000 AXNT20 KNHC 210559 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURES... TROPICAL STORM OPHELIA IS CENTERED 12.2N 40.1W AT 21/0300 UTC OR 1375 NM E-SE OF THE NORTHERN LEEWARD ISLANDS MOVING W AT 8 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 08N-11N BETWEEN 39W-46W...AND FROM 12N-16N BETWEEN 37W-40W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 10N-18N ALONG 21W 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-24W. NO DEEP CONVECTION IS NOTED WITH THE WAVE. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM NEAR 09N24W TO 08N28W TO NEAR TROPICAL STORM OPHELIA THEN TO 09N50W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 04N-11N BETWEEN 25W-32W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL 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 EVENING...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 24N89W. WEAK CYCLONIC WIND FLOW IN THE VICINITY OF THE SURFACE TROUGH IS PROVIDING LIMITED ISOLATED SHOWERS AND TSTMS S OF 24N BETWEEN 83W-90W. ELSEWHERE...SATELLITE IMAGERY AND MOSAIC DOPPLER RADAR INDICATE THAT ISOLATED LOW-TOPPED SHOWERS ARE OCCURRING E OF 84W...INCLUDING THE STRAITS OF FLORIDA. CARIBBEAN SEA... AN UPPER LEVEL LOW IS CENTERED IN THE WESTERN CARIBBEAN NEAR 16N78W AND IS PROVIDING MUCH OF THE CARIBBEAN SEA W OF 78W WITH NORTHERLY FLOW ALOFT AND GENERALLY WEST-SOUTHWESTERLY FLOW ALOFT E OF 78W. WATER VAPOR IMAGERY INDICATES MUCH OF THIS FLOW IS MODERATELY DRY ALOFT WITH VERY FEW SHOWERS OCCURRING THIS EVENING S OF A LINE FROM THE YUCATAN CHANNEL NEAR 22N86W TO 14N70W. NORTH OF THIS LINE HOWEVER...A SURFACE TROUGH IS ANALYZED FROM THE YUCATAN CHANNEL NEAR 22N86W TO 17N81W. 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 16N BETWEEN 69W-85W. FARTHER EAST...AN UPPER LEVEL RIDGE IS ALONG 61W OVER THE FAR EASTERN CARIBBEAN WITH ISOLATED SHOWERS AND TSTMS OCCURRING E OF 65W. 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 32N74W. SOUTHEASTERLY LOW-LEVEL FLOW PREVAILS OVER A LARGE PORTION OF THE W ATLC WITH ISOLATED SHOWERS AND TSTMS OCCURRING W OF 72W. FARTHER EAST OVER THE REMAINDER OF THE W ATLC...AN UPPER LEVEL LOW IS CENTERED NEAR 24N72W WITH TROUGH AXIS EXTENDING FROM 32N65W 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 64W-73W. WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING FROM 19N-28N BETWEEN 63W-76W. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE N OF 20N E OF 55W ANCHORED BY A 1025 MB HIGH CENTERED NEAR 31N44W. EMBEDDED WITHIN THE SW PERIPHERY OF THIS SURFACE RIDGE...A WEAK SURFACE TROUGH IS ANALYZED FROM 15N-19N ALONG 57W AND CONTINUES TO DRIFT WESTWARD. SCATTERED SHOWERS AND TSTMS ARE OCCURRING FROM 15N-18N BETWEEN 56W-59W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN