Tropical Storm TEMBIN Advisory Sun Aug 26

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 31//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (TEMBIN), LOCATED APPROXIMATELY 360 NM SOUTHWEST
OF TAIPEI, TAIWAN, HAS TRACKED SOUTHEASTWARD AT 05 KNOTS OVER THE
PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY INDICATES A
SIGNIFICANT WEAKENING TREND OVER THE PAST SIX HOURS DUE TO
INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH EQUATORWARD OUTFLOW
FROM TY 16W. THIS INTERACTION IS CLEARLY EVIDENT IN RECENT ANIMATED
WATER VAPOR IMAGERY. AS A RESULT OF THE EASTERLY VERTICAL WIND
SHEAR, CONVECTIVE ORGANIZATION HAS DEGRADED AND THE CENTER HAS
BECOME MORE DIFFICULT TO DISCERN; HOWEVER, A 261227Z SSMIS 37 GHZ
IMAGE REVEALS A DEFINED LOW-LEVEL CIRCULATION CENTER WITH TIGHTLY-
CURVED CONVECTIVE BANDING WRAPPING INTO A MICROWAVE EYE FEATURE THUS
PROVIDING FAIR CONFIDENCE IN THE INITIAL POSITION AND RECENT MOTION.
THE INITIAL INTENSITY IS ASSESSED AT 90 KNOTS BASED ON AN AVERAGE OF
DVORAK INTENSITY ESTIMATES RANGING FROM 77 TO 102 KNOTS FROM
KNES AND PGTW. TY 15W IS LOCATED WITHIN A WEAK STEERING ENVIRONMENT
BETWEEN A WEAK SUBTROPICAL RIDGE (STR) TO THE NORTH AND A BUILDING
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTH. ADDITIONALLY, THERE MAY BE
SOME WEAK INTERACTION OCCURRING WITH TY 16W, WHICH IS CENTERED 695
NM EAST-NORTHEAST OF TY 15W'S CENTER.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TY 15W IS FORECAST TO REMAIN WITHIN THIS WEAK STEERING
ENVIRONMENT THROUGH TAU 24 AND WILL TRACK INCREASINGLY NORTHEASTWARD
ALONG THE NORTHWESTERN PERIPHERY OF THE NER, WHICH IS FORECAST TO
BUILD TO THE EAST AS TY 16W TRACKS QUICKLY POLEWARD INTO THE YELLOW
SEA. THIS WILL ALLOW TY 15W TO TURN AND ACCELERATE NORTHWARD OVER,
OR PERHAPS JUST EAST OF TAIWAN. DYNAMIC MODEL GUIDANCE IS IN POOR
AGREEMENT WITH A 400 NM SPREAD AT TAU 72. THE JTWC FORECAST IS
POSITIONED CLOSE TO THE MODEL CONSENSUS BUT FAVORS THE ECMWF AND
JGSM SOLUTIONS, WHICH HAVE BEEN VERY CONSISTENT. TY 15W IS FORECAST
TO WEAKEN AFTER TAU 24 DUE TO INCREASED INTERACTION WITH LAND.
   C. AFTER TAU 72, TY 15W IS FORECAST TO TRACK NORTHWARD ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE TOWARD THE SHANGHAI
REGION. DYNAMIC MODEL GUIDANCE IS IN POOR AGREEMENT WITH A LARGE
SPREAD AT TAU 120. GFDN IS THE WESTERN-MOST OUTLIER WHILE UKMO
REMAINS THE EASTERN-MOST OUTLIER WITH A POLEWARD TRACK OVER THE
KOREAN PENINSULA. THE JTWC FORECAST ALSO FAVORS THE ECMWF SOLUTION
AND REMAINS CONSISTENT WITH PREVIOUS WARNINGS. TY 15W IS
EXPECTED TO WEAKEN SLOWLY DUE TO INTERACTION WITH LAND AND
SHOULD DECREASE TO 35 TO 40 KNOTS BY TAU 120. BASED ON THE COMPLEX
AND WEAK STEERING PATTERN AS WELL AS POSSIBLE WEAK INTERACTION WITH
TY 16W, THERE IS LOW CONFIDENCE IN THE FORECAST TRACK.//
NNNN
NNNN