WDPN31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (TEMBIN) WARNING NR 27//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (TEMBIN), LOCATED APPROXIMATELY 300 NM SOUTHWEST 
OF TAIPEI, TAIWAN, HAS TRACKED SOUTHWESTWARD AT 06 KNOTS OVER THE 
PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY AND A 251239Z 
SSMIS IMAGE DEPICT A 20 NM RAGGED EYE WITH INTENSE DEEP CONVECTION 
OVER THE SOUTHERN SEMI-CIRCLE. THERE IS GOOD CONFIDENCE IN THE 
INITIAL POSITION BASED ON THE EYE AND RADAR FIXES FROM TAIWAN. THE 
INITIAL INTENSITY IS ASSESSED AT 70 KNOTS BASED ON AN AVERAGE OF 
DVORAK ESTIMATES RANGING FROM 65 TO 77 KNOTS. TY 15W IS LOCATED 
WITHIN A WEAK STEERING ENVIRONMENT BUT IS BEGINNING TO WEAKLY 
INTERACT WITH TY 16W AND DRIFT SLOWLY IN A COUNTER-CLOCKWISE MOTION. 
THE 25/00Z 500MB ANALYSIS SHOWS THAT THE SYSTEM IS LOCATED SOUTH OF 
A WEAKNESS IN THE SUBTROPICAL RIDGE (STR) AND POLEWARD OF THE NEAR-
EQUATORIAL RIDGE (NER). TY 15W'S CENTER IS CURRENTLY ABOUT 755 NM 
WEST OF TY 16W'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 36 AND WILL TRACK INCREASINGLY EASTWARD 
ALONG THE NORTHERN PERIPHERY OF THE NER WITH WEAK BINARY INTERACTION 
POSSIBLE. AFTER TAU 36, THE NER 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 FAIR AGREEMENT 
WITH A 190 NM SPREAD AT TAU 72. THE JTWC FORECAST IS POSITIONED 
CLOSE TO THE MODEL CONSENSUS. TY 15W IS FORECAST TO INTENSIFY 
THROUGH TAU 36 BUT WILL THEN WEAKEN PRIMARILY DUE TO LAND 
INTERACTION AND POSSIBLY SOME INCREASED VERTICAL WIND SHEAR 
DUE TO THE PROXIMITY OF TY 16W (ABOUT 650-700 NM AT TAU 36-48).
   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 FAIR AGREEMENT WITH A LARGE 
SPREAD AT TAU 120. GFDN IS THE WESTERN-MOST OUTLIER WHILE GFS 
REMAINS THE EASTERN-MOST OUTLIER WITH A POLEWARD TRACK ALONG 125E. 
THE JTWC FORECAST IS POSITIONED CLOSE TO THE MODEL CONSENSUS AND 
FAVORS THE MORE CONSISTENT ECMWF AND JGSM SOLUTIONS. TY 15W IS 
EXPECTED TO WEAKEN SLOWLY DUE TO INTERACTION WITH LAND AND 
SHOULD DECREASE TO 50 TO 55 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