000 AXNT20 KNHC 161147 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST TUE DEC 16 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1115 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 7N12W 5N22W 4N32W 6N47W 5N52W. SCATTERED MODERATE CONVECTION IS WITHIN 60 NM N AND 180 NM S OF THE AXIS BETWEEN 26W-32W. ISOLATED MODERATE CONVECTION IS WITHIN 90 NM OF THE AXIS E OF 22W. ...DISCUSSION... GULF OF MEXICO... A STRONG COLD FRONT IS DRAPED ACROSS THE NW GULF EXTENDING FROM SE LOUISIANA TO 28N94W TO NE MEXICO NEAR 24N98W. NW OF THE FRONT...N TO NE 20-25 KT WINDS ARE ADVECTING MUCH COOLER AND DRIER CONDITIONS ACROSS THE NW GULF REGION...WITH SURFACE TEMPERATURES IN THE 30S F ACROSS MUCH OF SE TEXAS AND EVEN THE 20'S F WELL INLAND. THIS MODIFIED CONTINENTAL POLAR AIRMASS IS BEING ANCHORED BY A 1041 MB SFC HIGH OVER THE CENTRAL PLAINS. THE FRONT HAS BEEN MAKING SLOWER PROGRESS TO THE SE...AND IS FORECAST TO BECOME STATIONARY OVER THE NW GULF LATER TODAY...AS THE SURFACE HIGH TAKES MORE OF AN EASTWARD TRAJECTORY ACROSS THE NE CONUS. IN THE MEANTIME...MODERATE WESTERLY FLOW ALOFT CONTINUES ACROSS THE GULF ADVECTING TROPICAL/SUBTROPICAL MOISTURE FROM THE PACIFIC. HOWEVER...ONLY ISOLATED SHOWERS ARE EMBEDDED IN THIS MOISTURE PLUME. CARIBBEAN SEA... GENERALLY FAIR WEATHER CONDITIONS ARE IN PLACE ACROSS THE ENTIRE CARIBBEAN. A SURFACE RIDGE OVER THE CENTRAL ATLC IS ENHANCING MODERATE TO FRESH TRADE WINDS ACROSS THE REGION...STRONGEST IN THE ATLC PASSAGES AS NOTED IN RECENT SCATTEROMETER PASSES. WIDESPREAD SUBSIDENCE EXISTS IN WESTERLY AND NORTHWESTERLY ALOFT ACROSS THE CARIBBEAN...LIMITING THE DEVELOPMENT OF ANY DEEP CONVECTION. HOWEVER...SCATTERED SHALLOW SHOWERS AND LOW TOPPED TSTMS ARE MOVING THROUGH PUERTO RICO...HISPANIOLA AND MUCH OF THE NE CARIBBEAN ON STRONG NLY LOW-LEVEL FLOW TO THE W OF SFC TROUGHING IN THE SUBTROPICAL CENTRAL ATLC. TYPICAL SHALLOW ISOLATED SHOWERS ARE POSSIBLE ELSEWHERE...ESPECIALLY OVER HONDURAS AND NICARAGUA WHERE THE ATMOSPHERE ALOFT IS SLIGHTLY MORE MOIST IN A DIFFLUENT PATTERN. ATLANTIC OCEAN... THE WESTERN ATLC IS EXPERIENCING MAINLY FAIR WEATHER WITH ONLY SCATTERED HIGH LEVEL CLOUDS STREAMING IN ON NW FLOW AND PATCHY LOW LEVEL CLOUDS AND EMBEDDED SHOWERS DRIVEN BY STRONG ELY FLOW...ESPECIALLY NEAR A SFC TROUGH OFF THE NE FLORIDA COAST. THE PATTERN IS MORE ACTIVE IN THE CENTRAL ATLC AS A 1014 MB SFC LOW HAS TAKEN SHAPE NEAR 29N55W WITH AN ASSOCIATED TROUGH EXTENDING SSW TO 18N59W. A FRONTAL BOUNDARY JUST W OF THE LOW FROM 32N52W TO 25N58W IS SLOWLY RETREATING AND WEAKENING AS THE SFC LOW/TROUGH SHIFTS W. LOW LEVEL CONVERGENCE ASSOCIATED WITH THESE FEATURES COUPLED WITH INSTABILITY AND UPPER DIFFLUENCE ALONG AND E OF AN UPPER TROUGH IS RESULTING IN SCATTERED SHOWERS AND TSTMS N OF 22N BETWEEN 45W-58W. THE TIGHT PRES PATTERN BETWEEN THE LOW...FRONT...AND HIGH PRES OVER THE N CENTRAL ATLC IS PRODUCING GALE FORCE N TO NE WINDS JUST W OF THE FRONT. OVER THE NEXT COUPLE OF DAYS...STRONG UPPER LEVEL DIVERGENCE ASSOCIATED WITH AN UPPER LEVEL JET MAXIMUM NEAR THE BASE OF THE UPPER TROUGH IS FORECAST TO INDUCE SUFFICIENT SURFACE PRESSURE FALLS TO RESULT IN THE DEEPENING OF THE SURFACE LOW AS IT TRACKS SW STEERED BY THE E PERIPHERY OF A MID-LEVEL RIDGE. FARTHER E...A 1030 MB SURFACE HIGH NEAR THE AZORES IS PRODUCING FRESH TO STRONG NE TO E TRADES. STRONG WLY FLOW ALOFT IS SPREADING ABUNDANT HIGH LEVEL MOISTURE ACROSS THE DEEP TROPICS AND ENHANCING ITCZ CONVECTION. $$ COHEN/CANGIALOSI