000 AXNT20 KNHC 221745 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST MON DEC 22 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 1715 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 6N10W 4N20W 5N30W 3N40W 1N52W. A SURFACE TROUGH IS EMBEDDED WITHIN THE ITCZ ALONG 32W FROM 4N-12N. ISOLATED SHOWERS ARE ASSOCIATED WITH THE TROUGH. SCATTERED MODERATE CONVECTION IS FROM THE EQUATOR TO THE ITCZ AXIS BETWEEN 10W-20W. ...DISCUSSION... GULF OF MEXICO... A COLD FRONT EXTENDS FROM THE W ATLC ACROSS SOUTH FLORIDA AND THE KEYS INTO THE SE GULF OF MEXICO CONTINUING W ALONG 23N90W TO INLAND OVER MEXICO JUST N OF VERACRUZ. BROKEN/OVERCAST STRATOCUMULUS LOW CLOUDS WITH ISOLATED SHOWERS ARE N OF THE FRONT TO THE N GULF COAST AND INLAND OVER TEXAS AND NE MEXICO WITH CLEARING SKIES JUST WEST OF THE FLORIDA PENINSULA. IN THE WAKE OF THE FRONT...STRONG N TO NE WINDS WITH DRIER CONDITIONS ARE NOTED. A QSCAT PASS FROM AROUND 1230 UTC SHOWED GALE FORCE WINDS OVER THE WESTERN GULF...PARTICULARLY N OF 22N AND WEST OF 96W. A GALE WARNING IS IN EFFECT FOR THE SW PORTION OF THE GULF. AHEAD OF THE FRONT...A SFC TROUGH IS ANALYZED OVER THE YUCATAN PENINSULA 90W/91W. OVERCAST LOW/MID CLOUDS WITH EMBEDDED SHOWERS COVER THE BAY OF CAMPECHE. VILLAHERMOSA REPORTED HEAVY RAIN AT TIME THIS MORNING. A DEEP LAYERED TROUGH OVER THE EASTERN CONUS AND THE NW GULF SUPPORTS THE AFOREMENTIONED COLD FRONT. SW FLOW AHEAD OF THIS UPPER-LEVEL TROUGH IS TRANSPORTING MID/UPPER LEVEL MOISTURE ACROSS THE N GULF WATERS AND N FLORIDA. BROAD UPPER RIDGE CENTERED OVER THE CARIBBEAN SEA DOMINATES THE REMAINDER OF THE GULF REGION...SUPPORTING STRONG SUBSIDENCE AND DRY STABLE AIR S OF THE FRONTAL BOUNDARY. THE FRONT IS EXPECTED TO CLEAR THE GULF LATER TODAY. A STRONG SURFACE RIDGE WILL CONTINUE TO BUILD IN THE WAKE OF THE FRONT CURRENTLY ANCHORED BY A 1038 MB HIGH OVER THE CENTRAL PLAIN STATES. ADDITIONALLY...STRONG N WINDS ARE BLOWING ACROSS THE ISTHMUS OF TEHUANTEPEC PRODUCING A GAP WIND EVENT ON THE EPAC REGION. STRONG NE WINDS OF 20-25 KT ARE SEEN OVER THE BAY OF CAMPECHE PER A RECENT QSCAT PASS. CARIBBEAN SEA... THE CARIBBEAN SEA REMAINS UNDER THE INFLUENCE OF A BROAD UPPER RIDGE WHICH IS PRODUCING STRONG SUBSIDENCE IN DRY AIR ACROSS THE ENTIRE BASIN. THIS UPPER-LEVEL RIDGE ANCHORED NEAR THE ABC ISLANDS ALSO ENVELOPS CENTRAL AMERICA AND THE NRN PORTION OF SOUTH AMERICA. AS A RESULT...AREAS OF SHALLOW MOISTURE EMBEDDED IN THE TRADE WIND FLOW ARE NOTED OVER THE REGION PRODUCING ISOLATED TO SCATTERED PASSING SHOWERS. THE LARGEST AREA IS BETWEEN JAMAICA AND CABO GRACIAS A DIOS NICARAGUA. SIMILAR CLOUDINESS WITH POSSIBLE ISOLATED SHOWERS ARE OBSERVED ACROSS HONDURAS...BELIZE AND GUATEMALA. THE FRONT IN THE GULF OF MEXICO IS EXPECTED TO ENTER THE CARIBBEAN LATER TODAY THEN BEGIN TO WEAKEN INTO TUE. STRONG HIGH PRES BUILDING N OF AREA WILL MAINTAIN STRONG TRADE WINDS OVER ALL THE TROPICAL N ATLC AND MUCH OF THE CARIBBEAN SEA WED THROUGH FRI. ATLANTIC OCEAN... A COLD FRONT ENTERS THE W ATLC NEAR 31N72W EXTENDING ACROSS SOUTH FLORIDA AND THE KEYS INTO THE GULF OF MEXICO. BROKEN/OVERCAST STRATOCUMULUS LOW CLOUDS WITH ISOLATED SHOWERS ARE BEHIND THE FRONT. A BROAD UPPER LEVEL RIDGE EXTENDS FROM THE CARIBBEAN SEA GENERATING MOSTLY FAIR WEATHER CONDITIONS AHEAD OF THE COLD FRONT. A SURFACE TROUGH REMAINS IN THE CENTRAL ATLC ANALYZED FROM 29N41W TO 18N44W. THIS TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH OVER THE E/CENTRAL ATLC WITH AXIS ENTERING THE AREA NEAR 32N24W THEN CONTINUING SW INTO THE TROPICS TO NEAR THE WINDWARD ISLANDS. UPPER DIFFLUENCE E OF THIS UPPER TROUGH ALONG WITH AN UPPER RIDGE AMPLIFIED OVER THE E ATLC IS ENHANCING CONVECTION ALONG AND SOUTH OF THE ITCZ AXIS E OF 20W. A JET STREAM BRANCH ROUNDS THE BASE OF THIS UPPER TROUGH PRODUCING A WIDE BAND OF TRANSVERSE HIGH CLOUDS ACROSS THE ATLANTIC FROM NEAR THE SOUTHERN WINDWARD ISLANDS ALL THE WAY NE TO JUST SOUTH OF THE CANARY ISLANDS. SFC HIGH PRES CENTERED WELL N OF AREA COVERS THE E ATLC AND WESTERN AFRICA. NE TO E WINDS ARE EXPECTED TO INCREASE ACROSS THE TROPICS LATE MONDAY TO AT LEAST MIDWEEK AS STRONG HIGH PRES BUILDS N OF AREA. THE GFS COMPUTER MODEL SUGGESTS A 1039 MB HIGH LOCATED NEAR 36N65W WEDNESDAY MORNING RESULTING IN A TIGHT PRES GRADIENT ACROSS THE CARIBBEAN SEA THEN SPREADING E OVER THE TROPICAL ATLC THROUGH FRI. $$ GR