000 AXNT20 KNHC 310004 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT TUE AUG 30 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2345 UTC. ...SPECIAL FEATURE... TROPICAL STORM KATIA IS CENTERED NEAR 12.7N 35.4W AS OF 30/2100 UTC...OR ABOUT 750 MI...1210 KM W OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING WNW AT 17 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 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. MOST OF THE CONVECTION IS CENTERED WITHIN THE STORM WITH RAIN BANDS EXTENDING 226 NM FROM THE CENTER. MODERATE CLUSTERED CONVECTION IS FROM 10N-14N BETWEEN 33W-39. ...TROPICAL WAVES... TROPICAL WAVE IS LOCATED IN THE WESTERN CARIBBEAN FROM 22N82W TO HONDURAS COAST NEAR 15N84W. WATER VAPOR IMAGERY SHOW HIGH MOISTURE COVERING THE WRN HALF OF THE CARIBBEAN. THIS IS HELPING ENHANCE SHOWERS/THUNDERSTORMS ACROSS HALF WRN CUBA...AS WELL AS INLAND IN HONDURAS AND NICARAGUA. SHOWERS/THUNDERSTORMS ASSOCIATED TO THIS TROPICAL WAVE OVER THE SEA ARE FROM 14N-22N BETWEEN 79W-85W. CONTINUED SHOWER/THUNDERSTORM ACTIVITY IN THIS AREA CONTRIBUTED TO THE FORMATION OF THIS TROPICAL WAVE...WAVE FORMATION AND GROWTH IS POSSIBLE IN THE WRN CARIBBEAN AND CURRENT ATMOSPHERIC CONDITIONS WERE FAVORABLE FOR THIS TO OCCUR. MODEL GUIDANCE ALSO SUPPORTED ITS FORMATION. IN 24 HOURS THIS WAVE WILL CONTINUE MOVING IN A WNW-NW TRACK INTO THE GULF OF MEXICO. THIS WILL LIKELY SUPPORT CONTINUED SHOWER/THUNDERSTORM ACTIVITY OVER THE NW CARIBBEAN OVER THE NEXT DAY OR SO. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH IS ANALYZED ACROSS MAURITANIA FROM 21N10W SW TO THE CAPE VERDE ISLANDS NEAR 15N25W. THE CIRCULATION OF KATIA HAS DISRUPTED THE MONSOON TROUGH TO THE W OF THE CAPE VERDE ISLANDS. A SMALL PORTION OF THE ITCZ EXISTS TO THE W OF KATIA ALONG 11N48W TO THE COAST OF VENEZUELA NEAR 10N61W. THE CONVERGENCE ALONG THE ITCZ AXIS IS GENERATING SCATTERED SHOWERS WITHIN 148 NM N OF THE AXIS. AS KATIA MOVES WNW...THE MONSOON TROUGH WILL RE-ESTABLISH WHILE THE ITCZ WILL BEGIN TO BREAKDOWN. ...DISCUSSION... GULF OF MEXICO... AS OF 2100 UTC...THE STATIONARY FRONT IN THE NE GULF HAS DISSIPATED AS THE UPPER LEVEL TROUGH MOVED EASTWARD. AN UPPER LEVEL RIDGED IS CARRYING DRY AIR AND SUBSIDENCE TO THE SW REGION OF THE GULF N 26N SUPPORTING FAIR WEATHER. S OF 26N...DEEP LAYERED MOISTURE PREVAILS EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY AND WATER VAPOR IMAGERY. UPPER LEVEL DIFFLUENCE AROUND THE E SIDE OF THE UPPER TROUGH ALONG WITH THE ENHANCED MOISTURE IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FOR THE REST OF THE GULF. A SURFACE TROUGH JUST W OF THE YUCATAN PENINSULA ALONG 23N93W TO 19N94W IS ALSO SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 18N-23N BETWEEN 91W-96W. THIS TROUGH IS EXPECTED TO CONTINUE TO DRIFT WNW OVER THE NEXT COUPLE OF DAYS. THE SIGNIFICANT MOISTURE IS EXPECTED TO REMAIN OVER MUCH OF THE GULF OF MEXICO WITH A LIKELY CHANCE OF SCATTERED SHOWERS/THUNDERSTORMS. CARIBBEAN SEA... THE MAIN FEATURE IS A TROPICAL WAVE IN THE WESTERN CARIBBEAN. SEE ABOVE THE TROPICAL WAVES SECTION. CONFLUENCE TO THE W OF AN UPPER LEVEL INVERTED TROUGH WITH AXIS CENTERED NEAR 72W IS GENERATING SHOWERS INLAND LA HISPANIOLA AND SCATTERED SHOWERS TO THE CENTRAL CARIBBEAN W OF 68W. THE EASTERN CARIBBEAN IS UNDER FAIR WEATHER CONDITIONS DUE TO DRY AIR SUBSIDENCE FROM A WEAK UPPER LEVEL RIDGE CENTERED NEAR 60W. EXPECT SIMILAR WEATHER CONDITIONS IN THE NEXT 24 HOURS. ATLANTIC OCEAN... SCATTERED SHOWERS/THUNDERSTORMS COVER THE FAR WRN ATLC ASSOCIATED WITH HIGH MOISTURE VALUES AND UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL TROUGH OVER THE ERN SEABOARD AND AN UPPER LEVEL RIDGE EXTENDING FROM CUBA...TO THE NW BAHAMAS...TO 32N68W. AN UPPER LEVEL LOW IN THE CENTRAL ATLC NEAR 28N50W IS SUPPORTING SCATTERED SHOWERS FOR TWO SURFACE TROUGHS...ONE LOCATED FROM 30N50W TO 27N53W...THE SECOND TROUGH LOCATED FROM 26N43W TO 21N42W. TROPICAL STORM KATIA IS IMPACTING THE CENTRAL TROPICAL ATLC. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. KATIA IS EXPECTED TO MOVE WNW NEAR 17 KT. THE PAIR OF SURFACE TROUGHS ARE ALSO EXPECTED TO MOVE WWD AROUND A SURFACE SUB-TROPICAL RIDGE IN THE N CENTRAL ATLC. ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ RAMOS