000 AXNT20 KNHC 212359 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE AUG 21 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. ...SPECIAL FEATURES... TROPICAL STORM ISAAC CENTERED NEAR 15.4N 53.9W AT 21/2100 UTC OR ABOUT 435 NM E OF GUADELOUPE MOVING W AT 15 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY...MIATCPAT4/ WTNT34 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS NEAR THE CENTER FROM 13N TO 16N BETWEEN 54W -57W. TROPICAL STORM WARNINGS HAVE BEEN INITIATED BY THE INDIVIDUAL GOVERNMENTS OF THE EASTERN CARIBBEAN SEA ISLANDS FROM MARTINIQUE TO ST MARTIN AND ANGUILLA. AN ATLANTIC OCEAN TROPICAL WAVE EXTENDS FROM 18N30W TO AN EMBEDDED 1010 MB LOW AT 10N32W. THE SYSTEM IS MOVING W AT 1O TO 15 KT AND HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE WITHIN THE NEXT 48 HOURS. SCATTERED MODERATE CONVECTION IS OVER A LARGE AREA FROM 07N TO 14N BETWEEN 32W AND 38W. ...TROPICAL WAVES... A POORLY DEFINED TROPICAL WAVE EXTENDS OVER THE EASTERN CARIBBEAN FROM 19N65W TO 10N65W MOVING W AT 20-25 KT...BRINGING A FEW SHOWERS TO THE NE CARIBBEAN. THE WAVE WILL PUSH INTO THE CENTRAL CARIBBEAN WED. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE COAST OF SENEGAL NEAR 14N17W THE 1010 MB LOW NEAR 10N32W TO 07N36W AND 10N43W. SCATTERED MODERATE CONVECTION IS OVER A LARGE AREA FROM 07N TO 14N BETWEEN 32W AND 38W ASSOCIATED WITH THE LOW NEAR 10N32W. OTHERWISE NO SIGNIFICANT CONVECTION NOTED.. ...DISCUSSION... THE GULF OF MEXICO... A 1010 MB LOW IS CENTERED OVER THE W GULF OF MEXICO NEAR 23N97W. A SURFACE TROUGH EXTENDS FROM 26N96W TO THE LOW CENTER TO 22N97W. THIS SYSTEM IS DRIFTING W AND WILL LIKELY PUSH ONSHORE OVERNIGHT. THIS SYSTEM HAS A LOW CHANCE OF BECOMING A TROPICAL CYCLONE WITHIN THE NEXT 48 HOURS. NO SIGNIFICANT CONVECTION IS NOTED WITH THE LOW CENTER. SURFACE TROUGH EXTENDS FROM THE FLORIDA PANHANDLE AT 30N86W TO 28N93W MOVING E. THE SURFACE TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH DIGGING THROUGH THE LOWER MISSISSIPPI VALLEY INTO THE SOUTHEAST UNITED STATES AND NE GULF. A LINE OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION PERSISTS OVER THE EASTERN GULF AHEAD OF THE UPPER TROUGH WITHIN 60 NM EITHER SIDE OF A LINE FROM ROUGHLY TAMPA BAY TO NEAR 25N87W. THE CARIBBEAN SEA... A TROPICAL WAVE THAT HAD BEEN OVER THE GULF OF HONDURAS HAS SHIFTED W INTO THE YUCATAN PENINSULA AND THROUGH BELIZE. ASIDE FROM THE TROPICAL WAVE IN THE EASTERN CARIBBEAN...A 1009 MB LOW PERSISTS OVER N COLOMBIA AT 07N74W. SURFACE RIDGING EXTENDS FROM THE NW ATLC THROUGH CUBA. A SOMEWHAT TIGHT PRES GRADIENT BETWEEN THE RIDGE AND LOW PRES OVER THE SE CARIBBEAN IS TRADE WIND CONVERGENCE IS ALLOWING FRESH TO STRONG TRADE WINDS OVER THE SW CARIBBEAN. LOW LEVEL CONVERGENCE FROM THESE ENHANCED TRADES HAD GENERATED CLUSTERS OF CONVECTION OVER THE SW CARIBBEAN FROM PROVIDENCIA ISLAND TO THE NICARAGUAN COAST. MUCH OF THIS HAS DIMINISHED OVER THE PAST COUPLE OF HOURS. FAIRLY DRY CONDITIONS ELSEWHERE IS INHIBITING MUCH IN THE WAY OF CONVECTION IN MOST AREAS OF THE CARIBBEAN. THE NOTABLE EXCEPTION WILL BE THE WINDWARD AND LEEWARD ISLANDS WHERE THE FIRST OUTER SHOWERS FROM THE NEWLY NAMED TROPICAL STORM ISAAC ARE JUST REACHING THE AREA. RESIDENTS IN THESE AREAS SHOULD KEEP ABREAST OF THE LATEST FORECASTS AND ADVISORIES FROM NHC AND INFORMATION FROM LOCAL AUTHORITIES AND MEDIA ON THIS DEVELOPING STORM. THE ATLANTIC OCEAN... A 1023 MB HIGH IS ANCHORED OVER THE W ATLANTIC NEAR 29N65W. A 1022 MB HIGH IS CENTERED OVER THE CENTRAL ATLANTIC NEAR 33N49W. A SURFACE TROUGH IS OVER THE CENTRAL ATLANTIC FROM 32N32W TO 26N38W. AFRICAN DUST EXTENDS FROM 10N-33N E OF 30W...AND FROM 10N-26N BETWEEN 25W-65W. IN THE UPPER LEVELS...AN UPPER LEVEL LOW IS CENTERED OVER THE BAHAMAS NEAR 22N75W. UPPER LEVEL DIFFLUENCE N OF THE CENTER AND AHEAD OF A MID TO UPPER LEVEL TROUGH OVER THE EASTERN UNITED STATES IS PRODUCING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS MAINLY N OF 25N AND W OF 75W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ CHRISTENSEN