Advisories

WDPN31 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SAUDEL) WARNING NR 038//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.1N 122.6E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 293 NM WEST-NORTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON 
(TY) 17W (SAUDEL) WITH AN INCREASINGLY DETERIORATING CENTRAL DENSE 
OVERCAST (CDO) THAT IS PRIMARILY CENTERED TO THE SOUTHEAST OF THE 
LOW-LEVEL CIRCULATION CENTER (LLCC), DEVOID OF ANY VISIBLE EYE 
FEATURE IN EIR. ANIMATED RADAR IMAGERY DEPICTS A PARTIAL EYEWALL THAT 
IS ERODED ON THE NORTHWESTERN QUADRANT AND STRONGER RAINBANDS 
EXPANDING TO THE SOUTHEAST TOWARDS TAIWAN. LACKING ANY RECENT 
MICROWAVE IMAGERY, THE STRUCTURE IS ASSUMED TO CONTINUE TO BE TILTED 
TO THE SOUTHEAST WITH HEIGHT BASED ON PERSISTENCE FROM PREVIOUS 
MICROWAVE DATA. THE INITIAL POSITION IS THUS PLACED WITH LOW 
CONFIDENCE BASED ON A COMBINATION OF ANIMATED RADAR AND EIR. THE 
INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
VISIBLE DETERIORATION OF THE SYSTEM AND AGREEMENT BETWEEN AGENCY 
DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES LISTED BELOW. 
ENVIRONMENTAL CONDITIONS ARE ASSESSED TO BE MARGINAL AS WARM (28-29 
C) SEA SURFACE TEMPERATURES (SSTS) AND MODERATE OUTFLOW ALOFT ARE 
OFFSET BY HIGH (25-30 KTS) OF VERTICAL WIND SHEAR (VWS) FROM THE 
NORTHEAST.

INITIAL WIND RADII BASIS: WIND RADII ADJUSTED BASED ON 271159Z
METOP-B ASCAT DATA

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
NORTHWEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T4.0 - 65 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 68 KTS AT 271754Z
   CIMSS ADT: 69 KTS AT 271730Z
   CIMSS AIDT: 76 KTS AT 271730Z
   CIMSS D-MINT: 77 KTS AT 271756Z
   CIMSS D-PRINT: 68 KTS AT 271830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: HIGH
   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 IS EXPECTED TO MAKE LANDFALL OVER THE
COAST OF CENTRAL CHINA NEAR TAIZHOU WITHIN THE NEXT 12 HOURS. IT WILL 
TRACK WESTWARD AND MAKE A SLIGHT SOUTHWARD TURN AT TAU 24 AS THE 
STEERING INFLUENCE OF THE SUBTROPICAL RIDGE (STR) CENTERED TO THE 
NORTHWEST CONTINUES TO BUILD. REGARDING INTENSITY, 17W IS UNDERGOING 
A STEADY WEAKENING TREND CAUSED BY CURRENT HIGH VWS AND DRY AIR 
ENTRAINMENT. UPON LANDFALL, INTENSITY WILL SHARPLY DECREASE AS 17W 
LOSES ITS WARM OCEAN HEAT SOURCE AND BEGINS TO INTERACT WITH THE 
MOUNTAINOUS TERRAIN, DISSIPATING OVER LAND BY TAU 36.

MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE
REMAINDER OF THE FORECAST PERIOD WITH THE EXCEPTIONS OF NAVGEM AS A
MUCH SLOWER TRACK AND GFS WHICH IS THE SOLE MODEL DEPICTING A 
NORTHWARD TURN BY TAU 36. EXCLUDING THESE TWO TRACKERS, CROSS-TRACK 
SPREAD IS 60 NM AT TAU 36, WITH THE AI-BASED MODELS SHOWING A SHARPER 
SOUTHWARD TURN AT TAU 24 THAN THE REMAINDER OF PHYSICS-BASED MODELS. 
THE OFFICIAL JTWC FORECAST TRACK IS PLACED WITH HIGH CONFIDENCE USING 
AN ADJUSTED MULTI-MODEL CONSENSUS EXCLUDING THE AFOREMENTIONED 
OUTLIERS AND HEDGING MORE TOWARDS THE AI GUIDANCE FROM TAU 24 TO 36. 
INTENSITY GUIDANCE IS ALSO IN STRONG AGREEMENT ON A SHARP WEAKENING 
TREND HEREAFTER DUE TO THE INCREASINGLY HOSTILE CONDITIONS. THE 
OFFICIAL JTWC FORECAST INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, 
CLOSELY IN LINE WITH THE MULTI-MODEL CONSENSUS.

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