000 AXNT20 KNHC 141112 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 AM EST THU DEC 14 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1100 UTC. ...THE ITCZ... ITCZ AXIS IS ALONG 7N11W 4N22W 3N39W EQ50W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N AND 180 NM S OF THE AXIS BETWEEN 20W-32W AND WITHIN 240 NM N BETWEEN 32W-40W. ISOLATED MODERATE IS WITHIN 120 NM S OF THE AXIS E OF 20W. ...DISCUSSION... THE GULF OF MEXICO... A SFC TROUGH REMAINS NEARLY STATIONARY IN THE SRN GULF ALONG 86W/87W S OF 26N EXTENDING INTO THE WRN CARIB. RATHER DISTINCT LOW-LEVEL CYCLONIC TURNING IS NOTED IN SFC OBS...SATELLITE IMAGES AND SAT LOW-LEVEL DERIVED WINDS MAKING THE AXIS OF THE TROUGH EASY TO LOCATE. SCATTERED SHOWERS AND TSTMS ARE LOCATED TO THE E OF THE TROUGH AXIS TO 82W. THE ERN HALF OF THIS MOISTURE SWATH IS SHOWING UP ON THE KEY WEST AND TAMPA BAY 88-D'S WHICH DEPICT A FEW MODERATE ECHOES OFFSHORE. HOWEVER MOST OF THEM APPEAR TO BE LOSING SOME STEAM AS THEY HEAD TOWARDS THE COAST. SWIFT UPPER LEVEL WESTERLIES IS SHEARING THIS ACTIVITY AND SPREADING DEBRIS SHOWERS ACROSS SOUTH AND CENTRAL FLORIDA BETWEEN LAKE OKEECHOBEE AND ORLANDO. THE UPPER LEVEL FLOW IS A RATHER UNIFORM W-SWLY ACROSS THE ENTIRE AREA AHEAD OF AN APPROACHING SHORTWAVE TROUGH LOCATED ABOVE TEXAS AND NRN MEXICO. A PLUME OF HIGH LEVEL MOISTURE...ASSOCIATED WITH THE SUBTROPICAL JET ORIGINATING AT THE BASE OF THE TROUGH...IS BEING ADVECTED FROM THE EPAC ACROSS NRN MEXICO AND INTO THE NRN GULF. AS THIS TROUGH APPROACHES IT WILL SPREAD THIS UPPER LEVEL CLOUDINESS EASTWARD AND WILL LIKELY STEER THE SFC TROUGH IN THE SRN GULF NORTHEASTWARD ACROSS FLORIDA ON FRI. ONCE THE TROUGH MOVES OUT WEAK TO MODERATE HIGH PRES WILL BUILD IN. THE CARIBBEAN SEA... THERE ARE TWO WEAK SFC TROUGHS ANALYZED IN THE WRN CARIB. ONE OF THESE IS IN THE NW PART OF THE AREA ALONG 87W N OF 18N EXTENDING INTO THE SRN GULF. MOST OF THE ASSOCIATED SHOWER ACTIVITY IS N OF THE AREA BUT ISOLATED SHOWERS ARE LIKELY OCCURRING ACROSS THE YUCATAN PENINSULA. THE OTHER IS IN THE SW PORTION ANALYZED FROM 9N79W TO 16N83W. WHILE THIS AREA TYPICALLY HAS A CLIMATOLOGICAL VEERING IN THE WINDS OR TROUGH FEATURE...THE LOW-LEVEL TURNING TODAY IS A LITTLE MORE PRONOUNCED THAN USUAL SO IT REMAINS ANALYZED AS A SYNOPTIC WEATHER FEATURE. SOME SFC LIFT NEAR THE WEAK BOUNDARY ALONG WITH WEAK UPPER DIFFLUENCE...BETWEEN AN UPPER HIGH CENTERED OVER NICARAGUA AND STRONGER UPPER LEVEL WLY FLOW IN THE NW CARIB...IS SPARKING SCATTERED SHOWERS AND ISOLATED TSTMS FROM 12N-17N BETWEEN 81W-85W AND FURTHER S CLOSER TO THE ITCZ AXIS S OF 11N BETWEEN 78W-85W. THE REMAINDER OF THE AREA IS QUIET UNDER MODERATE DRY AIR ALOFT AND NW-WLY UPPER LEVEL FLOW. TRADE WINDS ARE MOSTLY IN THE 15-20 KT RANGE AND LITTLE CHANGE IS EXPECTED THRU FRI AS THE SFC RIDGE REMAINS TO THE NE OF THE REGION. SUBTROPICAL ATLANTIC... A RIDGE/TROUGH/RIDGE PATTERN IS ESTABLISHED ACROSS THE SUBTROPICAL ATLC. HIGHLY TILTED STACKED RIDGING EXISTS IN THE WRN ATLC WITH THE MEAN UPPER LEVEL AXIS EXTENDING FROM CUBA NEWARD TO BERMUDA. THE SFC HIGH IS LOCATED WELL TO THE N OF THE AREA. THE PRES GRAD BETWEEN THIS HIGH AND LOW PRES TO THE E IS SETTING UP A REGION OF 20-30 KT WINDS N OF 18N BETWEEN 35W-60W. FOR DETAILS ON THE WINDS AND SEAS REFER TO THE HIGH SEAS FORECAST ...MIAHSFAT2. A WEAK SFC TROUGH IS LOCATED N OF THE MONA PASSAGE ALONG 66W/67W FROM 19N-24N POSSIBLY PRODUCING ISOLATED SHOWERS AND TIGHTENING THE PRES GRAD SLIGHTLY. PLENTY OF DRY STABLE AIR ALOFT EXISTS BETWEEN 35W-70W PROVIDING A STRONG MID-LEVEL CAP WHICH IS KEEPING THE PATCHES OF LOW-LEVEL MOISTURE SHALLOW. A BROAD TROUGH DOMINATES THE CENTRAL ATLC WITH THE UPPER AXIS ALONG 39W. AN ASSOCIATED OLD FRONTAL BOUNDARY EXTENDS FROM A 1011 MB LOW NEAR 33N32W SW TO A NEWLY FORMED 1011 MB LOW NEAR 28N36W CONTINUING TO 17N40W. MULTILAYERED CLOUDS AND EMBEDDED ISOLATED SHOWERS ARE LOCATED MAINLY WITHIN 180 NM E OF THE TROUGH AXIS. THE DEEPEST MOISTURE IS N OF THE AREA WHERE STRONG UPPER LEVEL WINDS ARE PROVIDING MORE SUPPORT FOR UNSETTLED WEATHER. THE E ATLC IS DOMINATED BY AN UPPER RIDGE WITH THE MAIN HIGH CENTER NEAR 29N21W. HOWEVER THIS RIDGE IS BECOMING SQUASHED BETWEEN THE TROUGH IN THE CENTRAL ATLC AND A VERY LARGE CUT OFF IN THE SRN MEDITERRANEAN SEA. TROPICAL ATLANTIC... NEARLY ZONAL UPPER LEVEL FLOW ON THE N SIDE OF A BROAD FLAT RIDGE COVERS MUCH OF THE TROPICAL ATLC. WATER VAPOR IMAGERY INDICATES A FAIR AMOUNT OF MODERATE DRY AIR ALOFT ABOVE THE AREA PROVIDING A FAIRLY STABLE ENVIRONMENT LIMITING CONVECTION TO THE ITCZ. A WEAK SFC TROUGH IS LOCATED ALONG 50W FROM 12N-16N PRODUCING ONLY BROKEN LOW CLOUDS...ISOLATED SHALLOW SHOWERS AND A SLIGHT WIND SHIFT WITHIN 180 NM OF ITS AXIS. $$ CANGIALOSI