000 AXNT20 KNHC 291745 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 PM EST THU NOV 29 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1715 UTC. ...THE ITCZ... THE ITCZ AXIS IS CENTERED ALONG 6N9W 5N21W 5N35W 4N45W 1N51W. THE AXIS IS FAIRLY ACTIVE TODAY WITH SCATTERED MODERATE CONVECTION WITHIN 180 NM N AND 120 NM S OF THE AXIS BETWEEN 14W-43W. DISCUSSION... GULF OF MEXICO... A FEW WEAK SFC FEATURES ARE LOCATED IN THE GULF BUT NONE OF THESE AMOUNT TO MUCH SENSIBLE WEATHER. ONE OF THESE IS A COLD FRONT IN THE FAR NW CORNER ANALYZED FROM SRN LOUISIANA TO EXTREME S TEXAS. THE FRONT IS VERY DRY AND WEAK IN NATURE WITH ONLY THIN BROKEN CLOUDINESS ALONG IT. SLIGHTLY DENSER CLOUDINESS ...WHICH LIKELY CONTAIN ISOLATED SHOWERS...LIES TO THE S OF THE FRONT IN THE NW GULF FROM 25N-29N W OF 91W. SIMILAR CLOUDS ARE WITHIN 60 NM OF THE MEXICAN COAST S OF 25N ASSOCIATED WITH A WEAK COASTAL LOW-LEVEL TROUGH. ANOTHER WEAK LOW-LEVEL TROUGH IS ANALYZED ALONG 84W/85W FROM 25N-29N. VISIBLE IMAGERY SHOWS A SLIGHT TWIST TO THE FAINT CLOUDINESS IN THE AREA WHICH IS CONFIRMED BY THE WEAK CYCLONIC TURNING EVIDENT IN THE SFC OBS. IN THE MID AND UPPER LEVELS...RIDGING DOMINATES THE PATTERN EXTENDING NW FROM THE CARIBBEAN REACHING A CREST NEAR 29N89W. A RETREATING WEDGE OF VERY DRY AIR IS OVER THE FL PENINSULA SOON TO BE REPLACED BY PATCHY HIGH LEVEL CLOUDINESS. CARIBBEAN SEA... MAINLY QUIET CONDITIONS PREVAIL ACROSS THE CARIBBEAN SUPPORTED BY WIDESPREAD DRY STABLE AIR. THE DRIEST AIR IS E OF 80W WHERE THE UPPER FLOW BECOMES INCREASINGLY CONFLUENT TO THE SW OF A BROAD CENTRAL ATLC TROUGH. THERE IS SOME PATCHY CLOUDINESS AND POSSIBLE SCATTERED SHOWERS ACROSS THE FAR SW CARIB S OF 12N W OF 76W...AIDED BY SLY UPPER FLOW ON THE RETURN SIDE OF AN ELONGATED RIDGE WHICH RUNS FROM COLOMBIA THRU THE YUCATAN CHANNEL. TRADE WINDS REMAIN ON THE STRONG SIDE ACROSS THE S PORTION. THE STRONGEST WINDS ARE AROUND 25 KT NEAR THE COLOMBIAN COAST AS NOTED IN A RECENT QSCAT PASS. TYPICAL STREAMS OF QUICK MOVING SHALLOW SCATTERED SHOWERS ARE BEING STEERED BY THE NE TO E LOW-LEVEL FLOW...ESPECIALLY E OF 75W. ATLANTIC OCEAN... A HIGHLY ELONGATED MID TO UPPER RIDGE EXTENDS NE FROM THE CARIBBEAN COVERING MUCH OF THE AREA W OF 70W. ABUNDANT SUBSIDENCE IS EMBEDDED IN THE RIDGE PROVIDING FAIR WEATHER ACROSS THE WRN ATLC. IN THE LOWER LEVELS...SFC HIGH PRES EXTENDING SSW FROM THE MID-LATITUDES DOMINATES THE PATTERN. THE TAIL END OF A WEAK COLD FRONT BARELY CLIPS THE AREA ENDING NEAR 31N63W ONLY PRODUCING BROKEN CLOUDINESS IN ITS VICINITY. A WEAK SFC TROUGH IS OFF THE E COAST OF FLORIDA ALONG 79W/80W FROM 28N-31N. WEAK CONVERGENCE NEAR THE BOUNDARY IS GENERATING NARROW N-S LINES OF SCATTERED SHOWERS WITHIN 60 NM OF THE AXIS AS NOTED IN DOPPLER RADAR. THE MAIN FEATURE IN THE CENTRAL ATLC IS A VERY BROAD MID TO UPPER TROUGH WHICH HAS BEEN NEARLY STATIONARY OVER THE PAST COUPLE OF DAYS. THE ONCE WELL DEFINED CUT OFF EMBEDDED IN THE TROUGH HAS BEGUN TO OPEN UP BUT A SERIES OF SHORTWAVES UPSTREAM WILL LIKELY HELP TO MAINTAIN THE DEPTH OF THE TROUGH OVER THE NEXT DAY OR SO. AN ASSOCIATED WWD MOVING LOW-LEVEL TROUGH IS ANALYZED ALONG 29N48W 21N54W 12N55W. THIS BOUNDARY IS A LITTLE BETTER DEFINED TODAY IN THE SURROUNDING SHIP/BUOY DATA WHICH REVEALS SOME CYCLONIC TURNING IN THE WINDS AND LOWER PRES NEAR THE AXIS. THE COMBINATION OF INSTABILITY ALOFT AND LOW-LEVEL CONVERGENCE IS PRODUCING SCATTERED SHOWERS AND ISOLATED TSTMS MAINLY E OF THE SFC TROUGH FROM 20N-26N BETWEEN 40W-51W. SFC RIDGING EXTENDING SWD FROM A 1030 MB HIGH IN THE AZORES REMAINS WELL IN CONTROL ACROSS THE E ATLC ALLOWING MODERATE TO FRESH TRADES TO BE UNINTERRUPTED. THE MID-UPPER PATTERN HAS BECOME A LITTLE MORE AMPLIFIED THAN THE ZONAL FLOW OVER THE PAST COUPLE OF DAYS DUE TO A RIDGE STRETCHING NWD FROM THE EQUATOR ALONG EQ23W 19N29W 31N34W AND AN ELONGATED TROUGH EXTENDING SW FROM A DEEP LAYERED LOW IN THE SRN MEDITERRANEAN TO ABOUT 29N28W. A SWIFT SW TO W JET BRANCH BETWEEN THESE FEATURES IS ADVECTING PATCHY HIGH LEVEL CLOUDINESS S OF 22N AND AIDING IN THE DEVELOPMENT OF CONVECTION IN THE ITCZ BETWEEN 18W-42W. $$ CANGIALOSI