WDPN31 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 01W (VONGFONG) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 01W (VONGFONG), LOCATED APPROXIMATELY 266 NM EAST-
SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-NORTHWESTWARD AT 
04 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE 
IMAGERY SHOWS THE EYE HAS NOW CLOSED AND CONVECTION HAS DIMINISHED 
WITHIN THE EASTERN SEMICIRCLE OF THE SYSTEM, EVIDENT IN THE WARMING 
CLOUD TOPS. TY 01W IS CURRENTLY LOCATED OVER SAMAR ISLAND, 
PHILIPPINES. THE INITIAL INTENSITY IS SET AT 85 KNOTS, HEDGED BELOW 
MULTI-AGENCY DVORAK ESTIMATES RANGING FROM T5.0-T6.0 (90-115 KNOTS) 
FROM RJTD AND RCTP, DUE TO THE DEGRADED STRUCTURE AND FRICTIONAL 
EFFECTS AS IT CONTINUES ITS OVERLAND PASSAGE. THE INITIAL POSITION 
WAS PLACED WITH FAIR CONFIDENCE BASED ON INFRARED IMAGERY AS THE 
SYSTEM BECOMES MORE RAGGED AND LESS DEFINED. DESPITE ITS POSITION 
OVER LAND, THE REMAINING ENVIRONMENTAL PARAMETERS REMAIN FAVORABLE 
WITH ROBUST RADIAL OUTFLOW, NEARBY WARM SSTS AND LOW VERTICAL WIND 
SHEAR (10-15 KNOTS). TY 01W IS BEING STEERED BY A DEEP-LAYER 
SUBTROPICAL RIDGE (STR) POSITIONED NORTHEAST OF LUZON WHICH IS 
EXTENDING WEST TOWARD THE LUZON STRAIT.
3. FORECAST REASONING.
   A. THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE FORECAST 
PHILOSOPHY.
   B. TY 01W IS EXPECTED TO GRADUALLY SHIFT TO A NORTHWEST AND THEN 
NORTHWARD TRACK OVER THE NEXT 12-36 HOURS AS IT ROUNDS THE 
AFOREMENTIONED STR. THE TRACK FOLLOWS ALONGSIDE THE MULTI-MODEL 
CONSENSUS SOLUTION. AFTER TAU 48, TY 01W SHOULD COMPLETE ROUNDING 
THE STR AXIS. A CONTINUOUS WEAKENING TREND IS FORECAST AS TY 01W 
TRAVELS ACROSS THE PHILIPPINES AS FAVORABLE CONDITIONS OFFSET THE 
FRICTIONAL EFFECTS OF THE ISLANDS. A MORE PRONOUNCED WEAKENING TREND 
IS EXPECTED AS THE SYSTEM TRACKS OVER LUZON. CROSS TRACK SPREAD HAS 
BEEN REDUCED TO 80NM AT TAU 48, INCREASING OVERALL CONFIDENCE TO 
GOOD FOR THIS PORTION OF THE FORECAST.
   C. AFTER TAU 72, TY 01W WILL COMPLETE RECURVATURE AND BEGIN A 
NORTHEASTWARD TRACK AFTER ENTERING THE LUZON STRAIT. INCREASING VWS 
(25-30 KNOTS) AS TY 01W NEARS A BAROCLINIC ZONE, ALONG WITH COOLING 
SSTS WILL LEAD TO FURTHER WEAKENING OF THE SYSTEM TO 35 KTS BY TAU 
96. AT TAU 72, INTERACTION WITH STRONG UPPER LEVEL WESTERLY FLOW 
WILL CAUSE THE SYSTEM TO BEGIN EXTRATROPICAL TRANSITION, WITH 
COMPLETE EXTRATROPICAL TRANSITION COMPLETE BY TAU 96 AS IT IS FULLY 
ABSORBED INTO THE BAROCLINIC ZONE. THERE IS SIGNIFICANT ALONG TRACK 
SPREAD OF MODEL SOLUTIONS AFTER TAU 72. THE LARGE SPREAD IN MODEL 
GUIDANCE LENDS HIGH UNCERTAINTY DURING THIS PERIOD AND THUS 
LOW CONFIDENCE IN THIS PORTION OF THE JTWC FORECAST TRACK.//
NNNN