000 AGXX40 KNHC 011853 MIMATS MARINE WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 300 PM EDT SEP 01 2011 UPDATED TROPICAL N ATLC AND WARNINGS SECTION FOR FORECAST AND WARNING CONDITIONS REGARDING TROPICAL STORM KATIA 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... SURFACE PRES IS FALLING OVER THE N CENTRAL GULF THIS AFTERNOON...AS LOW PRES FORMS NEAR 27N91W. THE LOW SHOWS UP FAIRLY WELL IN A 15Z ASCAT PASS SUPPORTED BY WEATHER OBSERVATIONS FROM BUOYS AND OIL RIGS. WINDS ARE 20 TO 25 KT OVER THE N CENTRAL GULF...JUST OFF THE MISSISSIPPI DELTA...BETWEEN THE DEVELOPING LOW AND HIGH PRES OVER THE SOUTHEAST UNITED STATES. SEAS ARE UP TO AT LEAST 11 FT IN THIS AREA AS WELL. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE NOTED OVER MUCH OF THE EASTERN GULF DUE TO CONVERGENCE INTO THE LOW. MODEL GUIDANCE IS SLIGHTLY BETTER AGREEMENT THROUGH LATE SAT KEEPING THE LOW OFF THE LOUISIANA COAST...WITH BOTH THE GFS AND ECMWF SHOWING THE DEEPENING APPRECIABLY INTO A TROPICAL CYCLONE. THE NAM IS A LITTLE MORE AGGRESSIVE...AND SHOWS THE LOW MOVING CLOSER TO THE LOUISIANA COAST. INTERESTS IN THE NW AND NE CENTRAL GULF SHOULD MONITOR THE DEVELOPMENT OF THIS LOW OVER THE NEXT COUPLE OF DAYS. SW ATLC S OF 31N W OF 55W... A TROUGH EXTENDS FROM 21N67W TO 25N70W. LIGHT TO MODERATE NE WINDS ARE NOTED W OF THE TROUGH POSITION. HIGH PRES IS MOVING OFF THE CAROLINAS TOWARD BERMUDA...BUT IS WEAKENING AND WILL ALLOW A WEAK PRES PATTERN TO PREVAIL THROUGH THE WEEKEND. WINDS WILL VEER MORE SE THROUGH SAT WITH THE WEAK HIGH TO THE NE...BUT THEN BACK MORE TO THE NE AS HURRICANE KATIA APPROACHES THROUGH THE CENTRAL ATLC. SWELL WILL ENTER THE AREA FROM THE EAST AHEAD OF KATIA WITH HEIGHTS OF 8 TO 9 FT BY LATE SUN. THE STRONGER WINDS OF KATIA ARE EXPECTED TO STAY JUST TO THE E OF 65W THROUGH MON...WITH WINDS POSSIBLY APPROACHING TROPICAL STORM STRENGTH TUE N OF 25N E OF 67W AS KATIA APPROACHES. E SWELL OF 8 TO 12 FT WILL PUSH AS FAR W AS THE BAHAMAS BY TUE. CARIBBEAN SEA AND TROPICAL N ATLC S OF 22N W OF 55W...MODERATE TO FRESH WINDS OVER MUCH OF THE CENTRAL AND WESTERN CARIBBEAN...IN PART DUE TO HIGH PRES N OF THE AREA. THIS HIGH PRES WILL WEAKEN THROUGH THE WEEKEND...ALLOWING WINDS TO DIMINISH THROUGH EARLY NEXT WEEK. FURTHER EAST...HURRICANE KATIA...LOCATED NEAR 15.5N 47.5W WILL MOVE TO THE NE OF THE LEEWARD ISLANDS...THROUGH THE NE PORTION OF THE TROPICAL N ATLC ZONE FRI. WINDS TO HURRICANE FORCE ARE EXPECTED FRI...LASTING THROUGH SUN AS KATIA MOVES TO THE NE. SWELL OF 10 TO 15 FT IS LIKELY AHEAD OF THE KATIA...IMPACTING THE WATERS ON THE ATLC SIDE OF THE LEEWARD ISLANDS. PLEASE SEE THE LATEST INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADER MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS ON HURRICANE KATIA. WARNINGS... GULF OF MEXICO... .NONE. CARIBBEAN... .NONE. TROPICAL N ATLC... .AMZ087...HURRICANE WARNING N OF 16N E OF 61W FRI INTO EARLY MON... SW N ATLC... .NONE. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORECASTER CHRISTENSEN