Tropical Storm KAMMURI Advisory Cu, 26.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (KAMMURI) WARNING
NR 06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 17W (KAMMURI), LOCATED APPROXIMATELY 383 NM
SOUTHEAST OF IWO TO, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY CONTINUES TO DEPICT A VERY LARGE CYCLONE, SPANNING
OVER 700 NM, WITH MONSOON DEPRESSION CHARACTERISTICS - WEAK
CIRCULATION CENTER WITH MINIMAL CONVECTION AND DEEP CONVECTIVE BANDS
IN THE OUTER PERIPHERY. THE INITIAL POSITION IS BASED ON THE EIR LOOP
AND EXTRAPOLATED FROM A RAGGED WARM SPOT ON A 251546Z HIGH FREQUENCY
NPP MICROWAVE PASS. THE INITIAL INTENSITY IS AVERAGED FROM DVORAK
ESTIMATES FROM PGTW AND RJTD AND EXTRAPOLATED FROM A RECENT
SCATTEROMETRY PASS SHOWING THE RADIUS OF STRONGER WINDS OVER 2
DEGREES AWAY FROM THE CENTER. UPPER-LEVEL ANALYSIS CONTINUES TO
INDICATE THE SYSTEM IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW
(05 TO 10 KNOT) VERTICAL WIND SHEAR (VWS) AND EXCELLENT OUTFLOW
CHANNELS AS EVIDENT IN THE WATER VAPOR IMAGERY. TS 17W IS CURRENTLY
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A MID- TO DEEP-LAYERED
SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THE STR WILL REMAIN THE DOMINANT STEERING MECHANISM FOR TS 17W
THROUGH TAU 72. TS KAMMURI IS FORECAST TO TURN POLEWARD AFTER TAU 48
AS IT ROUNDS THE STR AXIS AND BEGINS TO RE-CURVE AHEAD OF AN
APPROACHING MID-LATITUDE SHORTWAVE TROUGH. IN ADDITION TO THE WARM
SEA SURFACE TEMPERATURES (SSTS), FAVORABLE UPPER-LEVEL ENVIRONMENT
IS EXPECTED TO PERSIST ALLOWING TS 17W TO INTENSIFY LEADING TO A
PEAK INTENSITY OF 65 KNOTS BY TAU 48.
   C. BEYOND TAU 72, TS 17W IS FORECAST TO ACCELERATE NORTHEASTWARD
AND BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS THE SYSTEM INTERACTS
WITH THE MID-LATITUDE WESTERLIES BY TAU 72. THE CYCLONE WILL BECOME A
STORM-FORCE COLD CORE LOW BY TAU 120. ADDITIONALLY, INCREASING VWS
AND COOLING SSTS WILL CAUSE A STEADY DECAY. AVAILABLE MODEL GUIDANCE
HAS IMPROVED OVER THE PAST SIX HOURS; HOWEVER, DUE TO UNCERTAINTY OF
THE TRACK SPEEDS IN THE SHORT-TERM AND LARGE SPREAD AMONG MODEL
TRACKERS AT THE TURN, THE CONFIDENCE IN JTWC FORECAST TRACK REMAINS
LOW.//
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