Tropical Storm VONGFONG Advisory czw., 14.05.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (VONGFONG) WARNING
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 01W (VONGFONG), LOCATED APPROXIMATELY 339 NM
EAST-SOUTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD
AT 09 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTI-SPECTRAL VISIBLE
SATELLITE IMAGERY INDICATES THE INTENSIFICATION TREND HAS STALLED,
WITH THE EYE BECOMING MORE RAGGED AND INTERMITTENTLY PARTIALLY
FILLING. VONGFONG HAS CONTINUED TO TRACK ALMOST DUE WEST, WITH
LANDFALL OVER EASTERN SAMAR EXPECTED WITHIN THE NEXT FEW HOURS. A
TUTT CELL OVER THE SOUTH CHINA SEA (SCS) MAY BE HELPING TO AMPLIFY
RIDGING TO THE NORTH MORE THAN PREVIOUSLY EXPECTED, RESULTING IN THE
CONTINUED WESTWARD MOTION. A 132101Z SSMIS PASS REVEALED A LARGE
SWATH OF DEEP CONVECTION AROUND THE NORTHERN SEMI-CIRCLE, WHILE THE
CORE CONVECTION ALONG THE SOUTHERN SIDE OF THE MICROWAVE EYE WAS
DEGRADED. A SMAP PARTIAL PASS HELPED ESTABLISH THE 34 KNOT WIND
RADII ALONG THE EASTERN SEMI-CIRCLE. THE INITIAL INTENSITY WAS
LOWERED SLIGHTLY TO 95 KNOTS, IN AGREEMENT WITH ADT AND CONSISTENT
WITH DVORAK CURRENT INTENSITY ESTIMATES OF T5.0 FROM PGTW AND RJTD.
THE INITIAL POSITION WAS PLACED WITH HIGH CONFIDENCE BASED ON EYE
FIXES FROM MULTIPLE AGENCIES. THE ENVIRONMENT REMAINS FAVORABLE WITH
ROBUST RADIAL OUTFLOW AND WARM SSTS PARTIALLY OFFSETTING MID-LEVEL
DRY AIR. TY VONGFONG IS BEING STEERED BY A DEEP-LAYER SUBTROPICAL
RIDGE POSITIONED TO THE EAST NEAR GUAM WHICH IS EXTENDING WEST
TOWARD THE LUZON STRAIT.
3. FORECAST REASONING.
   A. THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE GENERAL TRACK
FORECAST PHILOSOPHY, HOWEVER, DUE TO A WESTWARD SHIFT IN TRACK OVER
LAND THE INTENSITY FORECAST HAS BEEN LOWERED SIGNIFICANTLY.
ADDITIONALLY, THE TAU 96 AND 120 FORECAST POSITIONS HAVE BEEN MOVED
BACK SLIGHTLY DUE TO THE TRACK SHIFT.
   B. TY VONGFONG IS EXPECTED TO GRADUALLY SHIFT TO A WEST-NORTHWEST
AND THEN NORTHWESTWARD TRACK OVER THE NEXT 24-36 HOURS AS THE TUTT
CELL OVER THE SCS WEAKENS AND MOVES SOUTH, ALLOWING THE EXTENSION OF
THE STEERING RIDGE TO RECEDE BACK TO THE EAST. AS A RESULT OF THE
ADDITIONAL WESTWARD MOTION OVER THE PAST SIX HOURS, THE TRACK HAS
BEEN SHIFTED WESTWARD TOWARDS THE MULTI-MODEL CONSENSUS SOLUTION.
AFTER TAU 36, TY 01W SHOULD BEGIN TO ROUND THE RIDGE AND TURN MORE
NORTHWARD. LITTLE ADDITIONAL INTENSIFICATION IS EXPECTED IN THE FEW
HOURS PRIOR TO LANDFALL. A SLOW WEAKENING TREND IS FORECAST AS
VONGFONG TRAVELS OVER THE MARITIME CONTINENT AS FAVORABLE CONDITIONS
OFFSET FRICTIONAL EFFECTS OF THE ISLANDS. A MORE PRONOUNCED
WEAKENING TREND IS EXPECTED BEGINNING BY TAU 36 AS THE SYSTEM TRACKS
OVER LUZON. THE OFFICIAL JTWC FORECAST TRACK IS NOW HEDGED CLOSE TO
THE CONSENSUS TRACK, WHICH TAKES INTO ACCOUNT THE MORE WESTERLY
UKMET SOLUTION. DUE TO UNCERTAINTY OF WHEN THE NORTHWARD TURN WILL
OCCUR OVERALL CONFIDENCE IS POOR FOR THIS PORTION OF THE FORECAST.
   C. AFTER TAU 72, TY VONGFONG WILL COMPLETE RECURVATURE AND BEGIN
A NORTHEASTWARD TRACK AFTER ENTERING THE LUZON STRAIT. INCREASING
VWS (25-30 KNOTS) AS TY 01W NEARS A BAROCLINIC BOUNDARY, ALONG WITH
COOLING SSTS WILL LEAD TO FURTHER WEAKENING OF THE SYSTEM TO 35 KTS
BY TAU 96. AT THIS TIME, INTERACTION WITH STRONG UPPER LEVEL
WESTERLY FLOW WILL CAUSE THE SYSTEM TO BEGIN EXTRATROPICAL
TRANSITION, WITH FURTHER WEAKENING TO A 25 KTS SYSTEM BY TAU 120 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.//
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