WDPN31 PGTW 261500
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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