WDPN31 PGTW 160300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL//JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 25W (HAIYAN) WARNING NR 19//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 160000Z7 TO 190000Z0 OCT 01.
   A. TYPHOON (TY) 25W (HAIYAN), LOCATED APPROXIMATELY 200 NM WEST-
SOUTHWEST OF OKINAWA, HAS TRACKED NORTHWESTWARD AT 08 KNOTS DURING 
THE PAST SIX HOURS. THE WARNING POSITION IS BASED ON 152330Z4 
INFRARED AND VISIBLE SATELLITE IMAGERY AND AVAILABLE SYNOPTIC DATA. 
THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY 
ESTIMATES OF 90 TO 102 KNOTS. VISIBLE SATELLITE IMAGERY DEPICTS A  
CLOUD-FILLED RAGGED EYE FEATURE. ANIMATED INFRARED IMAGERY REVEALS 
THAT TY 25W HAS BEGUN TO INTERACT WITH MID TO UPPER LEVEL WESTERLIES 
AND ELONGATE TO THE NORTH-NORTHEAST. 
   B. TY 25W IS TRACKING NORTHWESTWARD WITHIN A WEAKNESS OF THE MID 
LEVEL SUBTROPICAL RIDGE AXIS. THE RIDGE IS EXPECTED TO CONTINUE TO 
SHIFT EQUATORWARD AS THE LONGWAVE PATTERN DEEPENS THE WESTERLIES, 
RESULTING IN A TURN POLEWARD IN 12 TO 24 HOURS. DURING THAT PERIOD, 
TY 25W SHOULD ENCOUNTER UNFAVORABLE VERTICAL WIND SHEAR, WEAKEN, AND 
SLOWLY TRACK NORTHEASTWARD UNDER THE INFLUENCE OF THE LOWER LEVEL 
STEERING FLOW. THE DYNAMICAL MODELS ARE GROUPED INTO THREE CLUSTERS. 
THE JMA TYPHOON AND GLOBAL MODELS, UKMET GLOBAL, GEOPHYSICAL FLUID 
DYNAMICS-NAVY MODEL, AND COAMPS INDICATE A RECURVE SCENARIO. SPEED 
DIFFERENCES ARE STILL PRESENT AMONG MODELS. NOGAPS INDICATES A 
QUICKLY WEAKENING SYSTEM WITH A SHARP TURN SOUTHWESTWARD AS IT 
INTERACTS WITH THE SOUTHWEST MONSOON IN THE SOUTH CHINA SEA. THE 
NCEP AVIATION MODEL ALSO INDICATES RAPID WEAKENING, YET KEEPS TY 25W 
QUASI-STATIONARY THROUGH THE PERIOD. THE FORECAST IS BASED ON 
PERSISTENCE, A RECURVATURE SCENARIO, AND A SLOW TRACK NORTHEASTWARD 
MIDWAY THR0UGH THE PERIOD.
   C. TY 25W IS EXPECTED TO WEAKEN AS IT ENCOUNTERS INCREASING 
VERTICAL WIND SHEAR AND DRY NORTHEAST WINDS ASSOCIATED WITH A 
MONSOON SURGE.
   D. WIND RADII ANALYSIS IS BASED ON IMAGERY AND SYNOPTIC DATA. 
FORECAST RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE SIZE TROPICAL 
CYCLONE.
FORECAST TEAM: JEFFRIES/VILPORS/MORRIS/JACOBS/CUTMAN//



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