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 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 14W (DOLPHIN), LOCATED APPROXIMATELY 493 NM
SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED LOW-
LEVEL CIRCULATION CENTER (LLCC). A 220350Z GMI 37GHZ MICROWAVE IMAGE
INDICATES MULTIPLE CONVECTIVE BANDS WRAPPING INTO A SMALL MICROWAVE
EYE FEATURE, WHICH SUPPORTS THE INITIAL POSITION WITH GOOD
CONFIDENCE. THE INITIAL INTENSITY IS HEDGED ABOVE PGTW/RJTD DVORAK
ESTIMATES OF T3.5 (55 KNOTS) BASED ON A 22/0406Z SATCON ESTIMATE OF
59 KNOTS. RECENT DATA CONTINUES TO SUPPORT A WARM-CORE TROPICAL
CYCLONE WITH A 20-25NM RADIUS OF MAXIMUM WINDS AND A +2C TEMPERATURE
ANOMALY AT 10-13 KM IN THE 22/0000Z AMSU CROSS-SECTION. UPPER-LEVEL
ANALYSIS REVEALS A FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (15 TO
20 KNOTS) VERTICAL WIND SHEAR (VWS) AND ROBUST POLEWARD OUTFLOW INTO
THE STRONG WESTERLIES TO THE NORTH. DESPITE SOME PRESSURE
(CONVERGENCE) OVER THE WESTERN PERIPHERY, ANIMATED WATER VAPOR
IMAGERY INDICATES THAT THE SYSTEM HAS MAINTAINED LIMITED OUTFLOW
OVER THE WESTERN SEMICIRCLE. 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. TS 14W IS FORECAST TO TRACK NORTH-NORTHEASTWARD TO
NORTHEASTWARD THROUGH TAU 48 AS IT ROUNDS THE STR AXIS AND TRACKS
OVER THE KANTO PLAIN REGION OF HONSHU. NUMERICAL MODEL GUIDANCE AND
THE 22/00Z ECMWF ENSEMBLE SOLUTIONS REMAIN IN GOOD AGREEMENT THROUGH
TAU 48 WITH A 110NM SPREAD IN SOLUTIONS AT TAU 48. THE SYSTEM IS
EXPECTED TO INTERACT WITH SUBTROPICAL WESTERLIES THROUGH TAU 24 WITH
MODERATE BAROCLINICITY, WHICH WILL LEAD TO A SUBTROPICAL TRANSITION
BY TAU 24. AFTER TAU 24, TS 14W WILL QUICKLY GAIN FRONTAL
CHARACTERISTICS AS IT APPROACHES A DEEP MIDLATITUDE TROUGH AND JET-
STRENGTH WINDS OVER CENTRAL HONSHU. VWS IS EXPECTED TO INCREASE
SIGNIFICANTLY BY TAU 48 TO 40-50 KNOTS WITH A CLEAR FRONTAL
STRUCTURE EVIDENT IN THE 1000-500MB THICKNESS FIELDS. THE SYSTEM
SHOULD COMPLETE EXTRA-TROPICAL TRANSITION BETWEEN TAU 36-48 AND WILL
TRACK OVER THE KANTO PLAIN AS A STORM-FORCE EXTRA-TROPICAL LOW.
AFTER TAU 48, THE EXTRA-TROPICAL LOW WILL ACCELERATE NORTHEASTWARD
PRODUCING GALE-FORCE WINDS OVER NORTHERN HONSHU. OVERALL, THERE IS
HIGH CONFIDENCE IN THE JTWC FORECAST TRACK, WHICH IS POSITIONED NEAR
THE MULTI-MODEL CONSENSUS.//
NNNN
NNNN