000 AXNT20 KNHC 041800 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST FRI DEC 04 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1700 UTC. ...ITCZ... THE ITCZ AXIS IS CENTERED ALONG 7N11W 5N20W 3N34W 2N54W. ISOLATED MODERATE CONVECTION IS FROM 3N-6N BETWEEN 25W-27W. SCATTERED MODERATE CONVECTION IS FROM 7N-11N BETWEEN 34W-39W. ...DISCUSSION... GULF OF MEXICO... AS OF 1500 UTC...A STATIONARY EXTENDS FROM THE SRN TIP OF THE FLORIDA PENINSULA NEAR 25N81W ALONG 25N85W TO THE YUCATAN PENINSULA NEAR 21N89W. RADAR IMAGERY INDICATES ISOLATED SHOWERS/THUNDERSTORMS WITHIN 75 NM OF THE FRONT AXIS...WITH SCATTERED SHOWERS/THUNDERSTORMS FARTHER N AFFECTING CENTRAL FLORIDA FROM 26N-28N E OF 84W. THE FRONTAL SYSTEM IS SUPPORTED BY AN UPPER LEVEL TROUGH DIGGING ACROSS THE CENTRAL CONUS INTO TEXAS AND NRN MEXICO. DIFFLUENT FLOW ALOFT BETWEEN THIS UPPER TROUGH AND AN UPPER LEVEL RIDGE EXTENDING FROM THE CARIBBEAN INTO THE W ATLC IS SUPPORTING THE SHOWER ACTIVITY NEAR THE FRONT...AS WELL AS SCATTERED SHOWERS/THUNDERSTORMS ACROSS N FLORIDA AND THE NE GULF WATERS FROM N OF 28N W OF 26W. A SURFACE TROUGH IS ANALYZED IN THE NW GULF...THE BEGINNINGS OF A LOW PRESSURE AREA EXPECTED TO FORM LATER THIS AFTERNOON. THE AXIS EXTENDS FROM 29N94W ALONG 26N95W TO 23N94W. GALE FORCE WINDS ARE EXPECTED TO DEVELOP ACROSS THE NW GULF AS A STRONG PRESSURE GRADIENT CONTINUES BUILDING BETWEEN THE LOW PRESSURE FORMING OVER WATER AND STRONG HIGH PRESSURE TO THE NW OVER NRN TEXAS. WINDS UP TO 30 KT ARE ALREADY BEING REPORTED OFF THE S TEXAS COAST. RADAR IMAGERY INDICATES CONTINUED SHOWER ACTIVITY OVER THE NW GULF N OF 24N W OF 92W...TURNING TO SNOW NEAR THE TEXAS/LOUISIANA COASTLINE. EXPECT CONTINUED SHOWER ACTIVITY ACROSS THE MAJORITY OF THE GULF OVER THE NEXT 24 HRS AS THE STATIONARY FRONT REMAINS IN PLACE OVER THE SE GULF...AND LOW PRESSURE FORMS OVER THE W GULF AND QUICKLY PUSHES E THEN NE. ALSO EXPECT GALE FORCE WINDS TO DEVELOP OVER THE NEXT FEW HRS IN THE NW GULF. CARIBBEAN SEA... THE MAJORITY OF THE CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER TODAY UNDER THE INFLUENCE OF DRY AIR AND STRONG SUBSIDENCE ACROSS THE BASIN NOTED IN WATER VAPOR IMAGERY. UPPER LEVEL ANTI-CYCLONIC FLOW DOMINATES THE AREA AROUND AN UPPER LEVEL RIDGE EXTENDING FROM COSTA RICA ACROSS THE WINDWARD PASSAGE INTO THE W ATLC. A NARROW UPPER LEVEL TROUGH ACCOMPANIED BY STRONG SUBSIDENCE EXTENDS FROM THE CENTRAL ATLC ACROSS THE LESSER ANTILLES TO NRN COLOMBIA. FRESH TO STRONG TRADEWINDS ARE ACROSS MUCH OF THE BASIN WITH THE STRONGEST WINDS NEAR THE COAST OF COLOMBIA. EXPECT LITTLE CHANGE ACROSS THE MAJORITY OF THE AREA WITH POSSIBLE SHOWERS FORMING ACROSS THE NW GULF AS A STATIONARY FRONT CURRENTLY OVER THE SE GULF GETS A SWD PUSH INTO THE NW CARIBBEAN WATERS. ATLANTIC OCEAN... A STATIONARY FRONT EXTENDS ACROSS THE SW ATLC ENTERING THE DISCUSSION AREA NEAR 31N74W CONTINUING ALONG 28N78W CLIPPING THE NW BAHAMAS TO THE SRN TIP OF THE FLORIDA PENINSULA NEAR 25N81W. SCATTERED SHOWERS/THUNDERSTORMS ARE WITHIN 50 NM NE OF THE FRONT BETWEEN 75W-80W. ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE ELSEWHERE BETWEEN THE FRONT AND THE UNITED STATES COASTLINE...AND WITHIN 50 NM AHEAD OF THE FRONT. A LONGWAVE UPPER LEVEL TROUGH COVERING THE CENTRAL AND ERN CONUS SUPPORTS THE FRONT. DIFFLUENT FLOW ALOFT BETWEEN THIS UPPER TROUGH AND AN UPPER LEVEL RIDGE EXTENDING FROM THE CARIBBEAN ACROSS THE WINDWARD PASSAGE INTO THE W ATLC IS SUPPORTING THE SHOWER ACTIVITY ALONG AND BEHIND THE FRONT. THE UPPER LEVEL RIDGE ALSO SUPPORTS A SURFACE RIDGE COVERING THE REMAINDER OF THE W ATLC ANCHORED BY A 1028 MB HIGH NEAR 34N45W. A PAIR OF SURFACE TROUGHS PROTRUDE INTO THE SURFACE RIDGE IN THE CENTRAL ATLC. THE FIRST...EXTENDING FROM 28N41W TO 22N45W...IS A SURFACE REFLECTION OF AN UPPER LEVEL LOW NEAR 22N43W. ISOLATED SHOWERS ARE E OF THE TROUGH AXIS FROM 22N-26N BETWEEN 39W-44W. THE SECOND IS THE TAIL END OF A STATIONARY FRONT EXTENDING FROM 31N42W TO 27N48W. NO SHOWERS ACCOMPANY THIS TROUGH. THE REMAINDER OF THE E ATLC IS DOMINATED BY A BROAD SURFACE RIDGE ANCHORED BY A 1028 MB HIGH BETWEEN THE AZORES ISLANDS AND THE CANARY ISLANDS NEAR 35N18W. A STRONG UPPER LEVEL WLY JET ACROSS THE TROPICAL ATLC IS SHEARING MOISTURE AND HIGH CLOUDS FROM THE CENTRAL ITCZ TO THE ENE. $$ WALTON