000 AXNT20 KNHC 262349 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT WED SEP 26 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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. ...SPECIAL FEATURES... KAREN REMAINS BELOW HURRICANE INTENSITY OVER THE CENTRAL NORTH ATLANTIC. AT 26/2100 UTC KAREN WAS NEAR 12.4N 43.6W OR ABOUT 1020 NM...1890 KM...EAST OF THE WINDWARD ISLANDS...MOVING WEST NORTHWEST NEAR 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 990 MB. MAXIMUM SUSTAINED WINDS ARE 60 KT WITH GUSTS TO 75 KT. SEE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS. THE DEEP CONVECTION IS MAINLY OCCURRING IN THE NORTHEASTERN SEMICIRCLE AND THE INTERMITTENT EYE IS NO LONGER PRESENT. KAREN REMAINS OVER WARM 28C WATER AND HAS ABUNDANT MOISTURE NEARBY BUT IS BEING IMPACTED BY MODERATE 15-20 KT WESTERLY SHEAR. LITTLE CHANGE IN STRENGTH IS FORECAST DURING THE NEXT 24 HOURS THOUGH A SMALL INCREASE WOULD BRING KAREN TO HURRICANE INTENSITY. A NOAA HURRICANE RECONNAISSANCE AIRCRAFT WILL BE INVESTIGATING THE TROPICAL STORM LATER THIS EVENING. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE FROM 11N-15N BETWEEN 40W-45W. TROPICAL DEPRESSION THIRTEEN HAS NOT STRENGTHENED YET. AT 26/2100 UTC IT WAS OVER THE SW GULF OF MEXICO NEAR 21.3N 94.5W OR ABOUT 195 NM...365 KM...EAST-SOUTHEAST OF TAMPICO MEXICO AND ABOUT 165 NM...305 KM...EAST OF TUXPAN MEXICO. THE DEPRESSION HAS BEEN MEANDERING...AND IS NEARLY STATIONARY. A SLOW AND ERRATIC MOTION IS EXPECTED DURING THE NEXT 12 TO 24 HOURS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB. MAXIMUM SUSTAINED WINDS ARE 25 KT WITH GUSTS TO 35 KT. THE CYCLONE'S CLOUD PATTERN IS WELL-ORGANIZED WITH DISTINCT BANDING FEATURES OVER THE SOUTHERN SEMICIRCLE AND A FAIRLY SYMMETRIC UPPER-LEVEL OUTFLOW...BUT RECENT DATA FROM AN AIR FORCE HURRICANE HUNTER MISSION INDICATE THAT THE SYSTEM IS NOT YET A TROPICAL STORM. SOME STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS...AND THE DEPRESSION COULD BECOME A TROPICAL STORM LATER TONIGHT OR EARLY THURSDAY. SEE LATEST NHC FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC AND THE PUBLIC ADVISORY UNDER MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS. SATELLITE IMAGERY SHOWS THAT THE DEEP CONVECTION HAS DIMINISHED OVER THE PAST FEW HOURS...WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 19N-21N BETWEEN 93W-96W. ...TROPICAL WAVES... A TROPICAL WAVE IS JUST EAST OF THE CAPE VERDE ISLANDS ALONG 22W SOUTH OF 16W MOVING W 10-15 KT. THE WAVE SHOWS UP WELL IN LOW LEVEL SATELLITE DERIVED WINDS AND VORTICITY...AND THE UW CIMSS TPW PRODUCTS. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF AXIS. ANY DEVELOPMENT OF THIS SYSTEM IS EXPECTED TO BE SLOW TO OCCUR AS IT MOVES WESTWARD. A TROPICAL WAVE IS MOVING ACROSS THE EASTERN CARIBBEAN. THE 1012 MB LOW PRESSURE AREA ASSOCIATED WITH THIS WAVE IS NO LONGER DISCERNIBLE IN SATELLITE IMAGERY OR SURFACE DATA. THE WAVE SHOWS A WELL DEFINED INVERTED-V PATTERN AND WAS MOVED SLIGHTLY AHEAD BASED ON THAT. THE AXIS IS CURRENTLY ALONG 69W GENERATING CLUSTERS OF MODERATE TO STRONG CONVECTION OVER HISPANIOLA AND NW VENEZUELA NEAR LAKE MARACAIBO. SCATTERED SHOWERS AND ISOLATED TSTMS ARE OVER THE EASTERN CARIBBEAN JUST BEHIND THE WAVE AXIS. THE SAN JUAN DOPPLER RADAR...AND LIGHTNING DATA DEPICT SCATTERED SHOWERS AND A FEW TSTMS MAINLY OVER THE CARIBBEAN WATERS. LOCALLY HEAVY RAINFALL IS POSSIBLE OVER HISPANIOLA TONIGHT AND TOMORROW BUT UPPER-LEVEL WINDS ARE NOT FAVORABLE FOR DEVELOPMENT OF THIS WAVE. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 9N13W 11N20W 6N30W 12N39W 4N55W. BESIDES FOR THE ACTIVITY ASSOCIATED WITH T.S. KAREN AND THE TROPICAL WAVE OVER THE E ATLC...SCATTERED MODERATE CONVECTION IS FROM 6N-9N BETWEEN 26W-33W. CLUSTERS OF MODERATE CONVECTION ARE OVER SIERRA LEONE AND LIBERIA. DISCUSSION... GULF OF MEXICO... THE MAIN WEATHER FEATURE ACROSS THE GULF OF MEXICO IS TROPICAL DEPRESSION THIRTEEN LOCATED IN THE SW PORTION. A TROPICAL STORM WATCH WILL LIKELY BE REQUIRED FOR A PORTION OF THE GULF COAST OF MEXICO LATER TONIGHT OR EARLY THURSDAY. SEE SPECIAL FEATURES ABOVE. A 1013 MB LOW FORMED THIS MORNING NEAR KEY WEST FLORIDA. THIS SYSTEM HAS REMAINED NEARLY-STATIONARY AND IS ACCOMPANIED BY A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS EXTENDING OVER SOUTH FLORIDA...THE FLORIDA STRAITS AND A PORTION OF THE NORTHWESTERN BAHAMAS. UPPER-LEVEL WINDS ARE MARGINALLY FAVORABLE AND THIS SYSTEM STILL HAS SOME POTENTIAL FOR DEVELOPMENT OVER THE NEXT DAY OR TWO. THE LOW IS EXPECTED TO MOVE SLOWLY TOWARD THE NORTHEAST OVER SOUTH FLORIDA AND THE ADJACENT ATLANTIC OCEAN. THE LOWEST SFC PRES ARE FOUND NEAR KEY WEST AND THE WINDS REMAINS OUT OF THE E AND SE OVER SOUTH FLORIDA. HOWEVER... DOPPLER RADAR IS SHOWING A CYCLONIC CIRCULATION NEAR FORT LAUDERDALE/HOLLYWOOD AREA PROBABLY ASSOCIATED WITH A MID LEVEL LOW. SOME SHOWER/TSTMS ACTIVITY HAS FLARED UP NEAR TAMPA BAY. A DECREASING TREND IN PRECIPITATION IS EXPECTED OVER SOUTH FLORIDA AS THE SFC LOW MOVES TOWARD THE NE TONIGHT AND TOMORROW. ELSEWHERE AT THE SFC...WEAK RIDGING DOMINATES THE NRN GULF WATERS. ALOFT...A RIDGE COVERS THE WESTERN HALF OF THE GULF ANCHORED ON A HIGH OVER NE MEXICO. THE EASTERN HALF OF THE REGION IS UNDER THE INFLUENCE OF AN UPPER-LEVEL TROUGH THAT EXTENDS ACROSS THE FLORIDA PENINSULA/WESTERN CUBA. DIFFLUENT BETWEEN THESE TWO UPPER LEVEL FEATURES IS HELPING TO INDUCE SCATTERED MODERATE CONVECTION OVER THE YUCATAN PENINSULA. CARIBBEAN SEA... A TROPICAL WAVE IS MOVING WWD ACROSS THE EASTERN CARIBBEAN. THE WAVE...COUPLED WITH A DIFFLUENT PATTERN ALOFT IS GENERATING A CLUSTER OF MODERATE TO STRONG CONVECTION OVER HISPANIOLA. SEE TROPICAL WAVE SECTION. OTHERWISE THE BASIN IS FAIRLY TRANQUIL. A DEEP LAYERED TROUGH OVER FLORIDA AND CENTRAL CUBA IS SUPPORTING SCATTERED SHOWERS AND TSTMS OVER EASTERN CUBA. MODERATE CONVECTION IS ALSO SEEN OVER NORTHERN COLOMBIA. TRADES REMAIN LIGHT TO MODERATE ACROSS THE BASIN...BUT WINDS/SEAS COULD BE HIGHER AT TIMES IN AREAS OF SHOWERS AND TSTMS ASSOCIATED WITH THE TROPICAL WAVE. ALOFT...A RIDGE/TROUGH/RIDGE PATTERN REMAINS IN PLACE. ATLANTIC OCEAN... A NEARLY-STATIONARY AREA OF LOW PRESSURE IS LOCATED JUST SOUTH OF KEY WEST FLORIDA AND IS ACCOMPANIED BY A LARGE AREA OF CLOUDINESS AND THUNDERSTORMS EXTENDING OVER SOUTH FLORIDA...THE FLORIDA STRAITS AND A PORTION OF THE NORTHWESTERN BAHAMAS. SEE THE GULF OF MEXICO SECTION FOR MORE DETAILS. UPPER FLOW IS VERY DIFFLUENT OVER THIS AREA BETWEEN THE TROUGH EXTENDING S THROUGH THE FLORIDA PENINSULA AND AN UPPER RIDGE OVER THE WRN ATLC. THE REMAINDER OF THE CENTRAL ATLC IS DOMINATED BY A SFC TROUGH ENTERING THE AREA NEAR 31N37W AND CONTINUING SW TO 23N54W WHERE THERE IS AN AREA OF SCATTRED SHOWERS AND ISOLATED TSTMS. THE TROUGH IS AHEAD OF A COLD FRONT CLIPPING THE AREA ALONG 31N44W 30N60W. MODERATE SFC RIDGING REMAINS ANCHORED OVER THE E ATLC...PRODUCING LIGHT TO MODERATE NE TRADES E OF 35W. A WELL DEFINED UPPER LOW IS JUST E OF THE MADEIRA ISLANDS NEAR 32N15W. THIS APPEARS TO BE GENERATING ISOLATED TO SCATTERED SHOWERS BETWEEN THE MADEIRA/CANARY ISLANDS. $$ GR