Tropical Storm DOLPHIN Advisory Çar, 23.09.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (DOLPHIN) WARNING
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 14W (DOLPHIN), LOCATED APPROXIMATELY 358 NM
SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTH-NORTHEASTWARD
AT 10 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS PERSISTENT DEEP CONVECTION
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC) WITH THE MAJORITY
OF THE DEEP CONVECTION SHEARED TO THE NORTHEAST QUADRANT. BASED ON
TURNING IN THE EIR WRAPPING UNDER THE SOUTHWESTERN PERIPHERY OF THE
DEEP CONVECTION, THERE IS FAIR CONFIDENCE IN THE INITIAL POSITION.
THE INITIAL INTENSITY REMAINS AT 55 KTS BASED ON MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T3.5 (55 KTS) BY PGTW AND RJTD AND
HEDGED SLIGHTLY ABOVE A 221840Z ADVANCED DVORAK TECHNIQUE OF T3.1
(47 KTS). AN ANALYSIS OF THE SURROUNDING ENVIRONMENT REVEALS WARM
(29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST) AND ROBUST POLEWARD
OUTFLOW BEING OFFSET BY STRONG (25-30 KT) WESTERLY VERTICAL WIND
SHEAR (VWS), WHICH MAINTAINS A MARGINALLY FAVORABLE ENVIRONMENT FOR
CONTINUED DEVELOPMENT. A 22/12Z AMSU RADIAL/HEIGHT VERTICAL CROSS
SECTION DEPICTS A BROAD WARM CORE TEMPERATURE ANOMALY (+2 CELSIUS)
CENTERED AROUND 8-12 KM AND EXTENDING TO THE SURFACE. THIS DATA
ALONG WITH THE WEAK TEMPERATURE GRADIENT DEPICTED IN MODEL FIELDS
AND THE INTERACTION WITH THE SUBTROPICAL WESTERLIES SUGGEST THAT TS
14W IS UNDERGOING SUBTROPICAL TRANSITION AT THIS TIME. TS 14W IS
TRACKING POLEWARD WITHIN A BROAD COL REGION ALONG THE WESTERN
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 NORTH-NORTHEASTWARD
THROUGH TAU 72 AS IT ROUNDS THE STR AXIS. OF NOTE, NUMERICAL MODEL
GUIDANCE HAS SHIFTED SLIGHTLY EASTWARD SINCE THE PREVIOUS FORECAST
AND IS IN GOOD AGREEMENT WITH THE 22/12Z ECMWF ENSEMBLE MODEL
SOLUTIONS. THE LARGEST MODEL SPREAD OF 114 NM OCCURS AROUND TAU 48,
BUT SOLUTIONS COME INTO TIGHTER AGREEMENT BY TAU 72 WHEN THE SYSTEM
BECOMES EMBEDDED IN THE WESTERLIES. TS 14W IS EXPECTED TO INTERACT
WITH THE SUBTROPICAL WESTERLIES THROUGH TAU 12, INCREASING
BAROCLINICITY AND LEADING TO A SUBTROPICAL TRANSITION BY TAU 12.
AFTERWARDS, TS 14W WILL BEGIN TO GAIN FRONTAL CHARACTERISTICS AS IT
APPROACHES A DEEP MIDLATITUDE TROUGH AND THE JET. CONCURRENTLY,
INCREASING (>35 KT) VWS WILL BEGIN TO IMPACT THE SYSTEM BY TAU 24.
THEREFORE, COMPLETION OF EXTRATROPICAL TRANSITION IS EXPECTED BY TAU
36 AS A FRONTAL STRUCTURE IS EVIDENT IN THE 1000-500 MB THICKNESS
FIELDS. AFTERWARDS, THE SYSTEM WILL CONTINUE TO TRACK NORTH-
NORTHEASTWARD AS AN EXTRATROPICAL LOW. OVERALL, THERE IS HIGH
CONFIDENCE IN THE JTWC FORECAST TRACK WHICH IS POSITIONED NEAR THE
ECMWF SOLUTION AND THE MULTI-MODEL CONSENSUS.//
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