000 AXNT20 KNHC 231804 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST TUE DEC 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 7N12W 5N20W 4N35W 3N45W EQUATOR AT 53W. SCATTERED MODERATE CONVECTION IS WITHIN 50 NM EITHER SIDE OF THE AXIS BETWEEN 20W-28W. SIMILAR CONVECTION IS N OF 2N TO THE SW COAST OF AFRICA BETWEEN THE PRIME MERIDIAN AND 12W. ...DISCUSSION... GULF OF MEXICO... AS OF 1500 UTC...A 1014 MB SFC LOW IS INLAND OVER TEXAS NEAR 29N96W. A COLD FRONT EXTENDS FROM THE LOW ACROSS THE FAR NW GULF ENTERING NE MEXICO JUST SOUTH OF BROWNSVILLE/MATAMOROS. A WARM FRONT ALSO STRETCHES FROM THE LOW ACROSS THE UPPER TEXAS COAST THEN CONTINUES AS A STATIONARY FRONT ALONG THE LOUISIANA COAST TO NEAR 29N89W. A SECOND STATIONARY FRONT THAT WAS PREVIOUSLY OVER THE GULF REGION HAS DISSIPATED. A SFC RIDGE DOMINATES THE SE CONUS AND MUCH OF THE EASTERN HALF OF THE GULF. TIGHT PRES GRADIENT BETWEEN THE RIDGE AND THE SFC LOW IS PRODUCING MAINLY E TO SE WINDS OF 20 TO 25 KT ACROSS MUCH OF THE AREA. THE LOW PRES WILL CONTINUE TO LIFT N INTO TEXAS AND MERGE WITH A WEAK COLD FRONT THAT IS FORECAST TO MOVE OFF THE COAST OF TEXAS COAST ON WED. BROKEN STRATOCUMULUS LOW CLOUDS WITH ISOLATED SHOWERS COVER A GOOD PORTION OF THE REGION BUT ARE BEGINNING TO PUSH N DUE TO THE RETURN FLOW AROUND THE SURFACE RIDGE. MODERATE/STRONG SUBSIDENCE AND DRY STABLE AIR ARE NOTED ACROSS S FLORIDA AND THE S GULF WATERS MAINLY S OF 25N. WLY FLOW ALOFT IS TRANSPORTING MID/UPPER LEVEL MOISTURE ACROSS THE N GULF WATERS AND N FLORIDA. CARIBBEAN SEA... THE CARIBBEAN REMAINS UNDER THE INFLUENCE OF A BROAD UPPER HIGH CENTERED NEAR THE ABC ISLANDS AND ENCOMPASSES THE ENTIRE BASIN WITH STRONG SUBSIDENCE IN DRY AIR. THIS UPPER LEVEL FEATURE ALSO ENVELOPS CENTRAL AMERICA AND THE N PORTION OF SOUTH AMERICA. HOWEVER...AREAS OF SHALLOW LOW-LEVEL MOISTURE WITH EMBEDDED SHOWERS CONTINUE TO STREAM ACROSS THE CARIBBEAN USHERED IN ON NE-E TRADE WIND FLOW. THESE PATCHES OF MOISTURE ARE MORE CONCENTRATED OVER THE EASTERN CARIBBEAN...JUST WEST OF THE ABC ISLANDS AND OVER THE NW CARIBBEAN. LOOKING AHEAD...STRONG HIGH PRESSURE IS FORECAST TO BUILD N OF AREA WITH INCREASING TRADE WINDS EXPECTED OVER THE TROPICAL ATLC AND MUCH OF THE CARIBBEAN SEA THROUGH THE REST OF THE WEEK. ATLANTIC OCEAN... A DEEP LAYERED TROUGH OVER THE W ATLC N OF 30N SUPPORTS A COLD THAT ENTERS THE FORECAST AREA NEAR 31N56W AND EXTENDS ACROSS THE CENTRAL BAHAMAS TO CENTRAL CUBA NEAR 23N80W. STRONG HIGH PRES... ANALYZED 1040 MB...OVER THE MIDDLE ATLANTIC STATES IS IN THE WAKE OF THE FRONT PRODUCING MODERATE TO STRONG NELY WINDS ACROSS THE W ATLC AND THE NW BAHAMAS JUST BEHIND THE FRONT. COLD AIR ADVECTION OVER THE RELATIVELY WARM OCEAN WATERS IS GENERATING A LARGE AREA OF BROKEN/OVERCAST STRATOCUMULUS LOW CLOUDS BETWEEN THE FRONT AND THE EASTERN SEABOARD. THE HIGH PRES WILL MOVE EWD ACROSS THE W ATLC DURING THE NEXT 24 HOURS. A BROAD UPPER LEVEL RIDGE EXTENDS FROM THE CARIBBEAN WITH AXIS ACROSS THE VIRGIN AND LEEWARD ISLANDS NE TO BEYOND 32N45W. MOSTLY FAIR WEATHER CONDITIONS ARE OBSERVED E OF THE COLD FRONT TO 30W WITH A WEAK SFC RIDGE DOMINATING THE CENTRAL ATLC. A SURFACE TROUGH IS ALSO IN THE CENTRAL ATLC EXTENDING ALONG 49W FROM 16N-26N SUPPORTED BY UPPER LEVEL TROUGHING WHICH EXTENDS FROM A STRONG UPPER-LEVEL LOW LOCATED MIDWAY BETWEEN THE MADEIRA AND THE AZORES ISLANDS TO 20N36W TO 10N53W. UPPER DIFFLUENCE AHEAD OF THIS UPPER TROUGH ALONG WITH AN UPPER RIDGE AMPLIFIED ALONG THE W AFRICAN COAST IS HELPING TO INDUCE CONVECTION ALONG AND NEAR THE ITCZ AXIS. NE TO E WINDS HAVE INCREASED ACROSS THE TROPICS AND WILL CONTINUE THROUGH FRI. $$ GR