000 AXNT20 KNHC 281804 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT TUE AUG 28 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 1715 UTC. ...SPECIAL FEATURES... RECENTLY UPGRADED HURRICANE ISAAC CENTERED NEAR 28.4N 88.7W AT 15/1800 UTC OR ABOUT 55 MILES S-SE OF THE MOUTH OF THE MISSISSIPPI RIVER...OR ABOUT 135 MILES SE OF NEW ORLEANS LOUISIANA MOVING NW AT 9 KT. MINIMUM CENTRAL PRESSURE IS 975 MB. MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. SCATTERED TO NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION IS WITHIN 120 NM OF THE CENTER OF ISAAC. ISAAC IS FORECAST TO REMAIN A HURRICANE PRIOR TO LANDFALL BEFORE GRADUALLY WEAKENING AS IT MOVES INLAND. THE MAIN THREATS ASSOCIATED WITH ISAAC WILL BE VERY HEAVY RAINFALL OVER THE N GULF COAST STATES...DANGEROUS STORM SURGE AND SURF CONDITIONS...AND STRONG WINDS WELL AWAY FROM THE CENTER AS THE OVERALL CIRCULATION OF ISAAC IS QUITE LARGE. FOR MORE DETAILED INFORMATION REFER TO HURRICANE LOCAL STATEMENTS ISSUED BY YOUR LOCAL NATIONAL WEATHER SERVICE OFFICE. 1011 MB LOW PRES IS POSITIONED NEAR 23N43W WITH A SURFACE TROUGH EXTENDING FROM 31N34W THROUGH THE LOW CENTER TO 15N47W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS BETWEEN 45 NM AND 240 NM IN THE NE SEMICIRCLE OF THE LOW. A RECENT ASCAT PASS SHOWED 20-25 KT WINDS WITHIN 240 NM IN THE N AND NE QUADRANTS OF THE LOW AND 8-10 FT SEAS ARE ACCOMPANYING THESE WINDS. THIS LOW IS MOVING TO THE NW AT 10 KT AND ENVIRONMENTAL CONDITIONS APPEAR TO BE CONDUCIVE FOR SLOW DEVELOPMENT DURING THE NEXT COUPLE OF DAYS. THIS LOW HAS A MEDIUM CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. ...TROPICAL WAVES... A TROPICAL WAVE EXTENDS FROM 21N24W TO LOW PRES NEAR 13N27.5W 1011 MB. SCATTERED MODERATE CONVECTION IS WITHIN 180-240 NM IN THE NW QUADRANT OF THE LOW. FRESH TO STRONG WINDS AND 8-10 FT SEAS ACCOMPANY THIS LOW AND THESE CONDITIONS WILL PERSIST THROUGH THE NEXT 48 HOURS AS THE LOW AND TROPICAL WAVE CONTINUE WESTWARD AT 15-20 KT. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH IS ALONG THE COAST OF MAURITANIA NEAR 18N16W TO NEAR 16N19W WHERE IT ENDS...THEN RESUMES FROM 9N29W TO 8N40W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 13N50W TO THE COAST OF VENEZUELA NEAR 9N61W. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 15N TO 17N BETWEEN 21W AND 24W...AND ALSO WITHIN 60 NM EITHER SIDE OF A LINE FROM 14N55W TO 13N59W TO 15N63W. ...DISCUSSION... GULF OF MEXICO... THE DOMINATE FEATURE IN THE GULF OF MEXICO IS HURRICANE ISAAC WITH THE LARGE AND VAST CIRCULATION COVERING ALMOST THE ENTIRE GULF...EXCEPT FOR THE SW PORTION AND BAY OF CAMPECHE. PLEASE REFER TO THE SPECIAL FEATURES SECTION ABOVE FOR MORE DETAILS ABOUT ISAAC. LIGHT TO MODERATE SW-W WINDS ARE IN THE SW GULF WITH 4-7 FT NW SWELL ASSOCIATED WITH ISAAC PROPAGATING INTO THE AREA. ATLC HIGH PRES WILL BUILD INTO THE AREA FROM THE W IN THE WAKE OF ISAAC LATE WED THROUGH THE END OF THE WEEK WITH MODERATE TO FRESH SE-S RETURN FLOW BECOMING ESTABLISHED ACROSS THE GULF BY FRI. AT THE UPPER LEVELS...A MID TO UPPER LOW IS NEAR THE NE MEXICAN COAST AT 24N98W AND IT IS MOVING WESTWARD TOWARD CENTRAL MEXICO. DRY AND STABLE AIR EXTENDS FROM THIS LOW TO THE SW GULF. A NEARLY STATIONARY UPPER LEVEL RIDGE IS N OF ISSAC ALONG THE N GULF COAST STATES FROM TEXAS NEAR 31N99W TO SOUTHERN ALABAMA NEAR 32N87W TO CENTRAL FLORIDA NEAR 27N81W. DRY AIR ALONG THE SOUTHERN PERIPHERY OF THE RIDGE IS ADVECTING INTO THE CIRCULATION OF ISAAC HELPING TO LIMIT ADDITIONAL DEVELOPMENT AND INTENSIFICATION. CARIBBEAN SEA... A RIDGE AXIS EXTENDS FROM HIGH PRES N OF THE AREA IN THE ATLC SW THROUGH THE WINDWARD PASSAGE TO ACROSS JAMAICA TO THE EASTERN COAST OF HONDURAS NEAR 15.5N83W. MEANWHILE NEARLY STATIONARY 1009 MB SURFACE LOW PRES IS JUST W OF THE COAST OF COLOMBIA NEAR 10N76W. THE PRES GRADIENT BETWEEN THE TWO FEATURES IS RESULTING IN FRESH TO STRONG NE-E TRADES ACROSS THE CENTRAL CARIBBEAN WITH MODERATE ANTICYCLONIC WINDS ELSEWHERE ACROSS THE BASIN. SEAS OF 8-10 FT ACCOMPANY THESE STRONGER WINDS WITH THE HIGHEST SEAS NW OF THE COAST OF COLOMBIA AT THE TAIL END OF THE EASTERLY FETCH. THESE CONDITIONS ARE FORECAST TO NOT CHANGE MUCH THROUGH THE NEXT 48 HOURS. ALOFT...A MID TO UPPER LEVEL LOW IS CENTERED SW OF THE COAST OF HAITI NEAR 17N74W WITH AN ATTENDANT TROUGH STRETCHING N-NE OF HAITI AND S-SW TO EASTERN PANAMA. SCATTERED SHOWERS AND ISOLATED TSTMS ARE PRESENT OVER THE NW CARIBBEAN AS WELL AS OVER THE E CARIBBEAN ISLANDS. AN UPPER LEVEL RIDGE EXTENDS FROM THE ATLC TO ACROSS THE E CENTRAL CARIBBEAN ISLANDS TO N CENTRAL VENEZUELA. ATLANTIC OCEAN... 1022 MB SURFACE HIGH PRES IS SE OF BERMUDA NEAR 25N61W WITH A RIDGE AXIS REACHING TO THE W-NW TO SE GEORGIA. LIGHT TO MODERATE WINDS DOMINATE THE WATERS W OF 50W WITH A CLUSTER OF SCATTERED SHOWERS AND TSTMS N OF HISPANIOLA TO ACROSS THE TURKS AND CAICOS...WITH ADDITIONAL CONVECTION E OF FLORIDA TO 77W. THE OTHER MAIN FEATURES IN THE ATLC ARE THE AREA OF LOW PRES AND ASSOCIATED TROUGH DISCUSSED IN THE SPECIAL FEATURES SECTION... AND THE TROPICAL WAVE AND ASSOCIATED LOW DISCUSSED IN THE TROPICAL WAVES SECTION ABOVE. AN UPPER LEVEL ANTICYCLONE IS NEAR 22N31W WITH AN UPPER RIDGE REACHING FROM 23N25W THROUGH THE ANTICYCLONE TO 21N67W. UPPER LEVEL EASTERLIES DOMINATE THE REGION S OF 20N ON THE SOUTHERN PERIPHERY OF THE ANTICYCLONE/RIDGE. OTHERWISE...AN UPPER LEVEL LOW IS E OF THE RIDGE NEAR 24N20W. DRY AIR COVERS THE WATERS N OF 24N E OF 25W. AN UPPER LEVEL TROUGH EXTENDS FROM 32N42W TO 27N50W AND THIS FEATURE IS SUPPORTING A SURFACE COLD FRONT N OF 32N...AS WELL AS A SURFACE TROUGH THAT REACHES NE FROM THE LOW IN THE SPECIAL FEATURES SECTION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ LEWITSKY