000 AXNT20 KNHC 151134 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST TUE DEC 15 2009 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 1030 UTC. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 5N7W 5N22W 6N38W 1N53W. ISOLATED MODERATE CONVECTION IS WITHIN 100 NM N OF THE AXIS BETWEEN 26W-32W...AND WITHIN 30 NM EITHER SIDE OF THE AXIS BETWEEN 38W-41W. ...DISCUSSION... GULF OF MEXICO... AS OF 0900 UTC...A SURFACE TROUGH HUGS THE NW GULF OF MEXICO COASTLINE FROM NEAR BATON ROUGE LOUISIANA CONTINUING PARALLEL TO THE TEXAS COASTLINE TO OFF THE NE MEXICO COAST NEAR 24N97W. A LINE OF STRONG SHOWERS/THUNDERSTORMS IS WITHIN 30 NM OF THE TROUGH AXIS...WITH SCATTERED SHOWERS EXTENDING TO THE NE ACROSS THE SE UNITED STATES. FLASH FLOOD WATCHES AND FLOOD WARNINGS REMAIN IN EFFECT FOR PORTIONS OF THE GULF COAST STATES. THE TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING OVER THE GREAT PLAINS. DIFFLUENT FLOW ALOFT BETWEEN THIS UPPER TROUGH AND AN UPPER LEVEL RIDGE EXTENDING FROM THE CARIBBEAN INTO THE W ATLC IS ENHANCING THE SHOWER ACTIVITY ACROSS THE GULF COAST. THE UPPER LEVEL TROUGH ALSO SUPPORTS A STRONG COLD FRONT CURRENTLY ACROSS TEXAS WHICH IS FORECAST TO REACH THE GULF WATERS LATER TODAY. BESIDES THE MOISTURE ACROSS THE NRN GULF...THE REMAINDER OF THE BASIN IS COVERED BY DRY AIR ALOFT SUPPORTING GENERALLY FAIR WEATHER ACROSS THE BASIN. ISOLATED SHOWERS ARE NOTED ACROSS S FLORIDA AND THE FAR SE GULF S OF 25N E OF 86W DUE TO CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM S OF WEST PALM BEACH TO N OF KEY WEST. EXPECT CONTINUED SHOWER ACTIVITY ACROSS THE N GULF AS THE COLD FRONT CURRENTLY OVER TEXAS MOVES OFF THE COAST LATER TODAY. CARIBBEAN SEA... STRONG ELY TRADEWINDS CONTINUE ACROSS THE CARIBBEAN AS A RESULT OF A STRONG PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE W ATLC AND LOW PRESSURE OVER NRN COLOMBIA. GALE FORCE WINDS TO 35 KT REMAIN NEAR THE COAST OF COLOMBIA AND ARE FORECAST TO PERSIST THROUGH THE AFTERNOON. STRONG SUBSIDENCE IS ACROSS THE BASIN AROUND AN UPPER LEVEL RIDGE CENTERED IN THE N CENTRAL CARIBBEAN NEAR 18N75W PROVIDING GENERALLY FAIR WEATHER ACROSS THE AREA. HOWEVER...ISOLATED LOW-LEVEL SHOWERS EMBEDDED IN THE ELY TRADES ARE MOVING QUICKLY ACROSS PORTIONS OF THE CARIBBEAN CONCENTRATED MOST E OF THE LESSER ANTILLES AND S OF HISPANIOLA. EXPECT THE STRONG PRESSURE GRADIENT ACROSS THE BASIN TO WEAKEN AS A COLD FRONT MOVES ACROSS THE GULF OF MEXICO ALLOWING THE GALE FORCE WINDS TO DIMINISH. ATLANTIC OCEAN... A SHORTWAVE UPPER LEVEL TROUGH OVER THE N CENTRAL ATLC N OF THE DISCUSSION AREA SUPPORTS A COLD FRONT THAT CLIPS THE AREA ALONG 32N55W 31N61W LIFTING N AS A WARM FRONT FROM 31N68W TO THE SOUTH CAROLINA COASTLINE NEAR 33N79W. POSSIBLE ISOLATED SHOWERS ARE S OF THE FRONT FROM 27N-30N BETWEEN 62W-68W. RADAR IMAGERY ALSO INDICATES ISOLATED SHOWERS ARE ALSO OFF THE S FLORIDA COAST BETWEEN THE COASTLINE AND THE BAHAMAS DUE TO SURFACE CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM NW OF FREEPORT BAHAMAS TO S OF WEST PALM BEACH FLORIDA TO N OF KEY WEST. ELSEWHERE ACROSS THE W ATLC...A BROAD SURFACE RIDGE DOMINATES ANCHORED BY A 1021 MB HIGH NEAR 27N64W. THE SURFACE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE EXTENDING FROM THE CARIBBEAN. FARTHER E...A DEEP LAYER UPPER LEVEL TROUGH IS SUPPORTING A COLD FRONT EXTENDING FROM E OF THE AZORES ISLANDS ENTERING THE DISCUSSION AREA NEAR 32N21W ALONG 25N25W 21N34W. A SHEAR LINE CONTINUES FROM THE FRONT ALONG 20N44W 18N54W. ISOLATED SHOWERS ARE POSSIBLE WITHIN 60 NM OF THE FRONT AND SHEAR AXIS. WEAK HIGH PRESSURE IS SE OF THE FRONT ANCHORED BY A 1015 MB HIGH NE OF THE CAPE VERDE ISLANDS NEAR 19N20W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE. $$ WALTON