WDPN32 PGTW 260300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 11W (SHANSHAN) WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.2N 133.9E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 416 NM SOUTH-SOUTHEAST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH POORLY DEFINED
UPPER-LEVEL ORGANIZED CAUSED BY MODERATE (15-20KT) VERTICAL WIND
SHEAR (VWS). WATER VAPOR IMAGERY DEPICTS STRONG POLEWARD AND
EQUATORWARD OUTFLOW THAT HAS REDEVELOPED OVER THE LAST SIX HOURS.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED ANIMATED MSI. THE INITIAL INTENSITY OF 80 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON AN EARLIER PARTIAL 252056Z
RCM-2 SYNTHETIC APERTURE RADAR (SAR) IMAGE REVEALING A BAND OF 80-
85KT WINDS IN THE EASTERN PERIPHERY OF THE SYSTEM.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) TO THE
NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 77 KTS AT 0030Z
   CIMSS ADT: 79 KTS AT 252330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST TRACK IS SLOWER THAN
THE PREVIOUS WARNINGS BETWEEN TAU 12-72 AS TYPHOON (TY) 11W ROUNDS
THE SUBTROPICAL RIDGE. ADDITIONALLY, THE TRACK LIES FARTHER WEST
THAN PREVIOUSLY FORECASTED, BRINGING THE FORECAST TRACK CLOSER TO
SASEBO AND IWAKUNI. 

FORECAST DISCUSSION: TY 11W IS FORECAST TO CONTINUE TRACKING
WEST-NORTHWESTWARD UNTIL TAU 48, AT WHICH TIME THE SYSTEM WILL
ROUND THE RIDGE AXIS AND SPEED UP IN A NORTHEASTWARD DIRECTION
THROUGH THE END OF THE FORECAST PERIOD. FOR THE FIRST 24 HOURS OF
THE FORECAST TY 11W WILL INTENSIFY GRADUALLY WHILE IN A MARGINALLY
FAVORABLE ENVIRONMENT DUE TO MODERATE (15-20KT) NORTHEASTERLY VWS.
ONCE THE VWS DECREASES, TY 11W IS FORECAST TO PEAK TO 110KTS AFTER 48 
HOURS. THE SYSTEM WILL BEGIN TO WEAKEN AFTER INTERACTING WITH LAND BY 
TAU 72 AND WEAKENING AS IT PASSES OVER SOUTHERN JAPAN. TY 11W WILL 
COME BACK OUT OVER WATER BY TAU 120 IN THE SEA OF JAPAN WHILE ALSO 
INTERACTION WITH AN UPPER-LEVEL TROUGH TO THE NORTH WHICH INITIATES 
EXTRATROPICAL TRANSITION (ETT).

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE OVERALL TRACK OF TY 11W BUT VARIES IN TRACK SPEED
GREATLY BY TAU 120 WITH A ALONG-TRACK SPREAD OF 740NM. GSM
REPRESENTS THE FASTEST SOLUTION IN THE MULTI-MODEL CONSENSUS,
REACHING HOKKAIDO BY TAU 120. ON THE OTHER HAND, THE SLOWEST MEMBER
IS GALWEM WHICH PASSES NEARLY IN TO BEPPU BAY BY TAU 120. THE
INTENSITY GUIDANCE DEPICTS VARYING PEAK INTENSITIES WITH HAFS-A
REACHING 120KTS AT TAU 36 AND THE JTWC SHIPS (GFS) MODEL ONLY
REACHING 90KTS AT TAU 60. 

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