000 AXNT20 KNHC 201738 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 205 PM EDT MON OCT 20 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1700 UTC. ...SPECIAL FEATURES... SCATTERED MODERATE TO STRONG CONVECTION IN THE NW CARIBBEAN IS ASSOCIATED WITH A BROAD AREA OF LOW PRESSURE CENTERED NEAR 17N86W...OR ABOUT 100 NM E OF THE COAST OF BELIZE. CONVECTION IS MOST PROMINENT N OF 16N AND W OF 80W. THE LOW IS NEARLY STATIONARY AND SFC OBSERVATIONS IN THE VICINITY INDICATE RISING PRESSURE. NE TO E WINDS 15-20 KT ARE OBSERVED TO THE NORTH AND EAST OF THE LOW. ANY TROPICAL DEVELOPMENT OF THESE SYSTEM WILL BE SLOW TO OCCUR...HOWEVER...HEAVY RAIN WILL PERSIST OVER PORTIONS OF HONDURAS...GUATEMALA...BELIZE...THE YUCATAN PENINSULA...AND THE NW CARIBBEAN SEA OVER THE NEXT COUPLE OF DAYS. ...TROPICAL WAVES... A TROPICAL WAVE HAS EMERGED OFF THE WEST COAST OF AFRICA AND IS ANALYZED ALONG 19W S OF 14N. UPPER AIR OBSERVATIONS AT DAKAR...SENEGAL INDICATE THE WAVE PASSED THE STATION NEAR 00Z THIS MORNING. INITIAL MOTION ESTIMATES MOVE THE WAVE WESTWARD AT 10-15 KT. VISIBLE SATELLITE IMAGERY REVEAL BROAD CYCLONIC CIRCULATION AND A DISTINCT INVERTED-V CLOUD SIGNATURE AROUND THE WAVE AXIS. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 150 NM AHEAD...100 NM BEHIND THE AXIS FROM 8N-11N. A TROPICAL WAVE IS ALONG 45W S OF 18N MOVING W NEAR 10 KT.MIMIC TPW PRODUCT INDICATES THE WAVE AXIS IS ALONG THE LEADING EDGE OF A MOISTURE SURGE...HOWEVER...CONVECTION PREVIOUSLY SURROUNDING THE WAVE IS RAPIDLY BEING DRAWN NORTHWARD BY AN UPPER-LEVEL LOW NEAR 20N49W. A TROPICAL WAVE IN THE CARIBBEAN HAS BEEN RE-LOCATED TO ALONG 70W S OF 15N. E TO SE WIND SHIFTS CORRESPONDING TO A WAVE PASSAGE OCCURRED AT THE SFC STATIONS IN THE NETHERLANDS ANTILLES EARLY THIS MORNING. IN ADDITION...UPPER AIR DATA FROM TRINIDAD AND TOBAGO INDICATE THE WAVE PASSED THE STATION NEAR 12Z ON OCT 18. THIS DATA IS THE BASIS BEHIND THE RE-LOCATION OF THE AXIS. RELATIVE VORTICITY FROM THE CMISS WAVETRAK PRODUCT SUPPORT THE LOCATION OF THE AXIS. SCATTERED MODERATE CONVECTION IS BETWEEN 70W-71W FROM 12N-14N. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N13W 9N18W 4N31W 9N47W TO 9N61W. IN ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...SCATTERED MODERATE CONVECTION IS WITHIN 90 NM S OF THE AXIS BETWEEN 24W-29W. SIMILAR CLUSTERS OF MODERATE CONVECTION ARE BETWEEN 49W-60W FROM 10N-13N. THIS AREA OF CONVECTION IS BEING ENHANCED BY UPPER-LEVEL FEATURES. ...DISCUSSION... GULF OF MEXICO... A MUCH DRIER AIR MASS WAS LEFT IN THE WAKE OF A COLD FRONT THAT EXITED THE GULF REGION EARLY THIS MORNING. A SFC HIGH OVER THE SE CONUS EXTENDS A RIDGE ACROSS THE NORTHERN GULF WITH E TO NE WINDS 10-15 KT COVERING THE AREA N OF 26N. WINDS INCREASE S OF 26N TO 20 KT IN THE VICINITY OF THE AFOREMENTIONED FRONTAL BOUNDARY WHICH NOW SPANS THE YUCATAN PENINSULA. ISOLATED SHOWERS ARE MOVING THROUGH THE STRAIGHTS OF FLORIDA..OTHERWISE CONVECTION IS LIMITED UNDER STRONG SUBSIDENCE ALOFT AND ONLY PATCHY CLOUDS ARE OBSERVED ON SATELLITE IMAGERY. EXPECT THE RIDGE ACROSS THE NORTHERN GULF TO WEAKEN IN ADVANCE OF A WEAK FRONT FORECAST TO MOVE OVER THE SE CONUS TUE NIGHT. CARIBBEAN SEA... MOIST SW FLOW ON THE LEADING EDGE OF UPPER TROUGH AXIS IN THE GULF OF MEXICO CONTINUES TO MOVE OVER THE NW CARIBBEAN...WHERE UPPER LEVEL DIVERGENCE CONTINUES TO ENHANCE CONVECTION AROUND A 1010 MB SFC LOW. SEE SPECIAL FEATURES SECTION FOR MORE DETAILS. A STATIONARY FRONT REMAINS SITUATED ACROSS CUBA THROUGH THE YUCATAN CHANNEL AND INTO THE YUCATAN PENINSULA. EXPECT THIS BOUNDARY TO DISSIPATE IN THE NEXT 24 HOURS. UPPER-LEVEL DIVERGENCE IS GENERATING AN AREA OF MODERATE CONVECTION FROM 12N-17N BETWEEN 78W-81W. THIS CONVECTION IS MOVING RAPIDLY TOWARD THE WNW IN MODERATE TRADE WIND FLOW. FURTHER EAST...CONVECTION IS LIMITED DUE TO MODERATE SUBSIDENCE ON THE SE QUADRANT OF AN UPPER-LEVEL HIGH. ATLANTIC OCEAN... A DEEP LAYER TROUGH OVER THE W ATLC IS SUPPORTING A COLD FRONT THAT...AS OF 15Z...ENTERS THE DISCUSSION AREA NEAR 31N63W AND EXTENDS ALONG 24N70W TO 22N79W WHERE IT BECOMES STATIONARY ACROSS CUBA. SCATTERED SHOWERS EXTEND UP TO 60 NM EITHER SIDE OF THE FRONT. TO THE EAST...A WEAK SFC LOW PRESSURE WAS EVIDENT ON SATELLITE IMAGERY AS WELL AS IN THE QUIKSCAT WIND DATA NEAR 24N60W. A SMALL CLUSTER OF MODERATE CONVECT ASSOCIATED WITH THIS FEATURE FLARED UP FROM 24N-25N BETWEEN 58W-59W. THIS CONVECTION IS SHORT-LIVED DUE TO STRONG WLY SHEAR ALOFT. AT THE SFC...STRONG HIGH PRESSURE DOMINATES THE ATLC E OF 55W...HOWEVER...A LARGE UPPER-LEVEL LOW NEAR 21N50W AND AN UPPER-LEVEL HIGH NEAR 20N37W CONTINUE TO FUNNEL DEEP-LAYER TROPICAL MOISTURE NORTHWARD INTO THE CENTRAL ATLC. THESE UPPER FEATURES ARE RESULTING IN SCATTERED MODERATE CONVECTION FROM 12N-26N BETWEEN 35W-46W. UPPER-LEVEL DIVERGENCE SOUTH OF THE UPPER-LEVEL LOW IS ENHANCING CONVECTION ALONG THE ITCZ FROM 78W TO THE WINDWARD ISLANDS. $$ WADDINGTON