WDPN33 PGTW 030300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (KRATHON) WARNING NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.4N 120.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 22 NM SOUTHWEST OF KAOHSIUNG, TAIWAN 
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) SHOWS THE SYSTEM
REMAINS SYMMETRICAL; HOWEVER, STRIATIONS AND WARMING CLOUD TOPS
ALONG THE NORTHERN SECTORS HAVE BECOME MORE PROMINENT AS THAT AREA OF
THE CYCLONE HAS BECOME INCREASINGLY EXPOSED TO HIGH VWS AS TY KRATHON
CLOSED IN ON TAIWAN. THE EYE HAS ALSO BECOME CLOUD-FILLED. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A DEFINED LLCC 
FEATURE IN A COMPOSITE RADAR LOOP. THE INITIAL INTENSITY OF 75KTS IS 
ALSO PLACED WITH HIGH CONFIDENCE BASED ON CLOSELY-VALUED AGENCY AND 
AUTOMATED DVORAK ESTIMATES THAT CAPTURED THE WEAKENING TREND AND 
REFLECTS THE 6-HR CONVECTIVE DETERIORATION AS EVIDENCED ON THE EIR 
LOOP.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA NEARBY SURFACE WIND
OBSERVATIONS. 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 74 KTS AT 022330Z
   CIMSS DPRNT: 77 KTS AT 022330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 20W WILL CONTINUE TO TRACK GENERALLY
NORTH-NORTHEASTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE
EAST, MAKE LANDFALL JUST NORTH OF KAOHSIUNG AROUND TAU 06 AND THEN
TRACK INTO CENTRAL TAIWAN. AFTER TAU 24, A NORTHEASTWARD EXTENSION
OF THE STR TO THE WEST WILL BUILD AND ASSUME STEERING, DRIVING THE
SYSTEM WESTWARD INTO THE TAIWAN STRAIT. THE UNFAVORABLE ENVIRONMENT
WILL GET WORSE WITH INCREASING VWS AND LAND INTERACTION OVER THE
EXCEPTIONALLY RAGGED TERRAIN OF TAIWAN, RAPIDLY ERODING THE SYSTEM
DOWN TO 40KTS BY TAU 24. BY TAU 36, AFTER THE SYSTEM EXITS BACK OVER
WATER IN THE TAIWAN STRAIT, COOLER SSTS AND INTRUSION OF COOL DRY
AIR ASSOCIATED WITH A NORTHEASTERLY COLD SURGE AS WELL AS THE
HIGH VWS, WILL DISSIPATE THE SYSTEM BY TAU 48. IT MAY BE SOONER, AS IT 
GETS EMBEDDED IN THE COLD SURGE EVENT. THE COLD SURGE WILL LIKELY MEET 
OR EXCEED 25-KT WINDS, NOT ASSOCIATED WITH 20W. 


MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT UP TO TAU
24, TRACKING THE VORTEX INTO CENTRAL TAIWAN. AFTERWARD THE MEMBERS
DIVERGE ERRATICALLY, AND SHOW AN INDICATION OF A WEAK VORTEX. IN VIEW 
OFTHIS, THERE IS ONLY MEDIUM CONFIDENCE IN THE JTWC TRACK AND
INTENSITY FORECASTS.  


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