Tropical Storm CHAN-HOM Advisory Tue Oct 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (CHAN-HOM)
WARNING NR 03//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TROPICAL STORM (TS) 16W (CHAN-HOM), LOCATED
APPROXIMATELY 781 NM SOUTH OF YOKOSUKA, JAPAN, HAS TRACKED
WESTWARD AT 02 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS FORMATIVE
BANDING WRAPPING INTO A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC). THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON THE PARTIALLY EXPOSED LLCC
IN THE MSI LOOP AND BANDING FEATURES PRESENT IN A 050650Z
SSMIS 91GHZ IMAGE. THE INITIAL INTENSITY OF 35 KTS IS
PLACED WITH FAIR CONFIDENCE AND IS HEDGED ABOVE MULTI-AGENCY
DVORAK CURRENT INTENSITY ESTIMATES OF T2.0 (30 KTS, PGTW AND
RJTD) AND A CIMSS ADVANCED DVORAK CURRENT INTENSITY ESTIMATE
OF T3.2 (32 KTS). TS 16W IS TRACKING SLOWLY ALONG THE
PERIPHERY OF A SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST
AND THROUGH AN ENVIRONMENT FAVORABLE FOR FURTHER DEVELOPMENT
WITH WITH LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS) AND WARM
(29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST). THE SYSTEM
IS UNDER SUPPORTIVE UPPER LEVEL EQUATORWARD OUTFLOW HOWEVER
CONVERGENT FLOW ALONG THE NORTHWESTERN PERIPHERY OF THE
SYSTEM HAS STIFLED DEVELOPMENT OVER THE PAST 6 HOURS.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS CHAN-HOM IS FORECAST TO CONTINUE TRACKING GENERALLY
NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR
THROUGH TAU 72. DURING THIS TIME, THE SYSTEM WILL STEADILY
INTENSIFY AND REACH A PEAK INTENSITY OF 85 KTS BY TAU 72,
LARGELY DUE TO THE CONTINUED LOW VWS AND WARM SSTS. NUMERICAL
MODEL TRACK SOLUTIONS HAVE CONTINUED TO CONVERGE WITH A MAXIMUM
ACROSS TRACK SPREAD OF 245 NM BY TAU 72. THE UKMET SOLUTIONS
REMAIN THE PRIMARY WESTWARD OUTLIERS WITH THE REMAINING MEMBERS
OF THE JTWC MULTI-MODEL CONSENSUS CONVERGING ON A MORE EASTWARD
TRACK. THE JTWC FORECAST IS LAID NEAR THE EASTWARD SOLUTIONS,
WHICH IS NEAR THE JTWC MULTI-MODEL CONSENSUS. DUE TO THE SPREAD
IN TRACK GUIDANCE, THERE IS OVERALL FAIR CONFIDENCE IN THIS
INITIAL PORTION OF THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, THE SYSTEM WILL ROUND THE STR AXIS AND BEGIN
A GENERALLY NORTHEASTWARD TRACK TOWARDS KYUSHU. TS CHAN-HOM WILL
GRADUALLY WEAKEN DURING THIS PERIOD AS VWS BEGINS TO INCREASE TO
20-25 KNOTSS BY TAU 96 AND THEN TO OVER 30 KNOTS BY TAU 120.
NUMERICAL MODEL TRACK GUIDANCE DIVERGES SIGNIFICANTLY BY TAU 120
WITH A 600 NM ACROSS TRACK SPREAD AT THIS TIME. DUE TO THIS HIGH
DEGREE OF DIVERGENCE IN MODEL SOLUTIONS, THERE IS ONLY POOR
CONFIDENCE IN THE REMAINDER OF THE JTWC FORECAST TRACK.//
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