000 AXNT20 KNHC 310004 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST FRI DEC 30 2011 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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2315 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 05N10W TO 05N14W....WHERE IT TRANSITIONS TO THE INTERTROPICAL CONVERGENCE ZONE...CONTINUING ON TO 05N20W TO 03N26W TO 03N39W TO THE BRAZILIAN COAST ALONG THE EQUATOR NEAR 50W. SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS OCCURRING WITHIN 180 NM N AND 90 NM S OF AXIS E OF 22W AND BETWEEN 27W AND 44W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY INDICATES WEST-SOUTHWESTERLY UPPER LEVEL FLOW OVER MOST OF THE GULF THIS EVENING AS DOWNSTREAM RIDGING PREVAILS ACROSS NORTHERN S AMERICA AND THE EASTERN TWO-THIRDS OF THE CARIBBEAN. AN UPPER LEVEL SHORTWAVE TROUGH HAS BEGUN TO SWEEP SEWD OFF THE UPPER TEXAS COAST...EXTENDING FROM AN UPPER CYCLONE APPROACHING SRN LAKE MICHIGAN...SSW ALONG THE MISSISSIPPI RIVER BASIN TO SE TEXAS NEAR 28N97W AND CONTINUING WSW ACROSS NRN MEXICO TO NEAR 26N107W. THE PARENT TROUGH AND CYCLONE WILL CONTINUE E AND SHARPEN DURING THE NEXT 24-36 HOURS...DRAGGING A WEAK MID TO UPPER LEVEL TROUGH EWD ACROSS N PORTIONS OF THE GULF ALONG ABOUT 28N. A WEAK CONVERGENCE ZONE AHEAD OF THE TROUGH WAS MOVING E-NE ACROSS PORTIONS OF THE SE U.S. AND NRN FLORIDA AND WILL YIELD WEAK AND SHALLOW CONVECTION ACROSS THE FAR NE GULF AND NRN FLORIDA OVERNIGHT. A WRN EXTENSION OF THE ATLC SURFACE RIDGE EXTENDED WWD ACROSS THE GULF...ANCHORED ON A 1020 MB HIGH CENTERED NEAR THE SW FLORIDA COAST NEAR 27N82W...EXTENDING W TO THE SE TEXAS COAST. THIS WEAK RIDGE WILL REMAIN IN PLACE THROUGH LATE SATURDAY. THE NEXT COLD FRONT IS EXPECTED TO ENTER THE NW GULF WATERS SUNDAY MORNING AND SINK S-SE ACROSS THE BASIN...AND INTRODUCE FRESH TO STRONG NORTH TO NORTHEAST WINDS BASIN-WIDE THROUGH TUESDAY. BRIEF AND MINIMAL GALES ARE SUGGESTED BY GLOBAL MODELS ALONG THE LOWER MEXICAN COAST OF THE WRN BAY OF CAMPECHE MONDAY AFTERNOON-EVENING. CARIBBEAN SEA... A BROAD TROUGH-RIDGE-TROUGH UPPER PATTERN SPANS FROM THE TROPICAL EPAC ACROSS THE CARIBBEAN TO THE TROPICAL E ATLC. A BROAD UPPER LEVEL RIDGE IS ACROSS THE CARIBBEAN...WITH MEAN AXIS ALONG 62W-63W...WITH WATER VAPOR IMAGERY SUGGESTING UPPER CONVERGENCE AND SUBSIDENCE EXTENDING BETWEEN THE TROPICAL NORTH ATLC FROM BEYOND 50W TO CENTRAL AMERICA AND SOUTHERN MEXICO ALONG 96W. WITH A STABLE ATMOSPHERE ALOFT...THE BASIN REMAINS TRANQUIL CONVECTIVELY. HOWEVER...AT THE SURFACE...A MODEST PRESSURE GRADIENT BETWEEN THE ATLC AND GULF OF MEXICO RIDGE AND LOWER PRESSURE OVER NORTHERN SOUTH AMERICA IS PRODUCING STRONG E-NE TRADES IN THE RANGE OF 20 TO 30 KT...WITH HIGHEST WINDS OFF THE CLIMATOLOGICALLY PREVALENT COLOMBIAN COAST. THESE CONDITIONS ARE EXPECTED TO PERSIST THROUGH EARLY MONDAY OF NEXT WEEK AS A COLD FRONT AND FRONTAL TROUGH ENTER THE SW NORTH ATLC... RELAXING THE PRESSURE GRADIENT. ATLANTIC OCEAN... UPPER LEVEL WESTERLIES PREVAIL ACROSS MOST OF THE SW N ATLC W OF 56W...WHILE WATER VAPOR IMAGERY SHOWS A MIDDLE TO UPPER LEVEL SHORTWAVE TROUGH PROGRESSING NE OF THE DISCUSSION AREA OVER THE W ATLC WITH AXIS FROM NEAR BERMUDA SW TO NEAR 27N72W...AND SUPPORTING A DYING STATIONARY FRONT FROM 31N66W TO THE CENTRAL BAHAMAS NEAR 24N76W. SYNOPTIC LIFT AHEAD OF THE SHORTWAVE IS PRODUCING SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN 150 NM SE OF FRONT. WEAK LOW TO MID LEVEL TROUGHING SE OF THE FRONT ALONG ABOUT 66W/67W WAS PROMOTING SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE OPEN WATERS BETWEEN 22N AND 27W. TO THE NW OF THE FRONT...A 1022 MB HIGH EARLIER TODAY HAS COLLAPSED WHILE GENERALLY LIGHT ANTICYCLONIC FLOW PERSISTS NW OF THE FRONT. AS THE UPPER SUPPORT LIFTS NE DURING THE NEXT 24 HOURS...THE FRONT WILL DRIFT NW AND DISSIPATE...WHILE THE GFS SHOWS A NEW CONVERGENCE BOUNDARY DEVELOPING SAT FROM NEAR BERMUDA TO THE SE BAHAMAS NEAR 23N75W...WITH SCATTERED MODERATE CONVECTION EXPECTED ALONG AND SE OF THE NEW BOUNDARY. THE REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE OF AN EXPANSIVE AND RELATIVELY STRONG 1039 MB HIGH CENTERED EAST OF THE AZORES NEAR 38N20W. THE INFLUENCE OF THE RIDGE EXPANDS SOUTHWARD TO 10N AND SW FROM THE HIGH TO 29N66W. WITH SUCH A STRONG HIGH PRESSURE SYSTEM IN PLACE...A STRONG PRESSURE GRADIENT EXISTS WITH GENERALLY MODERATE TO STRONG E-NE TRADES PREVAILING E OF 60W. EARLY MORNING ASCAT PASSES FROM METEO-FRANCE METAREA II HIGH SEAS FORECASTS INDICATING POSSIBLE INTERMEDIATE GALE FORCE NE WINDS IN THE AREAS OF CAPE VERDE... CAP BLANC...AND CAP TIMIRIS LOCATED OFF THE W AFRICAN COAST FROM 15N-25N E OF 22W. ALOFT E OF 56W...A VIGOROUS MIDDLE TO UPPER LEVEL CYCLONE WAS CUT OFF FROM THE MEAN FLOW...CENTERED NEAR 17N40W WITH TROUGH EXTENDING SW TO NEAR 06N44W. STRONG LOW LEVEL FLOW INDUCED BY THE PRESSURE GRADIENT COUPLED WITH MID LEVEL SWLY FLOW OCCURRING E THROUGH SE OF THIS CYCLONE CONTINUES TO YIELD WIDESPREAD CONVECTION N OF THE ITCZ TO NEAR 14N ACROSS THE ERN ATLC BETWEEN 40W AND THE W AFRICAN COAST ALONG 11N. THE CYCLONE WILL SLOWLY WEAKEN AND BECOME ELONGATED OVER THE NEXT FEW DAYS...WHILE THE REGION TO ITS SE REMAINS ACTIVE CONVECTIVELY. LOOK FOR THE FRESH TO STRONG TRADEWINDS TO PERSIST ACROSS THE TROPICAL ATLC THROUGH SUN BEFORE THE GRADIENT BEGINS TO WEAKEN LATE SUN INTO MON. 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