WDPN31 PGTW 101500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM) WARNING 
NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED APPROXIMATELY 217 NM 
SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED EASTWARD AT 09 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY DEPICTS A BROAD, DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) 
WITH A WEAK FRONTAL STRUCTURE AND DEEP CONVECTION SHEARED TO THE 
EAST. OVERALL, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION AND 
RECENT TRACK MOTION. A 101155Z MHS 89GHZ MICROWAVE IMAGE INDICATES 
SHALLOW BANDING WRAPPING INTO A WEAKLY-DEFINED LLCC WITH 
DISORGANIZED DEEP CONVECTION DISPLACED TO THE NORTHEAST. THE INITIAL 
INTENSITY REMAINS ASSESSED AT 50 KNOTS BASED ON A 101042Z ASCAT-A 
IMAGE SHOWING 45-50 KNOT WINDS OVER THE NORTHERN QUADRANT; PGTW/RJTD 
DVORAK CURRENT INTENSITY ESTIMATES ARE SLIGHTLY LOWER AT 3.0 (45 
KNOTS). ENVIRONMENTAL ANALYSIS REVEALS MARGINAL CONDITIONS WITH 
STRONG VERTICAL WIND SHEAR (VWS) AND DRY AIR ENTRAINMENT AS WELL AS 
BAROCLINIC INFLUENCES. THE SYSTEM IS EMBEDDED WITHIN THE ZONAL 
SUBTROPICAL WESTERLY FLOW AND IS TRACKING EASTWARD ALONG THE 
SOUTHERN PERIPHERY OF THE BAROCLINIC ZONE. ADDITIONALLY, THERE ARE 
BROAD LOW-LEVEL SUBTROPICAL RIDGES ENTRENCHED TO THE EAST AND 
SOUTHWEST OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. DUE TO THE PRESENCE OF THE AFOREMENTIONED LOW-LEVEL 
SUBTROPICAL RIDGES, TS 16W IS FORECAST TO DECELERATE AND TURN 
SOUTHEASTWARD TO SOUTHWARD THROUGH THE FORECAST PERIOD AS IT 
STEERS ALONG THE EASTERN PERIPHERY OF THE LOW-LEVEL STR POSITIONED 
TO THE SOUTHWEST. THE EASTERN STR IS FORECAST TO WEAKEN BUT WILL 
CONTINUE TO BLOCK EASTWARD PROGRESSION. TS 16W IS FORECAST TO WEAKEN 
THROUGH THE FORECAST PERIOD DUE TO STRONG (25-35 KNOTS) VWS AND DRY 
AIR ENTRAINMENT WITH DISSIPATION EXPECTED BY TAU 48. NUMERICAL MODEL 
GUIDANCE DIVERGES BUT SUPPORTS THE JTWC FORECAST TRACK WITH FAIR 
CONFIDENCE.//
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