Advisories

WDPN31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 052//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.2N 124.0E
   INITIAL INTENSITY: 75 KTS
   GEOGRAPHIC REFERENCE: 184 NM NORTHEAST OF TAIPEI, TAIWAN
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
(TY) 12W (DOLPHIN) YET AGAIN LOSING A DISCERNIBLE EYE FEATURE AS
THE COMPACT CENTER HAS BECOME CLOUD FILLED. TY 12W HAS MAINTAINED
STRONG BANDING FEATURES AND A MASSIVE OVERALL CONVECTIVE STRUCTURE,
MEASURING OVER 600 NM IN DIAMETER AS ITS OUTERMOST RAINBANDS BEGIN
TO MAKE LANDFALL OVER EASTERN CHINA. ENVIRONMENTAL ANALYSIS REVEALS
FAVORABLE CONDITIONS WITH LOW (5-10 KTS) OF VERTICAL WIND SHEAR,
WARM (29-30 C) SEA SURFACE TEMPERATURES (SSTS), AND GOOD OUTFLOW
ALOFT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON
THE DIMPLE EYE FEATURE IN EIR IMAGERY AS WELL AS EXTRAPOLATION FROM
A 071425Z GMI 89 GHZ MICROWAVE IMAGE DEPICTING A MICROWAVE EYE. THE
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
SPREAD BETWEEN AGENCY DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES
LISTED BELOW, HEDGING CLOSER TO THE MICROWAVE IMAGERY BASED DMINT
AS THE ADT VALUE HAS BEEN OBSERVED TO STRUGGLE DURING THESE TIME
PERIODS OF THE EYE QUICKLY APPEARING AND THEN FILLING.

INITIAL WIND RADII BASIS: WIND RADII ADJUSTED BASED ON AN 081153Z
METOP B ASCAT IMAGE.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
SOUTHERN HONSHU.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 69 KTS AT 081700Z
   CIMSS AIDT: 78 KTS AT 081700Z
   CIMSS D-MINT: 77 KTS AT 081423Z
   CIMSS D-PRINT: 84 KTS AT 081700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG 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 12W IS FORECAST TO CONTINUE ITS
WEST-NORTHWESTWARD TRACK AND MAKE LANDFALL OVER EASTERN CHINA
ROUGHLY 200 NM SOUTH OF SHANGHAI BETWEEN TAUS 12 AND 24. TY 12W IS
THEN EXPECTED TO TURN POLEWARD ON A NORTHWESTWARD TRACK FOR THE
REMAINDER OF THE FORECAST PERIOD UNDER THE STEERING INFLUENCE OF A
SUBTROPICAL RIDGE (STR) CURRENTLY CENTERED OVER SOUTHERN HONSHU.
THIS STR IS EXPECTED TO BUILD AND EXTEND SOUTHWARD, THUS GIVING 12W
A MORE POLEWARD TRACK. IN REGARDS TO INTENSITY, 12W IS FORECAST TO
DECREASE SLIGHTLY IN INTENSITY OVER WATER AS IT MOVES AWAY FROM AN
AREA OF HIGHER OHC. UPON MAKING LANDFALL, A STEEP DECLINE IN
INTENSITY IS FORECAST AS TERRAIN INTERACTION OCCURS, ULTIMATELY
RESULTING IN THE DISSIPATION OF TY 12W OVER LAND NO LATER THAN TAU
60.


MODEL DISCUSSION: TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT FOR THE
REMAINDER OF THE FORECAST PERIOD WITH THE EXCEPTION OF GFS WHICH
TRACKS 12W MUCH FARTHER TO THE SOUTH. AN ADJUSTED CONSENSUS WAS RUN
EXCLUDING THIS OUTLIER AND USING THE BEST PERFORMING MODELS
THROUGHOUT THE LIFESPAN OF 12W TO CREATE THE FORECAST TRACK. THE
OFFICIAL JTWC FORECAST TRACK IS LAID WITH HIGH CONFIDENCE FOR THE
REMAINDER OF THE FORECAST PERIOD, CLOSELY IN LINE WITH THE ADJUSTED
MULTI-MODEL CONSENSUS, AI CONSENSUS, AND EXPERIMENTAL GOOGLE
DEEPMIND MODEL. MODEL INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT
WITH THE EXCEPTION OF HWRF WHICH DOES NOT DEPICT AS SHARP OF A
DECREASE UPON LANDFALL WITH CHINA. EXCLUDING HWRF, THE REMAINDER OF
THE MODEL GUIDANCE MAINTAINS A 15 TO 20 KT SPREAD THROUGHOUT THE
FORECAST PERIOD. THE OFFICIAL JTWC FORECAST INTENSITY IS ASSESSED
WITH HIGH CONFIDENCE BASED ON THIS GENERAL AGREEMENT, SLIGHTLY
ABOVE THE MULTI-MODEL CONSENSUS.

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