000 AXNT20 KNHC 112350 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON MAY 11 2009 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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND RADAR. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 6N10W 3N20W 1N30W CROSSING THE EQUATOR NEAR 34W EXTENDING TO NE BRAZIL NEAR 1S46W. NO SIGNIFICANT AREAS OF CONVECTION IN THE VICINITY OF THE ITCZ. ...DISCUSSION... GULF OF MEXICO... W TO NW MID TO UPPER LEVEL FLOW IS PRESENT ACROSS THE REGION... WITH A WEAK SHORTWAVE TROUGH ACROSS ERN TEXAS. THIS TROUGH IS ENHANCING SCATTERED SHOWERS AND TSTMS ALONG A FRONTAL BOUNDARY LOCATED 60/90 NM INLAND OVER THE SE CONUS. THIS ACTIVITY IS EXPECTED TO CONTINUE SKIRTING ALONG THE IMMEDIATE NRN GULF COAST AND DIMINISH WITH THE LOSS OF MAXIMUM DAYTIME HEATING AS IT MOVES E-SE AROUND THE NRN PERIPHERY OF THE UPPER RIDGE. ELSEWHERE...MAINLY FAIR WEATHER EXISTS ACROSS THE ENTIRE ZONE AS A SURFACE RIDGE CONTINUES TO BE NEARLY STATIONARY ACROSS THE NE GULF WITH AN EMBEDDED 1019 MB HIGH CENTERED NEAR 27N86W. GIVEN THIS SYNOPTIC PATTERN...GENERALLY LIGHT WINDS ARE OBSERVED OVER MUCH OF THE ERN AND MIDDLE WATERS AND E TO SE 10-15 KT WINDS ARE LOCATED OVER A PORTION OF THE WRN WATERS...DUE TO A TIGHTENED PRESSURE GRADIENT BETWEEN THE HIGH AND BROAD TROUGHING OVER MEXICO. LITTLE CHANGE IN THE PATTERN IS EXPECTED OVER THE NEXT COUPLE OF DAYS AS THE SURFACE RIDGE HOLDS IN PLACE OVER THE NE GULF. CARIBBEAN SEA... BROAD RIDGING ALOFT COVERS MUCH OF THE CARIBBEAN...EXTENDING FROM CENTRAL VENEZUELA NW TO HONDURAS. UPPER DIFFLUENCE BETWEEN THE HIGH AND BROAD TROUGHING OVER THE EPAC...ALONG WITH THE PROXIMITY OF LOW-LEVEL CONVERGENCE ALONG THE ITCZ AXIS SOUTH OF PANAMA IS PRODUCING SCATTERED SHOWERS AND TSTMS OVER THE SW CARIBBEAN S OF 12N. ELSEWHERE...SURFACE HIGH PRESSURE N OF THE CARIBBEAN SEA IS RESULTING IN FRESH ELY TRADE WIND FLOW ACROSS THE BASIN. THESE TRADES ARE FORECAST TO PERSIST THROUGH THE WEEK WITH THE STRONGEST WINDS OF UP TO 25 KTS EXPECTED TO CONTINUE NEAR THE COAST OF COLOMBIA. ATLANTIC OCEAN... A SURFACE RIDGE ASSOCIATED WITH A 1026 MB SURFACE HIGH OVER THE CENTRAL ATLC NEAR 30N47W IS AFFECTING MUCH OF THE ATLC PORTION OF THE DISCUSSION AREA. THIS SURFACE HIGH IS FORECAST TO SHIFT NE DURING THE NEXT 24 HOURS. SUBSIDENCE ASSOCIATED WITH THE SURFACE RIDGE IS RESULTING IN GENERALLY FAIR WEATHER CONDITIONS ACROSS MUCH OF THE ATLC. HOWEVER...POCKETS OF LOW-LEVEL MOISTURE WITH ISOLATED SHOWERS ARE MOVING W ACROSS PORTIONS OF THE SW N ATLC AND TROPICAL N ATLC. THE MOST CONCENTRATED AREA OF SCATTERED SHOWERS ARE ASSOCIATED WITH A SURFACE TROUGH THAT EXTENDS FROM 15N60W TO 21N59W. THIS TROUGH IS MOVING W NEAR 15 KT TOWARD THE LEEWARD AND WINDWARD ISLANDS. OBSERVATIONS ACROSS THE NRN WINDWARD ISLANDS SHOW WINDS BACKING TO A NELY DIRECTION WITH THE APPROACH OF THIS FEATURE AS INCREASED SHOWER ACTIVITY IS FORECAST FOR THE NE CARIBBEAN AND ISLANDS OVER THE NEXT DAY OR TWO. ALSO...A MID/UPPER-LEVEL TROUGH WITH AXIS ALONG 32N23W 27N31W 24N44W 16N53W SUPPORTS A SURFACE TROUGH OVER THE E ATLC THAT EXTENDS FROM THE CANARY ISLANDS W-SW TO 25N31W. LOW-LEVEL CONVERGENCE ALONG THE TROUGH IS GENERATING SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF THE BOUNDARY. ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS PRESENT S OF 10N W OF 20W...WITH AN UPPER LEVEL HIGH NEAR 4N35W. ASSOCIATED UPPER LEVEL DIVERGENCE IS ENHANCING SCATTERED SHOWERS ALONG THE ITCZ. $$ HUFFMAN