000 AXNT20 KNHC 071057 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 AM EDT MON SEP 07 2009 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND 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 1015 UTC. ...SPECIAL FEATURES... A TROPICAL WAVE IS ALONG 22W S OF 20N MOVING W NEAR 18 KT WITH A 1007 MB LOW EMBEDDED ON THE WAVE AXIS NEAR 13N. A DEEP LAYERED MOISTURE MAXIMUM IS NOTED IN THE VICINITY OF THE WAVE ON THE TOTAL PRECIPITABLE WATER IMAGERY. SATELLITE IMAGERY AND CIMSS WAVETRAK MODEL GUIDANCE EXHIBITS LOW-LEVEL CYCLONIC CIRCULATION WITH SCATTERED MODERATE TO STRONG CONVECTION W OF THE LOW CENTER FROM 10N-16N BETWEEN 22W-26W. AN E-W BAND OF SCATTERED MODERATE/ ISOLATED STRONG CONVECTION...MORE LIKELY ASSOCIATED WITH THE ITCZ...IS FROM 6N-9N BETWEEN 19W-29W. CONDITIONS APPEAR FAVORABLE FOR THIS SYSTEM TO DEVELOP INTO A TROPICAL DEPRESSION WITHIN THE NEXT DAY OR SO. ...TROPICAL WAVES... TROPICAL WAVE PREVIOUSLY ALONG 41W S OF 17N HAS BEEN DROPPED FROM THE 07/0600 UTC ANALYSIS. MOST OF THE ENERGY FROM THIS WAVE FRACTURED NWD AS A SURFACE TROUGH AND SURFACE LOW OVER 24 HOURS AGO...AND ANY REMAINING SIGNATURE HAS BECOME FULLY ABSORBED INTO THE TROPICAL WAVE ALONG 50W. TROPICAL WAVE IS ALONG 50W S OF 21N MOVING W NEAR 15 KT. A 1012 MB LOW IS ALONG THE WAVE AXIS NEAR 17N. CIMSS WAVETRAK MODEL GUIDANCE INDICATES A BROAD AREA OF 850 MB VORTICITY N OF 15N BETWEEN 45W-55W SURROUNDING THE WAVE. SCATTERED MODERATE CONVECTION HAS DECREASED OVER THE PAST 6 HOURS ON SATELLITE IMAGERY AND ONLY SCATTERED SHOWERS REMAIN FROM 16N-21N BETWEEN 45W-53W. TROPICAL WAVE IS ALONG 72W S OF 18N MOVING W NEAR 20 KT. MOVING BENEATH DRY AIR AND MODERATE SUBSIDENCE ALOFT...THE WAVE REMAINS ILL-DEFINED AND DIFFICULT TO TRACK. NO DEEP CONVECTION ACCOMPANIES THE WAVE. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 17N16W 16N20W 8N24W 8N31W 16N47W 15N53W 11N64W. BESIDE THE CONVECTION ASSOCIATED WITH THE TROPICAL WAVES ACROSS THE TROPICAL ATLC...ISOLATED LOW-LEVEL SHOWERS ARE S OF 10N E OF 30W. ...DISCUSSION... GULF OF MEXICO... AN UPPER LEVEL TROUGH IS OVER THE LOWER MISSISSIPPI RIVER VALLEY ACROSS THE ERN CONUS WHILE AN UPPER LEVEL ANTICYCLONIC CIRCULATION IS CENTERED OVER SRN MEXICO NEAR 19N95W. STRONG WESTERLY UPPER LEVEL FLOW BETWEEN THE TWO UPPER LEVEL FEATURES DOMINATES ACROSS THE GULF OF MEXICO. THIS IS PROVIDING A LACK OF ANY SIGNIFICANT SURFACE FEATURES OTHER THAN A WEAK PRESSURE GRADIENT AND RELATIVELY LIGHT WINDS ACROSS THE GULF. HOWEVER...A SURFACE TROUGH EXTENDS FROM THE W ATLC ACROSS THE FAR SRN FLORIDA PENINSULA TO NEAR KEY WEST. THE UPPER LEVEL RIDGE IS ALSO PROVIDING UPPER DIFFLUENCE TO GENERATE SCATTERED SHOWERS AND A FEW ISOLATED TSTMS WITHIN 150 NM EITHER SIDE OF A LINE FROM APALACHICOLA BAY THROUGH 25N90W TO VERACRUZ MEXICO. THE MOST INTENSE ACTIVITY IS LOCATED OVER THE SW GULF AND BAY OF CAMPECHE S OF 23N W OF 93W. CARIBBEAN SEA... A TROPICAL WAVE WITH NO SIGNIFICANT CONVECTION IS OVER THE CENTRAL CARIBBEAN ALONG 72W. AN UPPER LEVEL SHORTWAVE TROUGH EXTENDS FROM THE W ATLC ACROSS CUBA...JAMAICA AND PORTIONS OF WRN HISPANIOLA. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE UPPER TROUGH IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS N OF 18N BETWEEN 74W-79W. SCATTERED SHOWERS AND DEBRIS CLOUDINESS SPREAD EWD OF 74W ACROSS THE REMAINDER OF HISPANIOLA AND PUERTO RICO. THE UPPER LEVEL ANTICYCLONIC CIRCULATION CENTERED OVER SRN MEXICO NEAR 19N95W EXTENDS UPPER RIDGING ACROSS MUCH OF CENTRAL AMERICA AND THE CENTRAL CARIBBEAN THROUGH 12N80W TO 14N65W. MODERATE SUBSIDENCE IS NOTED ON WATER VAPOR IMAGERY THUS LIMITING ANY DEEP CONVECTION...HOWEVER A FEW ISOLATED SHOWERS AND TSTMS ARE OVER THE SW CARIBBEAN S OF 15N W OF 80W. ATLANTIC OCEAN... A SHORTWAVE UPPER LEVEL TROUGH IS OVER THE SOUTH CAROLINA COASTLINE AND SUPPORTS A 1012 MB SURFACE LOW CENTERED NEAR 32N79W. AS OF 0900 UTC...A SURFACE TROUGH EXTENDS S FROM THE LOW ALONG 30N79W TO FT. LAUDERDALE FLORIDA AND OVER THE SERN FLORIDA PENINSULA. LOW-LEVEL CONVERGENCE COUPLED WITH UPPER LEVEL DIFFLUENCE IS GENERATING SCATTERED SHOWERS N OF 23N BETWEEN 75W-80W. AN UPPER LEVEL LOW IS CENTERED NEAR 27N68W AND EXTENDS TROUGHING ACROSS THE CAICOS ISLANDS AND CUBA. UPPER LEVEL DIFFLUENCE E OF THE UPPER TROUGH AXIS IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 20N-23N BETWEEN 73W-80W AND FROM 21N-29N BETWEEN 61W-69W. FARTHER TO THE E ACROSS THE CENTRAL ATLC AN UPPER LEVEL HIGH IS CENTERED NEAR 30N55W AND AN UPPER LEVEL LOW IS CENTERED NEAR 26N45W. NELY UPPER LEVEL DIFFLUENT FLOW IS LOCATED BETWEEN THESE TWO FEATURES AND IS PRODUCING POSSIBLE SCATTERED SHOWERS WITHIN 120 NM EITHER SIDE OF A LINE FROM 27N53W TO 32N43W. IN ADDITION...MOIST SWLY UPPER LEVEL FLOW LOCATED SE OF THE UPPER LEVEL LOW NEAR 26N45W IS SUPPORTING A FRACTURED PORTION OF ENERGY ANALYZED AS A SURFACE TROUGH EXTENDING FROM 17N35W THROUGH A 1013 MB LOW CENTERED NEAR 20N35W TO 24N33W. SCATTERED SHOWERS AND ISOLATED TSTMS EXTEND N OF THE SURFACE LOW FROM 21N-26N BETWEEN 30W-36W. $$ HUFFMAN