000 AGXX40 KNHC 311803 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 200 PM EDT WED AUG 31 2011 MARINE WEATHER DISCUSSION FOR THE GULF OF MEXICO...CARIBBEAN SEA AND TROPICAL N ATLC...AND SOUTHWEST NORTH ATLC S OF 31N W OF 55W. GULF OF MEXICO... A SURFACE TROUGH ALONG 96W S OF 23N WILL DRIFT NW THROUGH SAT. A TROPICAL WAVE EXTENDING FROM THE YUCATAN PENINSULA TO 85W WILL MOVE W TONIGHT AND INTO THE EASTERN BAY OF CAMPECHE THU THROUGH FRI AS LOW PRES FORMS ALONG THE TROUGH NEAR 27N93W. THE LOW IS EXPECTED TO MEANDER THROUGH THU NIGHT...THEN DRIFT N OR NE THROUGH THROUGH SUN. IT WILL BE ACCOMPANIED BY INCREASING WINDS AND SEAS. LATEST MODEL GUIDANCE CONTINUES TO SUGGEST THAT LOW PRES WILL DEVELOP OVER THE CENTRAL GULF WITHIN THE NEXT 3 DAYS. THE MAIN PLAYERS FOR THIS TO HAPPEN ARE BECOMING MORE READILY APPARENT WITH THE TROUGH ALONG 95W ALREADY THERE...AND THE WAVE COMING INTO THE AREA THU THROUGH FRI. IN ADDITION...WATER VAPOR IMAGERY SHOWS A NARROW UPPER LEVEL TROUGH THAT STRETCHES NE TO SW ACROSS WNW PORTION OF THE GULF WITH AMPLE MOISTURE AVAILABLE. VORTICITY ASSOCIATED WITH THE TROPICAL WAVE SHOULD COMBINE WITH TROUGH ENERGY ALREADY PRESENT TO INDUCE A SURFACE LOW IN THE VICINITY OF 27N93W BY FRI. MODEL DIFFERENCES ARE NOTED WITH RESPECT TO MAINLY THE TRACK OF THIS LOW FEATURE. ECMWF AND UKMET MODELS KEEP THE LOW MEANDERING ON A MUCH FURTHER S TRACK OVER THE WESTERN PART OF THE GULF BEFORE TRACKING IT NNE FRI THROUGH SUN. THE GFS IS MUCH FURTHER TO THE N...DEVELOPING A LOW OVER THE N CENTRAL GULF FRI NIGHT. WILL CONTINUE TO LEAN WITH GENERAL MODEL CONSENSUS...WITH LOW DEVELOPING NEAR 27N93W OVER THE NEXT 24-48 HOURS. WILL FORECAST LOW TO MEANDER OVER THE WESTERN GULF THROUGH FRI...THEN DRIFT N OR NE THROUGH SUN. IN ANY EVENT...IMPLICATIONS TO WINDS AND SEAS WILL BE SEEN WHEN THE PRES GRADIENT TIGHTENS NEAR AND TO THE N AND NE OF THE LOW TO RESULT IN E-SE AND SE-S WINDS OF 15-20 KT OVER THE MIDDLE AND WESTERN ZONES...WITH WINDS INCREASING TO E-SE 20-25 KT IN THE NORTHERN PORTION OF THE MIDDLE GULF FRI THROUGH SUN. THE TIGHT PRES GRADIENT SHOULD BUILD SEAS AS HIGH AS 9 FT IN THE FAR NORTHERN MIDDLE GULF SAT AND SUN. SW ATLC S OF 31N W OF 55W... A RIDGE ACROSS THE SW N ATLC WATERS WILL RETREAT EAST OVER THE NEXT COUPLE OF DAYS...ENABLING A WEAK COLD FRONT TO MOVE ACROSS THE N PART OF THE AREA THROUGH THE REMAINDER OF THE FORECAST. ASIDE FROM A SHIFT IN WIND DIRECTION THIS COLD FRONT WILL NOT BRING A SIGNIFICANT INCREASE TO WINDS OR SEAS. LOOKING BEYOND THE CURRENT FORECAST...WE ARE MONITORING THE TRACK OF TROPICAL STORM KATIA...WHICH MAY AFFECT THE SW N ATLC WATERS EARLY NEXT WEEK. KATIA IS EXPECTED TO APPROACH THE SE PORTION LATE SUN. AS A RESULT...EXPECT WINDS TO BECOME NE AND INCREASE TO 15 KT WITH BUILDING SEAS IN THE FAR SE PORTION LATE ON SUN. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W... CONVECTION ASSOCIATED WITH THE TROPICAL WAVE OVER THE YUCATAN PENINSULA IS LOCATED W OF 82W AND MOVING SLOWLY WESTWARD. THE SURFACE RIDGE TO THE NORTH OF THE AREA IS MAINTAINING MODERATE PRES AND SUPPORTING FRESH TRADE WIND FLOW OVER THE CENTRAL CARIBBEAN. TRADE WINDS WILL GRADUALLY DIMINISH OVER THE NEXT FEW DAYS AS THE RIDGE IN THE SW N ATLC RETREATS EASTWARD. E-SE WINDS OF 15-20 KT WILL SPREAD NORTHWESTWARD ACROSS THE NW CARIBBEAN THROUGH FRI AS THE GRADIENT BETWEEN THE ATLC RIDGE AND LOWER PRES OVER THE SOUTHERN CARIBBEAN SEA W OF 70W INCREASES. EXPECT SEAS TO 9 FT IN THE SW CARIBBEAN N OF 16N BETWEEN 68W AND 75W. TROPICAL STORM KATIA IN THE FAR EASTERN ATLANTIC IS EXPECTED TO INTENSIFY INTO A HURRICANE TONIGHT AND TRACK NW ACROSS ITS FAR NORTHERN WATERS FRI NIGHT THROUGH SUN. WINDS AND SEAS WILL INCREASE SIGNIFICANTLY FRI AS TROPICAL FORCE WINDS MOVE IN... FOLLOWED BY HURRICANE FORCE WINDS. SEE THE LATEST PUBLIC ADVISORY UNDER AWIPS/WMO HEADER MIATCPAT2/WTNT32 KNHC AND THE FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS ON TROPICAL STORM KATIA. WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN... .NONE. TROPICAL N ATLC... .AMZ087...HURRICANE CONDITIONS EXPECTED N OF 15N E OF 61W FRI THROUGH SUN... SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER MUNDELL