000 AXNT20 KNHC 161743 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST SUN NOV 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ... THE ITCZ AXIS IS ANALYZED ALONG 7N10W 5N22W 7N36W 11N49W 10N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 3N-9N BETWEEN 16W-25W. SCATTERED MODERATE CONVECTION IS FROM 3N-5N BETWEEN 26W-37W. SCATTERED MODERATE CONVECTION IS ALSO FROM 7N-11N BETWEEN 43W-49W. ...DISCUSSION... GULF OF MEXICO... A BROAD UPPER LEVEL TROUGH OVER THE EASTERN HALF OF THE CONUS EXTENDS INTO THE GULF...WITH WESTERLY FLOW ALOFT AND DEEP LAYER DRY AIR COVERING MUCH OF THE GULF REGION. ALSO...THE GULF REGION IS IN THE WAKE OF A SURFACE COLD FRONT THAT EXTENDS FROM THE SW ATLC INTO THE NW CARIBBEAN...WITH A MODIFIED CONTINENTAL POLAR AIRMASS IN PLACE ACROSS THE GULF REGION. AS A RESULT... TEMPERATURES ALONG THE N GULF COAST THIS AFTERNOON ARE BELOW SEASONAL AVERAGES. THIS RELATIVELY COOLER AND DRIER AIRMASS IS BEING SUPPORTED BY SURFACE HIGH PRESSURE OVER SE TEXAS...WITH A SURFACE RIDGE EXTENDING INTO THE W GULF. AS THE COOLER AIR IS BEING ADVECTED OVER THE RELATIVELY WARMER GULF WATERS...WEAK LOW LEVEL INSTABILITY IS SUPPORTING STRATOCUMULUS CLOUD DEVELOPMENT ACROSS THE GULF. HOWEVER...SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS HIGHER IN THE ATMOSPHERE ARE INHIBITING DEEP CONVECTION ACROSS THE GULF REGION. ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN STORM FORCE WINDS IN THE E PACIFIC REGION. CARIBBEAN SEA... ACROSS THE NW CARIBBEAN...A COLD FRONT IS MOVING TO THE SOUTHEAST...AND EXTENDS FROM W CUBA NEAR 23N81W TO 21N85W TO 20N88W. HOWEVER...THE MAJORITY OF THE UPPER LEVEL ENERGY THAT HAS BEEN SUPPORTING THIS COLD FRONT IS NOW WELL TO THE NORTH OF THE FRONT. AS A RESULT...THE TEMPERATURE AND DEWPOINT CONTRAST ACROSS THE FRONT IS WEAKENING SOMEWHAT. HOWEVER...LOW LEVEL CONVERGENCE AND MOISTURE ARE SUFFICIENT TO SUPPORT INCREASED CLOUDINESS AND ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE SURFACE COLD FRONT. ALSO...AN UPPER HIGH IS OVER THE W CARIBBEAN AND IS CENTERED NEAR 17N82W...WITH AN UPPER RIDGE AXIS EXTENDING FROM THE UPPER HIGH TO E CUBA NEAR 21N77W TO THE SW ATLC. OVER THE E CARIBBEAN...AN UPPER LEVEL TROUGH IS PRESENT...WHICH EXTENDS FROM NW COLOMBIA NEAR 10N75W TO 16N71W TO THE DOMINICAN REPUBLIC NEAR 19N70W. WEAK INSTABILITY IN THE VICINITY OF THIS UPPER TROUGH...COMBINED WITH GREATER DEEP MOISTURE OVER THE E CARIBBEAN...IS SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS S OF 14N E OF 69W INCLUDING PORTIONS OF THE WINDWARD ISLANDS... WITH ISOLATED SHOWERS AND THUNDERSTORMS ELSEWHERE E OF 79W. THE ACTIVITY IN THE SE CARIBBEAN IS BEING FURTHER ENHANCED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH THAT HAS BEEN ADDED TO THE 16/1200 UTC SURFACE ANALYSIS BASED ON CYCLONIC CURVATURE NOTED IN THE NEARBY SURFACE WIND OBSERVATIONS. THE SURFACE TROUGH EXTENDS FROM 15N66W TO 12N66W TO N VENEZUELA NEAR 9N65W. ATLANTIC OCEAN... A BROAD UPPER TROUGH OVER THE E HALF OF THE CONUS IS AFFECTING THE W ATLC...WHICH IS SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM W CUBA NEAR 23N81W TO THE BAHAMAS NEAR 25N77W TO 32N72W TO NE OF THE DISCUSSION AREA. ISOLATED SHOWERS AND THUNDERSTORMS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE COLD FRONT...WITH THE COVERAGE BEING LIMITED AS THE STRONGEST UPPER LEVEL ENERGY MOVES NORTH OF THE DISCUSSION AREA. IN THE WAKE OF THE COLD FRONT...A MODIFIED CONTINENTAL POLAR AIRMASS IS IN PLACE...WITH TEMPERATURES BELOW SEASONAL AVERAGES ACROSS THE FLORIDA PENINSULA. THIS RELATIVELY COOLER AND DRIER AIRMASS IS BEING REINFORCED BY A SURFACE COLD FRONT THAT EXTENDS FROM THE N FLORIDA PENINSULA NEAR 30N82W TO 31N80W TO 32N79W TO NE OF THE DISCUSSION AREA. FARTHER TO THE E...A SURFACE RIDGE IS N OF 20N BETWEEN 46W-63W...WHICH IS BEING SUPPORTED BY AN UPPER LEVEL RIDGE WITH AN AXIS EXTENDING FROM E CUBA NEAR 21N77W TO 26N66W TO 32N62W TO N OF THE DISCUSSION AREA. TO THE E...A SURFACE TROUGH EXTENDS FROM A 1006 MB SURFACE LOW NEAR 34N32W TO 28N33W TO 23N38W. LOW LEVEL CONVERGENCE NEAR THE SURFACE TROUGH AND SURFACE LOW IS SUPPORTING SCATTERED SHOWERS N OF 26N BETWEEN 27W-34W. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER TROUGH OVER THE CENTRAL ATLC AND AN UPPER RIDGE OVER THE NE ATLC. FARTHER TO THE S...AN UPPER RIDGE IS S OF 16N BETWEEN THE AFRICAN COAST AND 43W. UPPER LEVEL DIVERGENCE IN THE VICINITY OF THIS UPPER RIDGE IS ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ. $$ COHEN