000 AXNT20 KNHC 151136 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST MON DEC 15 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 8N13W 4N21W 3N40W 4N47W 3N51W. SCATTERED MODERATE TO STRONG CONVECTION IS WITHIN 150 NM N AND 60 NM S OF THE AXIS BETWEEN 20W-39W. SCATTERED MODERATE CONVECTION IS FROM 6N-9N BETWEEN 56W-58W. ...DISCUSSION... GULF OF MEXICO... STRONG WLY MID TO UPPER FLOW LIES OVER THE REGION ON THE N PERIPHERY OF A HIGH CENTERED OVER THE NW CARIBBEAN. THIS FLOW IS SPREADING PACIFIC HIGH LEVEL CLOUDINESS ACROSS THE N HALF OF THE GULF WITH DRIER AIR PRESENT IN LIGHTER FLOW OVER THE S HALF... CLOSER TO THE UPPER HIGH CENTER. IN THE LOWER LEVELS...A STRONG 1039 MB HIGH OVER THE WRN ATLC IS PRODUCING SE TO S 20-25 KT OVER MUCH OF THE AREA. THIS STRONG MOIST LOW-LEVEL FLOW IS PRODUCING PATCHY LOW-LEVEL CLOUDS WITH EMBEDDED SCATTERED SHOWERS OVER THE NRN WATERS. A VERY STRONG COLD FRONT WILL APPROACH THE TEXAS COAST BY MIDDAY BUT IT IS NOT EXPECTED TO MAKE MUCH PROGRESS INTO THE GULF AS IT QUICKLY LOSES ITS UPPER SUPPORT. HOWEVER...AN INCREASE IN SHOWERS AND TSTMS ARE LIKELY OVER THE NW WATERS NEAR THE BOUNDARY LATER TODAY THROUGH TUE. CARIBBEAN SEA... ABUNDANT STABLE AIR ALOFT COVERS THE ENTIRE CARIBBEAN...DRIEST OVER THE CENTRAL AND EASTERN PORTIONS WHERE THE UPPER FLOW IS MOST CONFLUENT BETWEEN AN UPPER RIDGE OVER THE NW WATERS AND AN UPPER TROUGH OVER THE W ATLC. NE TRADE WINDS HAVE INCREASED TO 20-25 KT AS THE STRONG ATLC HIGH HAS BUILT N OF THE AREA. TYPICAL PATCHES OF LOW-LEVEL CLOUDS AND EMBEDDED QUICK MOVING SHOWERS ARE BEING DRIVEN BY THE TRADES...BUT THE LARGE SCALE SUBSIDENT ENVIRONMENT IS KEEPING THE MOISTURE SHALLOW. WINDS MAY LIGHTEN OVER THE E CARIBBEAN TUE AND WED AS A SFC TROUGH MOVES CLOSER TO THE AREA. OTHERWISE...LITTLE SIGNIFICANT CHANGES ARE EXPECTED. ATLANTIC OCEAN... A COMPLEX UPPER TROUGH OVER THE CENTRAL ATLC IS PROVIDING LIMITED SUPPORT FOR A WEAKENING QUASI-STATIONARY FRONT FROM 32N50W TO 24N72W. THE TIGHT PRESSURE GRADIENT BETWEEN THIS FRONT AND A 1039 MB HIGH NEAR 39N62W IS PRODUCING N TO NE GALE FORCE WINDS N OF 28N W OF FRONT TO 60W AND 20-25 KT ELSEWHERE W OF THE FRONT. A SFC TROUGH IS BECOMING A LITTLE BETTER ORGANIZED JUST E OF THE FRONT ALONG 52W N OF 22N. IR IMAGES REVEAL AN INCREASED AREA OF CYCLONIC TURNING IN THE MID-LEVELS WITH ASSOCIATED SCATTERED SHOWERS AND TSTMS N OF 26N BETWEEN 46W-56W. SIMILAR ACTIVITY EXISTS FROM 19N-24N BETWEEN 42W-45W IN AN UPPER DIFFLUENT ZONE. THIS SFC TROUGH WILL LIKELY GAIN VORTICITY FROM THE WEAKENING FRONT AND POSSIBLY DEVELOP INTO A CLOSED LOW TUE...ACCORDING TO MANY OF THE NWP MODELS. MODELS ARE IN GOOD AGREEMENT IN SHOWING A TRACK TOWARD THE SW STEERED BY THE E PERIPHERY OF A BUILDING MID-LEVEL RIDGE. FARTHER E...A SFC TROUGH IS EVIDENT IN SCATTEROMETER AND BUOY DATA ALONG 51W/52W FROM 8N-14N. HOWEVER...MUCH OF THE ASSOCIATED WEATHER IS SHEARED WELL E OF THE TROUGH BY STRONG WLY WINDS. IN FACT...THIS FLOW IS SPREADING WIDESPREAD MOISTURE ACROSS THE TROPICAL E ATLC AND ENHANCING CONVECTION IN THE ITCZ AND N OF THE AXIS FROM 6N-11N BETWEEN 39W-44W. $$ CANGIALOSI