000 AXNT20 KNHC 092349 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST TUE DEC 09 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. ...THE ITCZ... THE ITCZ IS CENTERED ALONG 7N13W 7N30W 6N40W 5N51W. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 8N-10N BETWEEN 19W-22W... AND FROM 3N-5N BETWEEN 19W-33W. ...DISCUSSION... GULF OF MEXICO... A MAJOR CHANGE IN THE WEATHER PATTERN IS IN STORE FOR THE GULF REGION...AS A VIGOROUS AND DEEP TROUGH OVER THE CENTRAL PLAINS OF U.S. ADVANCES EASTWARD. THE ATTENDANT COLD FRONT IS FORECAST TO MOVE OFF THE TEXAS COAST LATE TONIGHT. FRESH TO STRONG SOUTHERLY WINDS ARE ALREADY BLOWING ACROSS THE WESTERN GULF AHEAD OF THIS FRONT. AN EARLIER ASCAT PASS SHOWED WINDS OF 20-25 KT. THESE WINDS CONTINUE TO DRAW MOIST AND UNSTABLE AIR ACROSS THE GULF REGION. GALE TO STORM CONDITIONS ARE EXPECTED W OF FRONT TUE NIGHT AND WED AS SURFACE PRESSURE GRADIENT STRENGTHENS. SCATTERED TO NUMEROUS SHOWERS AND TSTMS ARE ASSOCIATED WITH THE FRONTAL BOUNDARY WHICH PRESENTLY CROSSES NORTHERN LOUISIANA AND SE TEXAS. THE PRESENCE OF STRONG VERTICAL WIND SHEAR IS SUPPORTING THE THREAT FOR SEVERE THUNDERSTORMS OVER PORTIONS OF THE SE CONUS AHEAD OF THE FRONT. STRONG HIGH PRES OVER THE ATLC...ANALYZED 1038 MB NEAR 40N60W...EXTENDS A RIDGE OVER THE SE CONUS AND THE EASTERN GULF PRODUCING A FAIRLY DRY AND STABLE WEATHER CONDITIONS. ALOFT...A MAINLY ZONAL WESTERLY FLOW DOMINATES THE ENTIRE REGION WITH A JET STREAM BRANCH WITH CORE WINDS OF 90-110 KT OVER NORTHERN MEXICO AND SE TEXAS. AN UPPER-LEVEL HIGH CENTERED OVER THE GULF OF TEHUANTEPEC EXTENDS A RIDGE ACROSS SE MEXICO INTO THE BAY OF CAMPECHE. CARIBBEAN SEA... STRONG SURFACE HIGH PRES LOCATED NORTH OF THE AREA COMBINED WITH THE COLOMBIAN/PANAMANIAN LOW IS PRODUCING STRONG TRADE WINDS ACROSS THE BASIN. IN FACT...A GALE WARNING IS IN EFFECT FOR PORTIONS OF THE EAST AND CENTRAL CARIBBEAN...PARTICULARLY SOUTH OF 17N BETWEEN 72W AND 76W. UNDER AN E-NE WIND FLOW...PATCHES OF LOW LEVEL MOISTURE ARE MOVING ACROSS THE NE CARIBBEAN PRODUCING INTERVALS OF PASSING SHOWERS AND CLOUDS ACROSS MOST OF THE LEEWARD ISLANDS...THE UK/US VIRGIN ISLANDS AND PUERTO RICO. SIMILAR CLOUDINESS IS SEEN OVER PARTS OF HISPANIOLA AND JAMAICA AS WELL AS OVER NICARAGUA AND HONDURAS. IN THE UPPER LEVELS...A SHORT-WAVE TROUGH IS OVER THE WESTERN CARIBBEAN WHILE A BROAD ANTICYCLONIC FLOW DOMINATES THE REMAINDER OF THE BASIN THANKS TO AN UPPER-LEVEL HIGH SITUATED OVER NE VENEZUELA. MID/UPPER-LEVEL MOISTURE CONTINUES STREAMING ACROSS PANAMA AND COSTA RICA INTO THE SW CARIBBEAN IN SOUTHERLY FLOW ALOFT WEST OF THE UPPER HIGH. SUBSIDENCE AND IMPLIED DRY AIR MASS IS NOTED OVER THE EASTERN CARIBBEAN AND THE TROPICAL N ATLC. LOOKING AHEAD...THE NEXT COLD FRONT IS EXPECTED TO REACH THE YUCATAN CHANNEL AND THE FAR WESTERN CARIBBEAN THU MORNING. ATLANTIC OCEAN... AS PREVIOUSLY MENTIONED...A 1038 MB SURFACE HIGH LOCATED NEAR 40N60W EXTENDS A RIDGE OVER THE SE CONUS AND THE W ATLC. THE STRONG PRES GRADIENT ON THE SW SIDE OF THIS RIDGE IS PRODUCING STRONG EASTERLY FLOW OVER THE SW N ATLC AND THE BAHAMAS. THESE WINDS ARE EXPECTED TO DIMINISH ON WED AS THE HIGH PRES CONTINUES TO MOVE EWD ACROSS THE OPEN OCEAN WATERS. A COLD FRONT IS OVER THE CENTRAL ATLANTIC ENTERING THE DISCUSSION AREA NEAR 31N48W. THE FRONT CONTINUES SW TO 26N57W WHERE IT BECOMES STATIONARY TO 25N69W. SCATTERED SHOWERS ARE ALONG THE FRONT OVER THE FORECAST AREA. S OF THE FRONT...THERE IS A SFC TROUGH THAT LIES ALONG 52W SOUTH OF 14N. THE CLOUD PATTERN IS EXHIBITING SOME CYCLONIC TURNING ALONG THE TROUGH AXIS NEAR 10N. ANOTHER SURFACE RIDGE... ANCHORED ON A HIGH N OF THE AZORES COVERS THE REMAINDER OF THE ATLANTIC OCEAN. IN THE UPPER LEVELS...RIDGING EXTENDS FROM THE CARIBBEAN INTO THE CENTRAL ATLANTIC WITH MOISTURE WRAPPING AROUND THE RIDGE AND INTERACTING WITH THE AFOREMENTIONED FRONTAL SYSTEM. AN UPPER-LEVEL LOW NEAR 23N32W IS GENERATING SCATTERED SHOWERS N OF 20N BETWEEN 20W AND 34W. ZONAL WESTERLY FLOW ALOFT EXISTS ACROSS MUCH OF THE TROPICS. A WIND MAXIMA ASSOCIATED WITH ANOTHER JET STREAM BRANCH STRETCHES FROM THE CAPE VERDE ISLANDS TO OVER NORTHERN AFRICA. LURKING ON THE HORIZON IS A NOTICEABLE INCREASE IN SLY WINDS OVER THE NW PORTION OF THE AREA AHEAD OF THE NEXT COLD FRONT WED AND THU. THESE WINDS WILL LIKELY INCREASE TO GALE FORCE LATER THU. $$ GR