000 AXNT20 KNHC 030601 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURES... TROPICAL STORM LEE IS CENTERED NEAR 28.5N 91.8W AT 03/0600 UTC OR 150 NM WSW OF THE MOUTH OF THE MISSISSIPPI RIVER AND ABOUT 80 NM SSW OF MORGAN CITY LOUISIANA MOVING N AT 4 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. MOSAIC DOPPLER RADAR AND LIGHTNING DATA INDICATE NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION IS FROM 27N TO 31N BETWEEN 88W AND 92W...MAINLY LOCATED IN THE NE QUADRANT OF LEE...AND OVER INLAND PORTIONS OF SE LOUISIANA...SOUTHERN MISSISSIPPI AND EXTREME SOUTHWESTERN ALABAMA. ANOTHER CONVECTIVE BAND OF SCATTERED MODERATE CONVECTION IS FROM 24N TO 28N BETWEEN 84W AND 88W. 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 18.5N 54.3W AT 03/0300 UTC OR 500 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 10 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 16N TO 23N BETWEEN 51W AND 56W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 18N30W TO A 1011 MB LOW ON THE SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON TROUGH NEAR 10N32W MOVING W-NW AT 15 KT. TOTAL PRECIPITABLE WATER IMAGERY INDICATES MAXIMUM VALUES ALIGN ALONG THE WAVE AXIS WITH ISOLATED MODERATE CONVECTION OCCURRING WITHIN 120 NM WEST OF THE WAVE AXIS. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 17N16W ALONG 12N24W TO 07N37W TO 09N42W. THE MONSOON TROUGH THEN RESUMES IN THE WESTERN CARIBBEAN SEA NEAR 13N76W TO 11N84W. ISOLATED MODERATE CONVECTION IS FROM 06N TO 09N BETWEEN 22W AND 26W. ...DISCUSSION... GULF OF MEXICO... THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE AS IT IS FORECAST TO CONTINUE SLOWLY MOVING NORTHWARD THROUGH THE OVERNIGHT HOURS INTO MIDDAY SATURDAY. MOSAIC DOPPLER RADAR ACROSS THE NORTH-CENTRAL GULF INDICATES NUMEROUS SHOWERS AND SCATTERED TSTMS COVER A LARGE AREA N OF 27N BETWEEN 88W AND 92W. THIS PRECIPITATION SPREADS INLAND ACROSS SE LOUISIANA...SOUTHERN MISSISSIPPI...AND EXTREME SW ALABAMA. THE LATEST RAINFALL FORECAST IS FOR 10 TO 15 INCHES OVER SOUTHERN LOUISIANA... SOUTHERN MISSISSIPPI AND SOUTHERN ALABAMA THROUGH 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 THE OVERNIGHT HOURS INTO 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 AND EXTREME SOUTHERN MISSISSIPPI AND ALABAMA THROUGH THE OVERNIGHT HOURS. 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 EVENING. 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 70W WITH E-SE TRADES AT THE SURFACE IN THE RANGE OF 10 TO 20 KT WHICH ARE EXPECTED TO PERSIST THROUGHOUT 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 72W. THIS TROUGHING IS SUPPORTING A WEAK 1009 MB LOW CENTERED NEAR 33N66W WITH A SURFACE TROUGH EXTENDING SW FROM THE LOW ALONG 30N69W TO 28N77W. ISOLATED SHOWERS ARE WITHIN 45 NM EITHER SIDE OF THE SURFACE TROUGH...AND EAST OF THE BOUNDARY N OF 26N BETWEEN 61W AND 66W. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1027 MB HIGH CENTERED NEAR 33N40W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN