000 AXNT20 KNHC 080551 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT SAT SEP 08 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 AREA OF LOW PRESSURE OFF OF THE SOUTHEASTERN COAST OF THE UNITED STATES HAS BECOME SUBTROPICAL STORM GABRIELLE. GABRIELLE WAS CENTERED NEAR 30.5N 72.5W OR ABOUT 315 NM SE OF CAPE LOOKOUT NORTH CAROLINA AT 08/0600 UTC. THE STORM IS MOVING W-NW AT 9 KT...AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE DURING THE NEXT 24 HOURS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1011 MB. MAXIMUM SUSTAINED WINDS ARE 40 KT WITH GUSTS TO 50 KT. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24 HOURS. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT2/WTNT32 KNHC AND THE FULL FORECAST ADVISORY UNDER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. THE CIRCULATION ASSOCIATED WITH GABRIELLE REMAINS BROAD AND ELONGATED. THE CYCLONE IS DESIGNATED A SUBTROPICAL STORM DUE TO ITS LARGE RADIUS OF MAXIMUM WINDS...CONVECTIVE STRUCTURE...AND THE PROXIMITY OF THE UPPER LOW TO THE W-SW. THE DEEPEST CONVECTION ASSOCIATED WITH GABRIELLE IS CURRENTLY N/NE OF THE CENTER...WITH SCATTERED MODERATE FROM 30N-33N BETWEEN 69W-73W. OVERALL THE CONVECTIVE PATTERN REMAINS POORLY ORGANIZED. ...TROPICAL WAVES... AN EAST ATLANTIC TROPICAL WAVE IS ALONG 25W S OF 20N MOVING WEST NEAR 15 KT. THIS WAVE CONTINUES TO EXHIBIT A BROAD ENVELOPE OF CYCLONIC TURNING...THOUGH THE FOCAL POINT SEEMS TO BE NEAR 11N WHERE THE MOST PRONOUNCED MID LEVEL CIRCULATION IS. A RECENT ASCAT PASS DID NOT SHOW MUCH IN THE WAY OF A CLOSED SFC CIRCULATION THOUGH. SHOWER ACTIVITY HAS INCREASED THIS EVENING IN ASSOCIATION WITH THIS SYSTEM...WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION NOW FROM 10N-14N BETWEEN 23W-29W. SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE OVER THE NEXT COUPLE DAYS. AN ATLANTIC OCEAN TROPICAL WAVE IS GENERALLY ALONG 52W SOUTH OF 24N MOVING WEST NEAR 15 KT. SHORTWAVE-IR IMAGERY CONTINUES TO SHOW A WELL DEFINED REGION OF LOW TO MID LEVEL CYCLONIC TURNING IN THE VICINITY...BUT SHOWER AND TSTM ACTIVITY REMAINS MINIMAL NEAR THIS FEATURE. LIGHTNING DATA SHOWS THE ONLY ISOLATED TSTM ACTIVITY IS FROM 15N-22N BETWEEN 45W-56W. THIS WAVE MAY NEED TO BE ADJUSTED SLIGHTLY TO THE E ON THE NEXT MAP BASED ON WHERE THE MAIN AREA OF CYCLONIC TURNING IS ON SATELLITE IMAGERY...AND THE RECENT ASCAT PASS AT 08/0100 UTC. A SEPARATE 1014 MB LOW PRESSURE CENTER IS E OF THE WAVE AXIS NEAR 13N45W...NEARLY STATIONARY AND DISSIPATING. TROPICAL WAVE IS ALONG 84W/85W SOUTH OF 19N THROUGH CENTRAL AMERICA MOVING WEST 15 KT. THIS WAVE REMAINS DIFFICULT TO LOCATE IN SATELLITE IMAGERY AND THE SURROUNDING SFC OBSERVATIONS...THUS THE POSITION IS BASED MOSTLY ON EXTRAPOLATION. SCATTERED MODERATE CONVECTION IS IN THE SW CARIBBEAN S OF 12N...BUT THIS SEEMS MORE RELATED TO ITCZ ACTIVITY AND DIFFLUENT FLOW ALOFT. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 14N16W 7N30W 9N50W 8N60W. A CLUSTER OF MODERATE TO STRONG CONVECTION IS MOSTLY INLAND OVER AFRICA FROM 13N-17N BETWEEN 13W-18W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90 NM EITHER SIDE OF THE AXIS BETWEEN 27W-38W. DISCUSSION... THE GULF OF MEXICO... THERE ARE A COUPLE CONVECTIVE AREAS OVER THE GULF TONIGHT...BUT NOTHING ORGANIZED. FROM E TO W...THE FIRST ACTIVITY NOTED IS THE SCATTERED MODERATE CONVECTION PUSHING W FROM THE FLORIDA PENINSULA S OF 29N BETWEEN 82W-85W. CLOUD TOPS OVER THIS CONVECTION ARE BEING STRETCHED TO THE S INTO THE CARIBBEAN BY STRONG UPPER NLY FLOW BETWEEN THE UPPER LOW JUST TO THE W-SW OF SUBTROPICAL STORM GABRIELLE...AND RIDGING EXTENDING INTO THE GULF FROM AN UPPER HIGH OVER CENTRAL TEXAS. ANOTHER SMALL AREA OF SCATTERED MODERATE CONVECTION IS EXTENDING S FROM THE LOUISIANA COAST TO MIDDLE/WRN GULF WATERS N OF 23N BETWEEN 90W-94W. THIS SEEMS ASSOCIATED WITH THE WEAK SFC TROUGHING IN THE VICINITY...IN ADDITION TO THE DIFFLUENT FLOW ALOFT AROUND THE AFOREMENTIONED UPPER RIDGING. FINALLY...THE TYPICAL CONVECTION THAT FLARED UP OVER THE YUCATAN YESTERDAY AFTERNOON/EVENING HAS NOW PUSHED OVER THE FAR SE BAY OF CAMPECHE. OTHERWISE...WEAK SFC RIDGING DOMINATES EXCEPT FOR THE EMBEDDED TROUGH ALONG 26N89W 23N86W. THIS IS PRODUCING MOSTLY LIGHT WINDS/LOW SEAS ACROSS THE BASIN WHICH IS GENERALLY EXPECTED TO PERSIST THROUGH THE WEEKEND. HOWEVER...SCATTERED TSTMS ASSOCIATED WITH THE SFC TROUGHING IS GENERALLY EXPECTED TO PERSIST OVER THE GULF WATERS BETWEEN THE YUCATAN PENINSULA AND LOUISIANA. THE CARIBBEAN SEA... THE CARIBBEAN IS OVERALL PRETTY QUIET TONIGHT. THE MAIN AREA OF CONVECTION IS THE SCATTERED MODERATE IN THE SW CARIBBEAN S OF 12N BETWEEN THE COASTS OF COLOMBIA AND COSTA RICA. AFTERNOON/EVENING BUILDUPS OVER CUBA HAVE ALSO SPREAD SCATTERED TSTMS INTO THE WATERS N OF 19N BETWEEN 77W-81W. TRADES ARE LIGHT TO MODERATE WITH ONLY WEAK RIDGING IN PLACE. THESE TRADES ARE CARRYING TYPICAL PATCHES OF LOW LEVEL MOISTURE WITH EMBEDDED SHOWERS WWD...WITH A SLIGHTLY MORE CONCENTRATED AREA OF SHOWERS NOTED NEAR THE LEEWARD ISLANDS AND NOW IN VIEW OF THE SAN JUAN RADAR. THIS ACTIVITY IS OCCURRING DOWNSTREAM FROM A WEAK INVERTED UPPER TROUGH JUST E OF THE LEEWARD ISLANDS. THE REMAINDER OF THE UPPER PATTERN IS DOMINATED BY RIDGING OVER THE NW PORTION...WITH WLY UPPER FLOW OVER MUCH OF THE CENTRAL CARIBBEAN BETWEEN THE UPPER LOW JUST W-SW OF SUB T.S. GABRIELLE AND AND UPPER HIGH OVER NRN SOUTH AMERICA. LIGHT TO MODERATE TRADES EXPECTED TO PERSIST THROUGH THE END OF THE WEEKEND...STRONGEST NEAR THE N COAST OF COLOMBIA. THE ATLANTIC OCEAN... THE WRN ATLC IS DOMINATED BY SUBTROPICAL STORM GABRIELLE. SEE SPECIAL FEATURE SECTION ABOVE FOR MORE DETAILS. SFC TROUGHING TRAILING S/SW OF GABRIELLE EXTENDS THROUGH THE SE BAHAMAS AND IS SUPPORTING THE SCATTERED TSTMS FROM 22N-26N BETWEEN 74W-79W. THIS IS ALSO BEING SUPPORTED BY LIFT AHEAD OF THE UPPER LOW NEAR 28N77W. THE TAIL END OF A FRONTAL SYSTEM IN THE NORTH CENTRAL ATLC IS TRIGGERING ISOLATED TSTMS N OF 25N BETWEEN 40W-54W. THE ASSOCIATED DEEP LAYER LOW IS NEAR 41N44W THAT HAS TROUGHING ENTERING OUR AREA N OF 26N GENERALLY BETWEEN 45W-62W. A PAIR OF WEAK HIGHS DOMINATE THE REMAINDER OF THE SFC PATTERN ACROSS THE DISCUSSION AREA...WITH A 1019 MB CENTER ANALYZED NEAR 26N58W AND A 1020 MB HIGH NEAR 26N30W. $$ WILLIS