000 AXNT20 KNHC 091146 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT SUN SEP 09 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS... WEATHER OBSERVATIONS...AND RADAR. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1015 UTC. ...SPECIAL FEATURE... THE CENTER OF TROPICAL STORM GABRIELLE AT 09/1200 UTC WAS NEAR 34.2N 76.4W OR ABOUT 26 NM SSE OF CAPE LOOKOUT NORTH CAROLINA. GABRIELLE IS NOW MOVING N-NW NEAR 9 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE AS MEASURED BY AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS 1005 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 45 KT WITH GUSTS TO 55 KT. PLEASE REFER TO THE NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS...INCLUDING THE LATEST WATCH AND WARNING INFORMATION. GABRIELLE IS EXPECTED TO TURN TO THE NORTH LATER TODAY AND THEN TO THE NORTHEAST TONIGHT. ON THIS TRACK...THE CENTER OF GABRIELLE WOULD BE MOVING ACROSS THE OUTER BANKS THIS AFTERNOON. SOME STRENGTHENING IS EXPECTED PRIOR TO LANDFALL. NUMEROUS MODERATE CONVECTION IS WITHIN 60NM OF 33.5N76W. SCATTERED MODERATE...IN SPIRAL RAIN BANDS...IS ELSEWHERE FROM 32N-36N BETWEEN 74W-78W. THESE BANDS CONTINUE TO AFFECT THE OUTER BANKS OF NORTH CAROLINA AND WILL CONTINUE TO DO SO OVER THE NEXT SEVERAL HOURS. GABRIELLE IS EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 1 TO 3 INCHES ACROSS COASTAL SECTIONS OF NORTH CAROLINA AND SOUTHEASTERN VIRGINIA...WITH ISOLATED MAXIMUM AMOUNTS OF 5 INCHES. ISOLATED TORNADOES ARE POSSIBLE OVER THE OUTER BANKS TODAY. ...TROPICAL WAVES... AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 32W SOUTH OF 17N MOVING WEST NEAR 15 KT. A RATHER ILL DEFINED 1011 MB LOW IS ALONG THE WAVE AXIS NEAR 10N. WAVE REMAINS EMBEDDED IN A BROAD MONSOON-LIKE TROUGH THAT EXTENDS WSW FROM THE AFRICAN COAST NEAR 16N17W TO 6N41W. THERE ARE A FEW SWIRLS NOTED ALONG THIS TROUGHING THAT IS MAKING IT DIFFICULT TO NAIL DOWN ANY ONE LOW CENTER...AND THE WAVE AXIS ITSELF FOR THAT MATTER. HOWEVER...THE DEEPEST CONVECTION HAS REMAINED SITUATED CLOSER TO THE ANALYZED LOW/WAVE AXIS...WITH SCATTERED MODERATE NOW FROM 6N-12N BETWEEN 31W-37W. ISOLATED SHOWERS/TSTMS ARE ELSEWHERE WITHIN 150 NM EITHER SIDE OF THE AXIS. WHILE THERE ARE NO SIGNS OF ORGANIZATION AT THIS TIME...THIS SYSTEM HAS SOME POTENTIAL FOR SLOW DEVELOPMENT DURING THE NEXT FEW DAYS. AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 56W SOUTH OF 21N MOVING WEST 10-15 KT. THIS WAVE CONTINUES TO SHOW UP WELL IN SATELLITE IMAGERY WITH A BROAD INVERTED V PATTERN NOTED. A 1011 MB LOW WAS ADDED TO THE AXIS NEAR 14N BASED ON THE APPEARANCE IN SHORTWAVE IR IMAGERY IN ADDITION TO THE OBSERVATIONS FROM THE METEO FRANCE BUOY 41101. SCATTERED MODERATE CONVECTION IS OVER THE N PORTION OF THE AXIS FROM 14N-20N BETWEEN 54W-61W. THIS ACTIVITY IS EXPECTED TO AFFECT THE NRN LESSER ANTILLES/LEEWARD ISLANDS LATER TODAY AND MON. A TROPICAL WAVE IS INLAND OVER CENTRAL AMERICA ALONG 89W/90W SOUTH OF 21N MOVING WEST NEAR 15 KT. THE WAVE REMAINS DIFFICULT TO LOCATE FOR THE MOST PART WITH ITS POSITION BASED MAINLY ON FORWARD EXTRAPOLATION. HOWEVER...SOME OF THE ASSOCIATED MOISTURE/VORTICITY MAY HAVE ENHANCED THE ACTIVITY IN THE SRN GULF. ...THE ITCZ... AXIS CENTERED ALONG 14N16W 11N28W 6N40W 9N61W. BESIDES FOR THE ACTIVITY NOTED WITH THE TROPICAL WAVE SEVERAL HUNDRED MILES SW OF THE CAPE VERDE ISLANDS...SCATTERED MODERATE IS S OF THE AXIS FROM 8N-12N BETWEEN 14W-25W...AND N OF THE AXIS OFF THE COAST OF AFRICA FROM 16N-17N BETWEEN 16W-18W. SIMILAR ACTIVITY IS MAINLY N OF THE AXIS FROM 5N-11N BETWEEN 37W-47W. DISCUSSION... GULF OF MEXICO... THE MAIN AREA OF WEATHER THIS MORNING IS IN THE SRN GULF ASSOCIATED WITH A WEAK SURFACE TROUGH AND AN UPPER LOW. DISORGANIZED SCATTERED SHOWERS/ISOLATED TSTMS ARE GENERALLY OVER THE S/SE GULF S OF 26N E OF 95W. THE MOST PRONOUNCED AREA OF LOW TO MID LEVEL VORTICITY IS JUST N OF THE YUCATAN NEAR 23N88W. AS OF 09/0900 UTC THE SFC TROUGH AXIS IS ANALYZED ALONG 23N95W 23N87W TO THE W COAST OF FLORIDA NEAR 27N82W...AND CONTINUES THROUGH CENTRAL FLORIDA TO JUST OFFSHORE CAPE CANAVERAL IN THE ATLC. UPPER-LEVEL WINDS ARE NOT CURRENTLY FAVORABLE FOR DEVELOPMENT OF THIS SYSTEM. THE REMAINDER OF THE GULF IS RATHER TRANQUIL WITH WINDS MOSTLY 15 KT OR LESS AND SEAS 4 FT OR LESS. VERY DRY/STABLE MID TO UPPER AIR IS OVER THE NE GULF AND FL PANHANDLE...BEING ADVECTED SW BY NE UPPER FLOW BETWEEN THE UPPER LOW JUST E OF CENTRAL FLORIDA...AND THE UPPER HIGH OVER ERN TEXAS. THE WEAK SFC TROUGHING WILL DOMINATE OVER THE NEXT DAY OR SO AS IT MOVES SLOWLY NW. THIS WILL KEEP WINDS MOSTLY ON THE LIGHT TO MODERATE SIDE...THOUGH SCATTERED SHOWERS/TSTMS ANTICIPATED NEAR THE TROUGHING. CARIBBEAN SEA... OVERALL LITTLE DEEP CONVECTION IS AFFECTING THE CARIBBEAN THIS MORNING. ISOLATED SHOWERS/TSTMS ARE...HOWEVER...IN THE NW CARIBBEAN N OF 16N W OF 74W. THIS ACTIVITY IS ASSOCIATED WITH THE MOIST ENVIRONMENT S OF THE SFC TROUGHING IN THE SE GULF. FURTHER SUPPORT IS BEING LENT BY DIVERGENCE ALOFT BETWEEN THE UPPER LOW NEARING CENTRAL FLORIDA AND RIDGING OVER THE NW CARIBBEAN. THIS MOISTURE IS MOSTLY EXPECTED TO MOVE N OF THE AREA BY MON. ANOTHER SMALL AREA OF SCATTERED TSTMS IS JUST OFF THE COAST OF HISPANIOLA FROM 17N-19 BETWEEN 69W-72W. TYPICAL SCATTERED SHOWERS/ISOLATED TSTMS ARE ALSO OVER THE SW CARIBBEAN S OF 13N...ASSOCIATED WITH THE ITCZ. SHOWER ACTIVITY ELSEWHERE IS ISOLATED AND MOSTLY SHALLOW IN NATURE. HOWEVER...CONVECTION ASSOCIATED WITH THE TROPICAL ATLC WAVE ALONG 56W WILL AFFECT THE NE CARIBBEAN LATER TODAY AND MON. TRADES ARE ON THE LIGHT TO MODERATE SIDE...WITH A WEAKER THAN NORMAL GRADIENT IN PLACE IN RESPONSE TO THE TROUGHING OVER THE GULF/FLORIDA AND T.S. GABRIELLE. A SLIGHT INCREASE IN TRADES EXPECTED THROUGH EARLY WEEK AS MORE TYPICAL RIDGING BUILDS N/NE OF THE AREA. ATLANTIC OCEAN... T.S. GABRIELLE IS NOW N OF THE AREA JUST OFFSHORE THE SOUTHERN OUTER BANKS OF NC. HOWEVER...THE AFFECTS PERSIST. ALTHOUGH THE WINDS ARE NOT PARTICULARLY STRONG IN THE DISCUSSION AREA...NOW MOSTLY 15 KT OR BELOW...A MODERATE RESIDUAL NE SWELL CONTINUES TO AFFECT THE WRN ATLC WITH THE OUTER CANAVERAL BUOY 41010 REPORTING 6-7 FT SEAS AT 10 SECONDS. THE NAH WW3 SEEMS TO BE HANDLING THIS EVENT FAIRLY WELL AND SUGGESTS THE SWELL WILL SUBSIDE STEADILY DURING THE DAY TODAY AS GABRIELLE CONTINUES MOVING WELL N OF THE AREA. THE SFC TROUGHING FROM THE GULF EXTENDS INTO THE WRN ATLC...WHICH IS GENERATING SCATTERED SHOWERS AND TSTMS S OF 29N W OF 74W. THIS ACTIVITY IS AFFECTING THE BAHAMAS AND SOUTH FLORIDA...AND IS GENERALLY EXPECTED TO SPREAD N THROUGH MON. THE ACTIVITY IS ALSO BEING SUPPORTED BY LIFT ASSOCIATED WITH THE UPPER LOW NEAR 28N79W. THE NEXT AREA OF INTEREST IS THE SLOW MOVING FRONT ALONG 32N40W 25N55W 30N64W. SCATTERED SHOWERS AND ISOLATED TSTMS NOTED WITHIN 90 NM OF THIS BOUNDARY...AND MOST CONCENTRATED NEAR E OF 55W...JUST AHEAD OF THE ASSOCIATED DEEP LAYER TROUGHING THAT EXTENDS S/SW FROM THE WELL DEFINED LOW NEAR 41N45W. THIS ACTIVITY GENERALLY EXPECTED TO DIMINISH OVER THE NEXT COUPLE OF DAYS AS THE FRONT BECOMES DIFFUSE. THE REMAINDER OF THE SFC PATTERN IS DOMINATED BY WEAK RIDGING...WITH A 1022 MB HIGH CENTERED NEAR 29N29W. $$ WILLIS/WALLACE