000 AXNT20 KNHC 240001 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT THU OCT 23 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...TROPICAL WAVES... THE 59TH TROPICAL WAVE OF THIS SEASON HAS EMERGED OFF THE WEST COAST OF AFRICA TODAY AND IS ANALYZED ON THE 1800 UTC MAP ALONG 16W SOUTH OF 15N. THE WAVE SHOWS UP ON THE TPW PRODUCT FROM CIMSS WITH A SURGE OF MOISTURE BETWEEN THE WAVE AXIS AND THE AFRICAN COAST. THE HOVMOLLER DIAGRAM ALSO DEPICTS THE WWD PROPAGATION OF THE WAVE SINCE YESTERDAY. INITIAL MOTION ESTIMATES MOVE THE WAVE WWD AT 10-15 KT. SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS FROM 5N-9N BETWEEN 16W-19W. CLUSTERS OF MODERATE CONVECTION ARE BEHIND THE WAVE AXIS NEAR 9N13W AND 6N14W. A TROPICAL WAVE IS ALONG 30W S OF 14N MOVING W NEAR 10 KT. DEEP LAYER DRY AIR IS GENERALLY SUPPRESSING CONVECTION NEAR THE WAVE. HOWEVER...SCATTERED MODERATE CONVECTION IS NEAR THE INTERSECTION OF THE WAVE AXIS AND THE ITCZ. AN 850 MB VORTICITY MAXIMUM SUPPORTS THE POSITION OF THE WAVE AXIS. A TROPICAL WAVE IS ALONG 56W S OF 23N MOVING W NEAR 10 KT. SWLY FLOW ASSOCIATED WITH AN UPPER-LEVEL LOW LOCATED TO THE WEST OF THIS TROPICAL WAVE IS KEEPING MOST OF THE CONVECTION WELL BEHIND OF THE WAVE AXIS FROM 16N-21N BETWEEN 48W-52W. UPPER DIFFLUENCE AHEAD OF THIS UPPER TROUGH IS ALSO ENHANCING CONVECTION BETWEEN THE TROPICAL WAVE AND THE WINDWARD ISLANDS. A TROPICAL WAVE IS OVER THE NW CARIBBEAN AND CENTRAL AMERICA ALONG 86 S OF 20N MOVING W 10-15 KT. THIS FEATURE IS GENERATING ISOLATED MODERATE CONVECTION OVER THE NW CARIBBEAN...AND IS HELPING TO INDUCE SCATTERED SHOWERS AND ISOLATED TSTMS OVER PARTS OF HONDURAS AND NICARAGUA. THIS WAVE EXTENDS SOUTH INTO THE EPAC. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N12W 7N25W 9N40W 11N53W 10N62W. IN ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES... SCATTERED MODERATE CONVECTION IS FROM 3N-5N BETWEEN 24W-28W AND WITHIN 50-60 NM EITHER SIDE OF AXIS BETWEEN 30W-34W. ...DISCUSSION... GULF OF MEXICO... AS OF 2100 UTC...A COLD FRONT EXTENDS FROM SE LOUISIANA TO NEAR TAMPICO MEXICO. AS SUGGESTED BY THE COMPUTER MODELS...A 1012 MB SFC LOW HAS DEVELOPED OVER THE NORTH-CENTRAL GULF NEAR 27N90W WITH A WARM FRONT EXTENDING MAINLY EWD ALONG 28N86W TO NEAR THE TAMPA BAY AREA. MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS COVER THE NE QUADRANT OF THE GULF AND THE FLORIDA PANHANDLE N OF THE WARM FRONT. ABUNDANT CLOUDINESS IS ALSO SEEN OVER THE SE GULF AND THE FLORIDA PENINSULA. THE WARM FRONT SHOULD RAPIDLY LIFT ACROSS THE NE GULF AND NORTHERN FLORIDA EARLY FRI AND WILL BE NE OF THE AREA FRI AFTERNOON. AT THE SAME TIME...THE COLD FRONT IS FORECAST TO MOVE SE AND MERGE WITH THE AFOREMENTIONED SFC LOW PRES MOVING SLOWLY NE OVER THE SE CONUS. MODERATE TO STRONG NLY WINDS ARE FOUND BEHIND THE COLD FRONT EXPECTED TO BE EXTENDED FROM THE FLORIDA BIG BEND TO THE NE PORTION OF THE YUCATAN PENINSULA FRIDAY MORNING. IN THE UPPER LEVELS...SOUTHWESTERLY FLOW WITH CONSIDERABLE UPPER LEVEL MOISTURE PREVAILS OVER THE GULF OF MEXICO. ADDITIONALLY...STRONG NORTHERLY WINDS BEHIND THE COLD FRONT WILL BLOW THROUGH THE ISTHMUS OF TEHUANTEPEC AND PRODUCE GALE FORCE GAP WINDS INTO THE EASTERN PACIFIC REGION BY TONIGHT. CARIBBEAN SEA... A TROPICAL WAVE IS OVER OVER THE NW CARIBBEAN...AND ANOTHER IS APPROACHING THE LESSER ANTILLES. SEE TROPICAL WAVE SECTION. FRESH TO STRONG TRADEWINDS ARE BLOWING OVER THE CARIBBEAN SEA. IN THE UPPER LEVELS...A LARGE UPPER LEVEL HIGH CENTERED JUST WEST OF JAMAICA DOMINATES THE ENTIRE BASIN AND CONTINUES TO SUPPORT CONVECTION OVER THE NW CARIBBEAN AND CENTRAL AMERICA. SUBSIDENCE/DRY AIR IS NOTED OVER THE EASTERN CARIBBEAN UNDER THE INFLUENCE OF THIS UPPER HIGH...AND ONLY LOW TOPPED TRADE WIND SHOWERS ARE SEEN. CONVECTION HAS FLARED-UP OVER NORTHERN COLOMBIA LIKELY DUE TO THE COLOMBIAN OR PANAMANIAN LOW ANALYZED 1008 NEAR 8N75W. MODERATE TO ISOLATED STRONG CONVECTION IS AFFECTING PARTS OF PANAMA AND COSTA RICA. THIS ACTIVITY APPEARS TO BE ASSOCIATED WITH THE ITCZ. ATLANTIC OCEAN... A COLD FRONT ENTERS THE AREA NEAR 31N60W THEN CONTINUES MAINLY WWD TO NORTH-CENTRAL FLORIDA NEAR 28N82W. A NARROW BAND OF MAINLY LOW CLOUDS IS RELATED TO THIS FRONT. A STRONG HIGH PRES CENTERED OVER THE NE CONUS IS BEHIND THE FRONT. PRES GRADIENT BETWEEN THIS HIGH AND A BROAD AREA OF LOW PRES OVER THE GULF OF MEXICO WILL PRODUCE GALE FORCE WINDS IN ABOUT 12-24 HOURS OVER THE FAR NW PORTION OF THE FORECAST AREA. A SURFACE TROUGH... REFLECTION OF AN UPPER-LEVEL LOW PERSISTS OVER THE CENTRAL ATLANTIC ALONG 31N53W 25N54W. PATCHES OF LOW-LEVEL CLOUDS AND MODERATE TRADE WINDS ARE OBSERVED OVER THE E ATLC LARGELY IN PART TO A SURFACE RIDGE COVERING THE E ATLC E OF 40W. ALOFT...A RIDGE/TROUGH/RIDGE/TROUGH PATTERN DOMINATES THE ENTIRE FORECAST AREA. THE BROAD UPPER-LEVEL HIGH CENTERED OVER THE CARIBBEAN SEA EXTENDS A RIDGE NWD ACROSS THE BAHAMAS INTO THE W ATLC. ABUNDANT CLOUDINESS AND ISOLATED SHOWERS ARE ACROSS THE BAHAMAS AND THE W ATLC WEST OF 70W AS DEEP TROPICAL MOISTURE STREAMS EAST FROM THE EASTERN GULF OF MEXICO. AN UPPER-LEVEL LOW REMAINS OVER THE CENTRAL ATLC NEAR 25N53W. THIS LOW HAS A TROUGH EXTENDING SW INTO THE FAR SE CARIBBEAN THROUGH THE WINDWARD ISLANDS. UPPER DIFFLUENCE BETWEEN THIS TROUGH AND A WEAK RIDGE TO THE EAST CENTERED NEAR 30N38W IS GENERATING A WIDE BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS AND POSSIBLE ISOLATED TSTMS BETWEEN 48W-53W FROM THE ITCZ TO 31N. ANOTHER UPPER LEVEL LOW IS SPINNING OVER THE E ATLC NEAR 20N31W. A JET-STREAM BRANCH IS AROUND THE BASE OF THIS TROUGH PRODUCING A BAND OF TRANSVERSE HIGH CLOUDS WHICH EXTENDS FROM 10N35W ALL THE WAY NE CROSSING SE OF THE CAPE VERDE ISLANDS INTO WEST AFRICA. $$ GR