WDPN31 PGTW 072100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (YUN-YEUNG) WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.7N 137.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 199 NM SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXYVIS SATELLITE IMAGERY (PSI) DEPICTS TROPICAL STORM
YUN-YEUNG (12W) CONTINUING TO FIGHT AN UNFAVORABLE ENVIRONMENT AND
EXHIBIT CHARACTERISTICS OF EXTRATROPICAL TRANSITION. A FULLY
EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), OBSERVABLE ON PSI,
PERSISTS SHOWING ASYMMETRY IN THE LOW-LEVEL CLOUD STRUCTURE WITH
STRATIFORM WEST OF THE LLC AND THIN CONVECTIVE SHALLOW BANDS ON
THE EASTERN PERIPHERY WRAPPING INTO THE LLCC. ADDITIONALLY, RECENT
SCATTEROMETRY DATA DEPICTS AN UNEVEN DISTRIBUTION OF WINDS ABOUT
THE SYSTEM WITH MUCH HIGHER WIND INTENSITY (30 TO 40 KTS) EASTWARD
OF THE LLCC THAN WIND INTENSITY WEST OF THE LLCC (10 TO 15 KTS).  
ANIMATED SATELLITE DERIVED WATER VAPOR IMAGERY REFLECTS A VAST AMOUNT 
OF DRY AIR ENTRAINMENT CONTINUES TO ENCROACH THE SYSTEMS CORE, FURTHER
ACTING TO WEAKEN THE SYSTEM. THE NOTCHED DELTA REGION OF FLARING
CONVECTION OFFSET NORTHEASTWARD OF THE LLCC CONTINUES TO EXPERIENCE
INTENSE SOUTHWESTERLY VERTICAL WING SHEAR (46 KTS AT 071800Z). THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 071800Z
HM9 CIRA PROXYVIS 2KM IMAGE. THE INITIAL INTENSITY OF 40 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON MULTI-AGENCY DVORAK
SUBJECTIVE INTENSITY ESTIMATES AVERAGING TO 35KTS AND CIMSS OBJECTIVE
INTENSITY ESTIMATES AVERAGING TO 41 KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: STR TO THE EAST OF 12W.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 071900Z
   CIMSS ADT: 39 KTS AT 071940Z
   CIMSS AIDT: 43 KTS AT 071940Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 30+ KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 12W IS FORECAST TO CONTINUE ON A NORTHWARD
TRACK UNTIL IT MAKES LANDFALL NEAR TAU 12 ALONG THE SOUTHERN COAST
OF THE CHUBU REGION OF JAPAN.  THE AFOREMENTIONED VIGOROUS VWS, DRY
AIR ENTRAINMENT, AND SOON TO BE REALIZED INTERACTION WITH LAND WILL
QUICKLY WEAKEN THE SYSTEM AS IT PASSES OVER JAPAN FROM TAU 12 TO
TAU 24.  AFTER TAU 24, THE SYSTEM IS ANTICIPATED TO
ENTER THE SEA OF JAPAN AND FULLY DISSIPATE PRIOR TO TAU 36.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT 12W WILL TRACK OVER CENTRAL JAPAN, MAKING LANDFALL NEAR TAU 12
AND RETURNING TO THE SEA OF JAPAN NEAR TAU 24. INTENSITY GUIDANCE
SUGGESTS A RAPID FALL IN INTENSITY AS THE SYSTEM MAKES LANDFALL AND
COMPLETE DISSIPATION BEFORE TAU 36 OVER THE SEA OF JAPAN. THERE IS
A MODERATE CROSS-TRACK SPREAD AT TAU 18 OF 100NM, CONTRIBUTING TO
THE OVERALL FORECAST CONFIDENCE OF MEDIUM.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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