WDPN33 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 20W (KRATHON) WARNING NR 
026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.7N 120.7E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 151 NM SOUTH-SOUTHWEST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: EASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: OVER LAND

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD
AND DISORGANIZED MID-LEVEL CIRCULATION ASSOCIATED WITH TROPICAL
STORM 20W (KRATHON). SINCE MAKING LANDFALL THE SYSTEM HAS RAPIDLY
SLOWED DOWN AND DETERIORATED IN STRUCTURE AND INTENSITY, WITH
MINIMAL CONVECTIVE ACTIVITY. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON RADAR AND ENHANCED IT LOOPS. THE INITIAL
INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
RAPID CONVECTIVE STRUCTURE WEAKENING AND DPRINT OBJECTIVE ESTIMATE
OF 44 KTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 15-20 KTS
   SST: OVER LAND
   OUTFLOW: WEAK POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DUE TO RAPID DETERIORATION TRIGGERED
BY TERRAIN INTERACTION AND HIGH VERTICAL WIND SHEAR, THE SYSTEM IS
NOW FORECAST TO DISSIPATE OVER LAND BY TAU 24.

FORECAST DISCUSSION: TS 20W STALLED RIGHT AFTER LANDFALL TO A SPEED
OF 2 KTS AND AS A RESULT OF INTERACTION WITH RUGGED TERRAIN OF
SOUTH-CENTRAL TAIWAN ITS CURRENT INTENSITY DROPPED TO 45 KTS. THE
SYSTEM IS FORECAST TO TRACK NORTHWESTWARD, WHILE CONTINUING TO
WEAKEN DOWN TO 20 KTS BY TAU 24, AND THEREFORE DISSIPATE PRIOR TO 
REACHING THE STRAIT OF TAIWAN. REMNANTS OF THE SYSTEM WILL BE 
ABSORBED INTO THE PREDOMINANT NORTHEASTERLY FLOW ASSOCIATED WITH AN 
ONGOING COLD SURGE FLOW.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS CURRENTLY
DISPLAYING VERY ERRATIC GUIDANCE WITH NEARLY 180 DEGREE TRACK
DIRECTION VARIABILITY INDICATING A FURTHER WEAKENING OF THE VORTEX.
JTWC TRACK IS THEREFORE ASSESSED WITH LOW CONFIDENCE, BASED ON THE 
SUBTROPICAL RIDGE STEERING PATTERN. INTENSITY GUIDANCE HOWEVER 
REMAINS IN GOOD AGREEMENT, WITH ALL MODELS INDICATING FURTHER 
WEAKENING AND DISSIPATION BY TAU 24. AS A RESULT, THE JTWC INTENSITY 
FORECAST IS PLACED WITH MEDIUM CONFIDENCE.

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