Tropical Storm TEMBIN Advisory Sa, 28.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 15W (TEMBIN) WARNING NR
36//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 15W (TEMBIN), LOCATED APPROXIMATELY 195 NM
SOUTH OF TAIPEI, TAIWAN, HAS TRACKED EAST-NORTHEASTWARD AT 11 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY SHOWS DEEP CONVECTION IS LIMITED TO THE SOUTHWESTERN
QUADRANT OF THE LOW LEVEL CIRCULATION CENTER (LLCC). RADAR IMAGERY
FROM TAIWAN DEPICTS A WELL ORGANIZED LLCC BUT WITH DIMINISHED
CONVECTION ALONG THE NORTHEASTERN QUADRANT AS THE SYSTEM IS TRACKING
NEAR THE COAST OF TAIWAN. ADDITIONALLY, THERE APPEARS TO BE SOME
ELONGATION AND EXPANSION OF THE LLCC OVER THE PAST FEW HOURS. THE
CURRENT INTENSITY OF 55 KNOTS IS BASED ON A 3.5/3.5 DVORAK FROM
PGTW, AND IS CONSISTENT WITH THE RECENT WEAKENING OBSERVED. UPPER
LEVEL ANALYSIS INDICATES TS 15W IS LOCATED TO THE SOUTHWEST OF AN
ANTICYCLONE LOCATED OVER OKINAWA. UPPER LEVEL RIDGING EXTENDING FROM
THE ANTICYCLONE OVER TAIWAN IS CREATING MODERATE LEVELS OF
NORTHEASTERN VERTICAL WIND SHEAR (VWS) AND IS CAUSING THE
DISLOCATION OF CONVECTION WITHIN THE NORTHEASTERN QUADRANT. THERE IS
HIGH CONFIDENCE IN THE POSITION BASED ON AVAILABLE RADAR DATA. TS
15W IS TRACKING ALONG THE NORTHERN PERIPHERY OF A DEVELOPING NEAR
EQUATORIAL RIDGE (NER).
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 15W IS FORECAST TO REMAIN ON A NORTHEASTWARD TRACK FOR THE
NEXT 12 HOURS, TRANSITIONING TO A GENERAL NORTHWARD TRACK BEYOND TAU
12 THROUGH TAU 72 AS A BUILDING SUBTROPICAL RIDGE (STR) TO THE EAST
BECOMES THE DOMINANT STEERING INFLUENCE. THE INTENSITY IS EXPECTED
TO DECREASE OVER THE NEXT 24 HOURS AS IMPACTS FROM THE PROXIMITY TO
TAIWAN DISRUPTS LOW LEVEL INFLOW. BETWEEN TAU 24 AND 72 A SLIGHT
INTENSITIFICATION PERIOD IS EXPECTED AS THE SYSTEM REORGANIZES IN A
FAVORABLE SURFACE ENVIRONMENT. THE UPPER LEVEL WILL REMAIN MARGINAL
WHICH WILL LIMIT STRONGER INTENSIFICATION THROUGH TAU 48 WITH THE
OVERALL ENVIRONMENT BECOMING LESS FAVORABLE BETWEEN TAU 48 AND 72 AS
SEA SURFACE TEMPERATURES (SSTS) DECREASE AND VWS INCREASES. MODEL
GUIDANCE IS IN GOOD AGREEMENT WITH THE FORECAST THROUGH TAU 48, BUT
BEGINS TO SEPARATE SIGNIFICANTLY BY TAU 72. THERE IS HIGH CONFIDENCE
IN THE TRACK THROUGH TAU 48, BUT BECOMES LOW CONFIDENCE BY TAU 72.
   C. DYNAMIC MODEL GUIDANCE HAS SHIFTED OVER THE PAST SIX HOURS FOR
THE EXTENDED FORECAST, WITH THE MAJORITY OF AVAILABLE GUIDANCE
INDICATING A TRACK OVER THE KOREAN PENINSULA. THE CURRENT FORECAST
HAS SHIFTED SLIGHTLY EASTWARD IN THE EXTENDED TAUS, BUT REMAINS
ALONG THE WESTERN ENVELOP OF AVAILABLE GUIDANCE. THERE EXISTS
SIGNIFICANT UNCERTAINTY WITHIN THE MODEL FIELDS REGARDING THE
DEVELOPMENT OF THE DEEP LAYERED STR THAT IS EXPECTED TO STEER TS 15W
AS TY 16W (BOLAVEN) MOVES INTO THE MID-LATITUDE FLOW. THE INTENSITY
IS EXPECTED TO CONTINUE WEAKENING AS THE SSTS DECREASE AND VWS
INCREASES. EXTRA-TROPICAL TRANSITION IS EXPECTED TO BEGIN BY TAU 96
WITH COMPLETE TRANSITION BY TAU 120. BASED ON THE COMPLEX STEERING
PATTERN AND THE ERRATIC NATURE OF HALF THE DYNAMIC MODELS, THERE IS
LOW CONFIDENCE IN THE EXTENDED FORECAST TRACK.//
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