WDPN33 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (KRATHON) WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.0N 119.5E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 216 NM SOUTH-SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 31 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAGGED
EYE ENCIRCLED BY SYMMETRIC CONVECTIVE BANDING. THE SYSTEM HAS
REMAINED NEARLY STATIONARY OVER THE LAST SIX HOURS, CONTINUING TO
PRODUCE UPWELLING OF COOL SEA WATER BELOW 26C. HOWEVER, THE
INTENSITY HAS PLATEAUED WHILE COUNTERBALANCED WITH FAVORABLE
ELEMENTS OF LOW VERTICAL WIND SHEAR AND MODERATE UPPER-LEVEL
DIVERGENCE. AN EARLIER 021006Z F17 SSMIS 91GHZ MICROWAVE IMAGE
HIGHLIGHTS THE MINIMAL TRACK MOTION WITH A NEGLIGIBLE DIFFERENCE
BETWEEN THE IMAGE AND THE EYE POSITION IN THE MOST RECENT ANIMATED
EIR. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE AFOREMENTIONED ANIMATED EIR AND MICROWAVE IMAGERY. THE INITIAL
INTENSITY OF 100 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A COMPETING STEERING ENVIRONMENT
BETWEEN TWO SUBTROPICAL RIDGES TO THE EAST AND WEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T6.0 - 115 KTS
   CIMSS ADT: 97 KTS AT 021130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: LOW
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TYPHOON (TY) 20W REMAINS IN A COMPETING
STEERING ENVIRONMENT PINCHED BETWEEN TWO SUBTROPICAL RIDGES
POSITIONED TO THE EAST AND WEST. THE ERRATIC AND SLOW TRACK MOTION
WILL CONTINUE FOR THE REMAINDER OF THE FORECAST AS THE SYSTEM
TRACKS GENERALLY NORTHEASTWARD. THE SYSTEM WILL GRADUALLY WEAKEN
DUE TO THE UPWELLING OF COOL WATER WITHIN THE FIRST 12 HOURS. AFTER
LANDFALL BETWEEN TAU 12-24, THE SYSTEM WILL WEAKEN QUICKLY OVER
LAND DUE TO TOPOGRAPHIC INTERACTION WITH MAINLAND TAIWAN. IN THE
LATE-TERM TRACK, THE FORECAST HAS LESS CONFIDENCE AS THE SYSTEM
BECOMES SHALLOW AND EASILY INFLUENCED BY LOW-LEVEL FLOW. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE HAS RETURNED TO A
BIFURCATED STATE WITH TRACKERS SPREADING IN ALL DIRECTIONS AND
RESULTING IN EXTREMELY LOW CONFIDENCE IN THE JTWC TRACK FORECAST.
THE SPREAD OPENS MOSTLY AFTER INTERACTING WITH MAINLAND TAIWAN, AND
STRUGGLES TO FOLLOW THE SYSTEM AS THE VORTEX WEAKENS. THE INTENSITY
GUIDANCE IS IN GOOD AGREEMENT REGARDING CONSISTENT WEAKENING,
HOWEVER, THE JTWC INTENSITY TRACKERS ARE HIGHLY INFLUENCED BY GFS,
AND THE DRASTIC WESTWARD TRACK THAT THE GFS SOLUTION HAS RESUMED IS
ALSO SKEWING THE INTENSITY GUIDANCE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   INTENSITY 0 - 72 HR: LOW//
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