000 AXNT20 KNHC 282321 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST THU DEC 28 2006 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA... CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA... NORTHEASTERN 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 2315 UTC. ...THE ITCZ... ITCZ IS CENTERED ALONG 9N12W 5N25W 3N40W TO THE EQUATOR AND 49W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 28W-40W. ISOLATED MODERATE IS WITHIN 240 NM N OF THE AXIS W OF 42W. ...DISCUSSION... THE GULF OF MEXICO... THE BIGGEST WEATHER FACTOR THIS EVENING IS THE STRONG SOUTHERLY WINDS IN THE WRN GULF. SFC OBSERVATIONS INDICATE SLY FLOW FROM 25-30 KT ACROSS THE WRN PORTION WHERE A FAIRLY TIGHT PRES GRAD HAS SET UP BETWEEN A LARGE LOW PRES SYSTEM IN THE SW U.S. AND HIGH PRES CENTERED OFF THE MID-ATLANTIC COAST. THE FRONTAL BOUNDARIES... ASSOCIATED WITH THE SIGNIFICANT LOW IN THE SW...REMAIN W OF THE AREA. THE SFC FLOW GRADUALLY RELAXES AND VEERS MORE TO THE E IN THE E GULF...CLOSER TO THE SFC HIGH. PLENTY OF DRY AIR IN THE MID AND UPPER LEVELS EXISTS ABOVE THE AREA KEEPING THE SCATTERED LOW CLOUDS IN THE CENTRAL AND W GULF CAPPED. LOOKING AHEAD...THE TRAILING COLD FRONT...CURRENTLY IN MEXICO...WILL ENTER THE NW PORTION OF THE AREA LATE FRI/EARLY SAT AND TRACK E ACROSS THE N GULF. THIS FRONT WILL ERODE THE RIDGE AND BRING A SWATH OF MOISTURE WITH IT. THE CARIBBEAN SEA... THE TAIL END OF W ATLC FRONTAL BOUNDARY WAS ANALYZED ACROSS ERN CUBA AND JAMAICA WITH A SFC TROUGH EXTENDING S OF JAMAICA TOWARD PANAMA AT 18Z. EVIDENCE OF THIS SFC BOUNDARY IS DIMINISHING AND WILL LIKELY BE REDUCED TO A SFC TROUGH OR EVEN REMOVED FROM THE NEXT ANALYSIS AT 00 UTC. A VERY BROAD MID TO UPPER LEVEL RIDGE STRETCHES ACROSS THE REGION WITH A ROUGH AXIS ALONG 75W. VERY DRY AIR ALOFT LIES E OF 68W WHERE UPPER LEVEL CONFLUENCE IS QUIET STRONG. MODESTLY STABLE CONDITIONS EXISTS W OF 68W WITH ONLY A FEW PATCHES OF DEEP CLOUDINESS IN THE SW CARIB S OF 12N W OF 79W...LIKELY ASSOCIATED WITH THE ITCZ. TRADE WINDS ARE ON THE STRONG SIDE MAINLY IN THE 20 TO 25 KT RANGE ACROSS THE REGION. THESE WINDS WILL LIKELY REMAIN THAT WAY OVER THE NEXT FEW DAYS AS THE PRES GRAD IN THE AREA CHANGES LITTLE. MODELS ALSO SHOW LITTLE CHANGE IN MOISTURE AND THE UPPER LEVEL PATTERN. THE ATLANTIC OCEAN... THE MAIN FEATURE IN THE CENTRAL AND WESTERN ATLC IS THE GRADUALLY WEAKENING COLD FRONT WHICH RUNS ALONG 32N52W 26N65W 24N72W THEN STATIONARY ACROSS THE E BAHAMAS. MOIST SWLY UPPER LEVEL FLOW AND LOW-LEVEL LIFT IS GENERATING A SWATH OF MOISTURE MAINLY WITHIN 300 NM W OF THE FRONT N OF 23N. W OF THE MOISTURE SWATH...SFC HIGH PRES AND PLENTY OF DRY AIR NOTED ON WATER VAPOR IMAGERY IS THE RULE FROM BERMUDA TO FLORIDA. E OF THE FRONT...A VERY LARGE DEEP LAYER RIDGE COVERS THE AREA BETWEEN 20W AND 55W. WIDESPREAD DRY AIR IS ASSOCIATED WITH THIS RIDGE AND COVERS NEARLY THE ENTIRE AREA OUTLINED. A WEAK UPPER LEVEL LOW HAS PINCHED OFF NEAR 16N55W BUT IS CAUSING NO WEATHER DUE TO THE VERY STABLE ENVIRONMENT IN PLACE. THE SFC HIGH IS ANALYZED AT 1026 MB NEAR 29N31W ENHANCING FAIR WEATHER ACROSS MUCH OF THE ATLC. A SHARP TROUGH COVERS THE ERN-MOST ATLC WITH THE UPPER LEVEL AXIS STRETCHING FROM A CYCLONIC CIRCULATION NEAR MOROCCO TO 21N20W EXTENDING WELL SOUTH INTO THE DEEP TROPICS NEAR 15N32W. THE SRN END OF THIS TROUGH IS BREAKING OFF AND WILL LIKELY TRACK NW AS A CUT OFF UPPER LOW OVER THE NEXT FEW DAYS AS ADVERTISED BY GFS. A TROPICAL UPPER LEVEL JET BRANCH ORIGINATES NEAR THE BASE OF THE TROUGH AND RACES NE ALONG 11N32W 19N21W TO WRN AFRICA NEAR 24N12W. UW-CIMSS SATELLITE DERIVED WINDS SHOWS CORE WINDS BETWEEN 100-120 KT OVER W AFRICA. BROKEN TO OVERCAST SKIES AND SCATTERED SHOWERS ARE WITHIN 400 NM SE OF THE JET AXIS WHICH INCLUDES MOST OF THE CAPE VERDE ISLANDS. THIS DIFFLUENT PATTERN IS ALSO ENHANCING CONVECTION IN THE ITCZ BETWEEN 28W AND 40W. $$ CANGIALOSI