000 AXNT20 KNHC 182340 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST TUE DEC 18 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 ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 7N12W 5N25W 2N35W EQUATOR AT 51W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF AXIS BETWEEN 28W-41W. TROPICAL MOISTURE...ENHANCED BY AN AREA OF UPPER DIFFLUENCE IS GENERATING SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER EASTERN VENEZUELA AND THE WINDWARD ISLANDS. DISCUSSION... GULF OF MEXICO... A RIDGE...ANCHORED ON A 1031 MB HIGH LOCATED OVER THE CAROLINAS DOMINATES THE ENTIRE GULF. BROKEN COLD AIR STRATOCUMULUS CLOUDS ARE STILL SEEN OVER THE AREA. LIGHT TO MODERATE E TO SE WINDS ARE BLOWING ACROSS THE GULF. IN THE MID AND UPPER LEVELS... STRONG ZONAL FLOW DOMINATES THE REGION. A SUBTROPICAL JETSTREAM WITH CORE WINDS OF 90-110 KT CROSSES THE N GULF WATERS AND THE U.S. GULF STATES. THESE WINDS ARE TRANSPORTING ABUNDANT UPPER-LEVEL MOISTURE ACROSS THE AREA...PARTICULARLY N OF 25N. LOOKING AHEAD...SFC HIGH PRES WILL CONTINUE TO SHIFT E OVER AND OFFSHORE THE CAROLINAS THROUGH WED. THE NEXT COLD FRONT IS FORECAST TO MOVE IN LATE IN THE WEEK FOLLOWED BY STRONG NLY WINDS AND BUILDING SEAS. CARIBBEAN SEA... BROAD UPPER RIDGE COVERS MOST OF THE BASIN...INCLUDING THE GREATER ANTILLES WITH AN UPPER TROUGH ENTERING THE EASTERN CARIBBEAN BETWEEN GUADELOUPE AND DOMINICA AND CONTINUING TO WESTERN VENEZUELA/NORTHERN COLOMBIA. SWLY WINDS AHEAD OF THIS TROUGH ARE ADVECTING DEEP TROPICAL MOISTURE FROM SOUTH AMERICA INTO THE WINDWARD ISLANDS AND THE N TROPICAL ATLC. MODERATE TO STRONG UPPER LEVEL SUBSIDENCE AND IMPLIED DRY AIRMASS REIGNS OVER MOST OF THE CARIBBEAN EXCEPT W OF A SFC TROUGH THAT EXTENDS FROM EASTERN CUBA ACROSS THE CAYMAN ISLANDS TO NORTHERN HONDURAS. THIS TROUGH...REMNANTS OF THE FRONTAL BOUNDARY THAT BROUGHT THE COLDEST TEMPERATURES OF THE SEASON SO FAR...WILL CONTINUE TO WEAKEN AS IT MOVES WWD ACROSS BELIZE AND THE YUCATAN PENINSULA. MOSTLY OVERCAST LOW CLOUDS WITH MAINLY LIGHT SHOWERS/DRIZZLE ARE W OF THE FRONT AFFECTING N HONDURAS AND PARTS OF BELIZE. PATCHES OF LOW LEVEL CLOUDS WITH EMBEDDED SHOWERS ARE ALSO OVER EASTERN CUBA ALONG THE TROUGH AXIS. SOME LOW LEVEL CONVERGENCE IS PRODUCING SCATTERED SHOWERS ACROSS THE CARIBBEAN PLAINS OF NICARAGUA AND COSTA RICA. SIMILAR CONVECTION IS EXPECTED OVER PANAMA DUE TO THE CLOSE PROXIMITY OF THE EPAC ITCZ. THE REMAINDER OF THE CARIBBEAN IS PRETTY QUIET. FRESH ELY TRADES WILL PERSIST THROUGH THURSDAY. ATLANTIC OCEAN... SURFACE HIGH PRES CENTERED OVER THE CAROLINAS ALSO COVERS PARTS OF THE W ATLC AND THE FLORIDA PENINSULA. THIS SYSTEM WILL MOVE EAST INTO THE ATLANTIC TONIGHT AND WEDNESDAY. AHEAD OF THIS SFC HIGH THERE IS A COLD FRONT THAT ENTERS THE AREA NEAR 31N57W THEN CONTINUES SW TO 24N70W EXTENDING AS A SFC TROUGH ACROSS THE SE BAHAMAS AND E CUBA INTO THE CARIBBEAN SEA. SATELLITE IMAGERY SHOWS A 120 NM WIDE BAND OF MAINLY LOW CLOUDS WITH EMBEDDED SHOWERS ASSOCIATED WITH THE FRONT. BROKEN COLD AIR STRATOCUMULUS CLOUDS ARE FOUND BEHIND THE FRONTAL BOUNDARY. A DEEP LAYERED TROUGH OVER THE W ATLC SUPPORTS THIS FRONT. AN UPPER-LEVEL RIDGE DOMINATES THE CENTRAL ATLC WHILE A STRONG CUT-OFF LOW IS OVER THE E ATLC WITH AN ELONGATED TROUGH EXTENDING SW AND THEN W ALONG 18N-19N...ENTERING THE CARIBBEAN SEA THROUGH THE N LESSER ANTILLES. THE ASSOCIATED COLD FRONT EXTENDS ACROSS THE CANARY ISLANDS THEN CONTINUES MAINLY WWD ALONG 24N20W 21N35W 22N43W AND THEN NW TO NEAR 26N50W. A BAND OF BROKEN LOW CLOUDS DEFINES THE FRONTAL BOUNDARY ON SATELLITE PHOTOS WITH STRATOCUMULUS CLOUDS MOVING IN BEHIND THE FRONT. A WEAKENING 1026 MB HIGH IS BETWEEN THE ABOVE MENTIONED FRONTS NEAR 32N41W DOMINATING THE CENTRAL ATLC. THIS FEATURE IS FORECAST TO MOVE INTO THE DISCUSSION AREA DURING THE NEXT 24 HOURS OR SO. UPPER WESTERLY ZONAL FLOW COVERS THE TROPICS WITH A WEAK JETSTREAM BRANCH EXTENDING WEST TO EAST ALONG 15N-16N...CROSSING THE CAPE VERDE ISLANDS TO OVER AFRICA NEAR 16N15W. $$ GR