000 AXNT20 KNHC 271743 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST THU DEC 27 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 7N12W 3N25W 2N35W EQUATOR AT 49W... INTO NE BRAZIL. WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 80-100 NM EITHER SIDE OF AXIS EAST OF 30W. SIMILAR CONVECTION IS FROM THE EQUATOR TO THE AFRICAN COAST BETWEEN THE PRIME MERIDIAN AND 9W. ...DISCUSSION... THE GULF OF MEXICO... THE COLD FRONT THAT MOVED ACROSS THE GULF 24 HOURS AGO WITH A LINE OF VIGOROUS SHOWERS AND TSTMS HAS WEAKENED...AND A SFC TROUGH WAS ANALYZED ON THE 1200 UTC MAP EXTENDING FROM THE FLORIDA PANHANDLE THROUGH THE CENTRAL GULF TO THE COAST OF MEXICO BETWEEN TUXPAN AND JALAPA. A QUIKSCAT PASS FROM THIS MORNING AND SFC OBSERVATIONS SHOWED CLEARLY THE WINDS SHIFT ASSOCIATED WITH THE TROUGH...REMNANT OF THE FRONTAL BOUNDARY. SELY FLOW OF 10 TO 15 KT IS SEEN AHEAD OF THE TROUGH WITH NELY FLOW UP TO 15 KT BEHIND THE TROUGH AXIS. THESE WINDS WILL RAPIDLY VEER TO THE SE AND SOUTH AHEAD OF THE NEXT STORM SYSTEM CURRENTLY DEVELOPING OVER THE SOUTHERN ROCKIES. THIS LOW WILL MOVE NE THROUGH THE CENTRAL PLAINS WITH A NEW COLD FRONT ENTERING THE NW PORTION OF THE GULF FRIDAY MORNING. THIS FRONTAL SYSTEM IS ALSO FORECAST TO DISSIPATE OVER ERN GULF EARLY SUN. A STRONGER COLD FRONT IS IN STORE FOR NEW YEAR EVE. THIS FRONT IS EXPECTED TO MOVES RAPIDLY OFF THE TEXAS COAST EARLY MON AND EXTEND FROM THE FLORIDA PANHANDLE TO E BAY OF CAMPECHE LATE MON FOLLOWED BY STRONG NLY FLOW AND MUCH COOLER TEMPERATURES. UPPER LEVEL MOISTURE IS BEING TRANSPORTED BY A SUBTROPICAL JETSTREAM FROM THE EPAC ACROSS CENTRAL MEXICO AND THE GULF INTO THE W ATLC. NEARLY ZONAL FLOW DOMINATES THE ENTIRE GULF. THE CARIBBEAN SEA... THE CARIBBEAN REMAINS TYPICALLY TRANQUIL FOR THIS TIME OF YEAR UNDER THE INFLUENCE OF A MID/UPPER-LEVELS RIDGE WHICH IS PRODUCING STRONG SUBSIDENCE. NO AREAS OF ORGANIZED CONVECTION ARE PRESENT. ONLY PATCHES OF LOW LEVEL MOISTURE WITH MAINLY LIGHT SHOWERS DOT THE REGION. SURFACE HIGH PRESSURE BUILDING N OF THE AREA WILL MAINTAIN MODERATE TRADE WINDS ACROSS THE BASIN THROUGH THE UPCOMING WEEKEND. THE GFS COMPUTER MODEL SHOWS ELY WINDS OF UP TO 30 KT JUST OFF THE COLOMBIAN COAST SAT AND SUN. THE ATLANTIC OCEAN... A 1014 MB SURFACE LOW CONTINUES TO MEANDER NEAR 26N38W WITH A TROUGH EXTENDING SW TO 20N45W. SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN 90 NM OF THE TROUGH. HIGH PRESSURE DOMINATES MOST OF THE SUBTROPICAL NORTH ATLANTIC WITH A 1026 MB HIGH CENTERED AT 31N55W. FARTHER TO THE WEST...A WEAKENING FRONTAL BOUNDARY ENTERS THE AREA NEAR 31N70W THEN CONTINUES SW TO THE NW BAHAMAS. A BROKEN BAND OF MAINLY LOW CLOUDS IS ASSOCIATED WITH THE FRONT. THE WEATHER PATTERN ALOFT HAS CHANGED LITTLE SINCE CHRISTMAS EVE. THE AREA CONTINUES TO BE PRIMARILY DOMINATED BY A COUPLE OF FEATURES. THE FIRST ONE IS THE BROAD UPPER RIDGE THAT EXPANDS FROM THE CARIBBEAN SEA INTO THE W ATLC TO BEYOND 31N65W. A SUBTROPICAL JETSTREAM IS RIDING ON THE N PERIPHERY OF THIS ANTICYCLONE. THE SECOND ONE IS THE DEEP LAYERED TROUGH THAT REMAINS STUCK OVER THE CENTRAL ATLC EXTENDING SW FROM A CUT-OFF LOW NEAR 26N38W TO JUST EAST OF THE WINDWARD ISLANDS. AMPLE UPPER LEVEL MOISTURE IS OBSERVED AHEAD OF THE TROUGH AXIS. A JETSTREAM BRANCH LOCATED SE OF THIS TROUGH IS ENHANCING ADDITIONAL WIDESPREAD MODERATE CONVECTION FROM 14N-25N EAST OF 27W. $$ GR