000 AXNT20 KNHC 051800 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON SEP 05 2011 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 1745 UTC. ...SPECIAL FEATURES... HURRICANE KATIA IS CENTERED NEAR 24.6N 63.3W AT 05/1500 UTC OR ABOUT 540 MI...870 KM S OF BERMUDA MOVING NW AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 965 MB. MAXIMUM SUSTAINED WIND SPEED IS 95 KT WITH GUSTS TO 115 KT. 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. SCATTERED MODERATE TO STRONG CONVECTION IS FROM 21N-27N BETWEEN 60W-67W. HURRICANE-FORCE WINDS EXTEND OUTWARD UP TO 60 MILES...95 KM...FROM THE CENTER...AND TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 205 MILES...335 KM. LARGE SWELLS GENERATED BY KATIA ARE EXPECTED TO AFFECT MOST OF THE EAST COAST OF THE UNITED STATES...BERMUDA...THE GREATER ANTILLES...AND EAST-FACING BEACHES OF THE BAHAMAS DURING THE NEXT FEW DAYS. THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. SWELLS AFFECTING THE NORTHERN LEEWARD ISLANDS SHOULD CONTINUE TO SUBSIDE TODAY. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER SERVICE OFFICE FOR ADDITIONAL INFORMATION. A LOW PRESSURE SYSTEM ASSOCIATED TO A TROPICAL WAVE IS NEAR 9N29W MOVING W 10-15 KT. THIS FEATURE IS EMBEDDED WITHIN AN AREA OF DEEP LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE FROM 5N-13N BETWEEN 26W-35W. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO REMAIN CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM DURING THE NEXT DAY OR SO. THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS ...TROPICAL WAVES... TROPICAL WAVE IS IN THE CENTRAL TROPICAL ATLC EXTENDING FROM 19N46W TO 13N43W MOVING W NEAR 15 KT. AN EARLIER WIND OBSERVATION FROM BUOY 41041 SUGGESTED A LOW LEVEL CENTER IN THE WAVE AXIS NEAR 16N45W...EMBEDDED WITHIN AN AREA OF DEEP LAYER MOISTURE AS DEPICTED ON THE TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED WEAK TO MODERATE CONVECTION IS WITHIN 150 NM W OF THE WAVE AXIS. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH IS ANALYZED ACROSS AFRICA ENTERING THE ERN TROPICAL ATLC THROUGH THE COAST OF SENEGAL NEAR 16N16W... CONTINUING SW ALONG 11N22W TO THE SPECIAL FEATURE LOW NEAR 9N29W ...THEN W ALONG 9N35W TO NEAR 10N44W. CLUSTERS OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION ARE FROM 5N-13N BETWEEN 26W-35W. THIS AREA OF CONVECTION IS ALSO ASSOCIATED TO THE MONSOON TROUGH. ...DISCUSSION... GULF OF MEXICO... LOW-MID LEVEL TROUGHINESS ASSOCIATED TO LEE REMAINS ACROSS THE AREA THIS AFTERNOON. A SURFACE TROUGH EXTENDS INTO THE GULF ALONG THE MISSISSIPPI DELTA SOUTHWARD TO THE BAY OF CAMPECHE NEAR 20N92W...GENERATING BANDS OF SCATTERED HEAVY SHOWERS AND THUNDERSTORMS WITHIN 90 NM ON EITHER SIDE OF THE TROUGH AXIS. MODERATE TO SIGNIFICANT SUBSIDENCE IS TO THE E AND W OF THE CONVECTION AREA. A COOLER AIRMASS MOVES BEHIND THE TROUGH AND IT IS DEPICTED ON THE SURFACE MAP AS A SLOW MOVING COLD FRONT EXTENDING FROM THE COAST OF LOUISIANA NEAR 29N90W WSW INTO THE SOUTHERN COAST OF TEXAS ALONG 26N97W. SURFACE OBS ACROSS THE NORTHERN GULF INDICATE A BROAD CYCLONIC 25-30 KT TURNING ALONG THE TROUGH AXIS N OF 26N. THE COLD FRONT WILL DIG SE THROUGH THE W GULF TODAY AND BECOME STATIONARY FROM NE GULF TO BAY OF CAMPECHE WED THROUGH FRI. CARIBBEAN SEA... MOSTLY FAIR WEATHER CONDITIONS ARE NOTED ACROSS THE CARIBBEAN THIS AFTERNOON ON VISIBLE SATELLITE IMAGERY...ESPECIALLY E OF 80W...WHERE WATER VAPOR IMAGERY SHOWS THE GREATEST MID-UPPER LEVEL DRYNESS AND SUBSIDENCE. OBSERVATIONS ACROSS THE BASIN SHOW 10-15 KT EASTERLY TRADES WITH A FEW ISOLATED LOW TOP SHOWERS ACROSS THE AREA. THIS FLOW TURNS SSE W OF 80W IN RESPONSE TO THE BROAD LOWER PRESSURE FIELD ASSOCIATED TO LEE. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE DEVELOPING ALONG THE COASTAL WATERS OF NICARAGUA N OF 12N. THE SPECIAL FEATURE LOW PRESSURE SYSTEM IN THE TROPICAL ATLC WILL MOVE INTO THE E CARIBBEAN LATE WED AND INTO THE CENTRAL CARIBBEAN BY FRI. ATLANTIC OCEAN... MOST OF THE ATLC...EXCEPT THE AREA SURROUNDING HURCN KATIA...IS DOMINATED BY DRY AIR ALOFT W OF KATIA AND BROAD SURFACE RIDGING MAINLY N OF 20N. HURRICANE KATIA WILL CONTINUE TO MOVE THROUGH THE W ATLC THROUGH WED MOVING N OF THE AREA THU MORNING. LARGE SWELLS GENERATED BY KATIA ARE EXPECTED TO AFFECT MOST OF THE EAST COAST OF THE UNITED STATES...BERMUDA...THE GREATER ANTILLES...AND EAST-FACING BEACHES OF THE BAHAMAS DURING THE NEXT FEW DAYS. THESE SWELLS ARE LIKELY TO CAUSE LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS. SWELLS AFFECTING THE NORTHERN LEEWARD ISLANDS SHOULD CONTINUE TO SUBSIDE TODAY. PLEASE CONSULT PRODUCTS FROM YOUR LOCAL WEATHER SERVICE OFFICE FOR ADDITIONAL INFORMATION. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA