000 AXNT20 KNHC 131753 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT FRI APR 13 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1745 UTC. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS ACROSS THE TROPICAL REGIONS OF WEST AFRICA INTO THE ATLC WATERS THROUGH SIERRA LEONE ALONG 8N13W TO 3N19W...WHERE THE ITCZ CONTINUES ALONG 1S29W TO THE CAST OF BRAZIL NEAR 3S42W. SCATTERED TO NUMEROUS STRONG CONVECTIVE PRECIPITATION IS NOTICED N OF THE EQUATOR BETWEEN THE PRIME MERIDIAN AND 18W. SIMILAR CONVECTION IS WITHIN 90 NM ON EITHER SIDE OF A LINE EXTENDING FROM 4S30W ALONG 2N40W TO BRAZIL NEAR 2N50W. ...DISCUSSION... THE GULF OF MEXICO... THE BASE OF AN ELONGATED UPPER LEVEL RIDGE MOVES ACROSS THE GULF BRINGING DRY AIR ALOFT TO THE DISCUSSION AREA. THE STRONGEST SUBSIDENCE IS NOTICED N OF THE AREA OVER THE ERN CONUS ANCHORED BY A 1027 MB CENTERED OVER THE GREAT LAKES REGION. THE SURFACE RIDGE AXIS ASSOCIATED TO THIS HIGH PRESSURE SYSTEM EXTENDS INTO THE AREA SUPPORTING A MODERATE E-W PRESSURE GRADIENT WITH 10-20 KT ESE WINDS W OF 86W. AS THE SURFACE RIDGE MOVES OFF THE ERN CONUS SEABOARD...SHORT RANGE COMPUTER MODELS SUGGEST THIS FLOW COULD INCREASE UP TO 25 KT DURING THE NEXT 24 HOURS...ESPECIALLY NEAR THE COASTAL WATERS OF TEXAS. OTHERWISE...NO OTHER SIGNIFICANT CHANGES ARE EXPECTED DURING THE FORECAST PERIOD. THE CARIBBEAN SEA... MODERATE TO STRONG SUBSIDENCE AND DRY AIR ALOFT COVERS A GREAT PORTION OF THE DISCUSSION AREA THIS AFTERNOON. THIS IS KEEPING MOST OF THE AREA UNDER FAIR WEATHER CONDITIONS...EXCEPT OVER THE COASTAL WATERS BETWEEN WRN PUERTO RICO AND ERN DOMINICAN REPUBLIC N OF 15N BETWEEN 67W-71W. MODERATE TO HEAVY SHOWERS AND ISOLATED THUNDERSTORMS ARE OBSERVED IN THIS REGION. A RECENT SCATTEROMETER PASS REVEALED A SURFACE TROUGH IN THIS REGION. THIS TROUGH WILL BE ANALYZED DURING THE NEXT MAP CYCLE. IN THE MEAN TIME...A ROUGH ESTIMATE OF ITS AXIS COULD BE FROM 19N68W TO 13N71W. SIMILAR CONVECTION IS NOTICED OVER THE NE COASTAL WATERS OF JAMAICA MORE LIKELY ASSOCIATED TO DAY-TIME HEATING... INSTABILITY...AND OROGRAPHIC EFFECTS. AS UPPER LEVEL CIRRUS COVER PART OF THE EXTREME SE BASIN...TOTAL PRECIPITABLE WATER PRODUCT SHOWS A SPOT OF HIGH VALUES OF LOW LEVEL MOISTURE OFF THE COAST OF VENEZUELA. VISIBLE SATELLITE IMAGERY DEPICTS SCATTERED SHOWERS AND THUNDERSTORMS IN THIS REGION WITHIN 120 NM OFF THE COAST BETWEEN 62W-70W. OTHERWISE...TRADEWIND FLOW OF 10-15 KTS IS REPORTED ACROSS THE AREA. COMPUTER MODELS SUGGEST THE CONVECTION OVER THE NRN NRN CARIBBEAN LINGER AND SLOWLY SPREAD WESTWARD OVER THE NEXT 24 HOURS. THE ATLANTIC OCEAN... AN UPPER LEVEL TROUGH MOVES ACROSS THE WRN ATLC THIS AFTERNOON. WATER VAPOR IMAGERY SHOWS A VIGOROUS SHORTWAVE EMBEDDED AT THE SRN EXTENSION OF THE UPPER TROUGH SUPPORTING A 1008 MB LOW NEAR 33N57W. A CLOD FRONT EXTENDS SSW FROM THE LOW CENTER ALONG 25N60W TO 21N68W...WHERE THE BOUNDARY BECOMES WEAK AND NEARLY STATIONARY AS IT EXTENDS NW ACROSS THE TURKS/CAICOS...AND THE BAHAMAS ALONG 23N75W TO THE COAST OF FLORIDA NEAR BOCA RATON. A PRE FRONTAL TROUGH EXTENDS FROM 24N60W TO 20N65W. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 150-300 NM AHEAD OF THE COLD FRONT N OF 20N WHERE LOW LEVEL CONVERGENCE AND UPPER LEVEL DIFFLUENCE IS MAXIMIZED. A REGION OF SIMILAR CONVECTION IS FOUND WITHIN 80 NM NE OF THE STATIONARY PORTION OF THE FRONTAL BOUNDARY AFFECTING MOSTLY THE CENTRAL AND NW BAHAMAS N OF 23N. AS THE SOUTHERN MOST PORTION OF THE BOUNDARY BREAKS... SOME ISOLATED MODERATE TO STRONG CONVECTION QUICKLY RUSH AGAINST THE NRN COAST OF HISPANIOLA ON SATELLITE IMAGERY. COMPUTER MODELS SUGGEST THE FRONT WILL CONTINUE TO TRACK E OVER THE NEXT 24 HOURS LEAVING FRESH TO STRONG NORTHERLY WINDS IN ITS WAKE. FAIR WEATHER CONDITIONS ARE FOUND ELSEWHERE AHEAD OF THE FRONTAL CONVECTION...ASSOCIATED TO A N-S ELONGATED CENTRAL ATLC UPPER RIDGE SUPPORTING A 1032 MB HIGH NEAR 36N33W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA