000 AXNT20 KNHC 150542 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 105 AM EST FRI DEC 15 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0515 UTC. ...THE ITCZ... ITCZ AXIS IS ALONG 7N11W 4N26W 3N40W EQ50W. SMALL CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 120 NM EITHER SIDE OF THE AXIS E OF 41W. ...DISCUSSION... THE GULF OF MEXICO... A SFC TROUGH REMAINS OVER THE E GULF ALONG 85W FROM 22N-27N DRIFTING E. A FAIRLY EXTENSIVE SHIELD OF SHOWERS AND TSTMS ARE LOCATED TO THE E OF THE TROUGH AXIS ACROSS S FLORIDA...MOSTLY S OF LAKE OKEECHOBEE AS DEPICTED ON DOPPLER RADAR. THE TAIL END OF A STALLED FRONT STRETCHES ACROSS THE FL/GA BORDER. LOW-LEVEL CONVERGENCE NEAR THE FRONT IS PRODUCING SCATTERED SHOWERS AND TSTMS OFF THE NE COAST OF FLA. GFS SHOWS THE SFC TROUGH MERGING WITH THE FRONTAL BOUNDARY AND PUSHING INTO THE ATLC LATER TODAY. THE UPPER LEVEL FLOW IS A RATHER UNIFORM SWLY ACROSS THE GULF JUST E OF A SHORTWAVE TROUGH LOCATED ABOVE E TEXAS AND NRN MEXICO. A PLUME OF HIGH LEVEL MOISTURE...ASSOCIATED WITH THE SUBTROPICAL JET ORIGINATING AT THE BASE OF THE TROUGH...IS ADVECTED A CONSIDERABLE AMOUNT OF CLOUDINESS ACROSS THE CENTRAL AND NRN GULF. BROWNSVILLE DOPPLER RADAR INDICATES SCATTERED SHOWERS AND TSTMS NEAR THE EDGE OF ITS RADAR RANGE IN THE W GULF EMBEDDED IN THIS MOISTURE PLUME. WEAK SFC HIGH PRES IS LOCATED IN THE N GULF KEEPING WINDS RATHER LIGHT. THIS HIGH WILL SLIDE TO THE E AND STRENGTHEN THRU THE WEEKEND AS THE SFC TROUGH/FRONTAL BOUNDARY MOVES OUT OF THE AREA. THE CARIBBEAN SEA... CONDITIONS ACROSS THE CARIBBEAN ARE FAIRLY QUIET THIS MORNING. THE ONLY AREA OF ANY MENTIONABLE CLOUDINESS IS IN THE EXTREME WRN PORTION WHERE MULTILAYERED CLOUDS AND ISOLATED SHOWERS COVER A GOOD PORTION OF CENTRAL AMERICA AND THE CARIBBEAN SEA W OF 85W. THIS CLOUDINESS IS MAINLY CONTRIBUTED TO THE SFC TROUGH IN THE E GULF AND AN AREA OF WEAK UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER LEVEL HIGH OVER NRN COLOMBIA AND ANOTHER IN THE EPAC. THE REMAINDER OF THE CARIBBEAN IS STABLE WITH PLENTY OF DRY AIR ALOFT NOTED ON WATER VAPOR IMAGERY...WITH THE DRIEST AIR OVER THE ERN CARIBBEAN WHERE UPPER LEVEL CONFLUENCE IS STRONGEST. THE TYPICAL LOW-LEVEL CLOUD STREAKS...UNDERNEATH THE MID-LEVEL CAP...EVEN APPEAR RATHER THIN BASED ON SHORTWAVE IR IMAGES. TRADE WINDS ARE MOSTLY IN THE 15-20 KT RANGE AND LITTLE CHANGE OR SOME SLACKING IS EXPECTED THRU SAT AS A WEAKNESS IN THE SUBTROPICAL RIDGE DEVELOPS TO THE N OF THE AREA. THE ATLANTIC OCEAN... THE UPPER LEVEL PATTERN IS MUCH LESS AMPLIFIED THAN IT HAS BEEN THE PAST COUPLE DAYS. IN THE WRN AND CNTRL ATLC...DEBRIS MOISTURE ASSOCIATED WITH A SFC TROUGH AND FRONTAL BOUNDARY IN THE EXTREME W ATLC AND E GULF IS SPREADING TO ABOUT 70W MAINLY N OF 23N. AS THE UPPER LEVEL FLOW DEVELOPS A NLY COMPONENT...ON THE E SIDE OF A SLIGHT RIDGE AXIS ALONG 70W...THE UPPER ATMOSPHERE DRIES OUT CONSIDERABLY. THIS DRY STABLE AIR ALOFT COVERS A LARGE PORTION OF THE REGION BETWEEN 40W-70W. A SMALL UPPER LEVEL LOW APPEARS TO BE FORMING NEAR 20N56W BUT THIS FEATURE IS EMBEDDED IN THE DRY AIR MENTIONED ONLY MOISTENING THE AIR SLIGHTLY. AT THE SFC...A 1031 MB HIGH CENTERED NEAR 28N47W DOMINATES THE REGION HELPING TO PRODUCE MOSTLY FAIR WEATHER BETWEEN 40W-70W. IN THE E ATLC...A 1011 MB SFC LOW IS LOCATED NEAR 29N34W WITH A COLD FRONT DRAPED SWD FROM THE LOW ALONG 25N33W 19N39W. MOISTURE APPEARS MOST ORGANIZED ON THE N SIDE OF THE LOW AND E OF THE COLD FRONT WITHIN 120 NM OF A PRE-FRONTAL TROUGH FROM 31N28N TO 21N33W. THE MOST SIGNIFICANT WEATHER EFFECT IS THE STRONG WINDS AS A TIGHT PRES GRAD HAS SET UP BETWEEN THIS LOW AND THE HIGH TO IT'S NW PRODUCING GALE FORCE WINDS IN THE REGION BETWEEN THE LOW AND 40W N OF 28N. THE REMAINDER OF THE SUBTROPICAL E ATLC IS UNDER A NARROW UPPER RIDGE KEEPING CONDITIONS RATHER TRANQUIL E OF 25W. IN THE TROPICAL ATLC...EXTENSIVE ZONAL FLOW ON THE N SIDE OF VERY BROAD RIDGING IS THE RULE WITH CONVECTION CONFINED TO THE ITCZ. GFS SUGGESTS THAT THE PATTERN MAY BECOME MORE AMPLIFIED IN THE E ATLC OVER THE WEEKEND WITH A LARGE UPPER LOW DEVELOPING NEAR 30N30W. $$ CANGIALOSI