Tropical Storm HAIMA Advisory Fri Oct 21

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (HAIMA) WARNING NR 23//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 25W (HAIMA), LOCATED APPROXIMATELY 325 NM SOUTHEAST OF
HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 15 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE
SYSTEM HAS REGAINED A RAGGED 75NM EYE AS THE SYSTEM GRADUALLY
DETERIORATES AFTER IT TRACKED ACROSS NORTHERN LUZON, PHILIPPINES.
THE INITIAL POSITION IS BASED ON THE EYE FEATURE IN THE MSI WHICH
LINED UP WELL WITH A LOW REFLECTIVITY CIRCULATION FEATURE IN THE
200515Z ATMS MICROWAVE PASS. THE INITIAL INTENSITY IS BASED ON AN
OVERALL ASSESSMENT OF OBJECTIVE AND AGENCY DVORAK ESTIMATES RANGING
FROM T4.9 TO T5.5 AND REFLECTS THE SLIGHT WEAKENING OF THE SYSTEM.
UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS NOW UNDER INCREASING
VERTICAL WIND SHEAR WHICH IS SLIGHTLY OFFSET BY GOOD DUAL OUTFLOW
THAT IS PROVIDING VENTILATION TO THE REMNANT CONVECTION. THE CYCLONE
IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF THE DEEP-LAYERED
SUBTROPICAL RIDGE TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TYPHOON HAIMA IS EXPECTED TO ROUND THE WESTERN PERIPHERY OF
THE STEERING RIDGE DURING THE FORECAST PERIOD, MAKING LANDFALL TO THE
EAST OF HONG KONG JUST BEFORE TAU 24. SLOW WEAKENING IS EXPECTED
PRIOR TO LANDFALL AS THE SYSTEM CONTENDS WITH MODERATE EASTERLY
VERTICAL WIND SHEAR AND DECREASING ALONG-TRACK OCEAN HEAT CONTENT. TY
25W WILL THEN RAPIDLY ERODE AS IT DRAGS MORE POLEWARD OVER THE RUGGED
CHINESE TERRAIN, DISSIPATING BY TAU 48. NUMERICAL MODEL FORECAST
TRACK GUIDANCE REMAINS IN VERY GOOD AGREEMENT, AND THE CURRENT
FORECAST TRACK LIES NEAR THE MULTI-MODEL CONSENSUS WITH HIGH
CONFIDENCE.//
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