Tropical Storm KAMMURI Advisory 26.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (KAMMURI) WARNING
NR 07//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 17W (KAMMURI), LOCATED APPROXIMATELY 332 NM
EAST-SOUTHEAST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 07
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL 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 MSI LOOP
AND EXTRAPOLATED FROM A RAGGED WARM SPOT ON A 252130Z 37 GHZ
MICROWAVE PASS. THE INITIAL INTENSITY IS AVERAGED FROM DVORAK
ESTIMATES FROM PGTW AND RJTD. UPPER-LEVEL ANALYSIS INDICATES THE
SYSTEM IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW (05 TO 10 KNOT)
VERTICAL WIND SHEAR (VWS) AND EXCELLENT OUTFLOW 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 48. TS KAMMURI IS FORECAST TO TURN POLEWARD AFTER TAU 36
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. CONCURRENTLY, THE CYCLONE WILL
COMMENCE EXTRA-TROPICAL TRANSITION.
   C. BEYOND TAU 72, TS 17W IS FORECAST TO ACCELERATE NORTHEASTWARD
(ETT) AS THE SYSTEM INTERACTS WITH THE MID-LATITUDE WESTERLIES. THE
CYCLONE WILL BECOME A STORM-FORCE COLD CORE LOW BY TAU 96.
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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