WDPN32 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (VAMCO) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 25W (VAMCO), LOCATED APPROXIMATELY 70 NM NORTH-
NORTHWEST OF DA NANG, VIETNAM, HAS TRACKED NORTHWESTWARD AT
07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE 
IMAGERY (MSI) SHOWS THE SYSTEM HAS SLOWED SLIGHTLY, BUT REMAINS 
ON THE SAME TRACK. THE LOW LEVEL CIRCULATION CENTER (LLCC) IS NOW 
COVERED BY CONVECTION AND CENTRAL DENSE OVERCAST. THE INITIAL 
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE BANDING 
FEATURES IN THE MSI LOOP AND A THE LOW LEVEL CONVECTIVE STRUCTURE 
LOCATED NORTH OF THE SYSTEM CENTER AS DEPICTED IN A 142240Z AMSU 89GHZ
IMAGE. THE INITIAL INTENSITY OF 80KTS IS HEDGED BETWEEN MULTI-AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T4.5/77KTS (PGTW) AND T5.5/102KTS
(RJTD) ALONG WITH AN ADVANCED DVORAK TECHNIQUE (ADT) CURRENT 
INTENSITY ESTIMATE OF T4.3 (72KTS). THE UPPER LEVEL ANALYSIS CONTINUES
TO SHOW FAVORABLE DUAL CHANNEL OUTFLOW AND LOW (05-10KT) VWS; HOWEVER, THE 
SYSTEM IS DRIFTING OVER COOL (24-25 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 NEAR TAU 12. THE SYSTEM WILL CONTINUE 
TO WEAKEN DUE TO THE LOWER SSTS AND OHC VALUES IN THE SOUTH CHINA SEA 
WHILE APPROACHING VIETNAM, DOWN TO 55KTS 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 UKMET DETERMINISTIC TRACK, HOWEVER, 
DRIVES THE SYSTEM NORTHWEST WITH A RETROGRADING RIDGE CREATING A MODEL
TRACK SPREAD OF 294NM BETWEEN ECMWF, AND GFS. BASED ON THE MODEL
GUIDANCE, THE JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE NEAR THE 
MULTI-MODEL CONSENSUS.//
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