Tropical Storm KUJIRA Advisory 9月28日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (KUJIRA) WARNING NR
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 15W (KUJIRA), LOCATED APPROXIMATELY 94 NM
NORTHEAST OF MINAMI TORI SHIMA, HAS TRACKED NORTHWESTWARD AT 20
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY SHOWS A LOW LEVEL CIRCULATION CENTER (LLCC)
OBSCURED BY FLARING DEEP CONVECTION EXTENDING OVER THE NORTHERN
AND EASTERN SEMICIRCLES. A 271743Z SSMIS 91 GHZ MICROWAVE IMAGE
SHOWS IMPROVED BANDING WRAPPING INTO THE LLCC FROM ALL QUADRANTS;
THEREFORE, THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. THE
INITIAL INTENSITY REMAINS ASSESSED AT 35 KTS BASED ON A 271740Z
ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.5 (35 KTS) AND DVORAK
CURRENT INTENSITY ESTIMATES OF T2.0-2.5 (30-35 KTS) BY PGTW AND
RJTD. UPPER LEVEL ANALYSIS REVEALS AN IMPROVING ENVIRONMENT
CHARACTERIZED BY INCREASING POLEWARD OUTFLOW AND ROBUST EQUATORWARD
OUTFLOW BEING OFFSET BY A BROAD, CONVERGENT UPPER LOW LOCATED TO THE
SOUTHWEST OF THE SYSTEM. WARM (29-30 CELSIUS) SEA SURFACE
TEMPERATURES AND LOW (<10 KTS) VERTICAL WIND SHEAR (VWS) REMAIN
CONDUCIVE FOR CONTINUED DEVELOPMENT, ESTABLISHING AN OVERALL
MARGINALLY FAVORABLE ENVIRONMENT. TS 15W IS TRACKING NORTHWESTWARD
ALONG THE PERIPHERY OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE
NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 15W IS FORECAST TO TRACK NORTH-NORTHWESTWARD THROUGH TAU 12
WITH STEADY INTENSIFICATION. AFTER TAU 12, TS 15W WILL BEGIN TO
ROUND THE STR WITH FURTHER INTENSIFICATION DUE TO IMPROVING POLEWARD
OUTFLOW ASSOCIATED WITH A MAJOR SHORTWAVE TROUGH DIGGING SOUTH OF
JAPAN. THE SYSTEM IS EXPECTED TO PEAK AT 65 KNOTS BY TAU 36.
EXTRATROPICAL TRANSITION (ETT) IS EXPECTED TO BEGIN AROUND TAU 48,
IF NOT SOONER, AS TS 15W RECURVES INTO THE MIDLATITUDE WESTERLIES.
FOLLOWING THIS, TS 15W WILL STEADILY WEAKEN AS IT ENCOUNTERS
INCREASING VWS (25-30 KTS) AND TRACKS OVER COOL SST VALUES (20-23
CELSIUS). THE SYSTEM IS EXPECTED TO COMPLETE ETT NEAR TAU 72 AS IT
GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED WITHIN THE
MIDLATITUDE WESTERLIES. NUMERICAL MODEL GUIDANCE AND THE 27/12Z
ECMWF ENSEMBLE SOLUTIONS REMAIN IN TIGHT AGREEMENT THROUGHOUT THE
FORECAST PERIOD, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST
TRACK.//
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