Advisories

WDPN31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SAUDEL) WARNING NR 033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.6N 125.9E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 162 NM NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 17W EXHIBITING A BANDING EYE, DEFINED BY A DISTINCT SPIRAL
BAND THAT WRAPS TIGHTLY INTO THE CENTER, OFTEN WITH A CLOUD-FREE
SLOT SEPARATING THE INNER CORE FROM THE OUTER SPIRAL. THE POLEWARD
OUTFLOW ALOFT HAS BECOME RESTRICTED DUE TO 20-25 KTS OF NORTHERLY
VERTICAL WIND SHEAR (VWS). THE COMPARISON OF THE 260921Z SSMIS 91
GHZ AND 37 GHZ IMAGES INDICATES THAT THE VORTEX IS TILTED EASTWARD
WITH HEIGHT. THE CIRCULATION HAS CONTINUED TO TRAVEL
WEST-NORTHWESTWARD, DEFYING EXPECTATIONS OF A TURN TOWARD THE WEST,
THOUGH ITS TRANSLATION SPEED HAS SLOWED TO 06 KTS. A 260931Z RCM-1
SAR PASS REVEALED A SHRINKING WIND FIELD WITH ESTIMATED WINDS OF
80-90 KTS WITHIN THE NORTHERN SIDE OF THE EYEWALL. THE ENVIRONMENT
IS MARGINAL, CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES OFFSET
BY MODERATE VWS. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE DEFINED BANDING EYE FEATURE IN THE EIR
IMAGERY. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON A BLEND OF THE SAR DATA AND THE HIGHER SIDE OF THE
T4.0-5.0 DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: WEAK SUBTROPICAL RIDGE (STR) TO THE
NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 71 KTS AT 261000Z
   CIMSS ADT: 59 KTS AT 261130Z
   CIMSS AIDT: 65 KTS AT 261130Z
   CIMSS D-MINT: 74 KTS AT 261046Z
   CIMSS D-PRINT: 74 KTS AT 261130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 17W HAS BEEN RELUCTANT TO TURN WESTWARD,
INDICATING THAT THE STR TO THE NORTH IS WEAKER THAN MODELED. THE
SYSTEM WILL SOON BE CAPTURED BY A DEEP-LAYER ANTICYCLONE POSITIONED
OVER THE INTERIOR OF CHINA, FINALLY INDUCING A WESTWARD TO
WEST-SOUTHWESTWARD MOTION. THE LANDFALL POINT CONTINUES TO BE NEAR
THE CITIES OF WENZHOU AND TAIZHOU, CHINA. DESPITE THE WARM OCEAN
WATERS AHEAD, STRENGTHENING VWS WILL CAUSE TY 17W TO ACCELERATE ITS
WEAKENING TREND WHILE IT REMAINS OVER WATER. 30 KTS OF SHEAR
COMBINED WITH INCREASING LAND INTERACTION WILL LEAD TO RAPID
WEAKENING BY TAU 36, A TREND THAT WILL CONTINUE UNTIL THE STORM'S
DEMISE BY TAU 60.

MODEL DISCUSSION: THE GUIDANCE SUITE IS IN VERY TIGHT AGREEMENT IN
PREDICTING AN IMMINENT WESTWARD TURN IN THE NEXT 12 HOURS, FOLLOWED
BY A WEST-SOUTHWESTWARD MOTION. THE SPREAD INCREASES TO 80 NM AT
THE POINT OF LANDFALL AND 100 NM AT TAU 60. THE JTWC FORECAST TRACK
IS POSITIONED WITH HIGH CONFIDENCE NEAR THE JTWC CONSENSUS (CONW),
WHICH IS NEAR THE CENTER OF THE GUIDANCE ENVELOPE THROUGH TAU 48.
THE TRACK LEANS CLOSER TO THE AI CONSENSUS AT TAU 60. THE INTENSITY
AIDS ARE IN EXCELLENT AGREEMENT WITH A MAXIMUM SPREAD OF 10 KTS.
THE JTWC INTENSITY FORECAST IS SET ALONG THE CONSENSUS WITH HIGH
CONFIDENCE THROUGH TAU 48 AND COAMPS-TC AT TAU 60.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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