Tropical Storm CHAN-HOM Advisory 10月5日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN)
WARNING NR 01//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION 16W (SIXTEEN), LOCATED APPROXIMATELY 800 NM
SOUTH-SOUTHEAST OF IWAKUNI, JAPAN, HAS TRACKED WESTWARD AT 02 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
(EIR) DEPICTS A CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC)
WITH FLARING CONVECTION OVER THE SOUTHERN SEMICIRCLE. THE INITIAL
POSITION IS PLACED WITH FAIR CONFIDENCE BASED ON THE BROAD FORMATIVE
BANDING PRESENT IN 041643Z AMSR2 89GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY AT PGTW, RJTD AND KNES DVORAK CURRENT INTENSITY ESTIMATE OF
T1.5 (25 KTS), AS WELL AS DATA FROM AN EARLIER 041230Z ASCAT-B PASS.
THE WIND FIELD IS BROAD WITH WINDS IN EXCESS OF 25 KTS DISPLACED >
100 NM FROM THE SYSTEM CENTER TO THE SOUTHEAST. TD 16W IS SLOWLY
TRACKING ALONG THE PERIPHERY OF A SUBTROPICAL RIDGE POSITIONED TO THE
NORTHEAST AND THROUGH A FAVORABLE ENVIRONMENT FOR FURTHER DEVELOPMENT
WITH LOW (5-10 KTS) VERTICAL WIND SHEAR (VWS) AND WARM (30-31
CELSIUS) SEA SURFACE TEMPERATURES (SST). THE SYSTEM IS UNDER
SUPPORTIVE UPPER LEVEL EQUATORWARD OUTFLOW.
3. FORECAST REASONING.
   A. THIS IS THE FIRST PROGNOSTIC REASONING MESSAGE AND SETS THE
FORECAST PHILOSOPHY.
   B. TD 16W IS FORECAST TO CONTINUE TRACKING GENERALLY NORTHWESTWARD
ALONG THE SOUTHWESTERN PERIPHERY OF THE STR THROUGH TAU 72. DURING
THIS TIME, THE SYSTEM IS FORECAST TO REACH AN INTENSITY OF 85 KTS BY
TAU 72 DUE TO THE CONTINUED LOW VWS AND WARM SSTS. MODEL GUIDANCE
QUICKLY DIVERGES WITH A SPREAD OF OVER 400NM BY TAU 72, WITH AFUM AND
UKMET TRACKING TOWARDS KADENA, WHEREAS NAVGEM SHOWS A MUCH TIGHTER
RECURVE AROUND IWO TO. THE REMAINING MODELS LIE BETWEEN THESE
DISPARATE SOLUTIONS, WHERE THE JTWC FORECAST IS LAID NEAR CONSENSUS.
   C. AFTER TAU 72, THE SYSTEM WILL BEGIN TO ROUND THE STR AXIS WITH
A NORTHWARD TRACK AS IT MANEUVERS EAST OF KADENA, OKINAWA.
INTENSIFICATION WILL SLOW DURING THIS PERIOD AS THE VWS BEGINS TO
INCREASE TO GREATER THAN 20 KNOTS BY TAU 96. VWS WILL LIKELY PEAK
OVER 30 KNOTS BY TAU 120 WHICH WILL DROP THE INTENSITY TO 75 KNOTS.
NUMERICAL MODEL GUIDANCE IS IN VERY POOR AGREEMENT WITH A CROSS TRACK
SPREAD OF 800 NM AT TAU 96, LENDING POOR CONFIDENCE TO THE JTWC
FORECAST TRACK. DUE TO THIS POOR CONFIDENCE IN TRACK AND THE DYNAMIC
ENVIRONMENT WHICH TD 16W WILL NAVIGATE THROUGH, THERE IS OVERALL POOR
CONFIDENCE IN THE JTWC INTENSITY.//
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