000 AXNT20 KNHC 092259 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST SUN DEC 09 2007 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND THE 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC ...SPECIAL FEATURE... AN AREA OF SHOWERS AND THUNDERSTORMS HAS BECOME BETTER ORGANIZED TODAY ABOUT 550 MILES ENE OF PUERTO RICO AND THE LEEWARD ISLANDS...IN ASSOCIATION WITH A SHARP SURFACE TROUGH EXTENDING FROM 24N55W 17N58W TO 9N57W AND A LARGE UPPER-LEVEL LOW NEAR 20N58W. THE SYSTEM IS ALREADY PRODUCING GALE FORCE WINDS... MAINLY TO THE N AND NE OF THE MAIN AREA OF THUNDERSTORMS. THE SURFACE TROUGH IS MOVING W NEAR 15 KT...AND THIS MOTION IS EXPECTED TO CONTINUE OVER THE NEXT DAY OR TWO. WATER TEMPERATURES REMAIN WARM ENOUGH IN THIS AREA TO SUPPORT TROPICAL CYCLONE FORMATION...AND UPPER-LEVEL WINDS ARE NOT ESPECIALLY PROHIBITIVE FOR DEVELOPMENT. THIS SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL OR SUBTROPICAL STORM DURING THE NEXT 24 HOURS. INTERESTS IN THE N LEEWARD ISLANDS...THE VIRGIN ISLANDS...PUERTO RICO...HISPANIOLA...AND THE E BAHAMAS SHOULD MONITOR THE PROGRESS OF THIS SYSTEM. ...THE ITCZ... ITCZ AXIS IS CENTERED ALONG 8N12W 5N26W 5N41W 2N51W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE 150 NM OF LINE FROM 3N32W TO 7N42W AND IS ASSOCIATED WITH AN UPPER HIGH. DISCUSSION... GULF OF MEXICO... BROAD UPPER RIDGE EXTENDS FROM THE CARIBBEAN THROUGH THE YUCATAN CHANNEL TO OVER LOUISIANA COVERING THE ENTIRE GULF. A SURFACE RIDGE AXIS EXTENDS FROM THE W ATLC ACROSS THE SE US TO S TEXAS COVERING THE ENTIRE GULF. DRY STABLE AIR COVERS THE GULF EXCEPT WITH SOME ISOLATED LOW LEVEL RETURN FLOW SHOWERS IN THE CENTRAL GULF WITHIN 45 NM OF LINE FROM 24N87W TO 27N90W. OTHERWISE SKIES ARE CLEAR THIS EVENING. CARIBBEAN SEA... BROAD UPPER RIDGE COVERS THE W CARIBBEAN W OF 80W ANCHORED BY AN UPPER HIGH INLAND OVER HONDURAS NEAR 15N86W N THROUGH THE YUCATAN CHANNEL INTO THE GULF OF MEXICO. BROAD UPPER TROUGH COVERS THE REMAINDER OF THE CARIBBEAN EXTENDING FROM THE UPPER LOW MENTIONED IN THE SPECIAL FEATURES ABOVE. STRONG NE TO E SURFACE WINDS COVER THE CARIBBEAN DUE TO THE TIGHT PRESSURE GRADIENT INDUCED BY THE STRONG SURFACE RIDGE ACROSS THE ATLC. SCATTERED SHOWERS/WIDELY ISOLATED THUNDERSTORMS OVER THE NE CARIBBEAN N OF 17N E OF 70W INCLUDING PORTIONS OF HISPANIOLA TO OVER THE LEEWARD ISLANDS AND ARE ALSO ASSOCIATED WITH THE SYSTEM IN THE SPECIAL FEATURES. THE REMAINDER OF THE CARIBBEAN REMAINS MOSTLY CLEAR THIS EVENING WITH SOME ISOLATED SHOWERS INLAND AND WITHIN 60 NM ALONG THE COAST OF PANAMA AND COSTA RICA DUE TO THE CLOSE PROXIMITY OF THE ITCZ AXIS IN THE E PACIFIC REGION. ATLANTIC OCEAN... THE MOST SIGNIFICANT FEATURE THIS EVENING IS IN THE SPECIAL FEATURES ABOVE. OTHERWISE...BROAD UPPER RIDGE EXTENDING FROM THE CARIBBEAN OVER THE GULF OF MEXICO COVERS THE FAR W ATLC W OF 75W. UPPER TROUGH EXTENDS INTO THE CENTRAL ATLC N OF 27N FROM 39W-55W WITH THE ASSOCIATED FRONTAL BOUNDARY STILL N OF THE REGION. A CUT-OFF UPPER LOW IS IN THE E ATLC NEAR 29N33W COVERING THE AREA N OF 25N FROM 23W-39W. AN UPPER HIGH IS IN THE TROPICAL ATLC NEAR 4N42W COVERING THE AREA S OF 19N FROM 19W-54W PROVIDING UPPER DIFFLUENCE GENERATING THE ACTIVITY IN THE ITCZ SECTION ABOVE. BROAD SURFACE RIDGE COVERS THE ENTIRE ATLC AND THE GULF OF MEXICO WITH A WEAKNESS ALONG THE SURFACE TROUGH IN THE SPECIAL FEATURES. $$ WALLACE