000 AXNT20 KNHC 301746 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI SEP 30 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... HURRICANE OPHELIA IS CENTERED NEAR 23.5N 62.8W AT 30/1500 UTC OR ABOUT 505 NM S OF BERMUDA MOVING N AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 960 MB. MAXIMUM SUSTAINED WIND SPEED IS 100 KT WITH GUSTS TO 120 KT. NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION IS FROM 21N-28N BETWEEN 59W-65W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. TROPICAL STORM PHILIPPE IS CENTERED NEAR 22.9N 45.3W AT 30/1500 UTC OR ABOUT 995 NM N-NE OF THE LEEWARD ISLANDS MOVING NW AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 50 KT. SCATTERED MODERATE CONVECTION IS FROM 21N-26N BETWEEN 43W-47W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE PREVIOUSLY ANALYZED NEAR 35W HAS CONTINUED TO DISSIPATE OVER THE PAST 24 HOURS AND IS NO LONGER DISCERNIBLE IN LOW-LEVEL FLOW...SO THEREFORE IT HAS BEEN DROPPED FROM THE SURFACE ANALYSIS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W ALONG 13N21W 11N25W 08N28W TO 04N35W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 04N35W TO 04N51W. WIDELY SCATTERED MODERATE CONVECTION IS N OF 04N TO THE MONSOON TROUGH AXIS BETWEEN 13W-34W. ISOLATED MODERATE CONVECTION IS ALSO OCCURRING FROM 05N-13N BETWEEN 46W-51W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL WESTERLY FLOW DOMINATES ACROSS THE GULF BETWEEN UPPER LEVEL TROUGHING ACROSS THE EASTERN CONUS AND A BROAD EAST TO WEST UPPER LEVEL RIDGE AXIS ALONG 17N BETWEEN HISPANIOLA AND WEST-CENTRAL MEXICO. WATER VAPOR IMAGERY SHOWS A PROGRESSIVE SHORTWAVE TROUGH AXIS MOVING ACROSS MISSISSIPPI AND ALABAMA WHICH IS THE DRIVING FORCE FOR A COLD FRONT EXTENDING FROM VERMILION BAY LOUISIANA TO THE TEXAS COAST NEAR MATAGORDA BAY. A PRE-FRONTAL TROUGH EXTENDS FROM 29N94W TO 27N97W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 60 NM SE OF THE FRONTAL TROUGH AND EXTEND SOUTHWARD ACROSS PORTIONS OF THE WESTERN GULF WATERS S OF 24N W OF 94W. FARTHER EAST...A WEAK REMNANT FRONTAL BOUNDARY EXTENDS ACROSS THE NORTHERN FLORIDA PENINSULA INTO THE NE GULF WATERS NEAR 29N84W. WHILE THE BOUNDARY REMAINS FREE OF CONVECTION...A DRIER AIRMASS REMAINS TO THE NW ACROSS THE SE CONUS. AS THE COLD FRONT CONTINUES TO MARCH ACROSS THE GULF THROUGH TODAY AND OVER THE WEEKEND...A HIGH PRESSURE RIDGE IS FORECAST TO BUILD IN OVER THE CENTRAL PLAINS AND MISSISSIPPI RIVER VALLEY...REACHING SOUTHWARD OVER THE GULF...PROVIDING A DRY AND RELATIVELY COMFORTABLE AIRMASS TO REMAIN IN PLACE THROUGH EARLY WEDNESDAY OF NEXT WEEK. AS THE FRONT PASSES... MAINLY NE WINDS WILL DOMINATE OVER THE NEXT SEVERAL DAYS. CARIBBEAN SEA... AN UPPER LEVEL RIDGE AXIS EXTENDS FROM THE E PACIFIC REGION INTO THE WESTERN CARIBBEAN ALONG 18N TO 69W. A MODERATELY DRY AIRMASS ALOFT IS NOTED ON WATER VAPOR IMAGERY WITH THIS UPPER LEVEL RIDGE AND THEREFORE CONDITIONS OVER CENTRAL AMERICA AND THE WESTERN AND CENTRAL CARIBBEAN REMAIN FAIRLY FREE OF ANY SIGNIFICANT DEEP CONVECTION THIS AFTERNOON. EASTERLY TRADES EXTEND ACROSS THE CENTRAL CARIBBEAN AND MEET WITH GENERALLY LIGHT NORTHEASTERLY FLOW ACROSS THE WESTERN CARIBBEAN. A FEW ISOLATED SHOWERS AND TSTMS ARE ACROSS THE GULF OF HONDURAS... HOWEVER MOST OF THE ACTIVE CONVECTION IS A FEW ISOLATED SHOWERS AND TSTMS IN THE VICINITY OF THE WINDWARD PASSAGE REGION N OF 16N BETWEEN 72W-78W. ANOTHER AREA OF ISOLATED SHOWERS AND TSTMS IS NORTH OF THE PANAMA COAST IN THE VICINITY OF THE MONSOON TROUGH AXIS ALONG 10N. SCATTERED SHOWERS AND TSTMS ARE OCCURRING S OF 12N BETWEEN 76W-82W. FARTHER EAST...S-SE WINDS ARE NOTED OVER THE FAR EASTERN CARIBBEAN AND LESSER ANTILLES THIS AFTERNOON WITH WEAK LOW-LEVEL CONVERGENCE AIDING IN ISOLATED SHOWERS N OF 15N BETWEEN61W-67W. ATLANTIC OCEAN... UPPER LEVEL TROUGHING IS THE DOMINANT FEATURE ACROSS THE EASTERN CONUS AND THIS TROUGHING SUPPORTS A FRONTAL BOUNDARY FROM 32N78W TO THE NORTHERN FLORIDA PENINSULA NEAR 30N82W. A SURFACE TROUGH EXTENDS SOUTHWARD FROM THE FRONT NEAR 30N80W ALONG 26N80W TO WESTERN CUBA NEAR 23N81W. LOW-LEVEL CONVERGENCE EAST OF THE SURFACE TROUGH AND SUFFICIENT UPPER LEVEL DIFFLUENCE ALOFT IS GENERATING SCATTERED SHOWERS AND TSTMS NORTH OF THE BAHAMAS FROM 25N-32N BETWEEN 74W-78W. FARTHER EAST...THE REMAINDER OF THE SW NORTH ATLC IS CONCERNED WITH HURRICANE OPHELIA AS A GENERAL NORTHWARD MOVEMENT IS EXPECTED OVER THE NEXT 24 HOURS DUE TO THE UPPER LEVEL TROUGHING LOCATED W OF 66W. TROPICAL STORM PHILIPPE IS EXPECTED TO REMAIN OVER THE OPEN ATLC HIGH SEAS WATERS IN THE COMING DAYS. TO THE NORTH OF PHILIPPE...A LONGWAVE UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY ACROSS THE EASTERN ATLC WITH TROUGH AXIS ALONG 28W DIPPING INFLUENCE SOUTHWARD TO 27N BETWEEN 22W-42W. THIS TROUGH IS PRIMARILY IN SUPPORT OF A COLD FRONT ANALYZED FROM 32N25W TO 29N37W WHERE THE BOUNDARY TRANSITIONS TO A SHEAR LINE EXTENDING WESTWARD TO 28N46W. EARLIER MORNING ASCAT AND WINDSAT SCATTEROMETER PASSES INDICATED A NARROW ZONE WITH AN ABRUPT CHANGE IN THE HORIZONTAL WIND PARALLEL TO THE SHEAR LINE. STRONGER NE WINDS BY 10-15 KT WERE CAPTURED WITHIN 180 NM NORTH OF THE SHEAR LINE AS OPPOSED TO WEAKER E-NE WINDS BETWEEN THE SHEAR LINE AND TROPICAL STORM PHILIPPE. ELSEWHERE...THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE WITH AXIS FROM THE MADEIRA ISLANDS NEAR 31N16W TO 20N40W. FINALLY...EXAMINING METEOSAT-9 VISIBLE SATELLITE IMAGERY AND THE CIMSS SAHARAN AIR LAYER TRACKING PRODUCT...A LARGE AREA OF SAHARAN DUST COVERS THE EASTERN ATLC FROM 08N-27N E OF 38W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN