000 AXNT20 KNHC 301751 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...SPECIAL FEATURE... TROPICAL STORM KATIA IS CENTERED NEAR 12.3N 33.4W AS OF 30/1500 UTC...OR ABOUT 550 NM WSW OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING WNW AT 16 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 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 ASSOCIATED CONVECTION IS W OF THE STORM CENTER DUE TO SOME UPPER LEVEL SHEAR. SCATTERED MODERATE/STRONG CONVECTION IS FROM 9N-15N BETWEEN 33W-39W. THE SHEAR IS EXPECTED TO DECREASE WHICH WILL ALLOW FURTHER STRENGTHENING OVER THE NEXT SEVERAL DAYS. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH IS ANALYZED ACROSS MAURITANIA FROM 22N10W SW TO THE ERN CAPE VERDE ISLANDS NEAR 16N23W. 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 12N48W TO 9N62W. CONVERGENCE ALONG THIS AXIS IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 45 NM S...AND 120 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... A STATIONARY FRONT CONTINUES TO SIT OVER THE NE GULF FROM NEAR TALLAHASSEE TO PANAMA CITY FLORIDA TO S OF LOUISIANA NEAR 29N90W. THE FRONT IS SUPPORTING BY AN UPPER LEVEL TROUGH THAT EXTENDS DOWN THE ERN SEABOARD INTO THE NRN GULF ALONG 31N82W TO 23N100W. THE UPPER TROUGH IS ACCOMPANIED BY STRONG DRY AIR AND SUBSIDENCE WHICH IS SUPPORTING FAIR WEATHER NE OF A LINE FROM 31N82W TO 23N98W. S OF THIS LINE...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 HELPING SUPPORTS SCATTERED SHOWERS/THUNDERSTORMS FROM 24N-29N BETWEEN E OF 88W. A SURFACE TROUGH JUST W OF THE YUCATAN PENINSULA ALONG 22N90W TO 17N92W IS ALSO SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 21N-23N BETWEEN 91W-93W. THIS TROUGH IS EXPECTED TO CONTINUE TO DRIFT WNW OVER THE NEXT COUPLE OF DAYS. THE STATIONARY FRONT IN THE NE GULF IS EXPECTED TO DISSIPATE OVER THE NEXT 24 HOURS AS THE UPPER LEVEL TROUGH SUPPORTING IT MOVES TO THE E. SIGNIFICANT MOISTURE IS EXPECTED TO REMAIN OVER MUCH OF THE GULF OF MEXICO WITH A LIKELY CHANCE OF SCATTERED SHOWERS/THUNDERSTORMS. CARIBBEAN SEA... HIGH MOISTURE VALUES EVIDENT IN TOTAL PRECIPITABLE WATER IMAGERY COVER THE WRN HALF OF THE CARIBBEAN. THIS IS HELPING ENHANCE SCATTERED SHOWERS/THUNDERSTORMS ACROSS WRN CUBA...ERN NICARAGUA AS WELL AS ISOLATED SHOWERS/THUNDERSTORMS OVER WATER FROM 13N-21N BETWEEN 79W-85W. CONTINUED SHOWER/THUNDERSTORM ACTIVITY IN THIS AREA HAS CONTRIBUTED TO THE FORMATION OF A TROPICAL WAVE WHICH WILL LIKELY BE ADDED TO THE 1800 UTC ANALYSIS. WAVE FORMATION AND GROWTH IS ALSO POSSIBLE IN THE WRN CARIBBEAN...AND CONDITIONS ARE CURRENTLY FAVORABLE FOR THIS TO OCCUR. MODEL GUIDANCE IS ALSO IN FAVOR OF THIS FORMATION AND MOVES THE WAVE TOWARDS THE WNW-NW INTO THE GULF OF MEXICO OVER THE NEXT COUPLE OF DAYS. THIS WILL LIKELY SUPPORT CONTINUED SHOWER/THUNDERSTORM ACTIVITY OVER THE NW CARIBBEAN OVER THE NEXT DAY OR SO. AN AREA OF SCATTERED SHOWERS/THUNDERSTORMS ARE IN THE SW CARIBBEAN FROM 10N-13N BETWEEN 78W-80W. MUCH OF THE CENTRAL AND ERN CARIBBEAN IS UNDER MOSTLY FAIR CONDITIONS. ALOFT...AN UPPER LEVEL RIDGE COVERS THE WRN CARIBBEAN EXTENDING FROM NEAR 17N94W TO THE NW BAHAMAS AND W ATLC. A WEAK UPPER LEVEL LOW IS OVER HISPANIOLA EMBEDDED WITH DRY AIR ALOFT. WATER VAPOR IMAGERY ALSO INDICATES DRY AIR ALOFT OVER THE ERN CARIBBEAN WHICH IS SUPPORTING THE FAIR WEATHER ACROSS THIS AREA. ATLANTIC OCEAN... SCATTERED SHOWERS/THUNDERSTORMS COVER THE FAR WRN ATLC NW OF A LINE FROM 24N78W TO 32N69W...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 29N48W IS ALSO SUPPORTING AN AREA OF SHOWERS/THUNDERSTORMS FROM 22N-32N BETWEEN 62W-67W. THE UPPER LOW IS ALSO SUPPORTING A SURFACE TROUGH ALONG 31N49W TO 25N51W WITH SCATTERED SHOWERS/THUNDERSTORMS FROM 27N-30N BETWEEN 51W-54W. A SECOND SURFACE TROUGH IS ALONG 27N41W TO 22N42W. SCATTERED SHOWERS/THUNDERSTORMS ARE SHEARED TO THE E OF THE AXIS FROM 21N-24N BETWEEN 36W-41W. BROAD UPPER RIDGING COVERS MUCH OF THE TROPICAL ATLC CENTERED NEAR 20N27W SUPPORTING WEAK SURFACE RIDGING AROUND A 1025 MB HIGH NEAR 30N29W. TO THE S...TROPICAL STORM KATIA IS IMPACTING THE SRN TROPICAL ATLC. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. KATIA IS EXPECTED TO MOVE WNW NEAR 16 KT. THE PAIR OF SURFACE TROUGHS ARE ALSO EXPECTED TO MOVE WWD AROUND THE SUB-TROPICAL RIDGE IN THE N CENTRAL ATLC. ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON