000 AXNT20 KNHC 311136 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST MON DEC 31 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1115 UTC ...SPECIAL FEATURE... A LARGE LOW PRES SYSTEM IS LOCATED ABOUT 850 NM SW OF THE AZORES NEAR 26N36W. A FORTUITOUS REPORT FROM DRIFTING BUOY 62901 AT 00Z REPORTED A PRES OF 1004.6 MB VERY NEAR THE LOW-LEVEL CENTER...ACCORDINGLY THE MIN PRES WAS DROPPED TO 1004 MB. HOWEVER...THE OVERALL CLOUD PATTERN HAS DETERIORATED SINCE THAT TIME SO IT IS POSSIBLE THAT THE PRES MAY HAVE INCREASED SLIGHTLY. EARLIER THIS MORNING...CONVECTION WAS MOST ORGANIZED IN THE NW QUADRANT AND WAS GENERALLY MODERATE IN NATURE...CLOUD TOPS NEAR -60 C...ACROSS THE QUADRANT. THIS CONVECTION HAS NOW ROTATED TO THE SW QUADRANT AND HAS GENERALLY DECREASED IN AERIAL COVERAGE AS MODERATE CONVECTION IS CONFINED FROM 25N-27N BETWEEN 37W-39W. AN ASCAT PASS AROUND 00Z REVEALED A FEW 45 KT WIND VECTORS NEAR THE SWATH EDGE IN THE NW SEMICIRCLE...WHERE THE PRESSURE GRADIENT IS TIGHTEST DUE TO HIGH PRES CENTERED TO THE NW. AT ABOUT THE SAME TIME...A VERY CONVENIENT JASON ALTIMETER PASS CROSSED THE CIRCULATION REPORTING MAX SEAS NEAR 26 FT AND A 300 NM 12 FT SEA RADII N OF THE CENTER. MORE RECENTLY...A QSCAT PASS AROUND 0830Z SHOWED A FEW BELIEVABLE 40 KT WIND VECTORS W OF THE CENTER. AFTER MEANDERING ABOUT FOR THE PAST SEVERAL DAYS THE SYSTEM APPEARS TO BE ON A CONSISTENT SW HEADING AS AN UPPER SHORTWAVE HAS PASSED TO THE NE ALLOWING A BUILDING MID-LEVEL RIDGE TO BE THE MAIN STEERING ELEMENT. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT IN CONTINUING THIS MOTION AS IT WEAKENS TO AN OPEN TROUGH. THIS LOW...OR WHAT EVER IS LEFT OF IT...WILL LIKELY GET PICKED UP AND ABSORBED BY A LARGE UPPER TROUGH AND FRONTAL ZONE LATER THIS WEEK. ...THE ITCZ... THE ITCZ EXTENDS FROM THE LIBERIA COAST NEAR 6N10W ALONG 3N15W 2N23W 3N36W EQ45W. SCATTERED MODERATE CONVECTION IS FROM 2N-4N BETWEEN 46W-49W. A WEAK TROUGH ALONG 43W IS ENHANCING SCATTERED MODERATE CONVECTION WITHIN 180 NM E OF THE AXIS FROM 3N-5N. ...DISCUSSION... GULF OF MEXICO... A LINGERING FRONTAL BOUNDARY IS GRADUALLY WEAKENING AND BEGINNING TO STALL ONCE AGAIN FROM THE BIG BEND AREA OF FLORIDA NEAR 29N83W TO THE BAY OF CAMPECHE AND THEN NWD ALONG THE E SLOPES OF THE SIERRA MADRE MOUNTAINS IN MEXICO ALONG 27N87W 19N94W 22N99W. MOSAIC DOPPLER RADAR REVEALS THINNING WEAK LINES OF SHOWERS AND ISOLATED TSTMS AHEAD OF THE FRONT OVER CENTRAL FLORIDA. BROKEN CLOUDS AND ISOLATED TO SCATTERED SHOWERS ARE ANTICIPATED WITHIN 120 NM W OF THE FRONT. SCATTERED SHOWERS AND TSTMS ARE AHEAD OF THE FRONT MAINLY E OF 89W IN STRONG SWLY FLOW ALOFT. A BIG AIRMASS CHANGE IS ON THE WAY AS A STRONG COLD FRONT MOVES INTO THE NW WATERS MON EVENING AND TRACKS RAPIDLY ACROSS THE AREA...CLEARING THE ENTIRE REGION BY TUE EVENING. NLY GALE FORCE WINDS ARE FORECAST BEHIND THE FRONT USHERING IN POSSIBLY THE COLDEST AIR OF THIS WINTER SEASON FOR SOME PARTS OF THE GULF. CARIBBEAN SEA... TRANQUIL CONDITIONS PREVAIL ACROSS THE CARIB BENEATH AN AMPLIFIED MID TO UPPER HIGH CENTERED JUST S OF HAITI. WIDESPREAD DRY AIR ALOFT IS EVIDENT ON WATER VAPOR IMAGES ESPECIALLY E OF THE HIGH WHERE THE FLOW ALOFT IS CONFLUENT DUE TO THE PRESENCE OF AN ELONGATED TROUGH E OF THE AREA. THIS STABLE AIRMASS IS SUPPRESSING THE DEVELOPMENT OF ORGANIZED DEEP CLOUDINESS. PATCHY MID-HIGH LEVEL CLOUDS ARE STREAMING NWD ON THE W SIDE OF THE HIGH W OF 80W. A FEW SHORT LIVED TSTMS HAVE POPPED UP DURING THE OVERNIGHT HOURS NEAR THE YUCATAN CHANNEL ENHANCED BY STRONG SWLY FLOW ALOFT. TRADE WINDS ARE ON THE STRONG SIDE IN THE S CENTRAL CARIB AND EXPECTED TO REMAIN THAT WAY OVER THE NEXT COUPLE OF DAYS. NLY WINDS ARE ANTICIPATED TO INCREASE TO NEAR GALE FORCE IN THE NW CARIB BEHIND A STRONG COLD FRONT TUE NIGHT AND WED. ATLANTIC OCEAN... BESIDES FOR THE SPECIAL FEATURE DISCUSSED ABOVE...THE ATLC REGION IS VERY QUIET WITH HIGH PRES RIDGING DOMINATING THE SFC PATTERN SUPPORTED BY CENTERS LOCATED N OF THE DISCUSSION AREA. IN THE MID AND UPPER LEVELS...A SPRAWLING AMPLIFIED RIDGE CENTERED IN THE CARIB COVERS THE AREA W OF 55W. SCATTERED CLOUDS AND A FEW SHOWERS ARE OVER FLORIDA AND THE ATLC WATERS W OF 75W ASSOCIATED WITH DIFFLUENCE ALOFT BETWEEN THIS RIDGE AND A TROUGH FARTHER W. LARGE SCALE TROUGHING COVERS A GOOD PORTION OF THE CENTRAL AND E ATLC EXTENDING FROM THE SPECIAL FEATURE SW TO THE LESSER ANTILLES. A SWLY JET...WITH CORE WINDS OF 100 KT OR SO...ORIGINATES JUST E OF THE TROUGH BASE NEAR 12N56W AND EXTENDS NE TO AFRICA THRU 23N16W. UPPER DIFFLUENCE TO THE RIGHT OF THE JET AXIS IS GENERATING AND ADVECTING DENSE MID-HIGH LEVEL CLOUDS AND EMBEDDED SHOWERS WITHIN 480 NM S OF THE AXIS. $$ CANGIALOSI