000 AXNT20 KNHC 192339 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST WED DEC 19 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... THE ITCZ IS PRETTY ACTIVE THIS EVENING. IT AXIS IS CENTERED ALONG 7N11W 5N20W 4N30W 2N40W AND INTO SOUTH AMERICA NEAR THE EQUATOR AT 50W. CLUSTERS OF MODERATE TO STRONG CONVECTION ARE WITHIN 180 NM N OF AXIS BETWEEN 26W-45W. SIMILAR CONVECTION IS ALSO FOUND WITHIN 100 NM S OF AXIS BETWEEN 16W-23W. UPPER DIFFLUENCE IS ENHANCING THIS CONVECTIVE ACTIVITY. DISCUSSION... GULF OF MEXICO... HIGH PRES REMAINS IN CONTROL OF THE WEATHER PATTERN ACROSS THE GULF THIS EVENING GIVING THE AREA LIGHT TO MODERATE E TO SE WINDS WITH THE RETURN FLOW BRINGING INCREASED MOISTURE TO THE W GULF. SATELLITE IMAGERY SHOWS PATCHES OF LOW LEVEL CLOUDS WITH EMBEDDED SHOWERS OVER THE NW CORNER OF THE GULF AND NEAR 27N89W. ALOFT...A RIDGE DOMINATES THE ENTIRE REGION. A SUBTROPICAL JETSTREAM WITH CORE WINDS OF NEAR 120 KT IS RIDING ON THE N PERIPHERY OF THIS ANTICYCLONE FROM THE EPAC ACROSS N MEXICO AND THE N GULF WATERS DRAWING UPPER-LEVEL MOISTURE ACROSS THE AREA. THE NEXT COLD FRONT IS FORECAST TO ENTER THE REGION THIS WEEKEND. STRONG WINDS AND HIGH SEAS WILL BUILD IN THE GULF FOLLOWING THE FRONTAL PASSAGE. ACCORDING TO THE COMPUTER MODELS...GALE CONDITIONS ARE CURRENTLY EXPECTED BEHIND THE FRONT OVER THE SW GULF WATERS ON SUNDAY. CARIBBEAN SEA... A SFC TROUGH STRETCHES FROM EASTERN CUBA ACROSS THE CAYMAN ISLANDS TO NORTHERN BELIZE NEAR 18N88W. AN ASCAT PASS FROM AROUND 1500 UTC REVELED NE WINDS UP TO 20 KT BEHIND THE TROUGH. A BATCH OF LOW CLOUDS WITH EMBEDDED SHOWERS REMAINS OVER THE NW CARIBBEAN/GULF OF HONDURAS ASSOCIATED WITH THIS TROUGH. SIMILAR CLOUDINESS WITH SHALLOW CONVECTION COVERS PARTS OF CENTRAL AND EASTERN CUBA. MOISTURE FROM THIS TROUGH WILL CONTINUE TO AFFECT PARTS OF BELIZE...GUATEMALA AND HONDURAS TONIGHT AS IT DRIFTS WWD AND WEAKENS. A NELY FLOW OVER THE CENTRAL AND SW CARIBBEAN IS CARRYING FRAGMENTS OF LOW LEVEL CLOUDS ACROSS NICARAGUA... COSTA RICA AND PANAMA. MOISTURE IS ALSO STREAMING NWD WITH AN UPPER-LEVEL RIDGE FROM SOUTH AMERICA ACROSS THE LESSER ANTILLES INTO THE N TROPICAL ATLANTIC. AN UPPER-LEVEL HIGH CENTERED JUST N OF COLOMBIA IS CREATING STRONG SUBSIDENCE AND DRY STABLE AIR ACROSS MOST OF THE BASIN WITH A SHORT-WAVE TROUGH OVER THE LESSER ANTILLES. SE CARIBBEAN. A FEW SHOWERS ARE SEEN OVER THE ABC ISLANDS NEAR THE BASE OF THIS TROUGH. MODERATE TO FRESH ELY TRADE WINDS WILL CHANGE LITTLE THROUGH SATURDAY. ATLANTIC OCEAN... A 1024 MB SURFACE HIGH IS OVER SOUTHERN GEORGIA AND IS FORECAST TO MOVE EWD ACROSS THE W ATLC. A RIDGE EXTENDS FROM THIS HIGH ACROSS THE GULF OF MEXICO...THE FLORIDA PENINSULA AND THE W ATLC. UPPER-LEVEL MOISTURE IS BEING PUSHED OUT OVER THE W ATLC BY THE SUBTROPICAL JET OVER THE GULF OF MEXICO. FARTHER EAST...A COLD FRONT ENTERS THE REGION NEAR 31N48W AND STRETCHES SW TO 24N70W. AT THIS POINT THE FRONT CONNECTS TO THE SFC TROUGH THAT EXTENDS ACROSS THE BAHAMAS AND CENTRAL CUBA INTO THE CARIBBEAN. A BROKEN BAND OF MAINLY LOW LEVEL CLOUDS WITH ISOLATED SHOWERS IS RELATED TO THE FRONT/TROUGH. THE FRONT CONTINUES TO BE SUPPORTED BY A DEEP LAYERED TROUGH OVER THE W ATLC. THE BASE OF THIS TROUGH REACHES THE CENTRAL BAHAMAS. STRONG SUBSIDENCE IS ALONG THE TROUGH AXIS COVERING THE W ATLC W OF 70W. AN UPPER-LEVEL RIDGE DOMINATES THE CENTRAL ATLC. A DEEP-LAYERED TROUGH IS OVER THE E ATLC WITH THE ATTENDANT COLD FRONT EXTENDING BETWEEN THE CANARY ISLANDS AND THE AFRICAN COAST TO 20N20W WHERE IT TURNS WESTWARD AND STARTS TO DISSIPATE ALONG 17N30W 18N45W 24N50W. A BROKEN BAND OF MAINLY LOW CLOUDS AND ISOLATED SHOWERS IS ASSOCIATED WITH THE FRONT THAT IS NOW APPROACHING THE CAPE VERDE ISLANDS. SATELLITE IMAGERY ALSO SHOWS STRATOCUMULUS CLOUDS MOVING IN BEHIND THE FRONT. UPPER WESTERLY ZONAL FLOW COVERS THE TROPICS WITH A WEAK JETSTREAM BRANCH EXTENDING WEST TO EAST ALONG 15N-16N EAST OF 45W. A BAND OF TRANSVERSE HIGH CLOUDS IS ASSOCIATED WITH THIS FEATURE. $$ GR