WDPN32 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 06W (KHANUN) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.8N 131.6E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 304 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TYPHOON (TY) 06W HAS RAPIDLY INTENSIFIED 45 KNOTS OVER THE PAST 24
HOURS FROM 70 KNOTS AT 300600Z TO THE INITIAL INTENSITY OF 115
KNOTS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
SYMMETRIC EYEWALL SURROUNDING A 20-25NM ROUND EYE (EYE TEMPERATURE
ABOUT PLUS 16.2C) WITH INTENSE CONVECTIVE BURSTS PRODUCING A
GRAVITY WAVE PROPAGATING POLEWARD. THIS IMPROVED CORE STRUCTURE IS
CLEARLY EVIDENT IN A 310705Z SSMIS 91GHZ COLOR COMPOSITE MICROWAVE
IMAGE WITH SPIRAL BANDING PREDOMINANTLY OVER THE SOUTHERN
SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE MSI AND SSMIS IMAGERY. TY 06W HAS TURNED
NORTH-NORTHWESTWARD AS IT COMES UNDER THE STEERING INFLUENCE OF THE
DEEP-LAYER SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTH AND
NORTHEAST WHILE MAINTAINING A FORWARD MOTION OF 09 KNOTS. THE
310000Z 500MB UPPER-AIR SOUNDINGS OVER WESTERN JAPAN AND SOUTH
KOREA INDICATE EAST-SOUTHEASTERLY TO EASTERLY WINDS AT 15 TO 25 KNOTS 
WITH THE RIDGE AXIS EXTENDING FROM WESTERN JAPAN TO SOUTH KOREA. THE 
INITIAL INTENSITY OF 115 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED 
ON THE PGTW, KNES AND RJTD DVORAK ESTIMATES. THE RECENT AIDT AND ADT 
ESTIMATES RANGE FROM 113 TO 119 KNOTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER STR POSITIONED TO THE NORTH
AND NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   CIMSS SATCON: 111 KTS AT 310142Z
   CIMSS ADT: 119 KTS AT 310530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 06W WILL TRACK WEST-NORTHWESTWARD THROUGH
TAU 72 PASSING TO THE SOUTH OF OKINAWA WITH A PEAK INTENSITY OF
120-125 KNOTS BY TAU 24. GRADUAL WEAKENING SHOULD OCCUR AS THE
SYSTEM PASSES OKINAWA WITH MORE PRONOUNCED WEAKENING AS IT SLOWS
AND STALLS NORTHWEST OF OKINAWA AND UPWELLS COOLER WATER. DUE TO
THE SYSTEM'S LARGE SIZE AND CLOSE PROXIMITY TO OKINAWA AFTER CPA,
THERE REMAINS A HIGH PROBABILITY OF GALE-FORCE WINDS OR HIGHER IF
THE SYSTEM DRIFTS CLOSER WITHIN THE WEAK STEERING ENVIRONMENT. AS
DISCUSSED BELOW, THERE IS HIGH UNCERTAINTY (LOW CONFIDENCE) IN THE
JTWC FORECAST TRACK AFTER TAU 48.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT ONLY THROUGH TAU 48 WITH A 41NM CROSS-TRACK SPREAD AT TAU 
36 AND A 51NM CROSS-TRACK SPREAD AT TAU 48 LENDING HIGH CONFIDENCE TO
THIS PORTION OF THE JTWC FORECAST TRACK. JTWC FORECAST TRACKS HAVE
REMAINED WITHIN A TIGHT, 50NM ENVELOPE JUST TO THE SOUTH OF OKINAWA
OVER THE PAST FOUR DAYS. HOWEVER, ALONG-TRACK SPEEDS HAVE REMAINED
INCONSISTENT RESULTING IN A SIGNIFICANT CHANGE IN THE CPA TIMING
OVER THE PAST 12 HOURS. AFTER TAU 48, BOTH DETERMINISTIC AND
PROBABILISTIC GUIDANCE CONTINUE TO INDICATE A VERY LARGE SPREAD
(433NM SPREAD AT TAU 96 AND A 514NM SPREAD AT TAU 120) AND A HIGH
DEGREE OF UNCERTAINTY DUE TO THE RAPID WEAKENING OF THE STEERING
RIDGE TO THE NORTH. THIS RAPID WEAKENING OF THE STEERING RIDGE IS
DUE TO A COMBINATION OF THE WESTERLIES ACROSS THE KOREAN PENINSULA
AND THE UNUSUALLY LARGE SIZE OF TY 06W, WHICH IS CURRENTLY
ESTIMATED AT A 700-780NM DIAMETER. AFTER TAU 48, TY 06W WILL BE
POSITIONED WITHIN A COMPETING STEERING ENVIRONMENT WITH A STR TO
THE EAST AND ANOTHER WEAK STR TO THE WEST THUS A SLOW, POSSIBLY
ERRATIC TRACK THROUGH TAU 120. THIS UNCERTAIN SCENARIO IS EVIDENT IN 
THE 310000Z ECMWF (EPS) AND GFS (GEFS) ENSEMBLE SOLUTIONS.

FORECAST CONFIDENCE:
   TRACK 0 - 48 HR: HIGH
   TRACK 48 - 120 HR: LOW
   INTENSITY 0 - 48 HR: HIGH
   INTENSITY 48 - 120 HR: MEDIUM//
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