000 AXNT20 KNHC 101049 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1045 UTC. ...SPECIAL FEATURE... GABRIELLE HAS WEAKENED TO A TROPICAL DEPRESSION AS IT PULLS AWAY FROM THE MID-ATLANTIC COAST. AS OF 10/0900 UTC THE CENTER OF THE DEPRESSION WAS NEAR 37.0N 74.4W...OR ABOUT 120 NM NORTH-NORTHEAST OF CAPE HATTERAS NORTH CAROLINA AND ABOUT 325 NM SOUTHWEST OF NANTUCKET MASSACHUSETTS. GABRIELLE IS MOVING NORTHEAST AT 10 KT. MAXIMUM SUSTAINED WIND SPEED HAS DECREASED TO 30 KT WITH GUSTS TO 40 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 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. SATELLITE IMAGES DURING THE OVERNIGHT HOURS HAS INDICATED THAT GABRIELLE HAS BECOME NEARLY DEVOID OF ANY DEEP CONVECTION. A SMALL MODEST BURST HAS RECENTLY DEVELOPED TO THE SE OF THE CENTER. HOWEVER...THIS SMALL AREA AND ANY NEW BURSTS THAT DO FORM WILL LIKELY BE QUICKLY SHEARED OFF AS THE DEPRESSION IS EMBEDDED IN STRONG ZONAL FLOW. GIVEN THE UNFAVORABLE UPPER ENVIRONMENT AND SHRINKING TIME OVER WARM WATER...THE NHC OFFICIAL FORECAST SHOWS NO RECOVERY AND GABRIELLE WILL LIKELY BE ABSORBED BY EXTRATROPICAL ENERGY IN A FEW DAYS. ...TROPICAL WAVES... TROPICAL WAVE IS INTRODUCED ON THE 06Z ANALYSIS ABOUT 120 NM E OF THE CAPE VERDE ISLANDS ALONG 20W/21W S OF 19N ESTIMATED TO BE MOVING W 10-15 KT. SEVERAL DATA SOURCES SUPPORT THE EXISTENCE AND LOCATION OF THIS WAVE. THE CLEAREST IS THE CURRENT PRESENTATION ON VISIBLE IMAGES. WELL DEFINED LOW-LEVEL TURNING AND A CLASSIC INVERTED V-SHAPE TO THE LOW CLOUD FIELD IS PRESENT. THIS SATELLITE SIGNATURE MESHES UP WELL WITH THE SFC OBSERVATIONS IN THE AREA. MET-9 SAT HOVMOLLER DIAGRAMS AND THE UW-CIMSS TPW ANIMATION SHOW GOOD WWD CONTINUITY AND A SIGNIFICANT ASSOCIATED BULGE OF MOISTURE. CONVECTION IS FAIRLY MINIMAL AND CONFINED TO AN AREA W OF THE AXIS FROM 14N-16N BETWEEN 22W-25W WHERE SPEED CONVERGENCE IS NOTED ON A 07Z QSCAT PASS. ACTIVE TROPICAL WAVE IS ALONG 37W/38W S OF 16N MOVING W 10-15 KT OVER THE PAST 24 HOURS. A 1010 MB LOW IS ANALYZED ALONG THE WAVE NEAR 10N. SATELLITE IMAGES INDICATE THAT THIS LOW IS FAIRLY BROAD 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 IS BECOMING GRADUALLY BETTER ORGANIZED AND HAS THE POTENTIAL TO DEVELOP INTO A TROPICAL DEPRESSION DURING THE NEXT COUPLE OF DAYS. TROPICAL WAVE IS OVER THE LESSER ANTILLES ALONG 60W S OF 21N MOVING W 15 KT. A BURST OF CONVECTION RECENTLY DEVELOPED JUST W OF THE ANALYZED AXIS ACROSS THE ISLANDS FROM 14N-17N BETWEEN 61W-63W. THIS WAVE SHOWS UP FAIRLY WELL IN THE SHIP/BUOY DATA...WHICH WAS USED TO PIN DOWN THE POSITION. IN ADDITION...SYNOPTIC OBSERVATIONS SHOW A 2 MB DROP OVER THE PAST 24 HOURS INDICATING A FAIRLY DESCENT WAVE. SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT EXPECTED. THE NRN PORTION OF A TROPICAL WAVE ALONG 94W EXTENDS INTO THE BAY OF CAMPECHE S OF 20N MOVING W 10-15 KT. THERE IS A FAIR AMOUNT OF DEEP LAYER CYCLONIC 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 SECTION BELOW. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 13N22W 12N35W 9N41W 8N58W. BESIDES FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES ...SCATTERED MODERATE IS FROM 7N-12N BETWEEN 42W-55W. 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 TROUGH WHICH RUNS FROM THE SW ATLC TO AN UPPER LOW IN THE BAY OF CAMPECHE NEAR 23N93W. AN ASSOCIATED LOW-LEVEL TROUGH BASICALLY LIES DIRECTLY UNDERNEATH THE UPPER AXIS ANALYZED FROM THE FLORIDA PANHANDLE SWWD ALONG 30N84W 27N92W 22N94W. IR IMAGES AND LIGHTNING DATA SUGGEST ONLY POCKETS OF SCATTERED SHOWERS AND TSTMS...IN THIS MOIST ENVIRONMENT...WITHIN 240 NM OF THE UPPER LOW AND IN THE E GULF FROM 24N-28N BETWEEN THE FL COAST AND 85W. UPPER CONFLUENCE BETWEEN THE TROUGHING DESCRIBED AND A WELL DEFINED UPPER HIGH OVER THE S CENTRAL U.S. IS DRYING OUT THE AIR ACROSS MUCH OF THE NW HALF OF THE REGION SUPPORTING FAIR WEATHER. LOOKING AHEAD OF A COUPLE OF DAYS...THE WEAK SFC TROUGH WILL TRACK W AND GRADUALLY DISSIPATE. A NEW TROUGH OR WEAK FRONT IS EXPECTED TO PUSHING OFF THE TEXAS COAST ON TUE. THIS WILL ALLOW THE SFC 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 RATHER STRONG CLUSTERS EVIDENT OVER THE S CENTRAL CARIB EARLIER THIS MORNING HAVE QUICKLY FALLEN APART WITH ONLY SCATTERED SHOWERS AND ISOLATED TSTMS FROM 12N-20N BETWEEN 75W-83W. THIS WEAKENING ACTIVITY HAS LIMITED SUPPORT FROM A MODEST DIFFLUENT UPPER PATTERN BETWEEN WLY FLOW ON THE SW SIDE OF AN UPPER HIGH S OF PUERTO RICO NEAR 17N66W AND LIGHT FLOW NEAR THE BASE OF AN UPPER LOW CENTERED NEAR 17N81W. IN THE FAR E CARIB...AN AREA OF CLOUDINESS AND A RECENT BURST OF CONVECTION IS AFFECTING PORTIONS OF THE LESSER ANTILLES. THIS UNSETTLED WEATHER IS ASSOCIATED WITH A TROPICAL WAVE...FOR MORE DETAILS REFER TO THAT 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. TWO WEAK ASSOCIATED SFC TROUGHS STRETCH THROUGH THE AREA. THE MAIN OLD FRONTAL BOUNDARY ENTERS THE AREA NEAR 32N37W AND EXTENDS SW ALONG 27N46W 24N61W. CONVERGENCE ALONG THIS BOUNDARY IS PRODUCING ISOLATED SHOWERS AND TSTMS WITHIN 45 NM OF THE TROUGH. A POST-FRONTAL BOUNDARY HAS BEEN ADDED TO THE MAP ALONG 31N45W 32N59W. SIMILAR ISOLATED ACTIVITY EXISTS WITHIN 45 NM OF THIS AXIS. THE MOST SIGNIFICANT ASPECT OF THIS BROAD TROUGHING...IN OUR DISCUSSION AREA...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 AN EARLIER QSCAT NEAR THE CARIB ISLANDS AND THE AFRICAN COAST. BOTH OF THESE ZONES ARE TO THE S OR SE OF MODERATE HIGH PRES SYSTEMS. ALOFT...THE PATTERN IS QUIET MESSY IN THE W ATLC WITH AN UPPER HIGH LOCATED TO THE W OF BERMUDA NEAR 32N73W...INVERTED TROUGHING ALONG 70W S OF 28N AND AN SMALL 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 W OF 76W. IN THE CENTRAL ATLC...TROUGHING COVERS THE AREA N OF 23N ASSOCIATED WITH THE DEEP LAYERED LOW MENTIONED ABOVE. IN THE TROPICAL AND E ATLC...A DOMINATING RIDGE IS IN CONTROL CENTERED NEAR 22N25W PROVIDING FAIR WEATHER FOR MUCH OF THAT AREA. $$ CANGIALOSI