WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING 
NR 
030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 16W (CHAN-HOM), LOCATED APPROXIMATELY 
325 
NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED SOUTHWARD AT 04 
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL 
SATELLITE 
IMAGERY (MSI) REVEALS A FULLY-EXPOSED LOW LEVEL CIRCULATION CENTER 
(LLCC) WITH CONVECTIVE BANDING WRAPPING INTO THE CENTER. ALL 
ASSOCIATED 
DEEP CONVECTION HAS DISSIPATED OVER THE PAST SIX HOURS. AN 112358Z 
BULLSEYE ASCAT-B IMAGE SHOWS A FEW 25-30 KT WIND BARBS IN THE 
WESTERN 
SEMI-CIRCLE WITH WEAKER WINDS ELSEWHERE. THIS ASCAT PASS SUPPORTS 
THE 
INITIAL POSITION AND INTENSITY WITH GOOD CONFIDENCE. TD 16W IS 
LOCATED 
IN A MARGINAL ENVIRONMENT UNDER MODERATE TO HIGH (20-25 KT) VERTICAL 
WIND SHEAR (VWS). ADDITIONALLY, SIGNIFICANT DRY AIR HAS ENTRAINED 
INTO 
THE SYSTEM. AS IT IS EXPERIENCING SOME BAROCLINICITY, TD 16W APPEARS 
TO 
BE A HYBRID/SUBTROPICAL SYSTEM AND HAS AN ASYMMETRIC APPEARANCE IN 
BOTH 
THE WIND FIELD AND TOTAL PRECIPITABLE WATER IMAGERY. TD 16W IS 
TRACKING 
SOUTHWARD ALONG THE BACK EDGE OF AN UPPER-LEVEL SHORTWAVE TROUGH 
AROUND 
THE 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. TD 16W IS EXPECTED TO CONTINUE GENERALLY SOUTH-SOUTHEASTWARD 
AS 
IT TRACKS ALONG THE EASTERN PERIPHERY OF THE LOW-LEVEL STR 
THROUGHOUT 
THE FORECAST PERIOD. THE SYSTEM WILL STEADILY WEAKEN DUE TO 
CONTINUED 
DRY AIR ENTRAINMENT AND MODERATE TO HIGH (20-25 KT) VWS. SYSTEM 
DISSIPATION IS ANTICIPATED BY TAU 24. NUMERICAL MODEL GUIDANCE IS IN 
GOOD AGREEMENT THROUGH TAU 24 BUT BEGINS TO DIVERGE AFTERWARDS. 
OVERALL, THERE IS GOOD CONFIDENCE IN THE JTWC FORECAST TRACK. MODEL 
GUIDANCE SHOWS THERE IS SOME POTENTIAL FOR TD 16W TO SLOWLY 
REGENERATE 
AS A WARM-CORE TROPICAL SYSTEM AFTER TAU 48 AS THE SYSTEM TRACKS 
OVER 
WARM SEA SURFACE TEMPERATURES (28-29 CELSIUS) AND UNDER DECREASING 
VWS 
(<20 KTS).//
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