000 AXNT20 KNHC 130209 CCA TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST FRI DEC 12 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 8N13W 4N30W 4N45W 5N54W. A SURFACE TROUGH IS EMBEDDED WITHIN THE ITCZ. ITS AXIS EXTENDS ALONG 55W/56W SOUTH OF 14W. CONVECTION ASSOCIATED WITH THIS FEATURE HAS DIMINISHED SINCE YESTERDAY. A SWIRL OF LOW CLOUDS IS ALONG THE TROUGH AXIS NEAR 10N. ISOLATED MODERATE CONVECTION IS FROM 6N-10N BETWEEN 50W-56W. ELSEWHERE...SCATTERED MODERATE CONVECTION IS WITHIN 100 NM NE OF LINE 5N30W 7N38W 9N42W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS INLAND OVER SW AFRICA FROM 4N-8N BETWEEN THE PRIME MERIDIAN AND 10W. ...DISCUSSION... GULF OF MEXICO... A RELATIVELY COOLER AND DRIER AIRMASS IS PRESENT ACROSS THE GULF REGION IN THE WAKE OF A SURFACE COLD FRONT THAT EXTENDS FROM THE W ATLC INTO THE W CARIBBEAN. THIS AIRMASS IS BEING REINFORCED BY A SECONDARY COLD FRONT THAT LIES ACROSS SOUTH FLORIDA AND THE SE PORTION OF THE GULF TO NEAR 22N88W. THE INCREASED SURFACE PRESSURE GRADIENT IN THE VICINITY OF THIS SECONDARY COLD FRONT IS SUPPORTING NORTHERLY SURFACE WINDS OF 20 TO 25 KT ACROSS PORTIONS OF THE MIDDLE AND E GULF. BROKEN TO OVERCAST STRATOCUMULUS CLOUDS COVER THE SOUTHERN HALF OF THE GULF INCLUDING ALSO THE BAY OF CAMPECHE AND THE YUCATAN PENINSULA DUE TO THE COLD AIR ADVECTION OVER RELATIVELY WARM WATERS. MODERATE TO STRONG SUBSIDENCE IN STRONG WESTERLY AND NORTHWESTERLY FLOW ALOFT IS INHIBITING DEEP CONVECTION ACROSS THE GULF REGION. THIS SUBSIDENCE IS BEING ENHANCED OVER THE W GULF...WHERE A SURFACE RIDGE DOMINATES. THIS RIDGE IS BEING ANCHORED BY A 1028 MB SURFACE HIGH LOCATED OVER THE UPPER TEXAS COAST. ADDITIONALLY... STRONG N TO NE SURFACE WINDS ARE BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS IN THE E PACIFIC REGION. LOOKING AHEAD...THE RETURN FLOW IS EXPECTED TO INCREASE SAT THROUGH LATE SUN AS LOW PRES MOVES THROUGH CENTRAL PLAINS. CARIBBEAN SEA... THE COLD FRONT OVER THE W ATLC ENTERS THE CARIBBEAN SEA THROUGH EASTERN CUBA THEN CONTINUES MAINLY SOUTH AS A STATIONARY FRONT TO COSTA RICA NEAR 10N83W. SCATTERED SHOWERS ARE ALONG AND WITHIN 60 NM EITHER SIDE OF THIS FRONT. BEHIND THE FRONT...A RELATIVELY COOLER AND DRIER AIRMASS HAS INVADED THE NW CARIBBEAN INCLUDING ALSO WEST AND CENTRAL CUBA AND NORTHERN CENTRAL AMERICA WHERE BROKEN TO OVERCAST LOW TO MID CLOUDS WITH EMBEDDED LIGHT SHOWERS ARE NOTED. IN ADDITION...NLY WINDS OF 20 TO 30 KT ARE BLOWING W OF THE FRONT WITH THE STRONGEST WINDS NEAR THE COAST OF NICARAGUA. THE REMAINDER OF THE CARIBBEAN SEA REMAINS UNDER THE INFLUENCE OF A STRONG HIGH PRES SYSTEM...ANALYZED 1040 MB...NEAR THE AZORES. PATCHES OF LOW LEVEL MOISTURE CARRIED BY THE TRADE WINDS CONTINUE TO MOVE WWD AROUND THE PERIPHERY OF THIS SFC HIGH WHICH IS ALSO PRODUCING A WIDE SWATH OF MODERATE TO STRONG ELY WINDS ACROSS THE ATLANTIC OCEAN AND THE E-CENTRAL CARIBBEAN. SATELLITE IMAGERY REVEALS AN AREA OF LOW TOPPED SHOWERS JUST SOUTH OF JAMAICA MOVING W-SW AHEAD OF THE STATIONARY FRONT. ALOFT...A RIDGE EXTENDS FROM N COLOMBIA TO GUATEMALA AND SE MEXICO. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS UPPER RIDGE COMBINED WITH THE TAIL END OF THE ABOVE MENTIONED FRONT AND THE COLOMBIAN LOW IS HELPING TO INDUCE SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE SW CARIBBEAN INCLUDING ALSO COSTA RICA AND PANAMA. ATLANTIC OCEAN... A DEEP LAYERED TROUGH OVER THE EASTERN CONUS SUPPORTS A PAIR OF COLD FRONTS OVER THE W ATLC. THE MAIN ONE ENTERS THE FORECAST AREA NEAR 31N72W THE CONTINUES SW OVER THE CENTRAL BAHAMAS AND EASTERN CUBA WHERE IT BECOMES STATIONARY CONTINUING OVER THE CARIBBEAN SEA. THE SECONDARY FRONT CROSSES THE NW BAHAMAS... SOUTH FLORIDA AND THE SE PORTION OF THE GULF OF MEXICO. MUCH DRIER AND COOLER AIR WILL MOVE OVER SOUTH FLORIDA TONIGHT BEHIND THIS REINFORCING COLD FRONT. A PRE-FRONTAL TROUGH WITH A BAND OF SCATTERED SHOWERS AND ISOLATED TSTMS IS WITHIN AROUND 70 NM E OF THE LEAD FRONT N OF THE BAHAMAS. NWLY WINDS OF 20 TO 30 KT AND COLD AIR STRATOCUMULUS CLOUDS FOLLOW THE FRONTS. THE REMAINDER OF THE DISCUSSION AREA IS UNDER THE INFLUENCE OF A STRONG SFC HIGH PRES SYSTEM FORECAST TO REMAIN STATIONARY DURING THE NEXT 24 HOURS. SUBSIDENCE AROUND THIS 1040 MB SURFACE HIGH CENTERED NEAR THE AZORES IS GENERALLY SUPPORTING FAIR WEATHER CONDITIONS ACROSS MUCH OF THE E-CENTRAL ATLC. HOWEVER...AN UPPER-LEVEL LOW CENTERED NEAR 28N55W IS PRODUCING SCATTERED SHOWERS WITHIN 180 NM NE OF LINE 21N48W 28N57W. THIS SFC HIGH IS ALSO GENERATING A WIDE SWATH OF MODERATE TO STRONG ELY WINDS ACROSS THE OCEAN PARTICULARLY FROM 22N-30N EAST OF 55W. AN UPPER-LEVEL TROUGH EXTENDS SWD FROM THE ABOVE MENTIONED UPPER-LEVEL LOW INTO THE DEEP TROPICS ALONG 55W. A JET-STREAM BRANCH WITH CORE WINDS OF 70-90 KT ROUNDS THE BASE OF THIS TROUGH THEN CONTINUES MAINLY EWD CROSSING N OF THE CAPE VERDE ISLANDS AND ENTERING WEST AFRICA NEAR 20N17W. EARLY NEXT WEEK...COMPUTER MODELS HAVE COME INTO MUCH BETTER AGREEMENT ANTICIPATING THE DEVELOPMENT OF A DEEP LOW PRES SYSTEM OVER THE TROPICAL CENTRAL ATLC. THIS LOW MAY BE ASSOCIATED WITH THE SURFACE TROUGH THAT HAS BEEN NEARLY STATIONARY E OF THE LESSER ANTILLES DURING THE PREVIOUS DAYS. $$ GR