000 AXNT20 KNHC 311145 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT WED AUG 31 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...SPECIAL FEATURE... TROPICAL STORM KATIA IS CENTERED NEAR 13.9N 39.1W AS OF 31/0900 UTC...OR ABOUT 985 MI...1585 KM W OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING WNW AT 18 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 994 MB. MAXIMUM SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 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. KATIA IS IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY WARM WATER AND VERY LOW SHEAR. EXPECT GRADUAL INTENSIFICATION OF THIS SYSTEM OVER THE NEXT COUPLE OF DAYS. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 10N-15N BETWEEN 36W-42W. ...TROPICAL WAVES... A TROPICAL WAVE IS OVER THE SE GULF OF MEXICO AND THE YUCATAN PENINSULA FROM 23N86W TO 15N89W MOVING W AT 5-10 KT. WIDELY SCATTERED MODERATE CONVECTION IS MOSTLY E OF THE WAVE AXIS OVER THE NW CARIBBEAN FROM 15N-23N BETWEEN 80W-89W. ...THE ITCZ/THE MONSOON TROUGH... THE MONSOON TROUGH IS ANALYZED FROM THE COAST OF MAURITANIA AT 18N16W TO S OF THE CAPE VERDE ISLANDS NEAR 13N28W. 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 FROM 12N48W TO THE WINDWARD ISLANDS NEAR 12N62W. THE CONVERGENCE ALONG THE ITCZ AXIS IS GENERATING WIDELY SCATTERED MODERATE CONVECTION FROM 11N-14N BETWEEN 54W-60W. ...DISCUSSION... GULF OF MEXICO... A TROPICAL WAVE IS OVER THE SE GULF OF MEXICO AND YUCATAN PENINSULA. SEE ABOVE. ISOLATED MODERATE CONVECTION IS ALSO OVER S FLORIDA AND THE STRAITS OF FLORIDA FROM 24N-26N BETWEEN 80W-85W. ELSEWHERE...A SURFACE TROUGH IS OVER THE BAY OF CAMPECHE FROM 23N95W TO 18N96W. SCATTERED MODERATE TO STRONG CONVECTION IS OVER THE SOUTHERN BAY OF CAMPECHE FROM 17N-21N BETWEEN 92W-95W. ISOLATED MODERATE CONVECTION IS ALSO NEAR TAMPICO MEXICO FROM 21N-24N BETWEEN 95W-98W. MOSTLY FAIR WEATHER IS OVER THE NW GULF. IN THE UPPER LEVELS... AN UPPER LEVEL LOW IS CENTERED OVER THE FLORIDA PANHANDLE NEAR 30N85W. DIFFLUENCE SE OF THE LOW IS ENHANCING SHOWERS OVER S FLORIDA. EXPECT MORE TROPICAL MOISTURE AND CONVECTION TO SPREAD NW OVER THE GULF OVER THE NEXT 24 HOURS. CARIBBEAN SEA... A TROPICAL WAVE IS PRODUCING CONVECTION OVER THE NW CARIBBEAN. SEE ABOVE. A GOOD AMOUNT OF TROPICAL MOISTURE WITH ISOLATED MODERATE CONVECTION IS ALSO OVER N VENEZUELA...COLOMBIA...THE CENTRAL CARIBBEAN...THE WESTERN CARIBBEAN...AND CENTRAL AMERICA...W OF 70W. THE LEEWARD ISLANDS HAVE MOSTLY FAIR WEATHER WITH STRONG SUBSIDENCE ALOFT. 15-25 KT TRADEWINDS ARE OVER THE CARIBBEAN SEA WITH STRONGEST WINDS ALONG THE COAST OF N COLOMBIA. IN THE UPPER LEVELS...AN UPPER LEVEL LOW IS CENTERED E OF JAMAICA AT 18N75W MOVING W. UPPER LEVEL DIFFLUENCE W OF THE LOW IS ENHANCING THE CONVECTION OVER THE W CARIBBEAN. EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS. ATLANTIC OCEAN... THE MAIN FEATURE OF INTEREST IS TROPICAL STORM KATIA IN THE EASTERN ATLANTIC. SEE ABOVE. ELSEWHERE TWO PROMINENT SURFACE TROUGHS ARE EVIDENT OVER THE CENTRAL ATLANTIC. ONE EXTENDS FROM 30N44W TO 24N47W. ISOLATED MODERATE CONVECTION IS FROM 27N-31N BETWEEN 43W-48W. A SECOND TROUGH IS FROM 33N52W TO 25N55W. SCATTERED SHOWERS ARE WITHIN 90 NM OF THE TROUGH AXIS. A 1028 MB HIGH IS OVER THE CENTRAL ATLANTIC NEAR 38TWON41W. THE TRADEWINDS ARE QUITE WEAK ACROSS THE TROPICAL NORTH ATLANTIC. THIS SHOULD CONTINUE FOR THE NEXT DAY OR TWO. ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ FORMOSA