Tropical Storm CHAN-HOM Advisory Pzt, 12.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING NR 029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 301 NM
SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED SOUTHWARD AT 07 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY REVEALS AN EXPOSED, DEFINED LOW LEVEL CIRCULATION CENTER (LLCC)
WITH LIMITED, WEAKENING DEEP CONVECTION DISPLACED TO THE NORTHEAST. AN
111928Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALS CONVECTIVE BANDING
WRAPPING INTO A BROAD RAGGED LLCC. THERE IS GOOD CONFIDENCE IN THE
INITIAL POSITION WHICH IS PLACED NEAR THE PGTW AND RJTD FIXES DUE TO
THE FULLY-EXPOSED NATURE OF THE LLCC. THE INITIAL INTENSITY REMAINS
ASSESSED AT 35 KNOTS BASED ON RECENT ASCAT DATA AND MULTIAGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T2.0-2.5 (30-35 KTS) BY PGTW AND RJTD.
TS 16W IS LOCATED IN A MARGINAL ENVIRONMENT WITH SIGNIFICANT DRY AIR
ENTRAINING INTO THE SYSTEM AND STRONG (25-30 KTS) VERTICAL WIND SHEAR.
AS IT IS EXPERIENCING MODERATE BAROCLINICITY, TS 16W APPEARS TO BE A
HYBRID/SUBTROPICAL SYSTEM AND HAS AN ASYMMETRIC APPEARANCE IN BOTH THE
WIND FIELD AND TOTAL PRECIPITABLE WATER IMAGERY. TS 16W IS TRACKING
SOUTHWARD ALONG THE BACK EDGE OF AN UPPER-LEVEL SHORTWAVE TROUGH AND
THE EASTERN PERIPHERY OF A LOW-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED
TO THE WEST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TS 16W IS EXPECTED TO CONTINUE GENERALLY SOUTH-SOUTHEASTWARD AS
IT TRACKS ALONG THE EASTERN PERIPHERY OF THE LOW-LEVEL STR THROUGH THE
FORECAST PERIOD. THE SYSTEM WILL STEADILY WEAKEN DUE TO CONTINUED DRY
AIR ENTRAINMENT AND MODERATE TO HIGH (20-30 KT) VWS WITH DISSIPATION
ANTICIPATED BY TAU 36. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THROUGH TAU 24 BUT BEGINS TO DIVERGE AFTERWARDS. OVERALL, THERE IS FAIR
CONFIDENCE IN THE JTWC FORECAST TRACK. THERE IS SOME POTENTIAL FOR TS
16W TO SLOWLY REGENERATE AS A WARM-CORE TROPICAL SYSTEM AFTER TAU 60 AS
THE SYSTEM TRACKS OVER WARM SEA SURFACE TEMPERATURES (28-29C) AND UNDER
DECREASING VWS (<20 KNOTS).//
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