000 AXNT20 KNHC 122350 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU MAY 12 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 7N12W SOUTHWESTWARD ALONG 4N20W 1N30W EQ40W TO NE BRAZIL ALONG 1S50W. SCATTERED MODERATE CONVECTION IS WITHIN 150 NM ON EITHER SIDE OF THE AXIS W OF 30W. ...DISCUSSION... GULF OF MEXICO... A MESOSCALE CONVECTIVE SYSTEM IS EMERGING OFF THE TEXAS COAST THIS EVENING. THIS SYSTEM IS AHEAD OF A FRONTAL BOUNDARY MOVING ACROSS EASTERN TEXAS. THE LEADING EDGE OF CONVECTION IS ASSOCIATED TO A SQUALL LINE ANALYZED ALONG 29N94W 27N94W 26N97W. THIS LINE IS EXPANDING EASTWARD AT ABOUT 18 KT GENERATING HEAVY RAIN WITH POSSIBLE HAIL...STRONG STRAIGHT LINE WINDS...FREQUENT LIGHTNING...AND WATERSPOUTS W OF 94W N OF 26N. THIS SYSTEM WILL CONTINUE TO EXPAND ESE OVER THE NEXT 6 HOURS WITH CONVECTION... THEN LOOSE MOMENTUM AND DISSIPATE. IN THE MEAN TIME...THE NEXT COLD FRONT IS FORECAST TO EMERGE OFF THE TEXAS COAST FRIDAY LATE AFTERNOON. ELSEWHERE ACROSS THE GULF...WATER VAPOR IMAGERY INDICATES DRY AIR ALOFT ACROSS THE AREA. AT SURFACE...A 1016 MB HIGH IS OVER THE FAR NE BASIN NEAR 29N85W. WHILE LIGHT AND VARIABLE WINDS ARE OBSERVED NEAR THE HIGH CENTER...ESE FLOW IS ELSEWHERE ACROSS THE AREA RANGING FROM 10 TO 20 KT. THE HIGH PRESSURE RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY OVER THE NEXT 24 HOURS. A NEARLY STATIONARY TROUGH LINES THE CENTRAL FLORIDA PENINSULA ENHANCED BY SEA BREEZE CONVERGENCE IS GENERATING A FEW ISOLATED SHOWERS MOVING OFF THE SW FLORIDA COAST INTO THE STRAITS AND THE NW COAST OF CUBA S OF 25N E OF 84W. THIS ACTIVITY WILL PERSIST THROUGH THE NEXT 6-8 HOURS. CARIBBEAN SEA... WATER VAPOR IMAGERY INDICATES DRY AIR AND SUBSIDENCE ACROSS THE NW BASIN N OF 15N W OF 74W SUPPRESSING ANY CONVECTION IN THIS REGION. BROAD CYCLONIC TURNING COVERS THE REMAINDER OF THE CENTRAL AND EASTERN CARIBBEAN...UNDER THE INFLUENCE OF A BROAD AREA OF MODERATE TO STRONG SOUTHWESTERLY FLOW ALOFT AND DEEP TROUGHINESS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 55 NM ON EITHER SIDE OF A SURFACE TROUGH ANALYZED FROM THE ATLC BASIN ACROSS PUERTO RICO ALONG 18N67W...EXTENDING SW TO THE COAST OF COLOMBIA NEAR 11N74W. GLOBAL MODEL GUIDANCE INDICATES THIS SYNOPTIC SETUP WILL REMAIN IN PLACE OVER THE NEXT FEW DAYS. TOTAL PRECIPITABLE WATER VALUES REMAIN ELEVATED OVER THE FAR SW BASIN...WHERE LOW LEVEL CONVERGENCE ASSOCIATED TO MONSOONAL CONVECTION OVER THE FAR EAST TROPICAL PACIFIC IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 70 NM ALONG THE COASTS OF PANAMA...COSTA RICA...NICARAGUA AND COLOMBIA BETWEEN 74W AND THE COAST OF NICARAGUA S OF 12N. THIS AREA OF CONVECTION IS EXPECTED TO LINGER OVER THE NEXT 24 HOURS. ATLANTIC OCEAN... AN UPPER LEVEL RIDGE OF HIGH PRESSURE CONTINUES TO BUILD OVER THE WEST ATLC. AHEAD OF THIS RIDGE...A OCCLUDED DEEP LAYERED LOW IS OVER THE NW ATLC ROTATING AROUND 34N61W. THIS SYSTEM SUPPORTS A COLD FRONT ENTERING THE DISCUSSION AREA NEAR 30N50W CONTINUING SW AS A STATIONARY FRONT ALONG 26N54W 22N60W 20N67W. SE OF THIS FRONT...A SURFACE TROUGH IS ANALYZED FROM 21N59W INTO THE CARIBBEAN ACROSS PUERTO RICO ALONG 18N67W. THESE BOUNDARIES ARE SUPPORTED ALOFT BY A BROAD AND ELONGATED AREA OF DIFFLUENCE FLOW ALOFT ASSOCIATED TO A FAIRLY STRONG 110 KT UPPER LEVEL JET STREAK WITH AXIS FROM 18N67W TO 30N46W. A SECONDARY SURFACE TROUGH IS ANALYZED WEST OF THE STATIONARY FRONT ALONG 27N58W 24N64W 24N72W. SCATTERED WEAK SHOWERS ARE WITHIN 20 NM ON EITHER SIDE OF THE TROUGH. SURFACE RIDGING COVERS THE REMAINDER OF THE EASTERN ATLC. A WEAK SURFACE TROUGH ANALYZED FROM 25N41W TO 19N43W IS EMBEDDED WITHIN THE SURFACE RIDGE GENERATING SCATTERED SHOWERS FROM 21N-25N BETWEEN 38W-44W. A 1007 MB LOW IS JUST E OF THE CANARY ISLANDS GENERATING ISOLATED SHOWERS AND TSTMS FROM S OF 31N E OF 15W. THIS LOW IS EXPECTED TO MOVE NW IN THE NEXT 24 HOURS WITH CONVECTION AFFECTING MOSTLY THE COASTAL WATERS NEAR THE CANARY ISLANDS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA