Tropical Storm VONGFONG Advisory сб, 16.05.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (VONGFONG) WARNING
NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM 01W (VONGFONG), LOCATED APPROXIMATELY 96
NM NORTH OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD
AT 11 KNOTS OVER THE PAST SIX HOURS.
   TROPICAL STORM (TS) 01W (VONGFONG), LOCATED APPROXIMATELY 38 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT
11 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY (EIR) SHOWS DEEP CONVECTION CONTINUING TO ERODE AS
THE LOW-LEVEL CIRCULATION CENTER (LLCC) INTERACTS WITH THE
MOUNTAINOUS ISLAND OF LUZON. THE INITIAL INTENSITY IS ASSESSED AT 45
KNOTS BASED ON MULTI-PLATFORM CIRA WINDFIELD ANALYSES WITH DVORAK
ANALYSES RANGING FROM T3.5 TO T2.5 FROM RJTD AND RCTP OVER THE LAST
6 HOURS. THE INITIAL POSITION IS BASED WITH FAIR CONFIDENCE BASED ON
SURFACE OBSERVATIONS AND ANIMATED EIR. POLEWARD OUTFLOW IS GOOD
AHEAD OF AN APPROACHING MID-LATITUDE TROUGH, NEARBY SEA SURFACE
TEMPERATURES (SST) ARE WARM (30-31 DEGREES CELSIUS), AND VERTICAL
WIND SHEAR IS MODERATE (15-20 KNOTS). TS 01W IS TRACKING ALONG THE
WESTERN PERIPHERY OF A SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THERE HAS BEEN NO SIGNIFICANT CHANGE TO THE FORECAST
PHILOSOPHY, EXCEPT OVER-WATER DISSIPATION IS ANTICIPATED BEYOND TAU
48 RATHER THAN EXTRATROPICAL TRANSITION.
   B. TS 01W IS FORECAST TO TRACK NORTHWARD ALONG THE WESTERN
PERIPHERY OF THE STEERING STR THROUGH TAU 12 TO 24. AN UPPER-LEVEL
MID-LATITUDE TROUGH IS APPROACHING FROM THE NORTHWEST, WHICH WILL
ERODE THE STR BEYOND TAU 24. THIS WILL ALLOW 01W TO TURN TOWARD THE
NORTHEAST AND ACCELERATE, WITH GOOD AGREEMENT AMONG THE DYNAMICAL
MODEL GUIDANCE. TS 01W IS FORECAST TO CONTINUE TO WEAKEN, EVEN AFTER
IT EMERGES BACK OVER WARM WATER, DUE TO INCREASED VERTICAL WIND
SHEAR AHEAD OF THE APPROACHING TROUGH. BEYOND TAU 36, TS 01W WILL
ACCELERATE AND BEGIN TO DISSIPATE OVER WATER AS IT IS ABSORBED BY
THE BAROCLINIC ZONE. EXTRATROPICAL TRANSITION IS NOT EXPECTED, GIVEN
THE DECOUPLED STRUCTURE OF TS 01W AND WEAK UPPER-LEVEL DYNAMICS.
DEPENDING ON HOW MUCH OF THE WARM-CORE STRUCTURE OF TS 01W REMAINS
AFTER IT EMERGES FROM LUZON, TS 01W COULD DISSIPATE SOONER THAN
FORECAST. GIVEN THE TIGHT CLUSTERING IN DYNAMICAL MODEL GUIDANCE,
THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.
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