA OF CONVECTION IS OBSERVED IN THE FAR SW BASIN. LAST SATELLITE VISIBLE PICTURES OF THE DAY SHOWED CLUSTERS OF MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS S OF 17N W OF 80W...ASSOCIATED TO THE MONSOON TROUGH EXTENDING ACROSS NICARAGUA INTO NRN COLOMBIA. COMPUTER MODELS SUGGEST THIS FEATURE WILL REMAIN NEARLY STATIONARY OVER THE NEXT 24 HOURS. TROPICAL STORM OPHELIA IS CURRENTLY E OF THE LESSER ANTILLES AND SOME OF THE OUTER BANDS WILL PASS OVER THIS GROUP OF ISLANDS AND ADJACENT WATERS N OF MARTINIQUE TONIGHT. ATLANTIC OCEAN... AN ELONGATED 1012 MB LOW IS 130 NM E OF DAYTONA BEACH FLORIDA PRODUCING A LARGE AREA OF SHOWERS AND THUNDERSTORMS ACROSS THE SW NORTH ATLC INCLUDING MUCH OF THE BAHAMAS W OF 74W. THIS SYSTEM IS SUPPORTED ALOFT BY A BROAD UPPER LEVEL LONGWAVE MOVING OFF THE SE CONUS SEABOARD. THIS DISTURBANCE HAS NOT BECOME ANY BETTER ORGANIZED DURING THE PAST 6 HOURS...AND THE POTENTIAL FOR DEVELOPMENT HAS DIMINISHED. AN UPPER RIDGE IS AHEAD OF THIS AREA OF CONVECTION SUPPORTING A 1024 MB HIGH NEAR 34N64W. A WEAK UPPER LOW IS N OF HISPANIOLA AND CONTINUES TO SHEAR T.S. OPHELIA. A BROAD UPPER TROUGH COVERS THE ERN NORTH ATLC SUPPORTING A WEAK COLD FRONT THAT CLIPS THE AREA ALONG 32N31W TO 29N37W GENERATING ISOLATED SHOWERS WITHIN 50 NM OF THE AXIS. A WEAK 1020 MB HIGH IS E OF THE FRONT NEAR THE MADEIRA ISLANDS PROVIDING FAIR WEATHER ACROSS THE SE ATLC. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA