Tropical Storm KAMMURI Advisory Thu Sep 25

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 17W (KAMMURI) WARNING
NR 05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 17W (KAMMURI), LOCATED APPROXIMATELY 399 NM
SOUTHEAST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 07 KNOTS OVER THE
PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
DEPICTS A LARGE ROUND SIGNATURE WITH TIGHTLY-CURVED BANDING WRAPPING
INTO A CONSOLIDATING LOW-LEVEL CIRCULATION CENTER (LLCC). A 250917Z
SSMIS MICROWAVE IMAGE SHOWS INCREASED DEEP CONVECTION AROUND THE
LLCC. THE CURRENT POSITION IS BASED ON THE EIR ANIMATION AND SSMIS
IMAGE WITH FAIR CONFIDENCE. THE INITIAL INTENSITY HAS INCREASED TO
35 KNOTS BASED ON AN OVERALL ASSESSMENT OF DVORAK CURRENT INTENSITY
ESTIMATES FROM ALL REPORTING AGENCIES AS WELL AS THE ORGANIZING
STRUCTURE. UPPER-LEVEL ANALYSIS CONTINUES TO INDICATE THE SYSTEM IS
LOCATED IN A VERY 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. THE FORECAST INTENSITY HAS SLIGHTLY INCREASED THROUGH TAU 48
DUE TO AN INCREASE IN THE INITIAL INTENSITY AND OVERALL STATISTICAL-
DYNAMICAL INTENSITY GUIDANCE. 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 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 MIDLATITUDE 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 75 KNOTS BY TAU 72.
   C. BEYOND TAU 72, TS 17W IS FORECAST TO ACCELERATE NORTHEASTWARD
AND BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS THE SYSTEM INTERACTS
WITH THE MIDLATITUDE WESTERLIES BY TAU 96. 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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