000 AXNT20 KNHC 282335 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU APR 28 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...THE ITCZ... ITCZ AXIS IS ANALYZED ALONG 6N10W 5N15W 2N22W 1N35W 2N51W. CLUSTERS OF SCATTERED/NUMEROUS CONVECTION ARE N OF 2N TO INLAND OVER SW AFRICA E OF 4W ACROSS THE PRIME MERIDIAN. CLUSTERS OF SCATTERED STRONG CONVECTION ARE WITHIN 180/200 NM N OF THE ITCZ BETWEEN 12W-24W AND FROM THE ITCZ TO S OF THE EQUATOR BETWEEN 20W-23W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90 NM N OF THE ITCZ BETWEEN 41W-45W. ...DISCUSSION... GULF OF MEXICO... THE PRIMARY FOCUS THIS EVENING IS THE COLD FRONT MOVING ACROSS THE E CONUS AND GULF OF MEXICO. THIS FRONT IS RESPONSIBLE FOR THE SEVERE THUNDERSTORMS THAT HAS PLAGUED THE E HALF OF THE US SINCE TUE AND CONTINUE TODAY. A DEEP LAYERED LOW/TROUGH COVERS THE E CONUS INTO THE N GULF N OF 26N AND THE UPPER LOW MOVING INTO THE GREAT LAKES REGION. THIS UPPER LOW/TROUGH IS SUPPORTING A COLD FRONT THAT AT 28/2100 UTC EXTENDS ACROSS SE GEORGIA AND THE FLORIDA PANHANDLE NEAR 30N83W INTO THE GULF ALONG 29N84W THEN SW ALONG 22N95W THEN S TO 21N96W. NUMEROUS THUNDERSTORMS ARE WITHIN 60 NM E OF THE FRONT N OF 27N. SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS ARE WITHIN 90/120 NM W OF THE ENTIRE FRONT. A WEAK 1010 MB LOW HAS DEVELOPED SE OF THE FRONT IN THE BAY OF CAMPECHE NEAR 20N94W WITH ISOLATED SHOWERS WITHIN 60 NM OF THE LOW CENTER. HIGH PRESSURE IS BUILDING IN BEHIND THE FRONT WITH A 1021 MB HIGH OVER E TEXAS CLEARING SKIES W OF THE FRONT. AN UPPER RIDGE COVERS THE S GULF WITH THE AXIS EXTENDING FROM THE NW CARIBBEAN ACROSS CUBA NEAR HAVANA TO OFF THE E FLORIDA COAST ENHANCING THE ACTIVITY ASSOCIATED WITH THE FRONT. THE FRONT IS EXPECTED TO DISSIPATE FRI FROM SW FLORIDA TO THE YUCATAN CHANNEL. THE HIGH PRESSURE WILL MOVE E ACROSS N WATERS FRI AND SAT ALLOWING SE RETURN FLOW TO SET UP OVER THE W GULF. ANOTHER COLD FRONT IS EXPECTED TO PUSH OFF TEXAS LATE SUN NIGHT AND WILL EXTEND FROM SE LOUISIANA TO NEAR BROWNSVILLE TEXAS LATE MON NIGHT. CARIBBEAN SEA... AN UPPER RIDGE EXTENDS FROM THE GULF OF HONDURAS ACROSS CUBA NEAR HAVANA COVERING THE NW CARIBBEAN. A LARGE UPPER LOW IS OVER THE CENTRAL ATLC NE OF THE VIRGIN ISLANDS EXTENDING OVER THE NE CARIBBEAN N OF 16N E OF THE WINDWARD PASSAGE. A LARGE UPPER RIDGE COVERS THE S CARIBBEAN S OF 15N ANCHORED IN THE TROPICAL ATLC. DRY STABLE AIR ALOFT COVERS THE CARIBBEAN N OF 14N W OF 70W WITH MODERATE TO FRESH EASTERLY TRADE WINDS ACROSS THE ENTIRE BASIN. THE WESTERLY FLOW ALOFT COMBINED WITH THE EASTERLY SURFACE FLOW IS GENERATING AN AREA OF MULTILAYERED CLOUDS WITH SCATTERED SHOWERS OVER THE E CARIBBEAN E OF 70W ACROSS THE LESSER ANTILLES. THE UPPER LOW IS ENHANCING AFTERNOON THUNDERSTORMS THAT HAVE GENERATED INLAND OVER PUERTO RICO... HISPANIOLA...AND CUBA. A SURFACE TROUGH INLAND OVER THE YUCATAN PENINSULA IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS THAT ARE BEING DRAWN E TO OVER THE FAR W CARIBBEAN. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN UNDER MOSTLY CLEAR SKIES THIS EVENING. STRONG HIGH PRESSURE OVER THE CENTRAL AND W ATLC WILL GRADUALLY WEAKEN THROUGH SAT AND SHIFT E. THE COLD FRONT IN THE GULF OF MEXICO WILL DISSIPATE JUST NW OF THE CARIBBEAN FRI NIGHT. HIGH PRESSURE WILL THEN BUILD N OF THE CARIBBEAN OVER THE WEEKEND AND PREVAIL THROUGH THE FIRST OF NEXT WEEK. ATLANTIC OCEAN... AN UPPER RIDGE EXTENDS FROM THE NW CARIBBEAN OFF THE E FLORIDA COAST TO BEYOND 32N77W ENHANCING THE ACTIVITY AHEAD OF THE COLD FRONT CURRENTLY IN THE GULF OF MEXICO. A SEABREEZE SURFACE TROUGH IS INLAND OVER THE FLORIDA PENINSULA. COMBINED THESE FEATURES ARE GENERATING SCATTERED SHOWERS/THUNDERSTORMS W OF A LINE FROM MIAMI FLORIDA ALONG 30N80W TO BEYOND 32N78W. A LARGE UPPER LOW IS NE OF THE VIRGIN ISLANDS NEAR 26N53W COVERING THE AREA BETWEEN 35W-70W AND IS EMBEDDED WITHIN DRY STABLE AIR. A LARGE SURFACE RIDGE COVERS THE CENTRAL AND W ATLC N OF 20N W OF 25W TO OVER THE FLORIDA PENINSULA AND ANCHORED BY A 1029 MB HIGH 450 NM ENE OF BERMUDA. THIS IS LEAVING THE ATLC N OF 20N WITH FAIR WEATHER THIS EVENING. A WEAK 1008 MB LOW IS OVER THE FAR E ATLC NEAR 31N16W WITH A SURFACE TROUGH EXTENDING S ACROSS THE CANARY ISLANDS TO 24N17W AND NO SIGNIFICANT SHOWER ACTIVITY. AN E/W UPPER RIDGE COVERS THE TROPICAL ATLC FROM SW AFRICA TO OVER THE SOUTH AMERICA/S CARIBBEAN. THE WESTERLY FLOW ALOFT COMBINED WITH THE EASTERLY SURFACE FLOW IS PRODUCING MULTILAYERED CLOUDS WITH SCATTERED SHOWERS WITHIN 150/200 NM OF LINE FROM 15N53W ACROSS THE LESSER ANTILLES INTO THE E CARIBBEAN NEAR MARTINIQUE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ PAW