000 AXNT20 KNHC 011758 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT OCT 01 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 29.5N 62.9W AT 01/1500 UTC OR ABOUT 150 NM SE OF BERMUDA MOVING N AT 18 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 952 MB. MAXIMUM SUSTAINED WIND SPEED IS 105 KT WITH GUSTS TO 130 KT. NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION IS FROM 28N-31N BETWEEN 60W-65W. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/ WTNT31 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. TROPICAL STORM PHILIPPE IS CENTERED NEAR 24.8N 48.0W AT 01/1500 UTC OR ABOUT 995 NM N-NE OF THE LEEWARD ISLANDS MOVING NW AT 08 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS FROM 22N-28N BETWEEN 43W-48W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N17W ALONG 10N20W TO 07N33W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N33W TO 07N45W. ISOLATED MODERATE CONVECTION IS FROM 05N-09N BETWEEN 11W-15W...AND FROM 13N-17N BETWEEN 15W-19W. SCATTERED MODERATE CONVECTION IS FROM 06N-13N BETWEEN 45W-56W. ...DISCUSSION... GULF OF MEXICO... UPPER LEVEL WESTERLY FLOW DOMINATES ACROSS THE GULF BETWEEN AN UPPER LEVEL LOW AND ASSOCIATED TROUGHING ACROSS THE EASTERN CONUS AND A BROAD EAST TO WEST UPPER LEVEL RIDGE AXIS ALONG 15N BETWEEN HISPANIOLA AND WEST-CENTRAL MEXICO. WATER VAPOR IMAGERY SHOWS A VERY DRY AIRMASS MOVING ACROSS THE NORTHERN GULF N OF 27N WHICH IS THE DRIVING FORCE FOR A COLD FRONT EXTENDING FROM NEAR LAKE OKEECHOBEE FLORIDA TO 25N90W TO THE TEXAS COAST NEAR BROWNSVILLE. WHILE THE FRONT LACKS ANY SIGNIFICANT DEEP CONVECTION DUE TO A LACK OF SUFFICIENT MOISTURE AND STRONGER MIDDLE TO UPPER LEVEL LIFT...EXAMINING DEWPOINTS OVER THE NORTHERN GULF AND NORTHERN PORTIONS OF FLORIDA VERSUS THE SOUTHERN GULF AND THE EXTREME SOUTHERN FLORIDA PENINSULA...A STARK CONTRAST IN AIRMASSES IS APPARENT. DEWPOINTS REMAIN IN THE LOWER TO MID 70'S SOUTH OF THE FRONT...WHILE DEWPOINTS ARE IN THE 50'S AND UPPER 40'S IN SOME LOCATIONS ALONG THE NORTHERN GULF COAST. VISIBLE SATELLITE IMAGERY INDICATES A FEW ISOLATED SHOWERS ARE OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT. FARTHER SOUTH...LOW-LEVEL CONVERGENCE OVER THE SW GULF IS GENERATING ISOLATED SHOWERS AND TSTMS S OF 25N W OF A LINE FROM THE COLD FRONT TO 19N92W. AS THE COLD FRONT CONTINUES TO MARCH ACROSS THE GULF THROUGH THE WEEKEND...A HIGH PRESSURE RIDGE IS FORECAST TO BUILD IN OVER THE MISSISSIPPI RIVER VALLEY... REACHING SOUTHWARD OVER THE GULF...PROVIDING A DRY AND RELATIVELY STABLE AIRMASS TO REMAIN IN PLACE THROUGH EARLY WEDNESDAY OF NEXT WEEK. AS THE FRONT PASSES...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 15N TO 64W. A MODERATELY DRY AIRMASS ALOFT IS NOTED ON WATER VAPOR IMAGERY WITH THIS UPPER LEVEL RIDGE AND THEREFORE CONDITIONS OVER CENTRAL AMERICA AND MOST OF THE 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. THIS GENERALLY CYCLONIC LOW-LEVEL FLOW IS FOCUSED ALONG A SURFACE TROUGH ANALYZED FROM 20N85W TO 16N88W WITH SCATTERED SHOWERS AND TSTMS OCCURRING FROM 15N-20N BETWEEN 83W-89W. FARTHER EAST...UPPER LEVEL DIFFLUENCE IS SUPPORTIVE OF A FEW ISOLATED SHOWERS AND TSTMS ACROSS THE WINDWARD PASSAGE REGION N OF 16N BETWEEN 71W-77W. ANOTHER AREA OF ISOLATED SHOWERS AND TSTMS IS LOCATED IN THE SW CARIBBEAN IN THE VICINITY OF THE MONSOON TROUGH AXIS ALONG 09N/10N. ISOLATED SHOWERS AND TSTMS ARE OCCURRING S OF 12N BETWEEN 75W-79W...AND S OF 12N W OF 82W. FARTHER EAST...S-SE WINDS ARE NOTED OVER THE EASTERN CARIBBEAN AND LESSER ANTILLES THIS AFTERNOON WITH WEAK LOW-LEVEL CONVERGENCE AIDING IN ISOLATED SHOWERS N OF 16N BETWEEN 64W-68W...INCLUDING PUERTO RICO AND THE US/UK VIRGIN ISLANDS. ATLANTIC OCEAN... UPPER LEVEL TROUGHING IS THE DOMINANT FEATURE ACROSS THE EASTERN CONUS AND THIS TROUGHING SUPPORTS A FRONTAL BOUNDARY FROM 32N75W TO THE SOUTHERN FLORIDA PENINSULA NEAR 27N80W. A PRE-FRONTAL SURFACE TROUGH EXTENDS EAST OF THE FRONT FROM 32N73W TO THE CENTRAL BAHAMAS NEAR 25N78W. LOW-LEVEL CONVERGENCE EAST OF THE SURFACE TROUGH AND SUFFICIENT UPPER LEVEL DIFFLUENCE ALOFT IS GENERATING SCATTERED SHOWERS AND TSTMS IN A NARROW ZONE ACROSS THE SW NORTH ATLC WATERS FROM 20N-32N BETWEEN 69W-73W. FARTHER EAST...THE REMAINDER OF THE SW NORTH ATLC IS CONCERNED WITH HURRICANE OPHELIA AS A NORTHWARD MOVEMENT IS EXPECTED OVER THE NEXT 24 HOURS DUE TO THE APPROACHING UPPER LEVEL TROUGH LOCATED W OF 65W. TROPICAL STORM PHILIPPE IS EXPECTED TO REMAIN OVER THE OPEN ATLC HIGH SEAS WATERS IN THE COMING DAYS THAT REMAINS EMBEDDED WITHIN A SURFACE RIDGE COVERING MUCH OF THE CENTRAL ATLC N OF 15N BETWEEN 25W-55W. OVER THE EASTERN ATLC...AN UPPER LEVEL LOW IS CENTERED EAST OF THE AZORES NEAR 37N24W WITH A TROUGH AXIS EXTENDING SOUTHWARD TO A BASE NEAR 24N30W. THIS TROUGHING SUPPORTS A WEAKENING COLD FRONT EXTENDING INTO THE DISCUSSION AREA NEAR 32N17W TO 26N25W. ISOLATED SHOWERS ARE OCCURRING WITHIN 30 NM EITHER SIDE OF THE FRONT. FINALLY... EXAMINING METEOSAT-9 VISIBLE SATELLITE IMAGERY AND THE CIMSS SAHARAN AIR LAYER TRACKING PRODUCT...A LARGE AREA OF SAHARAN DUST COVERS THE EASTERN AND CENTRAL ATLC FROM 07N-22N BETWEEN 25W-45W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN