000 AXNT20 KNHC 211141 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT WED SEP 21 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURES... TROPICAL STORM OPHELIA IS CENTERED 12.7N 41.8W AT 21/0900 UTC OR 1190 NM E OF THE LEEWARD ISLANDS MOVING W AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 13N-16N BETWEEN 39W-42W... WHILE WIDELY SCATTERED MODERATE CONVECTION IS FROM 07N-12N BETWEEN 38W-48W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/ WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 11N23W TO 19N20W MOVING W AT 10-15 KT. SHORTWAVE INFRARED SATELLITE IMAGERY AND LOW-LEVEL STREAMLINE ANALYSIS INDICATES A BROAD CYCLONIC CIRCULATION IN THE VICINITY OF THE WAVE AXIS BETWEEN 18W-26W. ISOLATED MODERATE CONVECTION IS FROM 14N-17N BETWEEN 21W-25W. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM NEAR 10N25W TO 08N31W TO 09N35W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 04N-11N BETWEEN 24W-33W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL LOW AND ASSOCIATED LONGWAVE TROUGH IS LOCATED OVER THE CENTRAL CONUS PROVIDING THE NORTHWESTERN HALF OF THE GULF WITH MOSTLY SOUTHWESTERLY FLOW ALOFT. SE OF THE TROUGHING...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE YUCATAN PENINSULA NE OVER THE SOUTHERN FLORIDA PENINSULA AND INTO THE SW NORTH ATLC. WITH NO STRONGLY INFLUENTIAL UPPER LEVEL FEATURES ACROSS THE GULF THIS MORNING... A RELATIVELY WEAK PRESSURE GRADIENT EXISTS. THE NORTHERN EXTENT OF A SURFACE TROUGH EXTENDS FROM THE NW CARIBBEAN SEA THROUGH THE YUCATAN CHANNEL INTO THE SE GULF TO 24N90W. WEAK CYCLONIC WIND FLOW IN THE VICINITY OF THE SURFACE TROUGH IS PROVIDING MARGINAL LOW-LEVEL CONVERGENCE GENERATING ISOLATED SHOWERS AND TSTMS S OF 28N BETWEEN 82W-91W. ELSEWHERE...SATELLITE IMAGERY AND MOSAIC DOPPLER RADAR INDICATE THAT ISOLATED LOW-TOPPED SHOWERS ARE OCCURRING E OF 82W...INCLUDING THE STRAITS OF FLORIDA. CARIBBEAN SEA... AN UPPER LEVEL LOW IS CENTERED IN THE WESTERN CARIBBEAN NEAR 15N78W AND IS PROVIDING MUCH OF THE CARIBBEAN SEA W OF 80W WITH NORTHERLY FLOW ALOFT AND GENERALLY WEST-SOUTHWESTERLY FLOW ALOFT E OF 80W. WATER VAPOR IMAGERY INDICATES MUCH OF THIS FLOW IS MODERATELY DRY ALOFT WITH VERY FEW SHOWERS OCCURRING THIS MORNING S OF A LINE FROM THE YUCATAN PENINSULA NEAR 21N87W TO 14N80W. NORTH OF THIS LINE HOWEVER...A SURFACE TROUGH IS ANALYZED FROM THE YUCATAN CHANNEL NEAR 22N86W TO 16N81W. WIDELY SCATTERED SHOWERS AND TSTMS ARE PRIMARILY OCCURRING NORTH OF THIS BOUNDARY WHERE LOW-LEVEL MOISTURE CONVERGENCE IS MAXIMIZED. THIS CONVECTIVE ACTIVITY IS MOSTLY N OF 18N BETWEEN 76W-85W. FURTHERMORE...LOW-LEVEL SPEED CONVERGENCE OF EASTERLY TRADES ACROSS THE CENTRAL CARIBBEAN CONTINUES TO GENERATE SCATTERED SHOWERS AND ISOLATED TSTMS FROM 13N-16N BETWEEN 71W-79W...WHICH ARE ENHANCED BY MIDDLE TO UPPER LEVEL DIFFLUENCE. FARTHER EAST...AN UPPER LEVEL RIDGE AXIS IS ALONG 61W OVER THE FAR EASTERN CARIBBEAN WITH ISOLATED SHOWERS AND TSTMS OCCURRING FROM 14N-17N BETWEEN 62W-66W. AS THE UPPER LEVEL LOW AND SUBSEQUENT MIDDLE TO UPPER LEVEL DIFFLUENT FLOW EAST OF THE TROUGH AXIS IS FORECAST TO REMAIN IN PLACE ACROSS THE WESTERN CARIBBEAN THROUGH THURSDAY...THE INCREASED POSSIBILITY OF WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OVER HISPANIOLA AND CUBA IS EXPECTED THROUGH THE REMAINDER OF THE WEEK. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE SE GULF OF MEXICO OVER THE SOUTHERN FLORIDA PENINSULA INTO THE SW NORTH ATLC TO BEYOND 32N72W. SOUTHEASTERLY LOW-LEVEL FLOW PREVAILS OVER A LARGE PORTION OF THE W ATLC WITH ISOLATED SHOWERS AND TSTMS OCCURRING N OF 30N W OF 72W. FARTHER EAST OVER THE REMAINDER OF THE W ATLC...AN UPPER LEVEL LOW IS CENTERED NEAR 24N73W WITH TROUGH AXIS EXTENDING FROM 32N64W THROUGH THE LOW AND INTO THE WESTERN CARIBBEAN SEA. EAST OF THE UPPER LEVEL TROUGH AXIS... MIDDLE TO UPPER LEVEL TROPICAL MOISTURE CONTINUES TO ADVECT NORTHWARD BETWEEN 63W-73W WITH WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS OCCURRING FROM 20N-28N BETWEEN 64W-74W. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE N OF 20N E OF 60W ANCHORED BY A 1025 MB HIGH CENTERED NEAR 32N48W. EMBEDDED WITHIN THE SW PERIPHERY OF THIS SURFACE RIDGE...A WEAK SURFACE TROUGH IS ANALYZED FROM 15N-21N ALONG 58W AND CONTINUES TO MOVE WESTWARD. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS OCCURRING FROM 16N-19N BETWEEN 57W-61W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN