000 AXNT20 KNHC 112357 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED MAY 11 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...ITCZ... THE ITCZ AXIS IS ANALYZED FROM THE COAST OF SIERRA LEONE NEAR 8N13W SOUTHWESTWARD ALONG 6N20W 2N30W EQ40W TO NE BRAZIL ALONG 3N51W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 150 NM ON EITHER SIDE OF THE AXIS W OF 26W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL RIDGE MOVING ACROSS THE GULF THIS EVENING...ANCHORED BY A 1016 MB HIGH OVER THE NE BASIN NEAR 28N84W. THIS SCENARIO IS PROMOTING FAIR WEATHER ACROSS THE DISCUSSION AREA. WHILE LIGHT AND VARIABLE WINDS ARE OBSERVED NEAR THE HIGH CENTER...ESE FLOW IS ELSEWHERE ACROSS THE AREA RANGING FROM 10 TO 20 KT. A SOMEWHAT TIGHTER PRESSURE GRADIENT OVER THE NW BASIN IS GENERATING STRONGER ONSHORE FLOW UP TO 25 KT ALONG THE TEXAS COASTLINE. THE HIGH PRESSURE RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY OVER THE NEXT 24 HOURS. MEANWHILE...SOUTHERLY RETURN FLOW WILL INCREASE AHEAD OF THE NEXT COLD FRONT EXPECTED TO EMERGE OFF THE TEXAS COAST LATE FRIDAY INTO EARLY SATURDAY. CARIBBEAN SEA... WATER VAPOR IMAGERY INDICATES MODERATELY DRY AIR AND SUBSIDENCE ACROSS THE NW BASIN N OF 13N W OF 75W SUPPRESSING ANY AREAS OF CONVECTION IN THIS REGION. THE REMAINDER OF CARIBBEAN IS UNDER THE INFLUENCE OF SOUTHWESTERLY FLOW ALOFT ADVECTING MIDDLE TO UPPER LEVEL MOISTURE ACROSS THE REMAINDER OF THE DISCUSSION AREA. TOTAL PRECIPITABLE WATER VALUES REMAIN ELEVATED OVER THE FAR S CARIBBEAN...ESPECIALLY OVER THE SW BASIN...WHERE LOW LEVEL CONVERGENCE ASSOCIATED TO THE CYCLONIC TURNING OF THE EASTERLY TRADES ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 70 NM ALONG THE COASTS OF PANAMA...COSTA RICA...NICARAGUA AND COLOMBIA BETWEEN 72W AND THE COAST OF NICARAGUA S OF 12N. THIS AREA OF CONVECTION IS EXPECTED TO LINGER OVER THE NEXT 24 HOURS. REMAINING LOW-LEVEL MOISTURE ASSOCIATED WITH A WEAK SURFACE TROUGH...ANALYZED FROM TROPICAL NORTH ATLC INTO PUERTO RICO...HAS DECREASED OVER THE PAST SEVERAL HOURS AND NO SIGNS OF SHOWER ACTIVITY HAVE BEEN NOTICED THIS EVENING. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE OF HIGH PRESSURE IS SLOWLY BUILDING OVER THE WEST ATLC. IN THE MEANTIME...AND UPPER LEVEL JET STREAK DEEPS S ACROSS THE FAR WEST ATLC SUPPORTING SCATTERED SHOWERS NE OF THE BAHAMAS...AROUND A 1013 MB LOW NEAR 27N75W. A SURFACE TROUGH IS ANALYZED FROM 30N77W TO THE SURFACE LOW. THIS SYSTEM IS EXPECTED TO CONTINUE MOVING SOUTHEASTWARD OVER THE NEXT 24 HOURS. A OCCLUDED DEEP LAYERED LOW IS OVER THE NW ATLC ROTATING AROUND 36N61W. THIS SYSTEM SUPPORTS A COLD FRONT ENTERING THE DISCUSSION AREA NEAR 32N50W EXTENDING SW ALONG 27N51W TO 24N53W CONTINUING AS A DISSIPATING COLD FRONT TO 22N63W. SCATTERED SHOWERS ARE OCCURRING WITHIN 90 NM EAST OF THE FRONT N OF 24N. S OF THE COLD FRONT...AN AREA OF LOW LEVEL MOISTURE CONVERGENCE IS NOTED ALONG A SURFACE TROUGH ANALYZED FROM 21N55W TO THE CARIBBEAN ISLAND OF PUERTO RICO. WEAK SCATTERED SHOWERS ARE WITHIN 40 NM ON EITHER SIDE OF THE TROUGH AXIS. SURFACE RIDGING COVERS THE REMAINDER OF THE EASTERN ATLC ANCHORED BY A 1020 MB HIGH CENTERED NEAR 30N40W. A WEAK SURFACE TROUGH ANALYZED FROM 25N39W TO 20N41W IS EMBEDDED WITHIN THE SURFACE RIDGE GENERATING SCATTERED SHOWERS FROM 20N-25N BETWEEN 37W-42W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA