000 AXNT20 KNHC 241018 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0945 UTC. ...SPECIAL FEATURES... A BROAD AREA OF LOW PRESSURE IS ANALYZED AS A 1006 MB LOW INLAND OVER THE DOMINICAN REPUBLIC NEAR 18.5N70W AND CONTINUES TO BRING HEAVY RAINS TO HISPANIOLA AND 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. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 14N-18N BETWEEN 68W-71W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE FROM 18N-23N BETWEEN 61W-73W INCLUDING ISLANDS FROM THE LEEWARDS TO THE TURKS AND CAICOS. ...TROPICAL WAVES... TROPICAL WAVE IS ALONG 38W/39W S OF 18N MOVING W NEAR 15 KT. ALTHOUGH THE WAVE REMAINS EMBEDDED WITHIN A BROAD AREA OF DEEP LAYER MOISTURE AS INDICATED BY MIMIC TPW ANIMATION THERE IS NO ASSOCIATED SHOWERS/CONVECTION. TROPICAL WAVE IS ALONG 63W S OF 19N MOVING W 10-15 KT. WAVE IS EMBEDDED WITHIN SOME RATHER DRY STABLE AIR THAT COVERS THE LESSER ANTILLES...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 76W S OF 17N MOVING W 10-15 KT. WAVE HAS PULLED 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 89W S OF 18N MOVING W NEAR 10 KT. WAVE IS INLAND OVER CENTRAL AMERICA AND IN THE E PACIFIC REGION WITH ISOLATED SHOWERS/THUNDERSTORMS WITHIN 45 NM ALONG THE COAST OF HONDURAS. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N11W 6N22W 12N34W 11N46W 9N62W. CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION ARE FROM 2N-7N BETWEEN 11W-34W. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 60 NM OF LINE FROM 8N21W TO 12N28W. ...DISCUSSION... GULF OF MEXICO... DEEP LAYERED TROUGH THAT COVERS THE SE US INTO THE W ATLC EXTENDS S OVER THE E GULF N OF 23N E OF 86W BRINGING DRY STABLE AIR TO THE E GULF WATERS AND THE FLORIDA PENINSULA INTO THE FLORIDA STRAITS. 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 TO THE YUCATAN CHANNEL/W CUBA. UPPER DIFFLUENCE IS GENERATING SCATTERED SHOWERS/THUNDERSTORMS IS INLAND AND WITHIN 75 NM ALONG THE COAST OF S MEXICO IN THE BAY OF CAMPECHE BETWEEN 93W-97W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER THE W GULF S OF 28N W OF 87W. ISOLATED SHOWERS ARE OVER THE SE GULF S OF 26N E OF 87W. 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 80W WITH AN NARROW UPPER TROUGH/SHEAR AXIS 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 ISOLATED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS ACROSS THE CARIBBEAN W OF 78W. THE UPPER RIDGE ASSOCIATED WITH THE LOW PRESSURE SYSTEM IN THE SPECIAL FEATURES COVERS THE E CARIBBEAN N OF 11N BETWEEN 64W-75W ENHANCING THE ACTIVITY ASSOCIATED THERE AS WELL AS SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 15N TO THE COAST OF SOUTH AMERICA BETWEEN 65W-78W. 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 DEEP LAYERED TROUGH OVER THE SE US AND E GULF OF MEXICO COVERS THE W ATLC N OF 24N W OF 72W WITH THE ASSOCIATED COLD FRONT ENTERING THE REGION NEAR 32N72W TO OVER FLORIDA S OF LAKE OKEECHOBEE GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 180 E OF THE FRONT N OF 27N AND ISOLATED SHOWERS OVER THE REMAINDER OF THE AREA W OF THE A LINE FROM 30N70W TO THE COAST OF CUBA NEAR 22N78W. STRONG WINDS ARE W OF THE FRONT ALONG THE N PORTION OF THE AREA EXPECTING TO REACH GALE FORCE TODAY BUT DIMINISHING BY THU MORNING. A NARROWING UPPER TROUGH/SHEAR AXIS IS TO THE E EXTENDING THROUGH 32N62W TO ACROSS E CUBA TO JAMAICA. DRY STABLE AIR COVERS THIS NARROW SWATH LEAVING THAT AREA OF THE W ATLC CLEAR AGAIN THIS MORNING 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 26N63W SW INTO THE CARIBBEAN ACROSS THE E HISPANIOLA COVERING THE AREA WITHIN 200 NM OF THE RIDGE AXIS AND ENHANCING THE ACTIVITY ASSOCIATED THERE. A CUT-OFF UPPER LOW IS IN THE CENTRAL ATLC NEAR 26N53W AND COUPLED WITH THE UPPER RIDGE TO THE W IS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 23N-27N BETWEEN 48W-54W WITH ISOLATED SHOWERS FROM 13N-24N BETWEEN 53W-62W. A DEEP LAYERED LOW IS IN THE E ATLC N OF 20N E OF 35W TO THE COAST OF NW AFRICA WITH THE UPPER LOW NEAR 32N22W AND THE 1011 MB SURFACE LOW NEAR 33N23W AND A SURFACE TROUGH EXTENDING SW TO 24N32W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90 NM OF LINE FROM 27N24W TO 32N19W AND N OF 30W BETWEEN 22W-25W. THE TYPICAL E/W UPPER RIDGE THAT EXTENDS FROM AFRICA TO 35W ALONG 13N 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-60W WITH A 1019 MB HIGH NEAR 31N42W. $$ WALLACE