000 AXNT20 KNHC 252336 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT WED APR 25 2012 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 2315 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST OF GUINEA NEAR 10N14W TO 5N20W...WHERE THE ITCZ AXIS CONTINUES ALONG 2N32W TO THE COAST OF BRAZIL NEAR 1S46W. ISOLATED WEAK TO MODERATE CONVECTION IS WITHIN 50-85 NM ON EITHER SIDE OF THE ITCZ AXIS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 1N8N E OF 19W TO THE PRIME MERIDIAN. ...DISCUSSION... GULF OF MEXICO... AN ELONGATED UPPER LEVEL TROUGH AXIS EXTENDS ACROSS THE ERN CONUS SEABOARD INTO THE FAR SW GULF OF MEXICO ON WATER VAPOR IMAGERY. HOWEVER...VERY DRY AIR AND STRONG SUBSIDENCE ALOFT ACCOMPANIES THE BASE OF THIS UPPER TROUGH...WHICH COVERS THE ENTIRE GULF BASIN. THIS OVERALL STABLE ENVIRONMENT FILTERS DOWN TO THE SURFACE AS A 1020 MB HIGH CENTERED OFF THE WESTERN COAST OF THE FLORIDA PENINSULA NEAR 27N85W WITH CLEAR SKIES NOTED ON VISIBLE SATELLITE IMAGERY. WITH THE RIDGE SLOWLY SHIFTING EASTWARD OVER THE PAST 24 HOURS...E-SE WINDS IN THE RANGE OF 10 TO 15 KT INFLUENCE THE SOUTHEASTERN HALF OF THE BASIN WITH 10 TO 20 KT S-SW WINDS ESTABLISHING OVER THE NORTHWESTERN THIRD OF THE BASIN. THURSDAY INTO FRIDAY THE RIDGE WILL CONTINUE TO SLIDE INTO THE SW NORTH ATLC AS SOUTHERLY RETURN FLOW SPREADS EASTWARD OVER MUCH OF THE GULF FOR THE WEEKEND. CARIBBEAN SEA... HAZARDOUS WEATHER CONTINUES TO FOCUS ON THE CENTRAL CARIBBEAN BASIN AND INLAND PORTIONS OF HISPANIOLA THIS EVENING. A NEARLY STATIONARY FRONT CROSSES THE ISLAND INTO THE CARIBBEAN WATERS FROM 20N70W TO NEAR TO 15N77W. LAST VISIBLE SATELLITE PICTURES OF THE DAY SHOWED SCATTERED NUMEROUS MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS WITHIN 120 NM ON EITHER SIDE OF A LINE EXTENDING FROM 20N70W TO 12N78W TO 9N78W. GUSTY WINDS UP TO 30 KTS...FREQUENT DANGEROUS CLOUD TO GROUND LIGHTNING...AND POSSIBLE WATER SPOUTS ARE LIKELY OVER WATER WITHIN THE CONVECTIVE REGION...INCLUDING THE COASTAL WATERS OF HISPANIOLA. THE NATIONAL WEATHER OFFICE IN DOMINICAN REPUBLIC HAS REPORTED RAINFALL TOTAL ACCUMULATIONS RANGING FROM 4 TO 7 INCHES ACROSS THEIR TERRITORY...ESPECIALLY OVER REGIONS WHERE THE HIGH TOPOGRAPHY AND UPPER LEVEL DIFFLUENCE IS MAXIMIZED. TOTAL PRECIPITABLE WATER IMAGERY HAS SHOWN CONSISTENT HIGH VALUES OF LOW LEVEL MOISTURE AS WELL AS MIDDLE TO UPPER LEVEL MOISTURE CONCENTRATED WITHIN THE CONVECTION REGION ON WATER VAPOR IMAGERY. THIS SCENARIO IS SUPPORTING THE CONTINUOUS RAINFALL THAT HAS PERSISTED OVER THE PAST FEW DAYS. THE FRONT IS EXPECTED TO WEAKEN OVER THE NEXT 24 TO 36 HOURS AS SURFACE RIDGING BUILDS TO THE NORTH AND EASTERLY TRADES INCREASE DUE TO A STRONGER SURFACE PRESSURE GRADIENT. IT IS POSSIBLE THAT LOW-LEVEL MOISTURE WILL LINGER ACROSS THE NORTH-CENTRAL CARIBBEAN FOR THE NEXT DAY OR TWO AS THE FRONT BECOMES MORE DIFFUSE AND WILL CONTINUE TO PROVIDE INCREASED PROBABILITY OF PRECIPITATION FOR HISPANIOLA AND THE ADJACENT COASTAL WATERS THROUGH THE WEEKEND. THE POTENTIAL FOR LOCALLY HEAVY RAINFALL AND FLOODING ACROSS HAITI AND PORTIONS OF THE DOMINICAN REPUBLIC ARE EXPECTED OVER THE NEXT FEW DAYS. NO SIGNIFICANT WEATHER IS OCCURRING ELSEWHERE ACROSS THE DISCUSSION AREA THIS EVENING. ATLANTIC OCEAN... AN ELONGATED UPPER LEVEL TROUGH AXIS IS SLOWLY DRIFTING EASTWARD OVER THE FAR WRN ATLC...CURRENTLY EXTENDING ALONG THE ERN CONUS SEABOARD AND INTO THE GULF OF MEXICO. WATER VAPOR IMAGERY SHOWS VERY DRY AIR AND STRONG SUBSIDENCE ALOFT E AND S OF THE UPPER TROUGH AXIS. DESPITE THE DRY CONDITIONS ALOFT...THE CONVECTION ASSOCIATED TO THIS SYSTEM IS FOCUSED WELL EAST OF THE UPPER TROUGH...WITHIN 150-200 NM ON EITHER SIDE OF A NEARLY STATIONARY FRONT EXTENDING INTO THE DISCUSSION AREA ALONG 30N61W TO 24N64W THEN INTO THE N CENTRAL CARIBBEAN ACROSS HISPANIOLA NEAR 20N70W. SCATTERED NUMEROUS MODERATE TO HEAVY SHOWERS AND THUNDERSTORMS ARE EVIDENT ON SATELLITE IMAGERY WITHIN THE CONVECTIVE REGION. MAXIMUM LOW-LEVEL MOISTURE CONVERGENCE COUPLED WITH FAVORABLE UPPER LEVEL DIFFLUENCE ON THE REAR RIGHT QUADRANT OF A STRONG UPPER LEVEL JET STREAK CONTINUES TO SUPPORT THIS SYSTEM. OTHERWISE...FAIR WEATHER CONDITIONS AREA ELSEWHERE ACROSS THE DISCUSSION AREA...INFLUENCED BY A 1021 MB HIGH PRESSURE SYSTEM OVER THE NW BAHAMAS AND A STRONG/BROAD SUBTROPICAL RIDGE AXIS THAT EXTENDS IN TO THE REGION ANCHORED BY A 1036 MB HIGH CENTERED WELL NORTH OF THE DISCUSSION AREA NEAR 50N40W. A SLIGHT WEAKNESS REMAINS ON THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE DUE TO AN UPPER LEVEL LOW CENTERED NEAR 27N35W. THIS UPPER LEVEL FEATURE IS ONLY PROVIDING FOR A REGION OF MIDDLE TO UPPER LEVEL OVERCAST CLOUDINESS WITH A FEW POSSIBLE ISOLATED SHOWERS FROM 16N-27N BETWEEN 24W-40W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA