000 AXNT20 KNHC 240544 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 AM EDT WED SEP 24 2008 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0315 UTC. ...SPECIAL FEATURES... A BROAD AREA OF LOW PRESSURE IS ANALYZED AS A 1007 MB LOW ALONG THE S COAST OF THE DOMINICAN REPUBLIC NEAR 18N70W CONTINUES TO BRING HEAVY RAINS TO HISPANIOLA...PUERTO RICO...THE TURKS AND CAICOS AS WELL AS THE ADJACENT WATERS. THIS SYSTEM IS INTERACTING WITH LAND AND HAS NOT YET DEVELOPED A WELL-DEFINED SURFACE CIRCULATION BUT ATMOSPHERIC CONDITIONS REMAIN FAVORABLE FOR DEVELOPMENT AND A TROPICAL DEPRESSION COULD FORM LATER TODAY OR TONIGHT AS THIS SYSTEM MOVES N OF HISPANIOLA. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 16N-19N BETWEEN 68W-73W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 14N-22N BETWEEN 63W-74W INCLUDING THE VIRGIN ISLANDS AND PUERTO RICO. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 37W/38W S OF 18N MOVING W NEAR 15 KT. WAVE REMAINS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS INDICATED BY MIMIC TPW ANIMATION. WAVE IS VERY BROAD COVERING THE AREA BETWEEN 32W-43W WITH CLUSTERS OF SCATTERED MODERATE CONVECTION WITHIN 120 NM OF LINE FROM 12N30W TO 15N39W. TROPICAL WAVE IS ALONG 62W S OF 19N MOVING W 10-15 KT. WAVE IS EMBEDDED WITHIN SOME RATHER DRY STABLE AIR THAT COVERS THE WINDWARD ISLANDS WHILE THE N PORTION OF THE WAVE IS UNDER THE INFLUENCE OF THE UPPER RIDGE ASSOCIATED WITH THE LOW PRESSURE AREA IN THE SPECIAL FEATURES. TROPICAL WAVE IS ALONG 74W S OF 17N MOVING W NEAR 10 KT. THIS WAVE IS FINALLY PULLING AWAY FROM THE LOW PRESSURE SYSTEM DESCRIBED IN THE SPECIAL FEATURES BUT REMAINS UNDER THE INFLUENCE OF THE UPPER RIDGE ALSO ASSOCIATED THE SAME SYSTEM. NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE IS ALONG 88W S OF 18N MOVING W NEAR 10 KT. WAVE IS MOSTLY INLAND OVER CENTRAL AMERICA AND IN THE E PACIFIC REGION WITH NO ASSOCIATED SHOWERS/CONVECTION IN THE CARIBBEAN. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 11N15W 8N23W 12N36W 9N46W 10N64W. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE FROM 2N-8N BETWEEN 9W-33W. ...DISCUSSION... GULF OF MEXICO... AN UPPER TROUGH THAT COVERS THE E US INTO THE W ATLC EXTENDS S OVER THE E GULF N OF 25N E OF 87W BRINGING DRY STABLE AIR TO THE NE GULF WATERS AND MOST OF THE FLORIDA PENINSULA. A BROAD UPPER RIDGE COVERS THE REMAINDER OF THE GULF ANCHORED ALONG THE COAST OF MEXICO NEAR TAMPICO EXTENDING AN AXIS N OVER LOUISIANA AND E TEXAS. A WEAKENING SURFACE TROUGH IS BENEATH THIS UPPER RIDGE EXTENDING FROM 24N96W TO THE BAY OF CAMPECHE NEAR 19N95W. UPPER DIFFLUENCE IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE W GULF S OF 28N W OF 90W. CARIBBEAN SEA... THE MAIN CONCERN CONTINUES TO BE THE AREA OF LOW PRESSURE DESCRIBED IN THE SPECIAL FEATURES SECTION. THE UPPER RIDGE FROM THE GULF OF MEXICO COVERS THE W CARIBBEAN W OF 81W WITH AN NARROWING UPPER TROUGH EXTENDING FROM THE W ATLC ACROSS E CUBA TO JAMAICA JUST TO THE W OF THE SPECIAL FEATURES LOW PRESSURE. ALL THIS IS PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90 NM OF LINE FROM 18N75W TO 21N84W. THE UPPER RIDGE ASSOCIATED WITH THE LOW PRESSURE SYSTEM IN THE SPECIAL FEATURES COVERS THE E CARIBBEAN N OF 13N BETWEEN 63W-75W ENHANCING THE ACTIVITY ASSOCIATED THERE AS WELL AS SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 14N TO INLAND OVER SOUTH AMERICA BETWEEN 67W-72W. ATLANTIC OCEAN... A CONCERN FOR THE SW ATLC IS THE ACTIVITY ASSOCIATED WITH THE LOW PRESSURE AREA DESCRIBED IN THE SPECIAL FEATURES ABOVE AS THE LOW IS EXPECTED TO MOVE INTO THE SW ATLC WATERS. THE UPPER TROUGH OVER THE E US AND E GULF OF MEXICO COVERS THE W ATLC N OF 25N W OF 72W WITH THE ASSOCIATED COLD FRONT ENTERING THE REGION NEAR 32N73W TO OVER FLORIDA NEAR LAKE OKEECHOBEE AND A PRE-FRONTAL SURFACE TROUGH EXTENDING FROM 31N73W TO GRAND BAHAMA ISLAND. THIS IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF 28N FROM 70W TO THE COLD FRONT AND ISOLATED SHOWERS OVER THE REMAINDER OF THE AREA W OF THE A LINE FROM 28N70W TO THE COAST OF CUBA NEAR 23N80W. STRONG WINDS ARE W OF THE FRONT ALONG THE N PORTION OF THE AREA EXPECTING TO REACH GALE FORCE LATER TODAY BUT DIMINISHING BY THU MORNING. A NARROWING UPPER TROUGH IS TO THE E EXTENDING FROM A WEAK UPPER LOW NEAR 31N64W TO ACROSS E CUBA TO JAMAICA. DRY STABLE AIR COVERS THIS NARROW SWATH LEAVING THAT AREA OF THE W ATLC CLEAR AGAIN TONIGHT AND SHEARING THE LOW PRESSURE SYSTEM IN THE SPECIAL FEATURES. THE UPPER RIDGE ASSOCIATED WITH THE LOW PRESSURE SYSTEM IN THE SPECIAL FEATURES EXTENDS FROM 24N63W SW INTO THE CARIBBEAN ACROSS THE PUERTO RICO/HISPANIOLA COVERING THE AREA WITHIN 150 NM OF THE RIDGE AXIS AND ENHANCING THE ACTIVITY ASSOCIATED THERE. A CUT-OFF UPPER LOW IS IN THE CENTRAL ATLC NEAR 25N50W AND COUPLED WITH THE UPPER RIDGE TO THE W IS GENERATING A BROAD AREA OF CLOUDINESS WITH ISOLATED SHOWERS FROM 15N-27N BETWEEN 47W-62W. A DEEP LAYERED LOW IS IN THE E ATLC N OF 21N BETWEEN 14W-35W WITH A NEAR VERTICALLY STACK UPPER AND A 1010 MB SURFACE LOW NEAR 33N22W WITH A SURFACE TROUGH EXTENDING SW TO 23N33W GENERATING SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS N OF 26N BETWEEN 20W-25W. THE TYPICAL E/W UPPER RIDGE THAT EXTENDS FROM AFRICA TO 45W ALONG 14N CONTINUES TO BE SUPPRESSED TO THE S DUE TO THE UPPER TROUGH MENTIONED ABOVE. THE SURFACE RIDGE CONTINUES TO WEAKEN COVERING THE ATLC N OF 25N BETWEEN 35W-65W WITH A 1019 MB HIGH NEAR 32N54W. $$ WALLACE