000 AXNT20 KNHC 120548 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...SPECIAL FEATURE... A SLOW MOVING BROAD AREA OF LOW PRES ABOUT 1000 NM E OF THE LESSER ANTILLES IS SHOWING SINGS OF ORGANIZING THIS MORNING. THIS LOW WAS ANALYZED 1010 MB NEAR 13N43W...ALTHOUGH BUOY 41041 COULD SUGGEST A SLIGHTLY LOWER MINIMUM PRESSURE. 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 11N-14N BETWEEN 43W-46W. CONDITIONS APPEAR FAVORABLE FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL DEPRESSION WITHIN THE NEXT DAY OR SO AS IT MOVES SLOWLY WEST-NORTHWESTWARD. A BROAD AREA OF LOW PRES IN THE NW GULF IS CENTERED NEAR 27N95W...ANALYZED 1011 MB DRIFTING TO THE WEST-NORTHWEST. THIS LOW APPEARS RATHER RAGGED ON SATELLITE IMAGES WITH CONVECTION SPARSE AND THE LOW-LEVEL CIRCULATION STRETCHED OUT AND ELONGATED. SFC OBS CLEARLY SHOW A TROUGH AXIS WHICH EXTENDS BOTH NNE AND SSW OF THE LOW CENTER. PART OF THIS LOW/TROUGH IS IN RADAR RANGE WHICH DEPICTS ISOLATED TO SCATTERED SHOWERS AND TSTMS ROTATING ABOUT THE LOW/TROUGH WITHIN 60 NM. EVEN THOUGH THIS SYSTEM CURRENTLY LACKS ORGANIZATION...ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR SOME DEVELOPMENT AS IT CONTINUES ITS SLOW WNW DRIFT OVER THE NEXT DAY OR SO. ...TROPICAL WAVES... HIGH AMPLITUDE TROPICAL WAVE IN THE E ATLC ALONG 32W 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 PASSED DEPICTED A NEARLY CLOSED CIRCULATION ALONG THE WAVE AXIS NEAR 15N...THOUGH THIS IS HARD TO SEE ON NIGHT CHANNEL VIS IMAGES. DESPITE THE FAIR STRUCTURE...DEEP MOISTURE IS MINIMAL WITH ONLY ISOLATED 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 70W S OF 20N MOVING W 15-20 KT. THE INTERACTION WITH AN UPPER LOW HAS FUELED A CONVECTIVE AREA NEAR THE WAVE AXIS FROM 15N-18N BETWEEN 67W-71W. THIS ACTIVITY IS MOVING NWD STEERED BY THE UPPER FLOW. THE BEST TOOL USED TO FIND THE LOW-LEVEL AXIS IS THE CIMSS TPW ANIMATION WHICH CONTINUES TO SHOW A NARROW MOISTURE SURGE PROPAGATING JUST PASSED 70W. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N13W 11N31W 12N40W 10N60W. SCATTERED MODERATE CONVECTION IS FROM 10N-15N E OF 20W LIKELY ASSOCIATED WITH THE NEXT TROPICAL WAVE. SCATTERED MODERATE IS FROM 5N-8N BETWEEN 24W-29W. ISOLATED MODERATE IS FROM 9N-12N BETWEEN 33W-36W AND WITHIN 90 NM S OF THE AXIS W OF 45W. DISCUSSION... THE GULF OF MEXICO... A BROAD TROUGH OF LOW PRES IN THE NW GULF IS AN AREA 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 SE GULF AND THE SW COAST OF FLA ROUGHLY S OF 26N E OF 87W. THIS IS ASSOCIATED WITH A SMALL UPPER LOW IN THAT AREA. A WEAKENING PATCH OF SCATTERED MODERATE CONVECTION IS OVER THE WRN HALF OF THE YUCATAN PENINSULA AND THE BAY OF CAMPECHE E OF 92W LINKED TO DIFFLUENCE BETWEEN A SMALL UPPER HIGH AND AN UPPER LOW IN THE CARIB. A SLOW MOVING FRONTAL BOUNDARY...ASSOCIATED WITH A FLATTENING SHORTWAVE OVER THE ERN U.S...IS ANALYZED JUST INLAND ACROSS THE TEXAS COAST. THIS BOUNDARY MAY ENTER THE EXTREME NW WATERS LATER THIS MORNING BUT IS NOT EXPECTED TO HAVE MUCH OF AN IMPACT ON THE BULK OF THE AREA. THE CARIBBEAN SEA... A LARGE UPPER LEVEL LOW HAS BEEN MOVING SLOWLY NW CURRENTLY SPINNING ABOVE THE WINDWARD PASSAGE. DIFFLUENCE BETWEEN THIS SYSTEM AND AN UPPER HIGH TO THE E...ALONG WITH LOW-LEVEL ENERGY ASSOCIATED WITH A TROPICAL WAVE...IS SUPPORTING AN AREA OF SCATTERED SHOWERS AND TSTMS FROM 15N-18N BETWEEN 67W-71W. A HIGH CLOUD DECK...DEBRIS MOISTURE...LIES ACROSS THE REMAINDER OF THE AREA E OF 70W. INSTABILITY AND DIFFLUENCE PARTIALLY ASSOCIATED WITH THE UPPER LOW IS ALSO HELPING TO SUSTAIN SMALL CLUSTERS OF SCATTERED MODERATE CONVECTION 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 71W-80W. 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 32N58W 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 1009 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 IN THE WINDWARD PASSAGE...AN UPPER HIGH LOCATED N OF BERMUDA AND AN ELONGATED SHORTWAVE WHICH ENTERS THE AREA NEAR 32N38W AND EXTENDS FAIRLY FAR TO THE W ENDING NEAR 27N66W. THIS PATTERN IS HELPING TO SUSTAIN A LINEAR SHAPE SHIELD OF CLOUDINESS WITH SCATTERED SHOWERS AND TSTMS CONFINED TO 23N-26N BETWEEN 68W-76W. MUCH OF THE REMAINDER OF THE AREA IS DOMINATED BY AN E-W RIDGE AXIS COVERING THE AREA E OF THE LESSER ANTILLES WITH A MEAN AXIS ALONG 19N WITH SEVERAL EMBEDDED ANTICYCLONES. THIS RIDGE AND A CONFLUENT PATTERN TO THE NE IS KEEPING WX CONDITIONS FAIRLY TRANQUIL OUTSIDE OF THE AREAS OUTLINED ABOVE. $$ CANGIALOSI