WDPN33 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (ROKE) WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.7N 133.1E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 285 NM EAST OF KADENA AB, OKINAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A COMPACT
SYSTEM THAT CONTINUED TO SIGNIFICANTLY DEEPEN AND INTENSIFY OVER
THE LAST SIX HOURS. A RAGGED 10-NM ELONGATED EYE HAS INTERMITTENTLY
APPEARED BUT THE CONVECTIVE TOPS ALONG THE SEMI-CIRCULAR EYEWALL
REMAINED VERY COLD AT -82C. POLEWARD OUTFLOW ALSO REMAINED ROBUST
AS EVIDENCE BY CIRRUS TRANSVERSE BANDING EXTENDING DEEP INTO THE
PREVAILING WESTERLIES THAT, FOR NOW, OFFSETS THE INCREASING VERTICAL 
WIND SHEAR. THE INITIAL POSITION IS BASED ON THE INTERMITTENT EYE 
THAT LINED UP WELL WITH THE MICROWAVE EYE FEATURE IN THE 290859Z 
SSMIS 91GHZ IMAGE. THE INITIAL INTENSITY OF 85KTS IS BASED ON OVERALL 
ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND REFLECTS THE 
6-HR RAPID INTENSIFICATION.

INITIAL WIND RADII BASIS: PERSISTENCE.

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 87 KTS AT 290840Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: SHORTENED THE SLOW STORM MOTION
DURING THE MID-PORTION OF THE FORECAST FROM TAUS 36-72 AND SPED UP
NORTHEASTWARD AFTER TAU 72.  

FORECAST DISCUSSION: TY ROKE HAS IS NOW ON THE POLEWARD SIDE OF THE
STR AXIS AND WILL CONTINUE TO ACCELERATE NORTHEASTWARD. AFTER TAU 48, 
AN EXTENSION OF A LOW- TO MID-LAYER SECONDARY STR TO THE NORTHWEST 
WILL COMPETE FOR STEERING AND SLOW THE FORWARD MOTION OF THE CYCLONE. 
AFTER TAU 72, THE PRIMARY STR, NOW TO THE SOUTHEAST, WILL REGAIN 
STEERING AND RE-ACCELERATE THE SYSTEM NORTHEASTWARD. TY 20W HAS 
PEAKED INTENSITY AND WILL NOW GRADUALLY ERODE AS VWS INCREASES WITH 
FURTHER ADVANCE INTO THE STRONG WESTERLIES. ADDITIONALLY, WITH THE 
ENCROACHMENT OF THE SECONDARY STR, UPPER LEVEL SUBSIDENCE WILL ALSO 
SUPPRESS VERTICAL DEVELOPMENT. THESE, IN ADDITION TO COOLING SST 
SOUTHEAST OF JAPAN (BELOW 27C) WILL REDUCE THE SYSTEM TO 30KTS BY TAU 
120. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH 
GRADUAL SPREADING TO JUST 162NM BY TAU 72. AFTERWARD, THE TRACKERS
SIGNIFICANTLY DIVERGE ACROSS- AND ALONG-TRACK, LENDING HIGH 
CONFIDENCE IN THE NEAR- TO MID-PORTION OF THE FORECAST AND LOW
CONFIDENCE AFTERWARD. THERE IS MEDIUM CONFIDENCE IN THE INTENSITY
FORECAST UP TO TAU 72, THEN LOW CONFIDENCE AFTERWARD.


FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
NNNN