000 AXNT20 KNHC 031158 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SAT SEP 03 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 1015 UTC. ...SPECIAL FEATURES... TROPICAL STORM LEE IS CENTERED NEAR 29.4N 92.0W AT 03/1200 UTC OR 13 NM SSE OF INTRACOASTAL CITY LOUISIANA AND ABOUT 39 NM S OF NEW IBERIA LOUISIANA MOVING N-NW AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. MOSAIC DOPPLER RADAR AND LIGHTNING DATA INDICATE TWO MAIN BANDS OF NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION ON THE EASTERN SEMI-CIRCLE OF THE STORM BETWEEN 84W-92W N OF 24N TO INLAND OVER SE LOUISIANA...SOUTHERN MISSISSIPPI...EXTREME SOUTHWESTERN ALABAMA...AND THE FAR WESTERN FLORIDA PANHANDLE. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/WTNT33 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. HURRICANE KATIA IS CENTERED NEAR 19.3N 55.1W AT 03/0900 UTC OR 460 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION IS FROM 18N TO 23N BETWEEN 51W AND 57W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 21N31W TO A 1010 MB LOW ON THE SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON TROUGH NEAR 11N33W MOVING W-NW AT 15 KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MAXIMUM VALUES ALIGN ALONG THE WAVE AXIS...HOWEVER THE WAVE LACKS ANY SIGNIFICANT DEEP CONVECTION. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 18N16W ALONG 11N18W TO 11N32W TO 05N43W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 05N43W TO 04N51W. ISOLATED MODERATE CONVECTION IS FROM 10N TO 13N BETWEEN 17W AND 21W. ...DISCUSSION... GULF OF MEXICO... THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE AS IT IS FORECAST TO CONTINUE SLOWLY MOVING NORTH-NORTHWESTWARD THIS MORNING INTO THE LATTER PART OF SATURDAY. MOSAIC DOPPLER RADAR ACROSS THE NORTH-CENTRAL GULF INDICATES NUMEROUS SHOWERS AND SCATTERED TSTMS COVER A LARGE AREA N OF 28N BETWEEN 85W AND 93W. THIS PRECIPITATION SPREADS INLAND ACROSS SE LOUISIANA... SOUTHERN MISSISSIPPI...EXTREME SW ALABAMA...AND THE FAR WESTERN FLORIDA PANHANDLE. THE LATEST RAINFALL FORECAST IS FOR 10 TO 15 INCHES OVER SOUTHERN LOUISIANA...SOUTHERN MISSISSIPPI AND SOUTHERN ALABAMA THROUGH LATE SUNDAY WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 20 INCHES. THESE RAINS ARE EXPECTED TO CAUSE EXTENSIVE FLOODING. TROPICAL STORM FORCE WINDS ARE EXPECTED TO REACH LAND IN THE TROPICAL STORM WARNING AREA THROUGH SATURDAY EVENING. A STORM SURGE OF 2 TO 5 FT ABOVE GROUND LEVEL IS EXPECTED ALONG THE NORTHERN GULF COAST IN AREAS OF ONSHORE FLOW...AND DANGEROUS RIP CURRENTS ARE ALSO LIKELY ALONG THE NORTHERN GULF COAST. ISOLATED TORNADOES ARE POSSIBLE OVER PORTIONS OF SOUTHERN LOUISIANA...SOUTHERN MISSISSIPPI AND ALABAMA....AND THE FAR WESTERN FLORIDA PANHANDLE THROUGH THE DAY SATURDAY. REFER TO FLOOD PRODUCTS AND HURRICANE LOCAL STATEMENTS ISSUED BY LOCAL NWS FORECAST OFFICES FOR MORE DETAILED INFORMATION ON THESE THREATS. CARIBBEAN SEA... MOSTLY NORTHERLY UPPER LEVEL FLOW IS IMPACTING THE CENTRAL AND WESTERN CARIBBEAN AS AN UPPER LEVEL ANTICYCLONE IS POSITIONED OVER THE SOUTH-CENTRAL GULF OF MEXICO THIS MORNING. UPPER LEVEL DIVERGENCE IS AIDING IN SUSTAINING CONVECTION ASSOCIATED WITH TROPICAL STORM LEE...HOWEVER THE NORTHERLY FLOW IS PROVIDING FOR RATHER SUBDUED CONDITIONS OVER MUCH OF THE CARIBBEAN. MIDDLE TO UPPER LEVEL CONVECTIVE DEBRIS MOISTURE AND CLOUDINESS ARE NOTED ON SATELLITE IMAGERY W OF 74W WITH E-SE TRADES AT THE SURFACE IN THE RANGE OF 10 TO 20 KT WHICH ARE EXPECTED TO PERSIST THROUGH THE WEEKEND. ATLANTIC OCEAN... THE MAIN IMPACT IN THE ATLANTIC OCEAN IS HURRICANE KATIA AS DESCRIBED IN THE SPECIAL FEATURES SECTION ABOVE. WATER VAPOR IMAGERY INDICATES A FAIRLY AMPLIFIED MIDDLE TO UPPER LEVEL TROUGH IS LOCATED OVER THE SW NORTH ATLC WITH AXIS ALONG 71W. THIS TROUGHING IS SUPPORTING A WEAK 1010 MB LOW CENTERED NEAR 34N68W WITH A SURFACE TROUGH EXTENDING S THEN SW FROM THE LOW ALONG 31N68W TO 28N76W. ISOLATED SHOWERS ARE WITHIN 45 NM EITHER SIDE OF THE SURFACE TROUGH...AND E-SE OF THE BOUNDARY N OF 25N BETWEEN 61W AND 69W. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1025 MB HIGH CENTERED NEAR 33N42W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN