000 AXNT20 KNHC 221151 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT THU SEP 22 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 13.4N 47.0W AT 22/0900 UTC OR 885 NM E-SE OF THE LEEWARD ISLANDS MOVING W AT 12 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 70 KT. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 13N-18N BETWEEN 42W-47W LOCATED MAINLY IN THE NE QUADRANT...WHILE SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF A LINE FROM 13N42W TO 08N50W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 19N25W TO 10N30W MOVING W AT 10-15 KT. THE WAVE IS EMBEDDED WITHIN A POLEWARD EXTENSION OF DEEP LAYER MOISTURE AS DEPICTED BY TOTAL PRECIPITABLE WATER IMAGERY FROM 05N-25N BETWEEN 22W-31W. NO SIGNIFICANT DEEP CONVECTION IS ATTRIBUTED TO THE WAVE AT THIS TIME. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 15N17W TO 13N21W. SCATTERED MODERATE CONVECTION IS FROM 04N-13N BETWEEN 11W-20W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH COVERS THE CENTRAL CONUS WHICH EXTENDS INTO THE WESTERN GULF PROVIDING WEST TO SOUTHWESTERLY FLOW ALOFT. WATER VAPOR IMAGERY INDICATES THAT MODERATE TO STRONG DRY AIR IS LOCATED W OF 90W...HOWEVER E OF 90W... LOW-LEVEL MOISTURE AND MIDDLE TO UPPER LEVEL DIFFLUENCE IS SUPPORTIVE OF SCATTERED SHOWERS AND TSTMS OCCURRING N OF 25N E OF 90W. A SURFACE TROUGH IS ANALYZED FROM 29N87W TO 20N90W WHICH IS ALSO AIDING IN MAXIMIZING LOW-LEVEL MOISTURE CONVERGENCE E OF THE TROUGH AXIS. ANOTHER WEAK SURFACE TROUGH IS LOCATED EAST OF THE YUCATAN PENINSULA S OF 23N ALONG 87W AND IS PROVIDING FOCUS FOR ISOLATED SHOWERS OVER THE SE GULF...THE YUCATAN CHANNEL...S OF 23N BETWEEN 85W-87W. OTHERWISE THIS MORNING...A RELATIVELY WEAK PRESSURE GRADIENT REMAINS ACROSS THE GULF WITH GENERALLY LIGHT AND BROAD CYCLONIC FLOW AROUND THE SURFACE TROUGH ALONG 90W. BY FRIDAY...A COLD FRONT IS FORECAST TO ENTER THE NW GULF WATERS AND EVENTUALLY WEAKEN AS IT SKIRTS THE NORTH-CENTRAL AND NE GULF. CARIBBEAN SEA... A WEAK SURFACE TROUGH IS ANALYZED FROM 18N TO 23N ALONG 87W IN THE VICINITY OF THE YUCATAN CHANNEL AND REMAINS THE FOCUS FOR ISOLATED SHOWERS N OF 17N BETWEEN 85W-88W. AN UPPER LEVEL RIDGE EXTENDS FROM THE E PACIFIC ACROSS SOUTHERN MEXICO AND THE YUCATAN PENINSULA TO WESTERN CUBA WHICH IS PROVIDING MARGINAL SUPPORT FOR THIS CONVECTIVE ACTIVITY OVER THE NW CARIBBEAN THIS MORNING. FARTHER EAST...AN UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE WINDWARD PASSAGE NEAR 20N75W TO 11N84W. MIDDLE TO UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH AXIS ALONG WITH LOW-LEVEL SPEED CONVERGENCE OF EASTERLY TRADES IS GENERATING ISOLATED SHOWERS AND TSTMS FROM 09N-18N BETWEEN 76W-84W. THE REMAINDER OF THE EASTERN CARIBBEAN IS UNDER THE INFLUENCE OF AN UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 12N70W. HOWEVER...AT THE SURFACE..A WEAK 1011 MB LOW IS CENTERED OVER PUERTO RICO NEAR 18N66W WHICH CONTINUES TO MOVE SWIFTLY WESTWARD WITH ISOLATED SHOWERS AND TSTMS FROM 15N-19N BETWEEN 64W-68W. ANOTHER BAND OF LOW-LEVEL MOISTURE AND ISOLATED SHOWERS IS ACROSS THE LESSER ANTILLES AND ADJACENT COASTAL WATERS THIS MORNING FROM 11N-20N BETWEEN 59W-64W. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE IS ANCHORED IN THE SW NORTH ATLC NEAR 29N71W WITH AN UPPER LEVEL LOW POSITIONED TO THE S OVER THE SE BAHAMAS NEAR 23N74W. THIS IS GENERATING A LARGE AREAL COVERAGE OF ISOLATED SHOWERS AND POSSIBLE ISOLATED TSTMS N OF 20N W OF 69W. FARTHER EAST OVER THE REMAINDER OF W ATLC...AN UPPER LEVEL RIDGE AXIS EXTENDS FROM N OF PUERTO RICO NEAR 20N66W TO THE PREVIOUSLY MENTIONED UPPER LEVEL RIDGE NEAR 29N71W. AN OVERALL DIFFLUENT ENVIRONMENT FROM 22N-27N BETWEEN 55W-69W IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 22N-28N BETWEEN 55W-69W. OTHERWISE THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1028 MB HIGH CENTERED NEAR 38N59W WHICH IS FORECAST TO REMAIN QUASI- STATIONARY THROUGH EARLY SATURDAY. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN