Tropical Storm TALIM Advisory mer, 20.06.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (TALIM) WARNING NR
10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL STORM (TS) 06W (TALIM), LOCATED APPROXIMATELY 240 NM
SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTHEASTWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS BEEN
SEPARATED FROM DEEP CONVECTION BY OVER 60 NM FOR THE MAJORITY OF THE
PAST SIX HOURS. RECENTLY, A REGION OF DEEP CONVECTION HAS BEEN
BUILDING TO THE EAST OF THE LLCC. THE UPPER LEVEL SUBTROPICAL RIDGE
(STR), LOCATED OVER SOUTHEASTERN CHINA, CREATING THE VERTICAL WIND
SHEAR (VWS) OVER TS 06W HAS SLOWLY STARTED TO SHIFT TO THE
SOUTHWEST. THE VWS IS BEGINNING TO WEAKEN ALLOWING THE DEEP
CONVECTION TO SLOWLY BUILD ALONG THE SOUTHERN PERIPHERY. THE OVERALL
STEERING ENVIRONMENT WILL CONTINUE TO TRACK THE LLCC TO THE
NORTHEAST, TOWARDS THE TAIWAN STRAIT, AROUND THE NORTHWESTERN
QUADRANT OF A DEEP LAYERED STR. THE INITIAL POSITION IS BASED ON THE
EIR IMAGERY SHOWING THE FULLY EXPOSED LLCC. THE INITIAL INTENSITY
HAS BEEN MAINTAINED AT 45 KNOTS BASED ON THE NOTED SHEARING OF DEEP
CONVECTION WEAKENING AND THE CONVECTION BUILDING BACK TOWARDS THE
LLCC.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 06W WILL STRUGGLE OVER THE NEXT 12 HOURS TO MAINTAIN
INTENSITY AS VWS REMAINS AT MODERATE LEVELS (20 KNOTS). AS TS 06W
MOVES TOWARDS THE TAIWAN STRAIT, IT IS EXPECTED TO MOVE OUT FROM
UNDER THE STRONG NORTHEASTERLY FLOW AROUND THE STR AND INTO A REGION
OF WEAKER UPPER LEVEL WINDS. DURING THIS TRANSITION PERIOD,
SOUTHWESTERLY FLOW AROUND A STATIONARY UPPER LEVEL TROUGH IS
EXPECTED TO INCREASE THE POLEWARD OUTFLOW CHANNEL BETWEEN TAU 12 AND
24. THE SEA SURFACE TEMPERATURES WILL REMAIN FAVORABLE THROUGH TAU
24 (26 TO 28 CELSIUS), WHEN COMBINED WITH THE BRIEF IMPROVEMENT IN
THE POLEWARD OUTFLOW, WILL HELP TS 06W TO INTENSIFY. BEYOND TAU 36,
THE MID-LATITUDE FLOW WILL CAUSE AN INCREASE IN COLD AIR ADVECTION
WITHIN THE LOW- TO MID-LEVELS OF TS 06W, LEADING TO THE START OF THE
EXTRA-TROPICAL TRANSITION (ETT) PROCESS. THE STEERING STR WILL BUILD
CAUSING AN INCREASE IN TRACK SPEEDS OVER THE NEXT 24 HOURS, WITH
INCREASING SPEEDS AS THE LLCC IS ABSORBED INTO THE BAROCLINIC ZONE
ALONG THE EASTERN COAST OF JAPAN. FULL ETT TRANSITION IS EXPECTED BY
TAU 48. MODEL GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE
CURRENT FORECAST AS THE CONSENSUS HAS SHIFTED SOUTH IN LINE WITH THE
CURRENT FORECAST REASONING.//
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