WDPN31 PGTW 062100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (YUN-YEUNG)
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.6N 135.6E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 453 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXYVIS SATELLITE IMAGERY (PSI) DEPICTS A PARTIALLY
EXPOSED, DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) POSITIONED ALONG 
THE NORTHERN PERIPHERY OF INTERMITTENTLY FLARING DEEP CONVECTION. A
061652Z ATMS 88.2GHZ MICROWAVE IMAGE REVEALS TIGHTLY CURVED,
SHALLOW BANDING WRAPPING INTO A SLIGHTLY ELONGATED (NORTH TO SOUTH
SEMI-MAJOR AXIS) LLCC WITH A LINEAR BAND OF DEEP CONVECTION SHEARED
POLEWARD, AS EVIDENCED BY PSI. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON A 061730Z HM9 PROXYVIS SATELLITE IMAGE
SHOWING A PARTIALLY EXPOSED LLCC. THE INITIAL INTENSITY OF 40 KTS
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AN AVERAGE OF THE PGTW
AND KNES DVORAK ESTIMATES, CONSISTENT WITH THE CIMSS AIDT ESTIMATE
OF 37KTS AT 061800Z. REMNANTS OF 11W ARE OBSERVABLE IN PSI TRACKING
SOUTHWARD APPROXIMATELY 240NM NORTHWEST OF 12W LLCC.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: STR TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS AIDT: 37 KTS AT 061800Z
   CIMSS SATCON: 37 KTS AT 061900Z 

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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 TRACK NORTHEASTWARD
ALONG THE STR TO THE EAST THROUGH TAU 96. BETWEEN TAU 6 AND TAU 18,
AN UPPER-LEVEL TROUGH SETS UP WEST OF JAPAN AND ESTABLISHES A
SOUTHWEST TO NORTHEAST ORIENTED JET MAXIMA EAST OF JAPAN'S TOHOKU
REGION.  IN THE NEAR TERM, THIS MECHANISM IS ANTICIPATED TO IMPROVE
THE SYSTEMS POLEWARD OUTFLOW ALOFT AND INCREASE THE SYSTEMS
INTENSITY.  AFTER TAU 18, HOWEVER, DRY AIR ENTRAINMENT ALONG THE
WESTERN PERIPHERY OF THE FORECASTED TRACK AND HIGH VERTICAL WIND SHEAR
(25 TO 40 KTS) ARE EXPECTED TO RAPIDLY WEAKEN THE SYSTEM THROUGH
TAU 48 AND CAUSING IT TO DISSIPATE PRIOR TO TAU 96.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
THAT 12W WILL GENERALLY TRACK NORTHEASTWARD THROUGH THE FORECAST
PERIOD, DISSIPATING ENTIRELY PRIOR TO TAU 96.  THE JTWC TRACK
CONSENSUS, AND NOTABLY THE GFS DETERMINISTIC SOLUTION, CONTINUES TO 
TREND SLIGHTLY WESTWARD WITH EACH NEW WARNING PERIODS GUIDANCE, HENCE 
THE WESTWARD TRACK ADJUSTMENT.  INTENSITY GUIDANCE IS IN EXCEPTIONAL 
AGREEMENT AND SUPPORTS PEAK INTENSITY OF 12W OCCURRING NEAR OR JUST 
PRIOR TO TAU 24 (50KTS) AND THEN RAPIDLY WEAKENING THROUGH TAU 48 
(30 KTS), WITH DISSIPATION OCCURRING PRIOR TO TAU 96.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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