Tropical Storm KUJIRA Advisory Seg, 28-09

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (KUJIRA) WARNING NR
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 15W (KUJIRA), LOCATED APPROXIMATELY 150 NM
NORTH OF MINAMI TORI SHIMA, HAS TRACKED NORTHWESTWARD AT 21 KNOTS
(KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS A PARTIALLY-EXPOSED LOW LEVEL CIRCULATION CENTER
(LLCC) WITH DEEP CONVECTIVE BANDING WRAPPING INTO THE CENTER FROM
THE NORTH AND WEST. A 272301Z ASCAT-C PASS REVEALS A WELL-DEFINED
CIRCULATION WITH AN AREA OF 40-44KT WINDS TO THE EAST WITH WEAKER
WINDS ELSEWHERE. BASED ON THE ASCAT AND PARTIALLY-EXPOSED LLCC,
THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION. THE INITIAL
INTENSITY IS ASSESSED AT 40 KTS BASED ON THE AFOREMENTIONED ASCAT
DATA AND 272014Z SMAP DATA SHOWING 35 KT 10-MINUTE AVERAGE WINDS
(APPROXIMATELY 39 KT 1-MINUTE AVERAGE WINDS). FURTHERMORE, THE
INITIAL INTENSITY IS HEDGED BETWEEN DVORAK CURRENT INTENSITY
ESTIMATES OF T2.5-3.0(35-45 KTS, RJTD/PGTW), AN ADVANCED DVORAK
TECHNIQUE ESTIMATE OF T2.5 (35 KTS), AND A 272145Z SATCON ESTIMATE
OF 47 KTS WITH GOOD CONFIDENCE. ALL WIND RADII HAVE BEEN UPDATED
WITH RECENT ASCAT DATA. UPPER LEVEL ANALYSIS REVEALS IMPROVED
POLEWARD OUTFLOW ENHANCED BY THE APPROACHING SHORTWAVE TROUGH AND
DIMINISHED EQUATORWARD OUTFLOW DUE TO CONVERGENT FLOW FROM AN UPPER
LOW POSITIONED SOUTHWEST OF THE SYSTEM. SUPPORTED BY LOW (10-15 KTS)
VERTICAL WIND SHEAR (VWS) AND WARM (29-30 CELSIUS) SEA SURFACE
TEMPERATURES, THE SYSTEM IS TRANSITING THROUGH AN OVERALL MARGINALLY
FAVORABLE ENVIRONMENT. TS 15W IS TRACKING NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) 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 THEN TURN GENERALLY NORTHWARD AS IT
BEGINS TO ROUND THE STR. THROUGH TAU 36, THE SYSTEM SHOULD CONTINUE
TO INTENSIFY DUE TO ENHANCED POLEWARD OUTFLOW ASSOCIATED WITH THE
SHORTWAVE TROUGH DIGGING SOUTH OF JAPAN, PEAKING THE SYSTEM TO 65
KTS BY TAU 36. EXTRATROPICAL TRANSITION (ETT) IS EXPECTED TO BEGIN
NEAR TAU 36 AS TS 15W RECURVES INTO THE MIDLATITUDE WESTERLIES.
FOLLOWING THIS, TS 15W WILL STEADILY WEAKEN AS IT ENCOUNTERS
INCREASING VWS (25-35 KTS) AND TRACKS OVER COOLING SEA SURFACE
TEMPERATURES. THE SYSTEM IS EXPECTED TO COMPLETE ETT NEAR TAU 72, IF
NOT SOONER, AS IT GAINS FRONTAL CHARACTERISTICS AND BECOMES EMBEDDED
WITHIN THE MIDLATITUDE WESTERLIES. NUMERICAL MODEL GUIDANCE AND THE
ECMWF ENSEMBLE SOLUTIONS REMAIN IN EXCELLENT AGREEMENT THROUGHOUT
THE FORECAST PERIOD. THUS, THERE IS HIGH CONFIDENCE IN THE JTWC
FORECAST TRACK.//
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