WDPN33 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 20W (ROKE) WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 25.8N 132.2E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 241 NM EAST OF KADENA AB, OKINAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A COMPACT
SYSTEM THAT HAS SIGNIFICANTLY DEEPENED AND INTENSIFIED OVER THE
LAST SIX HOURS. A RAGGED BUT DEFINED 7X14 NM ELONGATED EYE HAS
EVOLVED AND CONVECTIVE TOPS ALONG THE SEMI-CIRCULAR EYEWALL HAVE
COOLED TO -82C. POLEWARD OUTFLOW HAS ALSO FURTHER IMPROVED AS
EVIDENCE BY CIRRUS TRANSVERSE BANDING NOW EXTENDING FURTHER NORTH
AND DEEP INTO THE PREVAILING WESTERLIES. THE INITIAL POSITION IS
BASED ON THE DEFINED EYE AND SUPPORTED BY A TIGHT CLUSTER OF
AGENCY, AUTOMATED, AND RJTD RADAR FIXES. THE INITIAL INTENSITY OF 
70KTS IS BASED ON THE HIGH END OF AGENCY AND AUTOMATED DVORAK 
ESTIMATES AND REFLECTS THE 6-HR RAPID INTENSIFICATION.

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

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


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T3.5 - 55 KTS
   KNES: T4.5 - 77 KTS
   CIMSS ADT: 72 KTS AT 290550Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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 ROKE HAS CRESTED THE STR RIDGE AXIS AND
WILL NOW ACCELERATE NORTHEASTWARD ON THE POLEWARD SIDE OF THE STR.
BY TAU 48, A SECONDARY STR TO THE NORTH WILL COMPETE FOR STEERING
AND STALL TY 20W IN A SLOW OR EVEN QUASI-STATIONARY MOTION. THE
ENVIRONMENT WILL SLOWLY BECOME UNFAVORABLE 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 150NM 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//
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