WDPN33 PGTW 090300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 31W (HAIYAN) WARNING NR 24//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 31W (HAIYAN), LOCATED APPROXIMATELY 312 NM WEST-
SOUTHWEST OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 20 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
INDICATES AN OVERALL WEAKENING TREND; HOWEVER, THE SYSTEM REMAINS 
STRONG WITH TIGHTLY-CURVED BANDING (TCB) AND A DEVELOPING EYE. A 
TRMM 090059Z 85GHZ IMAGE SHOWS THE TCB AS WELL AS A RE-BUILDING 
EYEWALL, WHICH HAS A BREAK IN THE NORTH QUADRANT. THERE IS GOOD 
CONFIDENCE IN THE INITIAL POSITION BASED ON THE AFOREMENTIONED 
IMAGERY. THE INITIAL INTENSITY IS ASSESSED AT 115 KNOTS BASED ON AN 
AVERAGE OF DVORAK FINAL-T ESTIMATES (102 KNOTS) AND CURRENT 
INTENSITY ESTIMATES (127 KNOTS) FROM KNES AND PGTW. UPPER-LEVEL 
ANALYSIS INDICATES THE SYSTEM HAS MAINTAINED FAVORABLE ENVIRONMENTAL 
CONDITIONS WITH RADIAL OUTFLOW AND WEAK VERTICAL WIND SHEAR (VWS). 
TY 31W IS CURRENTLY TRACKING ALONG THE SOUTHERN PERIPHERY OF AN EAST-
WEST ORIENTED SUBTROPICAL RIDGE (STR) ENTRENCHED TO THE NORTH.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. TY 31W IS FORECAST TO TRACK WEST-NORTHWESTWARD THROUGH TAU 24 
ALONG THE SOUTHWESTERN PERIPHERY OF THE STR. AFTER TAU 24, TY 31W 
SHOULD TURN POLEWARD AS IT TRACKS ALONG THE WESTERN PERIPHERY OF THE 
STR. DYNAMIC GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH TAU 36 WITH 
A 115-NM SPREAD IN SOLUTIONS AT LANDFALL NEAR TAU 24. GFDN REMAINS 
THE SOLE OUTLIER ON THE SOUTHERN EDGE OF THE ENVELOPE AND INDICATES 
A MORE WEST-NORTHWESTWARD TRACK AND A GRADUAL RE-CURVE NORTH-
NORTHWESTWARD. THE JTWC FORECAST CONTINUES TO FAVOR CONSISTENCY AND 
THE BULK OF THE GUIDANCE, WHICH SHOWS A SHARPER RE-CURVE INTO 
NORTHERN VIETNAM. TY 31W IS FORECAST TO RE-INTENSIFY SLIGHTLY DUE TO 
FAVORABLE ENVIRONMENTAL CONDITIONS THROUGH TAU 12 BUT SHOULD BEGIN 
TO WEAKEN AS IT APPROACHES THE VIETNAM COAST DUE TO SLIGHTLY COOLER 
SST AND INTERACTION WITH LAND. TY 31W WILL WEAKEN SIGNIFICANTLY 
AFTER TAU 36 AS IT TRACKS INTO VIETNAM AND IS EXPECTED TO DISSIPATE 
BY TAU 72. OVERALL, THERE IS HIGH CONFIDENCE IN THE JTWC FORECAST 
TRACK.//
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