000 AXNT20 KNHC 130553 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT WED APR 13 2011 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTION 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...ITCZ... ITCZ AXIS IS ANALYZED ALONG 07N13W TO THE EQUATOR NEAR 25W... THEN INTO NE BRAZIL NEAR 05S36W. ISOLATED MODERATE CONVECTION IS FROM THE EQUATOR TO 05N BETWEEN 17W-26W. ...DISCUSSION... GULF OF MEXICO... NW FLOW ALOFT IS ACROSS MUCH OF THE GULF THIS EVENING DUE TO AN EXPANSIVE UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER CENTRAL MEXICO NEAR 20N100W. WATER VAPOR IMAGERY INDICATES AN UPPER LEVEL TROUGH CONTINUE TO ROTATE OVER THE MID-ATLC STATES THAT SUPPORTS A COLD FRONT THAT AT 13/0300 UTC EXTENDS ACROSS THE FLORIDA PENINSULA FROM CAPE CANAVERAL TO BRADENTON AND INTO THE EASTERN GULF TO 26N87W. THE FRONT CONTINUES STATIONARY W-SW ALONG 26N90W TO 25N94W THEN INLAND OVER SOUTHERN MEXICO NEAR VERACRUZ. WHILE MUCH OF THE UPPER LEVEL SUPPORT FOR THIS FRONT CONTINUES TO LOCATE IN THE W ATLC...GENERALLY THE FRONT REMAINS FAIRLY BENIGN WITH A NOTICEABLE CONTRAST IN DEWPOINTS ACROSS THE BOUNDARY. RECENT SHIP AND BUOY OBSERVATIONS INDICATE A MUCH DRIER AIRMASS IN PLACE N OF 26N AS A 1019 MB HIGH SETTLES IN ACROSS THE NORTHERN GULF NEAR 29N90W. THE FRONT IS FORECAST TO GRADUALLY BECOME MORE DIFFUSE AND DISSIPATE THROUGH THE OVERNIGHT HOURS AS THE HIGH SHIFTS SLOWLY EASTWARD PROVIDING LIGHT ANTICYCLONIC FLOW THROUGH LATE WEDNESDAY. S-SE RETURN FLOW IS EXPECTED TO RE-ESTABLISH ACROSS THE WESTERN GULF BY EARLY THURSDAY AS THE NEXT SURFACE LOW PRESSURE AREA ORGANIZES OVER THE U.S. CENTRAL PLAINS. CARIBBEAN SEA... AN AMPLIFIED MIDDLE TO UPPER LEVEL TROUGH IS LOCATED OVER THE WESTERN CARIBBEAN WITH AXIS EXTENDING FROM THE SW NORTH ATLC NEAR 24N68W SW TO NORTHERN COSTA RICA NEAR 10N85W. STRONG SUBSIDENCE AND DRY AIR ACCOMPANY THIS UPPER LEVEL FEATURE AND THESE FACTORS CONTINUE TO PROVIDE OVERALL CLEAR SKIES AND FAIR CONDITIONS FOR THE WESTERN CARIBBEAN W OF 72W. EAST OF THE TROUGH AXIS...MOIST SOUTHWESTERLY FLOW IS ADVECTING A CONSIDERABLE AMOUNT OF MIDDLE TO UPPER LEVEL MOISTURE ACROSS THE EASTERN CARIBBEAN AND LESSER ANTILLES. A SURFACE TROUGH IS ANALYZED FROM THE MONA PASSAGE TO CURACAO WITH SCATTERED SHOWERS AND ISOLATED TSTMS E OF 70W. THE SURFACE TROUGH IS FORECAST TO DRIFT WESTWARD AND GRADUALLY WEAKEN THROUGH EARLY FRIDAY WITH EASTERLY TRADES REMAINING LIGHT DUE TO A RELAXED PRESSURE GRADIENT ACROSS THE ENTIRE BASIN. ATLANTIC OCEAN... A MIDDLE TO UPPER LEVEL TROUGH CONTINUES TO ROTATE OVER THE MID-ATLC STATES THIS EVENING THAT SUPPORTS A COLD FRONT ANALYZED INTO THE DISCUSSION AREA NEAR 32N77W EXTENDING SW TO THE FLORIDA PENINSULA NEAR CAPE CANAVERAL. A PRE-FRONTAL TROUGH ALSO EXTENDS FROM THE COLD FRONT NEAR 30N78W TO 25N80W. SATELLITE IMAGERY AND LIGHTNING DATA INDICATE SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN 60 NM EAST OF THE FRONT N OF 28N. THE REMAINDER OF THE W ATLC WEST OF 50W IS UNDER THE INFLUENCE OF A WEAK SURFACE RIDGE ANCHORED BY A 1026 MB HIGH CENTERED NE OF BERMUDA NEAR 34N56W. THE RIDGE AXIS EXTENDS FROM THE HIGH TO THE CENTRAL BAHAMAS. AN UPPER LEVEL LOW IS CENTERED NEAR 31N46W IN THE CENTRAL ATLC AND CONTINUES TO SUPPORT A FRONTAL BOUNDARY ANALYZED FROM 32N45W TO 23N48W. THIS AREA OF FRONTAL TROUGHING LARGELY EMBEDDED WITHIN THE SUBTROPICAL RIDGE IS PRODUCING AN AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS FROM 24N-32N BETWEEN 38W-45W. THIS ACTIVITY IS LIKELY ENHANCED BY UPPER LEVEL DIFFLUENCE E OF THE UPPER LEVEL LOW. STRONG HIGH PRESSURE IS EXPECTED TO BUILD IN OVER THE CENTRAL ATLC BY EARLY THURSDAY AND DISSIPATE ANY REMNANTS OF THE FRONT. NE WINDS ON THE SOUTHERN PERIPHERY OF A SURFACE RIDGE INFLUENCE THE EASTERN ATLC E OF 35W UNDER MOSTLY FAIR CONDITIONS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN