000 AXNT20 KNHC 121735 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT SUN MAY 12 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 THE COAST OF SIERRA LEONE NEAR 8N13W TO 7N16W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 4N20W TO EQ40W TO THE COAST OF BRAZIL AT 1N50W. SCATTERED MODERATE CONVECTION IS NOTED FROM 4N TO 8N BETWEEN 15W-18W. SIMILAR CONVECTION IS FROM 3N TO 6N BETWEEN 48W AND THE COAST OF BRAZIL AND FRENCH GUIANA. ISOLATED MODERATE CONVECTION IS WITHIN 240 NM N OF ITCZ AXIS W OF 30W AND WITHIN 180 NM S OF AXIS BETWEEN 28W AND 35W. WIDELY SCATTERED MODERATE CONVECTION IS N OF THE ITCZ FROM 2N-7N BETWEEN 48W-53W. ...DISCUSSION... GULF OF MEXICO... A WEAK LATE SEASON COLD FRONT EXTENDS FROM THE FLORIDA BIG BEND ACROSS THE CENTRAL GULF TO NEAR TUXPAN MEXICO. A 90 NM WIDE BAND OF SHOWERS AND TSTMS IS ASSOCIATED WITH THE FRONT S OF 26N. WINDS W OF THE FRONT ARE NORTHERLY AT 10 TO 15 KT. HOWEVER... BUOY 42002 JUST BEHIND THE FRONT IS REPORTING SUSTAINED WINDS OF 29 KT...LIKELY ASSOCIATED WITH THE STRONG CONVECTION. THE FRONT IS FORECAST TO CONTINUE E AND EXTEND FROM CEDAR KEY FLORIDA TO TO 18N93W TONIGHT...THEN IT WILL NEARLY STALL FROM SE FLORIDA TO 23N90W TO 19N93W ON MON. A PREFRONTAL SURFACE TROUGH IS ANALYZED FROM NORTHERN FLORIDA THROUGH TAMPA BAY TO NEAR 25N85W. ANOTHER TROUGH EXISTS IN THE BAY OF CAMPECHE AND EXTENDS NORTHEASTWARD TO NEAR 22N92W ALSO AHEAD OF THE FRONT. SOME CONVECTION WAS NOTED OVER SE MEXICO ON THE EAST SIDE OF THIS TROUGH...BUT CURRENTLY IS WEAKENING. HIGH PRESSURE WILL BUILD IN THE WAKE OF THE FRONT OVER THE GULF TONIGHT. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE CONTINUES TO DOMINATE THE GULF. ABUNDANT MID/UPPER LEVEL MOISTURE IS NOTE ON WATER VAPOR IMAGERY ACROSS MUCH OF THE REGION. CARIBBEAN SEA... TRADE WIND FLOW OF 10-15 KT DOMINATES THE MAJORITY OF THE EASTERN AND CENTRAL CARIBBEAN WITH WINDS OF 20 TO 25 KT NEAR THE COAST OF COLOMBIA. THIS REGIMEN IS FORECAST TO PERSIST OVER THE NEXT SEVERAL DAYS. A WEAK COLD FRONT WILL PASS E ACROSS CUBA AND THE CARIBBEAN WATERS N OF 20N AND W OF HISPANIOLA ON MON AND TUE. MODERATE TO FRESH NE WINDS WILL FOLLOW THE FRONT. LOW TOP TRADE WIND SHOWERS ARE SEEN ON VIS SATELLITE PICTURES ACROSS MOST OF THE BASIN. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OVER THE SW CARIBBEAN NEAR THE ATLC COAST OF COSTA RICA AND WESTERN PANAMA. ALOFT...AN UPPER ANTICYCLONE CENTERED BETWEEN SAN ANDRES AND PROVIDENCIA ISLANDS EXTENDS A RIDGE ACROSS THE WESTERN CARIBBEAN PROVIDING MOSTLY FAIR CONDITIONS THERE. AN UPPER LEVEL TROUGH PERSISTS ACROSS THE EASTERN CARIBBEAN EXTENDING FROM THE VIRGIN ISLANDS TO WESTERN VENEZUELA. STRONG UPPER LEVEL AND DRY AIR MASS IS NOW NOTED OVER HISPANIOLA AND PUERTO RICO LIMITING THE DEVELOPMENT OF SHOWER AND TSTM ACTIVITY. ATLANTIC OCEAN... A A RIDGE/TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE DISCUSSION AREA. AN UPPER LOW LOCATED NEAR 21.5N63W SUPPORTS A 1012 MB SURFACE LOW PRES CENTERED NEAR 23N67W. SCATTEROMETER DATA SHOW VERY WELL THE CYCLONIC CIRCULATION ASSOCIATED WITH THIS LOW WITH THE STRONGEST WINDS OF 20-25 KT WITHIN 240 NM N SEMICIRCLE OF LOW CENTER. IN ADDITION...VISIBLE SATELLITE IMAGERY REVEALS A WELL DEFINED SWIRL OF LOW CLOUDS IN ASSOCIATION WITH THIS FEATURE. MOST OF THE SHOWER AND TSTM ACTIVITY IS DISPLACED TO THE EAST AND NEAR THE UPPER LEVEL CENTER COVERING FROM 20N TO 23N BETWEEN 59W AND 63W. ENVIRONMENTAL CONDITIONS...ESPECIALLY THE VERTICAL SHEAR...DO NOT APPEAR TO BE CONDUCIVE FOR TROPICAL DEVELOPMENT. THE SURFACE LOW IS FORECAST TO DRIFT WESTWARD AND WEAKEN INTO A TROUGH NEAR THE SE BAHAMAS MON AFTERNOON. THE TROUGH WILL MERGE WITH A COLD FRONT FORECAST TO MOVE INTO THE NW WATERS OF THE FORECAST AREA THIS AFTERNOON. THE FRONT WILL EXTEND FROM 31N75W TO THE FLORIDA STRAITS MON. CURRENTLY... PRESSURE GRADIENT BETWEEN THE SURFACE LOW AND A RIDGE EXTENDING FROM BERMUDA TO SOUTH FLORIDA IS PRODUCING A LARGE AREA OF MAINLY FRESH WINDS ACROSS PARTS OF THE CENTRAL AND WESTERN ATLC. THE CENTRAL ATLC IS DOMINATED BY BROAD SURFACE RIDGING SUPPORTED BY AN UPPER LEVEL RIDGE ALONG 46W/47W. AN UPPER LEVEL TROUGH COVERS THE EASTERN ATLANTIC CENTERED AROUND AN UPPER LOW LOCATED JUST SOUTH OF THE AZORES. THE UPPER TROUGH SUPPORTS A SURFACE TROUGH THAT NOW EXTENDS FROM 31N33W TO 28N25W. SCATTERED SHOWERS AND TSTMS ARE NOTED MAINLY ON THE NORTH SIDE OF THE TROUGH. THE 1202 UTC ASCAT PASS SHOWS THE WIND SHIFT ASSOCIATED WITH THIS TROUGH WITH THE STRONGEST WINDS OF 20-25 KT JUST N OF 31N. A TROPICAL WAVE-LIKE HAS MOVED OUT OF AFRICA. A SURFACE TROUGH IS ANALYZED ALONG 17W FROM 2N TO 9N ON THE 1200 UTC SURFACE MAP. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WAS NOTED THIS MORNING IN ASSOCIATION WITH THIS SYSTEM...BUT CONVECTION IS NOW DIMINISHING. AN AREA OF SAHARAN DUST IS OBSERVED ON VIS AND SAHARAN AIR LAYER SATELLITE IMAGERY REACHING 55W. THE REMNANTS OF A SHEAR AXIS IS STILL EVIDENT ON THE SAME SATELLITE IMAGERY ACROSS THE TROPICAL ATLC JUST N OF THE AREA OF SAHARAN DUST. 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. $$ FORMOSA