000 AXNT20 KNHC 111730 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SAT MAY 11 2013 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/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM NEAR THE SENEGAL/GUINEA BISSAU BORDER TO 7N24W. THE INTERTROPICAL CONVERGENCE ZONE AXIS CONTINUES FROM 7N24W TO 2N40W TO THE COAST OF BRAZIL AT EQ50W. NO SIGNIFICANT CONVECTION ALONG THE ITCZ/MONSOON TROUGH AXES. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION CAN BE FOUND N OF 3N TO THE COAST OF AFRICA BETWEEN THE PRIME MERIDIAN AND 11W. ...DISCUSSION... GULF OF MEXICO... A COLD FRONT MOVED OFF THE COAST OF TEXAS THIS MORNING. AS OF 1200 UTC...IT EXTENDS FROM SW LOUISIANA TO SOUTH TEXAS THEN ALONG NORTHERN MEXICO. SOME HEAVY SHOWERS AND THUNDERSTORMS ARE NOTED AHEAD OF THE FRONT IMPACTING MUCH OF THE NORTHERN GULF WATERS. A DIFFLUENT PATTERN ALOFT IS HELPING TO ENHANCE THIS CONVECTIVE ACTIVITY. THE FRONT WILL EXTEND FROM THE WESTERN FLORIDA PANHANDLE TO THE NW BAY OF CAMPECHE TONIGHT. THE NORTHERN SEGMENT OF THE FRONT TO THE N OF 26N WILL MOVE E OF THE AREA SUN NIGHT WHILE THE SOUTHERN PORTION WILL GRADUALLY DISSIPATE FROM S FLORIDA TO THE CENTRAL BAY OF CAMPECHE SUN THROUGH MON. WEAK SURFACE RIDGING FROM THE ATLC DOMINATES THE REMAINDER OF THE REGION. GENTLE TO MODERATE SOUTHERLY WIND FLOW IS OBSERVED AHEAD OF THE FRONT WHILE MODERATE TO FRESH NORTHERLY WINDS WILL FOLLOW THE COLD FRONT. ALOFT...AN UPPER LEVEL RIDGE CENTERED OVER NORTHERN CENTRAL AMERICA COVERS THE MAJORITY OF THE GULF AND SE MEXICO...INCLUDING THE YUCATAN PENINSULA. ABUNDANT CLOUDINESS COVERS MOST OF THE NORTHERN GULF WHILE MOSTLY CLEAR SKIES ARE SEEN ON VISIBLE SATELLITE IMAGERY OVER THE SE GULF AND THE BAY OF CAMPECHE. CARIBBEAN SEA... THE UPPER ANTICYCLONE CENTERED OVER NORTHERN CENTRAL AMERICA ALSO EXTENDS A RIDGE ACROSS THE WESTERN CARIBBEAN PROVIDING MOSTLY FAIR CONDITIONS THERE. AN UPPER LEVEL TROUGH PERSISTS ACROSS THE EASTERN CARIBBEAN EXTENDING FROM THE MONA PASSAGE TO NORTHERN COLOMBIA. STRONG UPPER LEVEL SUBSIDENCE AND IMPLIED DRY AIR MASS HAS INVADED HISPANIOLA LIMITING THE DEVELOPMENT OF SHOWER AND TSTM ACTIVITY. PUERTO RICO AND THE VIRGIN ISLANDS ARE ON THE EAST SIDE OF THE UPPER TROUGH. THIS TROUGH WILL COMBINE WITH LOCAL EFFECTS AND DIURNAL HEATING TO PRODUCE SOME SHOWERS AND TSTMS OVER THOSE ISLANDS MAINLY DURING THE AFTERNOON. CONVECTION HAS DIMINISHED OVER THE SW CARIBBEAN. SCATTERED SHOWERS AND ISOLATED TSTMS ARE NOTED S OF 11N W OF 81W. A 1010 MB LOW PRES IS ANALYZED ON THE 1200 UTC SURFACE MAP OVER COSTA RICA...ALONG THE MONSOON TROUGH NEAR 9N84W. THE LOW IS FORECAST TO DRIFT WESTWARD INTO THE EPAC REGION DURING THE NEXT 24 HOURS. TRADE WIND FLOW OF 15-20 KT DOMINATES THE MAJORITY OF THE EASTERN AND CENTRAL CARIBBEAN WITH WINDS OF 20 TO 25 KT NEAR THE COAST OF COLOMBIA. ATLANTIC OCEAN... A RIDGE/TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE DISCUSSION AREA. AN UPPER LOW HAS DEVELOPED ALONG THE TROUGH THAT WAS AFFECTING WITH LOCALLY HEAVY RAIN THE GREATER ANTILLES DURING THE PREVIOUS DAYS. THIS UPPER LOW LOCATED NEAR 24N66W SUPPORTS A 1012 MB SURFACE LOW PRES CENTERED NEAR 23N67W. SOME SHIP OBSERVATIONS CONFIRMED THE PRESENCE OF THE SURFACE LOW THIS MORNING. A TROUGH EXTENDS FROM THE LOW CENTER TO THE MONA PASSAGE. THE SURFACE LOW IS FORECAST TO DRIFT TOWARD HISPANIOLA ON SUN WHILE WEAKENING TO A TROUGH. THIS TROUGH WILL MOVE WESTWARD. CURRENTLY...PRES GRADIENT BETWEEN THE SURFACE LOW AND A RIDGE EXTENDING FROM BERMUDA TO SOUTH FLORIDA IS PRODUCING A LARGE AREA OF FRESH TO STRONG WINDS TO N...NE AND SE QUADRANTS OF THE LOW...PARTICULARLY S OF 27N BETWEEN 60W AND 67W. SCATTEROMETER DATA PROVIDED OBSERVATIONS OF THESE WIND SPEEDS. HEAVY SHOWERS AND TSTMS ARE E OF THE LOW CENTER...COVERING THE AREA FROM 22N TO 26N BETWEEN 62W AND 66W. STRONGEST WINDS CAN BE FOUND NEAR TSTMS. THE CENTRAL ATLC IS DOMINATED BY BROAD SURFACE RIDGING SUPPORTED BY AN UPPER LEVEL RIDGE ALONG 54W/55W. AN UPPER LEVEL TROUGH COVERS THE EASTERN ATLC CENTERED AROUND AN UPPER LOW NEAR 31N34W. THE UPPER LOW SUPPORTS A WEAK 1020 MB SURFACE LOW NEAR 31N32W. A SURFACE TROUGH EXTENDS FROM THE LOW CENTER TO NEAR 25N35W. THE 1224 UTC ASCAT PASS REVEALS THE WIND SHIFT ASSOCIATED WITH THE TROUGH. SCATTERED SHOWERS AND TSTMS ARE NOTED MAINLY ON THE NORTH SIDE OF THE LOW CENTER AND AHEAD OF THE TROUGH AXIS. AN AREA OF SAHARAN DUST IS OBSERVED ON VIS SATELLITE IMAGERY REACHING 45W...AND IS CONFIRMED BY THE SAHARAN AIR LAYER TRACKING PRODUCT FROM UW-CIMSS. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE AT THE REQUEST OF METEO-FRANCE AND THE METEOROLOGICAL SERVICES OF HAITI AND THE DOMINICAN REPUBLIC...THE TROPICAL ANALYSIS AND FORECAST BRANCH (TAFB) WILL BEGIN PROVIDING...ON A TEMPORARY BASIS...A SEPARATE DETAILED SECTION WITHIN THE ATLANTIC TROPICAL WEATHER DISCUSSION (TWDAT). IT WILL COVER BOTH HAITI AND THE DOMINICAN REPUBLIC DUE TO THE SHARED GEOGRAPHY OF BOTH COUNTRIES ON THE ISLAND OF HISPANIOLA. THE SECTION BEGINS ON MAY 15 2013 AT 1800 UTC...2 PM EDT. IT WILL PROVIDE GUIDANCE FOR SIGNIFICANT WEATHER EVENTS THAT ARE EXPECTED TO IMPACT THE REGION THROUGH 48 HOURS...WITH THE FOCUS ON ASSESSING THE POTENTIAL FOR HEAVY RAINFALL. $$ GR