000 AXNT20 KNHC 121744 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...ITCZ... ITCZ AXIS IS ALONG 08N13W 03N29W CROSSING THE EQUATOR NEAR 38W THEN ALONG THE EQUATOR TO 50W. WIDELY SCATTERED MODERATE CONVECTION IS FROM 02N-06N BETWEEN THE PRIME MERIDIAN AND 09W... AND FROM THE EQUATOR TO 07N BETWEEN 34W-53W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL RIDGE IS LOCATED OVER THE GULF WITH AXIS EXTENDING FROM THE SW GULF WATERS N-NE TO THE FLORIDA PANHANDLE THEN SHARPLY AMPLIFIED OVER THE SE CONUS NORTHWARD TO THE GREAT LAKES REGION. THE UPPER LEVEL RIDGE IS SUPPORTIVE OF OVERALL FAIR WEATHER AND CLEAR SKIES THIS AFTERNOON OVER MUCH OF THE GULF AS A 1017 MB HIGH IS CENTERED IN THE NE GULF NEAR 29N87W. WHILE GENERALLY LIGHT AND VARIABLE WINDS ARE OVER THE NE CORNER OF THE GULF IN THE VICINITY OF THE BIG BEND OF FLORIDA...THE REMAINDER OF GULF OBSERVATIONS CONTINUE TO INDICATE SE WINDS IN THE RANGE OF 10 TO 15 KT. THE HIGH PRESSURE RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY OVER THE NEXT 24 HOURS THEN BEGIN TO SHIFT EASTWARD INTO THE SW NORTH ATLC BY SATURDAY. THE SOUTHERLY RETURN FLOW IS EXPECTED TO PERSIST AS THE NEXT COLD FRONT IS FORECAST TO EMERGE OFF THE TEXAS COAST LATE FRIDAY INTO EARLY SATURDAY. CARIBBEAN SEA... NW FLOW ALOFT IS NOTED ON WATER VAPOR IMAGERY OVER THE NW CARIBBEAN AND THIS DRY AIR AND SUBSIDENCE IS PROMOTING CLEAR SKIES AND OVERALL FAIR CONDITIONS THIS AFTERNOON N OF 13N W OF 72W. THE REMAINDER OF CARIBBEAN SEA IS UNDER THE INFLUENCE OF SOUTHWESTERLY UPPER LEVEL FLOW LOCATED EAST OF AN UPPER LEVEL TROUGH AXIS EXTENDING FROM NEAR 25N70W IN THE SW NORTH ATLC TO 13N77W. THIS UPPER LEVEL FLOW IS ADVECTING MIDDLE TO UPPER LEVEL MOISTURE OVER MUCH OF THE BASIN E OF 75W. EAST OF THE TROUGH AXIS...LOW-LEVEL MOISTURE...ASSOCIATED WITH A SURFACE TROUGH ANALYZED FROM TROPICAL NORTH ATLC NEAR 20N64W THROUGH THE MONA PASSAGE TO 16N70W IS GENERATING WIDELY SCATTERED AND ISOLATED TSTMS WITHIN 180 NM EITHER SIDE OF A LINE FROM THE US/UK VIRGIN ISLANDS TO 13N72W. TYPICAL EASTERLY TRADES HAVE BEEN DISRUPTED DUE TO THE SURFACE TROUGHING EXTENDING ACROSS THE CENTRAL PORTION OF THE BASIN...AND GLOBAL MODEL GUIDANCE INDICATES THIS SYNOPTIC SETUP WILL REMAIN IN PLACE OVER THE NEXT FEW DAYS AS A BROAD AND LARGE DEEP LAYER LOW CONTINUES TO SPIN OVER PORTIONS OF THE WESTERN NORTH ATLC. ELSEWHERE...SCATTERED SHOWERS AND ISOLATED TSTMS CONTINUE OVER PORTIONS OF THE SW CARIBBEAN S OF 12N...INCLUDING WESTERN PANAMA AND COASTAL COSTA RICA. ATLANTIC OCEAN... AN UPPER LEVEL LOW IS CENTERED IN THE WESTERN NORTH ATLC NEAR 35N63W THAT SUPPORTS A MIDDLE TO UPPER LEVEL TROUGH AXIS EXTENDING SW TO 20N73W THEN INTO THE WESTERN CARIBBEAN SEA. A FRACTURED FRONTAL BOUNDARY ENTERS THE DISCUSSION AREA NEAR 32N48W EXTENDING AS A DISSIPATING STATIONARY FRONT TO 28N50W. THE FRONT CONTINUES AS A DISSIPATING STATIONARY FRONT NEAR 28N53W THEN MEANDERS SW THEN W ALONG 25N58W TO 22N64W TO 22N70W. SOUTHWESTERLY UPPER LEVEL FLOW ALONG WITH THE WEAK SURFACE FRONT IS CONTINUING TO GENERATE A WIDE SWATH OF WIDELY SCATTERED SHOWERS AND ISOLATED TSTMS WITHIN 180 NM EITHER SIDE OF A LINE FROM 30N46W TO 18N64W. MEANWHILE WEST OF THE FRONTAL ZONE...A SECONDARY SURFACE TROUGH IS ANALYZED FROM 25N67W TO THE SOUTHERN FLORIDA PENINSULA COAST NEAR 26N80W. ISOLATED SHOWERS ARE OCCURRING WITHIN 75 NM EITHER SIDE OF THE TROUGH AXIS THIS AFTERNOON. ELSEWHERE E OF 45W...A MAJORITY OF THE EASTERN ATLC IS UNDER THE INFLUENCE OF SURFACE RIDGING ANCHORED BY A 1021 MB HIGH CENTERED NEAR 31N40W. A WEAK SURFACE TROUGH ANALYZED FROM 24N41W TO 19N43W IS EMBEDDED WITHIN THE SURFACE RIDGE AND CONTINUES TO DRIFT SLOWLY WESTWARD. POSSIBLE ISOLATED SHOWERS ARE FROM 22N-25N BETWEEN 38W-43W. LASTLY...AN UPPER LEVEL LOW IS CENTERED NEAR 35N24W AND SUPPORTS A 1009 MB SURFACE LOW CENTERED OVER THE EASTERN CANARY ISLANDS NEAR 28N14W. UPPER LEVEL DIFFLUENCE EAST OF THE TROUGH AXIS IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS NORTH OF THE MADEIRA ISLANDS FROM 32N-36N BETWEEN 14W-19W. CLOSER TO THE CANARY ISLANDS SURFACE LOW...A SURFACE TROUGH EXTENDS FROM THE LOW ACROSS WESTERN SAHARA TO 24N12W. ISOLATED SHOWERS AND TSTMS ARE OCCURRING FROM 26N-29N BETWEEN 10W-13W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN