Tropical Storm VAMCO Advisory 11月15日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (VAMCO) WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (VAMCO), LOCATED APPROXIMATELY 44 NM EAST-
NORTHEAST OF DA NANG, VIETNAM, HAS TRACKED WEST-NORTHWESTWARD AT
09 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS THE SYSTEM IS CONTINUING TO WEAKEN AS
THE EYEWALL HAS CLOSED, AND THE CONVECTION ON THE WESTERN SIDE OF THE
SYSTEM IS NOW ERODING DUE TO COOLER AIR FROM THE NORTH WHICH IS BEING
DRAWN INTO THE LOWER LEVELS. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE BANDING FEATURES IN THE EIR LOOP AND A THE LOW
LEVEL CONVECTIVE STRUCTURE LOCATED NORTH OF THE SYSTEM CENTER AS
DEPICTED IN A 141823Z ATMS 88.2GHZ IMAGE. THE INITIAL INTENSITY OF
80KTS IS HEDGED BETWEEN MULTI-AGENCY DVORAK CURRENT INTENSITY ESTIMATES
OF T4.5/77KTS (PGTW) AND T5.0/90KTS (RJTD) ALONG WITH AN ADVANCED DVORAK
TECHNIQUE (ADT) CURRENT INTENSITY ESTIMATE OF T4.5 (77KTS). THE UPPER
LEVEL ANALYSIS INDICATES A FAVORABLE DUAL CHANNEL OUTFLOW AND LOW
(05-10KT) VWS; HOWEVER, THE SYSTEM IS DRIFTING OVER COOL (25-26 CELSIUS)
SEA SURFACE TEMPERATURES (SST) AND VERY LOW (<10KJ/CM^2) OCEAN HEAT
CONTENT (OHC) OFFSETTING THE FAVORABLE OUTFLOW AND VWS. THE CYCLONE IS
TRACKING ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE
(STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY VAMCO WILL CONTINUE ON ITS WEST-NORTHWESTWARD TRACK UNDER THE
STR THROUGHOUT THE FORECAST PERIOD AND MAKE LANDFALL OVER CENTRAL
VIETNAM NORTHWEST OF HUE SHORTLY BEFORE TAU 12. THE SYSTEM WILL CONTINUE
TO WEAKEN DUE TO THE LOW SST AND OHC VALUES IN THE SOUTH CHINA SEA
WHILE APPROACHING VIETNAM, DOWN TO 60KTS BY TAU 12. AFTER LANDFALL, THE
RUGGED TERRAIN WILL RAPIDLY ERODE THE SYSTEM DOWN TO 35KTS BY TAU 24
AND DISSIPATE IT BY TAU 36 AFTER IT CROSSES VIETNAM, CENTRAL LAOS, AND
INTO THAILAND. NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT WITH MOST
MODELS LOSING THE VORTEX SHORTLY AFTER LANDFALL. SPECIFICALLY, GFS, NAVGEM
AND THE ECMWF ENSEMBLE MEAN TRACKS BRING THE SYSTEM WEST WITH DISSIPATION
OCCURRING OVER LAOS AND THAILAND. THE ECMWF DETERMINISTIC TRACK, HOWEVER,
DRIVES THE SYSTEM NORTHWEST WITH A RETROGRADING RIDGE. BASED ON THE MODEL
GUIDANCE, THE JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE NEAR THE
MULTI-MODEL CONSENSUS.//
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