000 AXNT20 KNHC 100548 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT MON SEP 10 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURE... THE CENTER OF TROPICAL STORM GABRIELLE AT 10/0300 UTC IS NEAR 36.3N 75.6W...OR ABOUT 65 NM NORTH OF CAPE HATTERAS NORTH CAROLINA AND ABOUT 385 NM SOUTHWEST OF NANTUCKET MASSACHUSETTS. GABRIELLE IS MOVING NORTHEAST AT 9 KT. MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 40 KT WITH GUSTS TO 50 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB. PLEASE REFER TO THE NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND/OR THE PUBLIC ADVISORY MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. IR IMAGES SHOW CONVECTION ON A STEADY DECLINE OVER THE PAST SEVERAL HOURS WITH THE ONLY AREA LEFT WELL REMOVED TO THE S AND SE OF THE CENTER...AND EVEN THIS AREA IS WEAKENING. THE CIRCULATION SHOWS UP NICELY IN THE SFC DATA WITH SURROUNDING BUOYS REPORTING 20-30 KT WINDS AT THIS TIME. GIVEN THE STRONG SHEAR AND SHRINKING TIME OVER WARM WATER THE NHC OFFICIAL FORECAST SHOWS SOME WEAKENING BEFORE GABRIELLE BECOMES ABSORBED BY AN EXTRATROPICAL SYSTEM. ...TROPICAL WAVES... ACTIVE TROPICAL WAVE IS ALONG 37W S OF 15N MOVING W 15 KT OVER THE PAST 24 HOURS. A 1012 MB LOW IS ANALYZED ALONG THE AXIS NEAR 9N. SATELLITE IMAGES INDICATE THAT THIS LOW IS FAIRLY BROAD THOUGH IT IS PRODUCING A LARGE AREA OF CONVECTION IN IT'S VICINITY...ROUGHLY WITHIN 180 NM EITHER SIDE OF THE AXIS. LESS ORGANIZED CONVECTION EXTENDS FURTHER W WITHIN THE ITCZ. THIS SYSTEM HAS BECOME A LITTLE BETTER ORGANIZED AND HAS THE POTENTIAL TO DEVELOP INTO A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS. TROPICAL WAVE IS NEARING THE LESSER ANTILLES ALONG 59W S OF 22N MOVING W 10-15 KT. MOST OF THE SHOWER ACTIVITY THAT WAS EVIDENT EARLIER APPEARS TO HAVE DIMINISHED. NIGHT CHANNEL VIS IMAGES SHOW A WELL DEFINED SMALL CYCLONIC SWIRL ALONG THE NRN PORTION OF THE WAVE. A PAIR OF SHIP REPORTS INDICATE SOME SFC TURNING ASSOCIATED WITH THIS SWIRL...THOUGH ITS GREATEST AMPLITUDE IS LIKELY IN THE MID-LEVELS. FURTHER DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED TO BE SLOW TO OCCUR. THE NRN PORTION OF A TROPICAL WAVE ALONG 93W/94W EXTENDS INTO THE BAY OF CAMPECHE S OF 22N MOVING W 10-15 KT. THERE IS A FAIR AMOUNT OF TURNING AND MOISTURE IN THIS AREA. HOWEVER...IT IS DIFFICULT TO TELL HOW MUCH OF THIS IS RELATED TO THE WAVE ITSELF AS THERE IS A WELL DEFINED UPPER TROUGH AND LOW-LEVEL TROUGHING IN THIS GENERAL AREA AS WELL. MORE ON THIS IN THE GULF OF MEXICO DISCUSSED BELOW. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 15N17W 12N26W 10N34W 7N46W 6N59W. BESIDES FOR THE CONVECTION ASSOCIATED WITH THE WELL DEFINED TROPICAL WAVE APPROACHING 40W...SCATTERED MODERATE IS FROM 7N-12N BETWEEN 41W-54W. AS A SIDE NOTE...A PRELIM LOOK AT THE DATA SUGGESTS THAT A NEW TROPICAL WAVE LIES OFF THE COAST OF AFRICA. THIS MAY BE ADDED TO THE NEXT SYNOPTIC MAP. DISCUSSION... THE GULF OF MEXICO... THERE IS FAIR AMOUNT OF MOISTURE ACROSS THE SE HALF OF THE GULF. THE CONTRIBUTING UPPER LEVEL COMPONENT IS A HIGHLY STRETCHED UPPER LEVEL TROUGH WHICH RUNS FROM THE W ATLC TO AN UPPER LOW IN THE BAY OF CAMPECHE NEAR 22N93W. AN ASSOCIATED LOW-LEVEL TROUGH BASICALLY LIES DIRECTLY UNDERNEATH THE UPPER AXIS ANALYZED FROM THE FLORIDA PANHANDLE SWWD ALONG 30N83W 27N89W 24N93W. IR IMAGES AND LIGHTNING DATA SUGGEST ONLY POCKETS OF SCATTERED SHOWERS AND TSTMS...MOST ORGANIZED WITHIN 240 NM OF THE UPPER LOW AND IN THE E GULF FROM 24N-28N BETWEEN THE FL COAST AND 86W. UPPER CONFLUENCE BETWEEN THE TROUGHING DESCRIBED AND A WELL DEFINED UPPER HIGH OVER THE S CENTRAL U.S. IS DRYING OUT THE AIR ACROSS MOST OF THE NW HALF OF THE REGION SUPPORTING FAIR WEATHER. LOOKING AHEAD OF A COUPLE OF DAYS...THE WEAK SFC TROUGH IN THE AREA WILL GRADUALLY DISSIPATE AND WILL SOON BE REPLACED BY ANOTHER TROUGH OR WEAK FRONT PUSHING OFF THE TEXAS COAST. THIS WILL ALLOW THE PATTERN TO REMAIN WEAK KEEPING WINDS MOSTLY LIGHT. THE CARIBBEAN SEA... THE CARIB IS RELATIVELY QUIET THIS EARLY MORNING...ALTHOUGH THERE ARE A FEW AREAS OF CONVECTION WORTH MENTIONED. THE MOST PERSISTENT IS AN AREA IN THE S CENTRAL CARIB FROM 12N-15N BETWEEN 73W-80W. THIS ACTIVITY IS LIKELY RELATED TO SOME ITCZ ENERGY ENHANCED BY A DIFFLUENT UPPER PATTERN BETWEEN STRONG WLY FLOW ON THE SW SIDE OF AN UPPER HIGH S OF PUERTO RICO NEAR 16N66W AND LIGHT FLOW ASSOCIATED WITH THE BASE OF AN UPPER LOW CENTERED NEAR 18N79W. A LINE OF WEAKENING SHOWERS AND TSTMS HAVE PUSHED S...DRIVEN BY THE UPPER FLOW...WITHIN 60 NM S OF THE COAST OF HAITI AND CUBA BETWEEN 73W-79W. THIS ACTIVITY IS LIKELY RELATED TO LEFT OVER EVENING TSTM ACTIVITY OVER THE ISLANDS. IN THE FAR E CARIB...AN AREA OF CLOUDINESS AND ISOLATED SHOWERS ARE OVER THE LESSER ANTILLES ASSOCIATED WITH A TROPICAL WAVE. FOR MORE DETAILS REFER TO THE TROPICAL WAVES SECTION ABOVE. ELSEWHERE ...SKY CONDITIONS ARE PREDOMINATELY FAIR ALTHOUGH TYPICAL QUICK MOVING SHOWERS COULD OCCUR JUST ABOUT ANYWHERE. TRADES ARE MODERATE ACROSS THE REGION WITH 20 KT WINDS CONFINED TO NEAR THE COLOMBIAN COAST. THESE WINDS ARE ANTICIPATED TO INCREASE E OF 75W OVER THE NEXT COUPLE OF DAYS AS THE GRADIENT TIGHTENS. THE ATLANTIC OCEAN... A LARGE NEARLY STATIONARY VERTICALLY STACKED LOW PRES SYSTEM IS LOCATED WELL N OF THE AREA IN THE CENTRAL ATLC. AN ASSOCIATED SFC TROUGH STRETCHES THROUGH THE AREA EXTENDING FROM 32N37W SW ALONG 27N46W 25N60W 27N65W. CONVERGENCE ALONG THIS BOUNDARY IS PRODUCING ISOLATED SHOWERS AND TSTMS WITHIN 45 NM OF THE TROUGH. THE MOST SIGNIFICANT ASPECT OF THIS TROUGH IS THE LARGE INTERRUPTION IT HAS PRODUCED IN THE TYPICAL SUBTROPICAL RIDGING. THIS WEAKNESS HAS ALLOWED SFC WINDS TO BE VERY LIGHT ACROSS THE BULK OF THE CENTRAL ATLC. SLIGHTER STRONG WINDS ARE DEPICTED ON QSCAT NEAR THE CARIB ISLANDS AND THE AFRICAN COAST. BOTH OF THESE ZONES ARE TO THE S OR SE OF MODEST HIGH PRES SYSTEMS. ALOFT...THE PATTERN IS QUIET MESSY IN THE W ATLC WITH AN UPPER HIGH LOCATED TO THE W OF BERMUDA NEAR 32N71W...INVERTED TROUGHING ALONG 69W S OF 28N AND AN UPPER LOW OFF THE NE FLORIDA COAST. OVERALL THIS PATTERN IS LEADING TO ISOLATED SHOWERS AND TSTMS ACROSS THE BAHAMAS AND THE ATLC WATERS FROM 24N-29N BETWEEN 76W-79W. IN THE CENTRAL ATLC...TROUGHING COVERS THE AREA N OF 23N ASSOCIATED WITH THE DEEP LAYERED LOW MENTIONED ABOVE. A MID LEVEL LOW HAS DEVELOPED E OF THE LESSER ANTILLES. IN THE E ATLC...A DOMINATED RIDGE IS IN CONTROL CENTERED NEAR 22N26W PROVIDING FAIR WEATHER FOR MUCH OF THAT AREA. $$ CANGIALOSI