000 AXNT20 KNHC 040553 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SUN SEP 04 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 29.5N 92.6W AT 04/0600 UTC OR 75 NM W OF MORGAN CITY LOUISIANA AND ABOUT 50 NM SW OF LAFAYETTE LOUISIANA MOVING N AT 2 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. MOSAIC DOPPLER RADAR AND LIGHTNING DATA INDICATE VERY LITTLE DEEP CONVECTION IS NEAR THE CENTER OF LEE WITH NUMEROUS SHOWERS AND ISOLATED TSTMS FROM 29N TO 31N BETWEEN 92W AND 95W. FARTHER EAST OF THE CENTER...TWO MAIN CONVECTIVE BANDS ARE ACTIVE OVER THE NE GULF WATERS...WHICH CONTINUE TO STREAM HEAVY PRECIPITATION INLAND OVER SOUTHERN MISSISSIPPI...SW ALABAMA...AND THE WESTERN FLORIDA PANHANDLE. THE NUMEROUS MODERATE AND ISOLATED STRONG CONVECTION OVER THE GULF WATERS IS LOCATED FROM 25N TO 31N BETWEEN 84W AND 89W. 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. TROPICAL STORM KATIA IS CENTERED NEAR 20.3N 57.4W AT 04/0300 UTC OR 350 NM E-NE OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 992 MB. MAXIMUM SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SCATTERED MODERATE AND ISOLATED STRONG CONVECTION REMAINS TIGHTLY CLUSTERED NEAR THE CENTER FROM 18N TO 24N BETWEEN 55W AND 60W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 21N34W TO A 1012 MB LOW ON THE SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON TROUGH NEAR 12N36W 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 17N16W ALONG 09N20W TO 12N36W TO 07N41W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N41W TO 06N46W. ISOLATED MODERATE CONVECTION IS FROM 05N TO 12N BETWEEN 20W AND 27W. SIMILAR CONVECTION IS FROM 06N TO 10N BETWEEN 45W AND 52W. ...DISCUSSION... GULF OF MEXICO... THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE AS IT IS FORECAST TO MOVE ONSHORE OF THE LOUISIANA COAST DURING THE OVERNIGHT HOURS AND CONTINUE A SLOW NORTHWESTWARD TRACK DURING THE DAY SUNDAY. MOSAIC DOPPLER RADAR ACROSS THE NORTH-CENTRAL GULF INDICATES NUMEROUS SHOWERS AND SCATTERED TSTMS COVER A BROAD AREA EAST OF THE CIRCULATION CENTER ACROSS THE NE GULF N OF 25N BETWEEN 83W AND 90W. THIS PRECIPITATION SPREADS INLAND ACROSS MUCH OF LOUISIANA...SOUTHERN AND CENTRAL MISSISSIPPI... SOUTHWESTERN ALABAMA...AND THE WESTERN FLORIDA PANHANDLE. THE LATEST RAINFALL FORECAST IS FOR 10 TO 15 INCHES FROM THE CENTRAL GULF NORTHWARD INTO THE TENNESSEE RIVER VALLEY THROUGH MONDAY WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 20 INCHES. THESE RAINS ARE EXPECTED TO CAUSE EXTENSIVE FLOODING AND FLASH FLOODING. 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 WESTERN CARIBBEAN AS AN UPPER LEVEL RIDGE AXIS IS POSITIONED OVER THE EASTERN GULF OF MEXICO ALONG 85W. UPPER LEVEL DIVERGENCE IS AIDING IN SUSTAINING CONVECTION ASSOCIATED WITH TROPICAL STORM LEE OVER THE EASTERN GULF...HOWEVER THE NORTHERLY FLOW IS PROVIDING FOR RATHER SUBDUED CONDITIONS OVER MUCH OF THE CARIBBEAN. MIDDLE TO UPPER LEVEL CONVECTIVE DEBRIS MOISTURE W OF 76W AND A FEW ISOLATED SHOWERS N OF 15N BETWEEN 76W AND 83W ARE NOTED ON SATELLITE IMAGERY. OTHERWISE LIGHT E-SE TRADES WERE NOTED ON AN EARLIER ASCAT PASS AROUND 04/0202 UTC WHICH ARE EXPECTED TO PERSIST THROUGH THE REMAINDER OF THE WEEKEND. ATLANTIC OCEAN... THE MAIN IMPACT IN THE ATLANTIC OCEAN IS TROPICAL STORM KATIA AS DESCRIBED IN THE SPECIAL FEATURES SECTION ABOVE. WATER VAPOR IMAGERY INDICATES A FAIRLY ELONGATED MIDDLE TO UPPER LEVEL LOW CENTERED NEAR 33N71W WITH AXIS DIPPING SOUTHWARD TO 24N ALONG 71W. THIS TROUGHING IS SUPPORTING A WEAK 1014 MB LOW CENTERED NEAR 33N71W WITH A SURFACE TROUGH EXTENDING S THEN SW FROM THE LOW ALONG 30N70W TO 27N76W. ISOLATED SHOWERS AND TSTMS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH...AND S-SE OF THE BOUNDARY WITHIN 120 NM OF A LINE FROM 32N64W TO THE CENTRAL BAHAMAS NEAR 24N80W. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A 1025 MB HIGH CENTERED NEAR 34N43W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ HUFFMAN