000 AXNT20 KNHC 151738 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT THU SEP 15 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 MARIA IS CENTERED NEAR 33.8N 66.5W AT 15/1800 UTC OR ABOUT 125 NM NW OF BERMUDA MOVING N-NE AT 28 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 991 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SCATTERED MODERATE CONVECTION IS FROM 26N-36N BETWEEN 64W-70W. THIS IS DUE IN PART TO A MODERATE AMOUNT OF WESTERLY MIDDLE TO UPPER LEVEL SHEAR AND AN UPPER LEVEL TROUGH LOCATED OFF THE EASTERN U.S. SEABOARD THAT EXTENDS OVER THE FAR WESTERN SW NORTH ATLC WATERS ALONG 78W S-SW OVER THE FLORIDA STRAITS AND INTO THE NW CARIBBEAN SEA. WITH THIS UPPER LEVEL TROUGH IN PLACE...MARIA IS FORECAST TO CONTINUE TRACKING QUICKLY N-NE WITH TROPICAL STORM FORCE CONDITIONS EXPECTED ON BERMUDA THROUGH THE REMAINDER OF TODAY WITH RAINFALL AMOUNTS OF 1 TO 3 INCHES. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 13N17W ALONG 11N29W TO 07N45W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N45W TO 09N61W. A PAIR OF 1014 MB SURFACE LOWS ARE LOCATED ALONG THE MONSOON TROUGH NEAR 11N28W AND 09N35W WHICH CONTINUE TO FOCUS LOW-LEVEL DEEP TROPICAL MOISTURE N OF THE EQUATOR TO 14N E OF 40W. THIS LARGE AND STRETCHED OUT MONSOON GYRE IS PRODUCING WIDELY SCATTERED MODERATE CONVECTION FROM 02N-11N BETWEEN 11W-40W. FARTHER WEST...ISOLATED MODERATE CONVECTION IS FROM 09N-16N BETWEEN 46W-61W...LOCATED N OF THE ITCZ AXIS. THIS AREA OF CONVECTION IS LIKELY ENHANCED DUE TO SOUTHWESTERLY MIDDLE TO UPPER LEVEL FLOW ASSOCIATED WITH AN UPPER LEVEL LOW CENTERED NEAR 19N54W. ...DISCUSSION... GULF OF MEXICO... NW FLOW ALOFT IS DOMINATE OVER THE GULF BASIN THIS AFTERNOON ON THE EASTERN PERIPHERY OF A LARGE ANTICYCLONIC CIRCULATION CENTERED OVER EAST-CENTRAL MEXICO NEAR 21N99W. WATER VAPOR IMAGERY INDICATES THAT MUCH OF THE GULF IS UNDER THE INFLUENCE OF MODERATE TO STRONG MIDDLE TO UPPER LEVEL SUBSIDENCE AND DRY AIR. THIS UPPER LEVEL RIDGING IS SUPPORTIVE OF A 1017 MB SURFACE HIGH CENTERED NEAR 28N92W THAT IS FORECAST TO WEAKEN AND DRIFT WESTWARD AS AN APPROACHING COLD FRONT CURRENTLY ANALYZED INLAND ACROSS THE GULF COASTAL PLAIN WILL INTRODUCE A MILDER AIRMASS TO THE NORTH-CENTRAL AND NE GULF WATERS THROUGH EARLY SATURDAY. CURRENTLY MUCH OF THE GULF IS UNDER MOSTLY CLEAR SKIES AND FAIR WEATHER CONDITIONS HOWEVER A FEW ISOLATED LOW-TOPPED SHOWERS ARE WITHIN 45 NM EITHER SIDE OF A LINE FROM 24N84W TO 26N89W. WIDELY SCATTERED SHOWERS ARE ALSO OCCURRING S OF 20N IN THE SW GULF. CARIBBEAN SEA... LINGERING SURFACE TROUGHING EXTENDING FROM TROPICAL STORM MARIA IN THE W ATLC EXTENDS ACROSS THE SE BAHAMAS TO EASTERN CUBA NEAR 20N76W THEN INTO THE WESTERN CARIBBEAN TO NEAR 17N81W. LOW-LEVEL MOISTURE CONVERGENCE IS FOCUSED ALONG THIS BOUNDARY AND IS GENERATING ISOLATED SHOWERS WITHIN 180 NM SE AND 120 NM NW OF THE BOUNDARY. EARLIER SCATTEROMETER PASSES FROM WINDSAT AND ASCAT DEPICT 15-20 KT SE WINDS ACROSS THE EASTERN AND CENTRAL CARIBBEAN E OF 80W WHILE W OF 80W WEAKER WINDS ARE ANALYZED. ELSEWHERE THE REMAINDER OF THE BASIN REMAINS UNDER FAIRLY TRANQUIL CONDITIONS. HOWEVER...SCATTERED SHOWERS AND TSTMS ASSOCIATED WITH THE E PACIFIC MONSOON TROUGH ARE OCCURRING S OF 12N BETWEEN 76W-85W. ATLANTIC OCEAN... TROPICAL STORM MARIA IS TRACKING QUICKLY N-NE ACROSS THE HIGH SEAS WATERS OF THE WESTERN ATLC THIS AFTERNOON DUE TO AN UPPER LEVEL TROUGH TO ITS WEST WITH AXIS FROM THE OUTER BANKS OF NORTH CAROLINA NEAR 36N75W TO THE FLORIDA STRAITS NEAR 23N81W. WATER VAPOR IMAGERY INDICATES THAT VERY DRY AIR AND STRONG SUBSIDENCE ASSOCIATED WITH THE TROUGHING IS ALOFT AND W OF 72W WHICH IS MAINTAINING MOSTLY FAIR SKIES OVER THE NW BAHAMAS AND FLORIDA PENINSULA. WHILE SCATTERED MODERATE CONVECTION IS OCCURRING N OF 26N BETWEEN 64W-70W IN THE VICINITY OF MARIA...A LOW-LEVEL CONVERGENCE BOUNDARY IS ANALYZED AS A SURFACE TROUGH FROM 25N73W TO EASTERN CUBA NEAR 20N76W. ISOLATED SHOWERS ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE BOUNDARY. FARTHER SE...A CUT OFF UPPER LEVEL LOW IS CENTERED NEAR 19N54W. A FEW ISOLATED SHOWERS AND TSTMS ARE OCCURRING FROM 17N-24N BETWEEN 52W-59W. OTHERWISE THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE N OF 17N E OF 62W ANCHORED BY A 1025 MB HIGH CENTERED NEAR 35N51W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN