000 AXNT20 KNHC 281753 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED SEP 28 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURES... TROPICAL STORM OPHELIA IS CENTERED NEAR 18.7N 59.9W AT 28/1500 UTC OR ABOUT 185 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING N-NW AT 3 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE CONVECTION IS FROM 15N-21N BETWEEN 57W-60W CONTINUING TO BE SHEARED TO THE EAST DUE TO AN UPPER LEVEL TROUGH AXIS ALONG 63W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. TROPICAL STORM PHILIPPE IS CENTERED NEAR 16.4N 38.8W AT 28/1500 UTC OR ABOUT 850 NM W OF THE CAPE VERDE ISLANDS MOVING W-NW AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SCATTERED MODERATE CONVECTION IS SHEARED TO THE NORTH OF THE CENTER OF PHILIPPE AND IS OCCURRING FROM 16N-20N BETWEEN 35W-39W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/ WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 04N29W TO 11N28W MOVING W AT 10-15 KT. THIS RELATIVELY LOW-LATITUDE WAVE CONTINUES TO EXHIBIT CYCLONIC TURNING OF THE LOW-LEVEL CLOUD FIELD IN THE VICINITY OF THE WAVE AXIS BETWEEN 25W-32W. NO SIGNIFICANT DEEP CONVECTION IS OBSERVED ON VISIBLE SATELLITE IMAGERY AT THIS TIME. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W TO 08N21W. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 90 NM EITHER SIDE OF A LINE FROM 08N16W TO 04N22W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL WESTERLY FLOW DOMINATES ACROSS THE GULF THIS AFTERNOON BETWEEN AN UPPER LEVEL LOW CENTERED OVER THE GREAT LAKES REGION AND AN ANTICYCLONIC CIRCULATION CENTERED OVER SOUTHERN MEXICO NEAR 17N95W. WATER VAPOR IMAGERY INDICATES A MODERATELY DRY AIRMASS IS IN PLACE ACROSS MUCH OF THE GULF. AT THE SURFACE...A 1015 MB HIGH IS CENTERED IN THE CENTRAL GULF NEAR 27N88W. A WEAKNESS WITHIN THE RIDGE IS APPARENT WITHIN THE PRESSURE ANALYSIS OVER THE WEST-CENTRAL AND SW GULF WHERE WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING S OF 25N W OF 94W. THIS ACTIVITY IS LIKELY ENHANCED DUE TO AN UPPER LEVEL DIFFLUENT ENVIRONMENT ON THE NORTHERN PERIPHERY OF THE UPPER LEVEL ANTICYCLONE OVER SOUTHERN MEXICO. ALSO OF NOTE...AN AREA OF SCATTERED SHOWERS AND TSTMS IS OCCURRING OVER SOUTHERN ALABAMA AND THE FLORIDA PANHANDLE...INCLUDING THE ADJACENT COASTAL WATERS...N OF 29N BETWEEN 85W-89W. THE REMAINDER OF THE GULF IS EXPERIENCING CLEAR SKIES AND FAIR WEATHER CONDITIONS DUE TO THE SURFACE HIGH AND IS FORECAST TO REMAIN QUASI-STATIONARY OVER THE CENTRAL GULF THROUGH THURSDAY. CARIBBEAN SEA... AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER SOUTHERN MEXICO NEAR 17N95W AND IS PROVIDING MUCH OF THE WESTERN AND CENTRAL CARIBBEAN W OF 65W WITH NORTHWEST TO NORTHERLY FLOW ALOFT. THIS DRY AND GENERALLY SUBSIDENT AIR IS MAINTAINING MOSTLY FAIR WEATHER CONDITIONS AND CLEAR SKIES...HOWEVER...GIVEN AN UPPER LEVEL DIFFLUENT ENVIRONMENT AND AREAS OF TRADEWIND CONVERGENCE...ISOLATED SHOWERS ARE OCCURRING FROM 15N-18N BETWEEN 71W-77W. ANOTHER AREA OF ISOLATED SHOWERS AND TSTMS IS OCCURRING OFF THE COAST OF NICARAGUA FROM 11N-15N W OF 82W. THE REMAINDER OF THE EASTERN CARIBBEAN E OF 65W FALLS UNDER THE INFLUENCE OF TROPICAL STORM OPHELIA WHICH CONTINUES TO PROVIDE SW TO W SURFACE WINDS ACROSS THE LESSER ANTILLES AND A FEW ISOLATED SHOWERS AND TSTMS N OF 14N E OF 64W. ATLANTIC OCEAN... UPPER LEVEL DIFFLUENT FLOW IS NOTED W OF 70W ON WATER VAPOR IMAGERY BETWEEN AN UPPER LEVEL LOW CENTERED OVER THE GREAT LAKES REGION AND AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER SOUTHERN MEXICO. SOUTHWESTERLY UPPER LEVEL FLOW BETWEEN THESE TWO FEATURES AND A SURFACE TROUGH ANALYZED FROM 24N80W TO 31N79W IS PROVIDING FOCUS FOR SCATTERED SHOWERS AND ISOLATED TSTMS N OF 30N BETWEEN 71W-78W...WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH BOUNDARY...AND FROM 20N-25N BETWEEN 72W-78W...INCLUDING THE CENTRAL AND SE BAHAMAS. EAST OF 70W...AN UPPER LEVEL TROUGH AXIS EXTENDS ALONG 63W AND CONTINUES TO ADVECT MIDDLE TO UPPER LEVEL MOISTURE ASSOCIATED WITH CONVECTIVE DEBRIS FROM TROPICAL STORM OPHELIA NORTHWARD TO 29N. OPHELIA REMAINS UNDER A SHEARED ENVIRONMENT DUE TO THE UPPER LEVEL TROUGH AND WIDELY SCATTERED SHOWERS ARE OCCURRING OUTSIDE OF THE INFLUENCE OF OPHELIA FROM 21N-29N BETWEEN 55W-65W AS THE MOISTURE AND CLOUDINESS FANS N-NE. NEARLY THE SAME SYNOPTIC SETUP IS PLAGUING TROPICAL STORM PHILIPPE AS AN UPPER LEVEL LOW IS CENTERED TO THE WEST OF PHILIPPE NEAR 18N45W. NUMEROUS SHOWERS AND SCATTERED TSTMS ARE OCCURRING FROM 16N-20N BETWEEN 35W-39W. THE CENTRAL ATLC FALLS WITHIN A WEAKNESS OF THE SUBTROPICAL RIDGE WITH A SURFACE TROUGH ANALYZED FROM 32N37W TO 26N50W AHEAD OF A COLD FRONT DRAPED NORTH OF THE DISCUSSION AREA ALONG 34N BETWEEN 40W-55W. ISOLATED SHOWERS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH. THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1021 MB HIGH CENTERED SW OF THE MADEIRA ISLANDS NEAR 32N18W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN