000 AXNT20 KNHC 090605 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURE... THE CENTER OF TROPICAL STORM GABRIELLE AT 09/0600 UTC WAS NEAR 33.5N 75.9W OR ABOUT 75 NM SSE OF CAPE LOOKOUT NORTH CAROLINA. GABRIELLE IS NOW MOVING N-NW NEAR 10 KT. A TURN TOWARD THE NORTH IS EXPECTED LATER TODAY. THE CENTER OF GABRIELLE SHOULD MOVE OVER OR VERY NEAR THE COAST OF NORTH CAROLINA LATE THIS MORNING OR EARLY THIS AFTERNOON. HOWEVER...THE OUTER RAIN BANDS ARE ALREADY SPREADING ONSHORE AT THIS TIME. THE ESTIMATED MINIMUM CENTRAL PRESSURE AS MEASURED BY AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS 1005 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 35 KT WITH GUSTS TO 45 KT. SOME STRENGTHENING IS FORECAST BEFORE THE CENTER REACHES THE NORTH CAROLINA COAST. 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. NUMEROUS MODERATE CONVECTION IS MOSTLY IN THE W SEMICIRCLE FROM 32N-34W BETWEEN 75.5W-78W. SCATTERED MODERATE...IN SPIRAL RAINBANDS...IS ELSEWHERE FROM 32N-35N BETWEEN 74W-78W. ...TROPICAL WAVES... AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 29W/30W SOUTH OF 17N MOVING WEST NEAR 15 KT. A RATHER ILL DEFINED 1012 MB LOW IS ALONG THE WAVE AXIS NEAR 10N...WHICH IS MORE OR LESS A MEAN CENTER OF AN ELONGATED AREA OF CYCLONIC TURNING THAT HAS AN ASSOCIATED TROUGH AXIS STRETCHING ENE FROM 7N43W TO NEAR 14N20W. THE DEEPEST CONVECTION ASSOCIATED WITH THE WAVE IS TO THE W OF THE AXIS...WITH SCATTERED MODERATE FROM 7N-12N BETWEEN 31W-36W. ISOLATED SHOWERS/TSTMS ARE ELSEWHERE WITHIN 150 NM EITHER SIDE OF THE AXIS. THIS SYSTEM HAS CHANGED LITTLE IN ORGANIZATION DURING THE PAST 24 HOURS...BUT STILL HAS THE POTENTIAL FOR SOME DEVELOPMENT DURING THE NEXT FEW DAYS. AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 54W/55W SOUTH OF 21N MOVING WEST 10-15 KT. THIS WAVE CONTINUES TO SHOW UP WELL IN SATELLITE IMAGERY AND THE SURROUNDING BUOY OBS...WITH A BROAD INVERTED V PATTERN NOTED. SCATTERED MODERATE CONVECTION IS OVER THE N PORTION OF THE AXIS FROM 14N-19N BETWEEN 54W-59W. THIS ACTIVITY IS EXPECTED TO AFFECT THE NRN LESSER ANTILLES/LEEWARD ISLANDS LATE SUN INTO MON. A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 88W SOUTH OF 22N MOVING WEST NEAR 15 KT. THE AXIS OF THE WAVE IS NOW MOSTLY INLAND OVER CENTRAL AMERICA. 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 14N17W 10N28W 6N42W 9N61W. BESIDES FOR THE ACTIVITY NOTED WITH THE TROPICAL WAVE SEVERAL HUNDRED MILES SW OF THE CAPE VERDE ISLANDS...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 300 NM N OF THE AXIS BETWEEN 36W-46W. SIMILAR ACTIVITY IS JUST OFF THE COAST OF AFRICA FROM 8N-18N E OF 21W. SOME OF THIS MAY BE ASSOCIATED WITH THE NEXT TROPICAL WAVE...BUT I STILL DO NOT HAVE A GOOD FEEL FOR THIS WAVE SO WILL WAIT FOR MORE EVIDENCE AND VISIBLE IMAGERY BEFORE ADDING TO THE MAP. DISCUSSION... THE GULF OF MEXICO... THE MAIN AREA OF WEATHER TONIGHT IS IN THE SE 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 28N E OF 89W. THE MOST CONCENTRATED AREA OF MODERATE CONVECTION IS JUST OFFSHORE SW FLORIDA. THE MOST PRONOUNCED AREA OF LOW TO MID LEVEL VORTICITY IS JUST N OF THE YUCATAN CHANNEL NEAR 23N87W. AS OF 09/0300 UTC THE SFC TROUGH AXIS IS ANALYZED ALONG 23N89W TO THE 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. THE REMAINDER OF THE GULF IS RATHER TRANQUIL WITH WINDS MOSTLY 15 KT OR LESS AND SEAS 4' OR LESS. VERY DRY/STABLE MID TO UPPER AIR IS OVER THE NE GULF...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. THE CARIBBEAN SEA... VERY LITTLE DEEP CONVECTION IS AFFECTING THE CARIBBEAN TONIGHT. ISOLATED SHOWERS/TSTMS ARE...HOWEVER...IN THE NW CARIBBEAN N OF 17N W OF 73W. 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 NICARAGUA FROM 12N-14N BETWEEN 82W-84W WHICH APPEARS TO BE PUSHING SLOWLY INLAND. SHOWER ACTIVITY ELSEWHERE IS ISOLATED AND MOSTLY SHALLOW IN NATURE. HOWEVER...CONVECTION ASSOCIATED WITH THE TROPICAL ATLC WAVE ALONG 54W WILL AFFECT THE NE CARIBBEAN LATE SUN AND MON. TRADES ARE ON THE LIGHT TO MODERATE SIDE...WITH TO 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. THE ATLANTIC OCEAN... T.S. GABRIELLE IS NOW N OF THE AREA JUST OFFSHORE THE SOUTHERN NORTH CAROLINA COAST. HOWEVER...THE AFFECTS PERSIST. ALTHOUGH THE WINDS ARE NOT PARTICULARLY STRONG IN THE 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 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 27N W OF 72W. 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 32N39W 26N55W 31N64W. SCATTERED SHOWERS AND ISOLATED TSTMS NOTED WITHIN 90 NM OF THIS BOUNDARY...AND MOST CONCENTRATED NEAR 26N49W...JUST AHEAD OF THE ASSOCIATED DEEP LAYER TROUGHING THAT EXTENDS S/SW FROM THE WELL DEFINED LOW NEAR 41N44W. 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 1021 MB HIGH CENTERED NEAR 29N25W. $$ WILLIS