Tropical Storm KAMMURI Advisory Sat Sep 27

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (KAMMURI) WARNING
NR 08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 17W (KAMMURI), LOCATED APPROXIMATELY 302 NM
EAST-SOUTHEAST OF IWO TO, HAS TRACKED NORTH-NORTHWESTWARD AT 06
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY AND A 260451Z SSMI DEPICT A ROUND SIGNATURE WITH SPIRAL
BANDING WRAPPING INTO A LOW-LEVEL CIRCULATION CENTER. THE CURRENT
POSITION IS BASED ON THE MSI LOOP AND SSMI IMAGE WITH FAIR
CONFIDENCE. THE INITIAL INTENSITY OF 45 KNOTS IS AVERAGED FROM
DVORAK CURRENT INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES.
UPPER-LEVEL ANALYSIS INDICATES THE SYSTEM IS LOCATED IN A FAVORABLE
(05 TO 10 KNOT) VERTICAL WIND SHEAR (VWS) ENVIRONMENT. ADDITIONALLY,
A POINT SOURCE IS LOCATED OVER THE SYSTEM PROVIDING 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. 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 (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 TAU 96. ALSO,
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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