Tropical Storm DOLPHIN Advisory Wed Sep 23

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (DOLPHIN) WARNING NR
011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 14W (DOLPHIN), LOCATED APPROXIMATELY 256 NM
SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHEASTWARD AT 20
KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) REVEALS AN OBSCURED LOW LEVEL CIRCULATION CENTER (LLCC)
WITH DEEP CONVECTION LOCATED OVERHEAD AND SHEARED OVER THE NORTHEAST
QUADRANT. A 230017Z ASCAT-A IMAGE DEPICTS HIGHER WINDS (50 KTS)
LOCATED TO THE NORTH OF AN ELONGATED LLCC. THE INITIAL INTENSITY IS
ASSESSED AT 50 KTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES OF
T3.0-3.5 (45-55 KTS), A 232340Z ADVANCED DVORAK TECHNIQUE ESTIMATE OF
T3.1 (47KTS), AND A 232211Z SATCON ESTIMATE OF 48 KTS. ALL WIND RADII
HAVE BEEN UPDATED WITH RECENT ASCAT DATA. UPPER LEVEL ANALYSIS REVEALS
HIGH (25-30 KT) VERTICAL WIND SHEAR BEING OFFSET BY WARM SEA SURFACE
TEMPERATURES (SST) AND ROBUST POLEWARD OUTFLOW THAT IS BEING ENHANCED
BY THE WESTERLIES TO THE NORTH. OVERALL, THIS PRESENTS AN OVERALL
MARGINALLY FAVORABLE ENVIRONMENT FOR CONTINUED DEVELOPMENT AS HIGH
SHEAR IMPACTS THE SYSTEM. DUE TO THE ELONGATED NATURE OF THE LLCC,
WEAK TEMPERATURE GRADIENT, AND EXPANDING WIND FIELD, THIS SYSTEM IS
CURRENTLY ASSESSED AS SUBTROPICAL. TS 14W IS TRACKING NORTHEASTWARD
ALONG THE NORTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. IN THE NEAR TERM, TS 14W SHOULD TRACK NORTHEASTWARD THROUGH TAU
36 UNDER THE INFLUENCE OF THE STR. AFTERWARDS, IT WILL SHIFT TO A
NORTH-NORTHEASTWARD TRACK AS THE SYSTEM BECOMES EMBEDDED IN THE JET
FLOW. AROUND TAU 24, TS 14W IS EXPECTED TO BEGIN EXTRATROPICAL
TRANSITION AS BAROCLINICITY INCREASES AND THE SYSTEM STARTS TO GAIN
FRONTAL CHARACTERISTICS AS IT APPROACHES A DEEPENING MIDLATITUDE
TROUGH. AROUND THIS TIME, INCREASING VERTICAL WIND SHEAR (>40 KTS)
WILL BE IMPACTING THE SYSTEM AS WELL. EXTRATROPICAL TRANSITIONS
COMPLETION IS EXPECTED BY TAU 36 AS THE 1000-500 MB THICKNESS FIELDS
SHOW A FRONTAL SYSTEM. AFTERWARDS, TS 14W SHOULD TRACK NORTH-
NORTHEASTWARD AS AN EXTRATROPICAL LOW. NUMERICAL MODEL GUIDANCE IS IN
TIGHT AGREEMENT THROUGH TAU 36 AND THEN SLOWLY DIVERGES TO 80 NM
SPREAD AT TAU 48 AND 150 NM BY TAU 72. THE 22/18Z ECMWF ENSEMBLE
SOLUTIONS REMAIN IN GOOD AGREEMENT AND DEPICT PASSAGE EAST OF HONSHU.
PLACED NEAR THE ECMWF SOLUTION AND THE MULTI-MODEL CONSENSUS, THERE IS
HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.//
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