000 AXNT20 KNHC 121054 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT WED SEP 12 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... A SLOW MOVING AREA OF LOW PRESSURE CENTERED NEAR 13N43W OR ABOUT 1000 NM E OF THE LESSER ANTILLES CONTINUES TO ORGANIZE THIS MORNING. THE MINIMUM PRES IS ANALYZED 1009 MB BASED ON BUOY 41041 LOCATED ABOUT 180 NM TO THE NW OF THE BROAD LOW. SATELLITE IMAGERY SHOWS A CONSOLIDATING AND INCREASINGLY CIRCULAR MASS OF CLOUDS ASSOCIATED WITH THIS SYSTEM. THE LOW-LEVEL CENTER IS DIFFICULT TO PIN DOWN EXACTLY ALTHOUGH IT APPEARS TO BE PARTIALLY TUCKED UNDER THE CLOUDINESS NEAR THE ERN EDGE OF SCATTERED MODERATE CONVECTION FROM 12N-14N BETWEEN 43W-46W. CONDITIONS APPEAR FAVORABLE FOR A TROPICAL DEPRESSION TO FORM LATER TODAY OR TONIGHT AS THE SYSTEM MOVES WEST-NORTHWESTWARD AT 5-10 KT. THE AREA OF LOW PRES IN THE NW GULF HAS BECOME BETTER ORGANIZED OVERNIGHT. AS OF 09Z...THE LOW WAS ANALYZED NEAR 27N95W 1008 MB...WHICH IS 2 MB LOWER THAN OBSERVED 3 HOURS EARLIER AT 06Z. IN ACCORDANCE...SHIP AND BUOY DATA DEPICT AN INCREASE IN WINDS WITH THE HIGHEST REPORT NEAR 29 KT E OF THE CENTER. HOWEVER ...THIS REPORT SEEMS SUSPECT AND UNREPRESENTATIVE WHEN COMPARED TO THE SURROUNDING 10-20 KT REPORTS. THESE OBSERVATIONS ALSO REVEAL THAT THIS SYSTEM IS STILL AN ELONGATED N-S TROUGH AXIS...THOUGH DOPPLER RADAR AND SATELLITE IMAGERY CLEARLY SHOW AN IMPROVED AREA OF CYCLONIC TURNING TO THE CLOUD AND RAIN ELEMENTS. PROBABLY THE CLEAREST INDICATION OF THE IMPROVED STRUCTURE IS THE INCREASED SHOWER ACTIVITY WHICH HAS STARTED TO SPREAD ACROSS EXTREME SE TEXAS. CURRENTLY SCATTERED SHOWERS AND TSTMS ARE ROUGHLY WITHIN 90-120 NM OF THE LOW. ENVIRONMENTAL CONDITIONS APPEAR TO BE CONDUCIVE FOR SOME DEVELOPMENT OF THIS SYSTEM OVER THE NEXT DAY OR SO AS IT DRIFTS SLOWLY WEST-NORTHWESTWARD. ...TROPICAL WAVES... HIGH AMPLITUDE TROPICAL WAVE IN THE E ATLC ALONG 33W/34W S OF 23N MOVING W 15 KT. IN GENERAL...THIS WAVE HAS CHANGED LITTLE OVER THE PAST COUPLE OF DAYS. THE STRUCTURE REMAINS WELL DEFINED WITH A LARGE SHIELD OF CYCLONIC TURNING NOTED IN THE LOW TO MID LEVEL CLOUD FIELD. IN ADDITION...THE UW-CIMSS TPW ANIMATION REVEALS A LARGE WWD PROPAGATING SURGE OF MOISTENED AIR. AN EARLIER QSCAT PASS DEPICTED A NEARLY CLOSED CIRCULATION ALONG THE WAVE AXIS NEAR 15N AND EARLY MORNING VIS IMAGES SUGGEST THE SAME...SO A LOW MAY BE ADDED ALONG THE WAVE ON THE NEXT SYNOPTIC MAP. DESPITE THE FAIR STRUCTURE...DEEP MOISTURE IS MINIMAL WITH ONLY A FEW SHOWERS AND TSTMS WITHIN 90 NM OF THE AXIS. CONVECTION IS MORE SCATTERED IN NATURE NEAR THE INTERSECTION OF THE ITCZ. TROPICAL WAVE IS IN THE CENTRAL CARIB ALONG 72W S OF 20N MOVING W 15-20 KT. THE INTERACTION WITH AN UPPER LOW HAS FUELED A CONVECTIVE AREA OVER AND S OF HISPANIOLA FROM 17N-19N BETWEEN 68W-72W. THIS ACTIVITY IS MOVING NNW STEERED BY THE UPPER FLOW. IT IS NOTABLE THAT THE CURRENT POSITION HAS BEEN ADJUSTED SLIGHTLY TO THE W IN AGREEMENT WITH A RATHER QUICK NARROW MOISTURE SURGE EVIDENT ON THE CIMSS TPW ANIMATION...WHICH WAS PARTICULARLY HELPFUL IN LOCATING THIS WAVE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 9N16W 14N32W 14N41W 9N53W 9N62W. WEAKENING SCATTERED MODERATE CONVECTION IS FROM 10N-14N BETWEEN 17W-22W LIKELY ASSOCIATED WITH THE NEXT TROPICAL WAVE. SCATTERED MODERATE IS FROM 5N-8N BETWEEN 25W-30W AND NEAR THE BASE OF THE E ATLC WAVE FROM 8N-11N BETWEEN 32W-36W. ISOLATED MODERATE IS WITHIN 150 NM EITHER SIDE OF THE AXIS W OF 45W. DISCUSSION... THE GULF OF MEXICO... THE TROUGH OF LOW PRES IN THE NW GULF HAS BECOME BETTER ORGANIZED OVERNIGHT AND IS BEING CLOSELY MONITORED FOR DEVELOPMENT. FOR DETAILS REFER TO THE SPECIAL FEATURE SECTION ABOVE. ELSEWHERE...WATER VAPOR IMAGES AND THE CIMSS TPW PRODUCT SHOW A MOISTENED STATE ACROSS THE ENTIRE AREA. A COMPLEX UPPER PATTERN IS ONE OF THE PRIMARY CONTRIBUTING FACTORS. THE LARGE SCALE UPPER FLOW IS MAINLY OUT OF THE N OR NE...HOWEVER THERE ARE SMALL SYSTEMS PERTURBING THE FLOW WHICH HAS CAUSED SOME DEEPENING OF THE AVAILABLE MOISTURE. ONE AREA OF SCATTERED SHOWERS AND TSTMS IS OVER THE S CENTRAL GULF FROM 24N-27N BETWEEN 84W-88W. THIS IS ASSOCIATED WITH A SMALL UPPER LOW IN THAT AREA. SCATTERED SHOWERS AND TSTMS ARE OVER THE NE GULF AND FL PANHANDLE N OF 28N E OF 88W AHEAD OF A SLOW MOVING FRONTAL BOUNDARY WHICH IS ANALYZED JUST INLAND ACROSS THE GULF COAST STATES. THIS BOUNDARY IS NOT EXPECTED TO PUSH VERY FAR...IF AT ALL...INTO THE OFFSHORE WATERS TODAY BEFORE RETREATING AND WEAKENING. THE CARIBBEAN SEA... A LARGE UPPER LEVEL LOW IS MOVING NWWARD...CURRENTLY SPINNING OVER ERN CUBA. DIFFLUENCE BETWEEN THIS SYSTEM AND AN UPPER HIGH IN THE TROPICAL ATLC...ALONG WITH LOW-LEVEL ENERGY ASSOCIATED WITH A TROPICAL WAVE...IS SUPPORTING AN AREA OF SCATTERED SHOWERS AND TSTMS OVER AND S OF HISPANIOLA FROM 17N-19N BETWEEN 68W-72W. A HIGH CLOUD DECK...DEBRIS MOISTURE...LIES ABOVE THE REMAINDER OF THE AREA E OF 70W. INSTABILITY AND DIFFLUENCE PARTIALLY ASSOCIATED WITH THE UPPER LOW IS ALSO HELPING TO SUSTAIN SCATTERED SHOWERS AND TSTMS IN THE NW CARIB. NONE OF THESE CLUSTERS ARE VERY DEEP OR ORGANIZED IN NATURE. MUCH DRIER AIR LIES OVER THE CENTRAL CARIB WITHIN THE CIRCULATION OF THE UPPER LOW BETWEEN 72W-79W. TRADE WINDS CONTINUE TO BE ON A SLOW INCREASE...AS ADVERTISED...WITH 20-25 KT WINDS BLOWING OVER MUCH OF THE CENTRAL AND E PORTIONS. THE ATLANTIC OCEAN... AN ORGANIZATION AREA OF LOW PRES LOCATED NEAR 13N43W IS BEING CLOSELY MONITORED THIS MORNING. FOR DETAILS REFER TO THE SPECIAL FEATURE SECTION ABOVE. ELSEWHERE AT THE SFC...NOT MUCH HAS CHANGED OVER THE PAST DAY OR TWO. MODERATE SUBTROPICAL RIDGING IS THE GENERAL THEME WITH A 1022 MB HIGH CENTER LOCATED NEAR 32N57W AND RIDGING EXTENDING SW INTO THE NE ATLC. THE PATTERN IS WEAKENED IN THE CENTRAL ATLC...ALBEIT LESS SO THAT THE PAST FEW DAYS...DUE TO A 1011 MB LOW AND TRAILING SFC TROUGH N OF THE AREA. THIS HAS ALLOWED WINDS TO BE VERY LIGHT ACROSS THE SUBTROPICAL CENTRAL ATLC WITH MORE TYPICAL MODERATE ELY TRADES ELSEWHERE. IN THE MID AND UPPER LEVELS...A DIFFLUENT PATTERN EXISTS ACROSS THE W ATLC. THE CONTRIBUTING LARGE SCALE FEATURES CONSIST OF A NWWD MOVING UPPER LOW CENTERED OVER ERN CUBA...AN UPPER HIGH LOCATED NE OF BERMUDA AND AN ELONGATED SHORTWAVE WHICH ENTERS THE AREA NEAR 32N38W AND EXTENDS FAIRLY FAR TO THE W ENDING NEAR 28N67W. THIS PATTERN IS HELPING TO SUSTAIN A LINEAR SWATH OF CLOUDINESS WITH SCATTERED SHOWERS AND TSTMS CONFINED TO 23N-26N BETWEEN 68W-77W. MUCH OF THE REMAINDER OF THE AREA IS DOMINATED BY AN E-W RIDGE COVERING THE AREA E OF THE LESSER ANTILLES WITH A MEAN AXIS ALONG 18N WITH SEVERAL EMBEDDED ANTICYCLONES. THIS RIDGE AND A CONFLUENT PATTERN...TO THE S OF A LARGE UPPER LOW NEAR SRN PORTUGAL...IS KEEPING WX CONDITIONS FAIRLY TRANQUIL OUTSIDE OF THE AREAS OUTLINED ABOVE. $$ CANGIALOSI