Tropical Storm KAMMURI Advisory Fri Sep 26

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (KAMMURI) WARNING
NR 09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 17W (KAMMURI), LOCATED APPROXIMATELY 252 NM
EAST-SOUTHEAST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 10
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS A CONSOLIDATING LOW-LEVEL CIRCULATION
CENTER (LLCC) WITH SPIRAL BANDING WRAPPING INTO THE LLCC. A SERIES
OF MICROWAVE IMAGERY INCLUDING A 261143Z NOAA-19 IMAGE SHOW TIGHTLY-
CURVED CONVECTIVE BANDING SURROUNDS A ROUND SIGNATURE MICROWAVE
CENTER. THE CURRENT POSITION IS BASED ON THE EIR ANIMATION AND
AFOREMENTIONED NOAA-19 IMAGE WITH FAIR CONFIDENCE. THE INITIAL
INTENSITY HAS INCREASED TO 55 KNOTS BASED ON AN INCREASED
CONSOLIDATION AND OVERALL ASSESSMENT OF DVORAK CURRENT INTENSITY
ESTIMATES FROM ALL REPORTING AGENCIES. UPPER-LEVEL ANALYSIS
INDICATES THE SYSTEM IS LOCATED IN A FAVORABLE ENVIRONMENT WITH LOW
(05 TO 10 KNOT) VERTICAL WIND SHEAR (VWS) AND RADIAL 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. THE FORECAST INTENSITY HAS INCREASED IN THE NEAR-TERM DUE TO
THE INCREASED CONSOLIDATION. OTHERWISE, 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 REACH TYPHOON STRENGTH
OVER THE NEXT 24 HOURS. CONCURRENTLY, THE CYCLONE WILL COMMENCE
EXTRA-TROPICAL TRANSITION (ETT).
   C. BEYOND TAU 72, TS 17W IS FORECAST TO ACCELERATE NORTHEASTWARD
AS THE SYSTEM INTERACTS WITH THE MID-LATITUDE WESTERLIES. THE
CYCLONE WILL BECOME A STORM-FORCE COLD CORE LOW BY THE END OF THE
FORECAST PERIOD. ALSO, INCREASING VWS AND COOLING SSTS WILL CAUSE A
STEADY DECAY. AVAILABLE MODEL GUIDANCE IS OVERALL IN FAIR AGREEMENT;
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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