000 WTPZ44 KNHC 050251 TCDEP4 TROPICAL STORM MARIE DISCUSSION NUMBER 16 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP142008 800 PM PDT SAT OCT 04 2008 MARIE IS SUCCUMBING TO THE EFFECTS OF COLDER WATER AND STABLE ENVIRONMENTAL AIR. MICROWAVE IMAGERY SUGGESTS THAT THE LOW- AND MID-LEVEL CENTERS HAVE BEGUN TO DECOUPLE...AND THE SYSTEM IS MAINTAINING ONLY A SMALL AMOUNT OF DEEP CONVECTION. THE INITIAL INTENSITY IS LOWERED TO 45 KT BASED ON AN AVERAGE OF DVORAK T AND CI NUMBERS FROM TAFB AND SAB...AS WELL AS A 45-KT ADT ESTIMATE FROM UW-CIMSS AT 0000 UTC. DEGENERATING EAST PACIFIC TROPICAL CYCLONES LIKE MARIE TEND TO WEAKEN RATHER QUICKLY ONCE THEY ENCOUNTER A HOSTILE THERMODYNAMIC ENVIRONMENT...SINCE THEY CANNOT MAINTAIN CONVECTIVE ACTIVITY. AS A RESULT...THE OFFICIAL FORECAST WEAKENS MARIE A LITTLE FASTER THAN THE PREVIOUS FORECAST BUT NOT QUITE AS FAST AS THE DVORAK TECHNIQUE WOULD ALLOW SHOULD THE DEEP CONVECTION COMPLETELY DISSIPATE. MARIE IS EXPECTED TO BECOME A REMNANT LOW BY 48 HOURS ALTHOUGH SOME MODELS...SUCH AS THE SHIPS AND FSU SUPERENSEMBLE...DISSIPATE THE SYSTEM BY THEN. THE REMNANT CIRCULATION SHOULD BECOME ABSORBED WITHIN THE INTERTROPICAL CONVERGENCE ZONE BY DAY 5. MARIE HAS BEEN MOVING NORTH ALL DAY BUT MAY BE FINALLY MAKING A SLIGHT NORTH-NORTHWESTWARD TURN AT 335/3. A GENERAL WEST TO WEST-NORTHWEST MOTION IS ANTICIPATED OVER THE NEXT COUPLE OF DAYS AS MARIE'S CIRCULATION IS ADVECTED BY THE LOWER-LEVEL TRADE WIND FLOW. THE NHC TRACK FORECAST LIES CLOSE TO THE MODEL CONSENSUS AND THE ECMWF...WHICH WAS THE ONLY MODEL THAT CORRECTLY ANTICIPATED THE NORTHWARD MOTION THAT HAS OCCURRED DURING THE PAST 24 HOURS. ONCE MARIE BECOMES A REMNANT LOW...MOST OF THE GUIDANCE SHOWS A SHARP SOUTHWARD...AND IN SOME CASES SOUTH-SOUTHEASTWARD TURN...BETWEEN 72-120 HOURS. THE OFFICIAL FORECAST IS NOT AS DRAMATIC...BUT TRENDS TOWARD A WEST-SOUTHWESTWARD MOTION WITH DISSIPATION WITHIN THE ITCZ BY DAY 5. FORECAST POSITIONS AND MAX WINDS INITIAL 05/0300Z 18.9N 122.3W 45 KT 12HR VT 05/1200Z 19.0N 122.6W 40 KT 24HR VT 06/0000Z 19.0N 123.3W 35 KT 36HR VT 06/1200Z 19.0N 124.3W 30 KT 48HR VT 07/0000Z 18.9N 125.4W 25 KT...REMNANT LOW 72HR VT 08/0000Z 18.2N 127.6W 20 KT...REMNANT LOW 96HR VT 09/0000Z 17.5N 129.0W 20 KT...REMNANT LOW 120HR VT 10/0000Z...DISSIPATED $$ FORECASTER BERG/STEWART