000 AXNT20 KNHC 130005 TWDAT TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 705 PM EST MON DEC 12 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 2345 UTC. ...THE ITCZ... ITCZ AXIS IS ALONG 7N11W 4N30W 3N52W. SCATTERED MODERATE CONVECTION LIES FROM 2N-7N BETWEEN 20W-35W. SIMILAR CLUSTER NOTED OFF NE SOUTH AMERICA NEAR 1N49W. ...DISCUSSION... THE GULF OF MEXICO... A WEAK COLD FRONT IS MOVING THROUGH THE NW GULF BETWEEN SE LOUISIANA AND 24N96W AS OF 2100 UTC. A WIND SHIFT AND DEWPOINT GRADIENT IS NOTED WITH THIS BOUNDARY...THOUGH VERY LITTLE TEMP GRADIENT IS EVIDENT. THIS FRONT IS MUCH TAMER THAN THE LAST SEVERAL HAVE BEEN...WITH NW/N FLOW ONLY TO 10 KT BEHIND THE FRONT. A PREFRONTAL TROUGH IS ANALYZED ALONG 29N89W 25N91W. THIS TROUGH IS MARKED BY A LINE OF SHOWERS WITH EMBEDDED TSTMS WITHIN 50NM OF THE AXIS. ANOTHER SFC TROUGH EXTENDS THROUGH THE NW CARIBBEAN...NE YUCATAN...AND INTO THE SRN MIDDLE GULF WATERS TO 24N88W. THIS TROUGH HAS A SMALL CLUSTER OF MODERATE CONVECTION WITH IT NEAR 23N86W. GFS SUGGESTS A WEAK LOW WILL DEVELOP FROM THIS IN THE SE GULF LATER IN THE WEEK AND EVENTUALLY MOVE ACROSS FLORIDA. TODAYS GUIDANCE IS LESS ROBUST WITH THIS FEATURE THAN IT WAS YESTERDAY IN THE GULF...AND NOW PREFERS TO DEEPEN THE LOW IN THE SW NORTH ATLC. SW TO W UPPER FLOW PERSISTS OVER THE GULF...W OF AN UPPER RIDGE EXTENDING N THROUGH THE BAHAMAS. THE PVA AHEAD OF A SHORTWAVE UPPER TROUGH EXPECTED TO MOVE THROUGH THE GULF FRI EXPECTED TO PROVIDE THE ENERGY FOR THE AFOREMENTIONED SFC LOW PROGGED. THE CARIBBEAN SEA... MAIN FEATURE IN THE CARIBBEAN THIS EVENING IS THE SFC TROUGH IN THE NW PORTION...EXTENDING THROUGH THE NE YUCATAN AND INTO THE GULF. THE LAST FEW GOES 12 VISIBLE PICTURES SHOW CLEAR CYCLONIC TURNING IN THE LOW CLOUD FIELD ABOUT THE TROUGH AXIS. SEE GULF SECTION ABOVE AND MIAMIMATS FOR FORECAST NOTES ON THIS FEATURE. TRADE WINDS OVER THE NW CARIBBEAN ARE SLOWLY DIMINISHING AS THE W ATLC HIGH PRES AREA MOVES E. WINDS OVER THE CENTRAL CARIBBEAN REMAIN ON THE FRESH TO STRONG SIDE DUE TO A SLIGHTLY STRONGER GRADIENT WITH THE HIGH AND LOWER PRESSURE OVER COLOMBIA. NO MAJOR CHANGES ARE EXPECTED OVER THE CARIBBEAN WATERS THROUGH THE END OF THE WEEK WITH THE PRES GRADIENT EXPECTED TO REMAIN QUASI CONSTANT. ALOFT...AN UPPER RIDGE DOMINATES WITH THE AXIS EXTENDING N FROM ITS ORIGIN NEAR 11N77W THROUGH ERN CUBA. THE ATLANTIC OCEAN... AN AMPLIFIED UPPER RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE ATLC WATERS N OF 15N. A SMALL UPPER LOW IS EMBEDDED IN THIS PATTERN NNW OF THE CAPE VERDE ISLANDS NEAR 24N31W. NEARLY ZONAL UPPER FLOW DOMINATES THE DEEP TROPICS S OF 15N. THE SRN PERIPHERY OF SFC HIGH PRESSURE DOMINATES THE SW NORTH ATLC WATERS BEHIND A CENTRAL ATLC COLD FRONT ENTERING THE AREA AT 32N45W TO 22N57W. SCATTERED MODERATE CONVECTION IS AHEAD OF THIS FRONT FROM 25N-30N BETWEEN 40W-45W. A SFC TROUGH IS ANALYZED ALONG 22N43W 12N48W...AND IS MARKED BY A WEAK LOW LEVEL CONFLUENT ZONE WHICH IS PRODUCING MOSTLY LOWER TO MID CLOUDS WITH POSSIBLE ISOLATED SHOWERS WITHIN 90 NM OF THE AXIS. THE REMAINDER OF THE E ATLC SFC PATTERN IS DOMINATED BY THE SRN PORTION OF A 1030 MB HIGH NEAR 36N24W...OR JUST SE OF THE AZORES. A WEAK COLD FRONT MOVES OFF THE GEORGIA/N FLORIDA COAST LATE WED BUT QUICKLY STALLS JUST OFFSHORE THROUGH FRI. AS INDICATED ABOVE...THE GFS IS SHOWING A LESS AGGRESSIVE LOW DEVELOPMENT SCENARIO OVER THE GULF OF MEXICO ALTHOUGH IT STILL SHOWS SPIN-UP OVER THE W ATLC LATE FRI THROUGH SUN. THIS SEEMS A LITTLE OVERDONE WITH THE ENSEMBLE MEAN THE CURRENT PREFERRED SOLUTION. $$ WILLIS