000 AXNT20 KNHC 042351 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST WED JAN 04 2012 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 2335 UTC. ...ITCZ/MONSOON TROUGH... MOST OF THE MONSOON TROUGH REMAINS INLAND OVER AFRICA. ONLY A SMALL PORTION OF IT EXTENDS FROM THE COAST OF LIBERIA NEAR 6N11W TO ABOUT 4N17W. THE ITCZ EXTENDS WESTWARD FROM THIS POINT ALONG 3N25W 4N39W TO THE COAST OF BRAZIL NEAR EQ49W. SCATTERED WEAK TO ISOLATED MODERATE CONVECTION IS WITHIN 130 NM ON EITHER SIDE OF THE ITCZ AXIS BETWEEN 25W-45W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY SHOWS WESTERLY FLOW CARRYING DRY AIR AND STRONG SUBSIDENCE ALOFT ACROSS THE GULF THIS EVENING. THIS UPPER LEVEL ENVIRONMENT SUPPORTS A PAIR OF 1028 MB HIGHS NEAR 28N83W AND 26N91W. MARINE OBSERVATIONS INDICATE A LIGHT AND VARIABLE WINDS IN THE VICINITY OF THE SURFACE HIGHS...WHILE ANTICYCLONIC FLOW ELSEWHERE ACROSS THE AREA. THE COOLER AIRMASS MOVING OVER RELATIVELY WARM WATERS IS GENERATING A BROAD AREA OF LOW LEVEL STRATOCUMULUS CLOUDS SW OF A LINE EXTENDING FROM 29N95W TO 24N81W. COMPUTER MODELS ARE IN GOOD AGREEMENT KEEPING RIDGING CONDITIONS ACROSS THE DISCUSSION AREA THROUGH SATURDAY...AS THE NEXT COLD FRONT ENTERS THE NW BASIN ON SUNDAY. CARIBBEAN SEA... THE SRN EXTENSION OF A COLD FRONT MOVING ACROSS THE ATLC EXTENDS SW INTO THE CENTRAL CARIBBEAN AS A SHEAR LINE THROUGH THE MONA PASSAGE ALONG 18N68W TO THE COAST OF PANAMA NEAR 9N82W. AN EARLIER ASCAT PASS INDICATED NORTHERLY WINDS 20-25 KT AND EASTERLY WINDS 10-15 KT CONVERGING ALONG THE SHEAR LINE... GENERATING SCATTERED WEAK SHOWERS WITHIN 90 NM ON EITHER SIDE OF THE LINE. A COOLER AIRMASS REMAINS OVER THE NW CARIBBEAN W OF THE SHEAR LINE WITH LOW LEVEL STRATOCUMULUS ROAMING THIS REGION. A FEW CLUSTERS OF WEAK SCATTERED SHOWERS ARE E OF THE LINE EMBEDDED IN THE EASTERLY FLOW. IN THE UPPER LEVELS...DRY AIR ALOFT AND STRONG SUBSIDENCE REMAINS ELSEWHERE ACROSS THE BASIN. THE SHEAR LINE IS EXPECTED TO CONTINUE TO WEAKEN OVER THE NEXT 24 HRS. ATLANTIC OCEAN... AN UPPER LEVEL LONGWAVE/TROUGH MOVES ACROSS THE N CENTRAL ATLC SUPPORTING A COLD FRONT THAT ENTERS THE REGION ALONG 32N55W EXTENDING S-SW ALONG 25N61 INTO THE CARIBBEAN SEA ALONG THE MONA PASSAGE. THE COMBINATION OF LOW LEVEL CONVERGENCE OF NW AND SOUTHERLY WINDS AND UPPER LEVEL DIFFLUENCE ALONG THE BOUNDARY IS GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WITHIN 100 NM E OF IT N OF 25N. AS THE MAIN UPPER LEVEL SUPPORT FOR THIS FRONT CONTINUES TO QUICKLY MOVE NE INTO THE POLAR REGIONS...COMPUTER MODELS SUGGEST THE FRONT WILL BECOME SLOWER TO NEARLY STATIONARY OVER THE NEXT 24 HRS WITH SOME LIMITED CONVECTION REMAINING ALONG THE BOUNDARY. OTHERWISE...SURFACE RIDGING AROUND A STRONG 1039 MB HIGH CENTERED OFF THE COAST OF PORTUGAL NEAR 41N17W IS KEEPING FAIR WEATHER CONDITIONS ACROSS THE REMAINDER OF THE DISCUSSION AREA THIS EVENING. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA