000 AXNT20 KNHC 032338 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST TUE JAN 03 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 2330 UTC. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH REMAINS INLAND OVER AFRICA. THE ITCZ EXTENDS WSW FROM THE COAST OF SIERRA LEONE NEAR 8N12W ALONG 5N30W TO THE COAST OF BRAZIL NEAR EQ50W. SCATTERED WEAK TO ISOLATED MODERATE CONVECTION IS WITHIN 100 NM ON EITHER SIDE OF THE AXIS BETWEEN 20W-40W. ...DISCUSSION... GULF OF MEXICO... WATER VAPOR IMAGERY DEPICTS A VERY DRY ATMOSPHERE ACROSS THE GULF THIS EVENING...AS AN UPPER RIDGE APPROACHES THE S CENTRAL CONUS SUPPORTING SURFACE RIDGING OVER THE N GULF STATES. MARINE OBSERVATIONS INDICATE A LIGHT ANTICYCLONIC FLOW N OF 25N... AROUND A 1033 MB HIGH CENTERED OVER THE CENTRAL LOUISIANA COAST NEAR 29N92W. THE LIGHT ANTICYCLONIC FLOW BECOMES NORTHERLY 10-20 KT S OF 25N...HELPING TO MAINTAIN A FAIRLY DEEP LAYER OF COLD AIR ACROSS THE AREA. THIS FLOW IS BANKING UP SOME LOW LEVEL MOISTURE OVER THE FAR SW BASIN...WITH A FEW POSSIBLE ISOLATED SHOWERS WITHIN 75 NM OFF THE COAST OF MEXICO FROM THE CITY OF TAMPICO TO LAGUNA DE TERMINOS. OTHERWISE...THE AIRMASS MOVING OVER RELATIVELY WARMER WATERS IS GENERATING A BROAD AREA OF LOW LEVEL STRATOCUMULUS CLOUDS SEEN ON VISIBLE IMAGERY S OF 27N. MEDIUM RANGE COMPUTER MODELS SUGGEST THE SURFACE RIDGE WILL MOVE TO THE NRN FLORIDA PENINSULA OVER THE NEXT 24-36 HRS MAINTAINING FAIR WEATHER CONDITIONS ACROSS THE AREA AND PROMOTING A WARMING TREND TO THE WRN AND N CENTRAL BASINS. CARIBBEAN SEA... THE COLD FRONT MOVING ACROSS THE WRN N ATLC EXTENDS SW INTO THE NW CARIBBEAN ACROSS THE WINDWARD PASSAGE ALONG 20N74W TO THE ERN COAST OF HONDURAS NEAR 15N84W. WHILE THE FRONT HAS BROUGHT NORTHERLY WINDS 20-30 KT TO THIS REGION...A FAIRLY DRY ATMOSPHERE OVER IT HAS LIMITED THE CONVECTION ASSOCIATED WITH IT...KEEPING MOST OF THE ACTIVITY WITHIN 60 NM ON EITHER SIDE OF THE BOUNDARY S OF 17N. A SIX HOUR LOOP OF VISIBLE IMAGERY INDICATES THE FRONT HAS REDUCED ITS FORWARD MOVEMENT. FURTHERMORE...CURRENT THETA-E FROM MODEL DATA SUGGEST THAT FRONTOLISIS MAY BE OCCURRING OR SOON TO OCCUR WITH THIS BOUNDARY. THESE CONDITIONS SUGGEST THE FRONT WILL CONTINUE TO WEAKEN AND BECOME NEARLY STATIONARY DURING THE NEXT 24 HOURS. OTHERWISE...DRY AIR ALOFT AND STRONG SUBSIDENCE REMAINS ELSEWHERE ACROSS THE BASIN SUPPRESSING DEEP CONVECTION OVER MOST OF THE DISCUSSION AREA. THE ONLY AREA OF WEAK CONVECTION IS NOTICED OVER THE N CENTRAL BASIN N OF 14N BETWEEN 68W-74W. AN EARLIER ASCAT PASS AND SURFACE OBSERVATIONS INDICATED 15-20 KT TRADEWINDS OVER THE ENTIRE CARIBBEAN SEA E OF THE FRONT...WITH THE STRONGEST WINDS REACHING UP TO 25 KT ALONG THE COAST OF COLOMBIA. ATLANTIC OCEAN... AN UPPER LEVEL LONGWAVE/TROUGH MOVES OFF THE SE CONUS SEABOARD SUPPORTING A COLD FRONT THAT ENTERS THE REGION ALONG 32N65W EXTENDING S-SW ACROSS THE SE BAHAMAS ALONG 22N74W AND INTO THE NW CARIBBEAN SEA ALONG THE WINDWARD PASSAGE. THE COMBINATION OF LOW LEVEL CONVERGENCE OF NW AND SOUTHERLY WINDS AND UPPER LEVEL DIFFLUENCE ALONG THE BOUNDARY IS GENERATING SCATTERED HEAVY SHOWERS AND THUNDERSTORMS WITHIN 50 NM ON EITHER SIDE OF IT. THE PRESSURE GRADIENT BETWEEN THE STRONG SURFACE RIDGE OVER THE N CENTRAL GULF OF MEXICO AND THE DEEP LAYER TROUGH IS GENERATING AN AREA OF GALE FORCE WINDS BEHIND THE FRONT N OF 27N TO 80W GENERATING SEAS 14 TO 21 FT IN NW SWELL. AS THE FRONT CONTINUES TO TRACK EASTWARD...THE ACTIVITY IS EXPECTED TO DECREASE BELOW GALE FORCE CRITERIA OVER THE NEXT 18 HRS. OTHERWISE...AN UPPER LEVEL ANTICYCLONE COVERING THE CENTRAL BASIN BETWEEN 40W-60W... AND A STRONG 1034 MB HIGH CENTERED OFF THE COAST OF PORTUGAL NEAR 38N11W ARE DOMINATING THE REMAINDER OF THE DISCUSSION AREA WITH FAIR WEATHER. THE SURFACE RIDGE ALONG WITH LOWER PRESSURES NEAR THE ITCZ CONTINUE TO GENERATE A SOMEWHAT TIGHT SURFACE PRESSURE GRADIENT THAT COVERS A BROAD AREA IN THE S CENTRAL BASIN FROM 10N-22N BETWEEN 30N-55W WITH MOSTLY ENE WINDS AT 20 KT. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ GARCIA