WDPN31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (YUN-YEUNG) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 23.9N 133.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 765 NM SOUTH-SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXYVIS SATELLITE IMAGERY DEPICTS TROPICAL DEPRESSION
(TD) YUN-YEUNG (12W) CONTINUING TO CONSOLIDATE AND BETTER ALIGN
VERTICALLY OVER THE PAST SIX HOURS.  FLARING CONVECTION PERSISTS
OVER A PARTIALLY OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). 
FORMATIVE BANDING IN THE MID AND LOW LEVELS ARE OBSERVED WRAPPING
INTO THE CENTER OF CIRCULATION AND PROTRUDE FROM THE NORTHERN
EDGE OF THE CIRRUS CANOPY. ANIMATED SATELLITE DERIVED WATER VAPOR
IMAGERY DEPICTS MODERATE POLEWARD AND EQUATORWARD OUTFLOW ALOFT.
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON
ANIMATED ENHANCED INFRARED IMAGERY SHOWING A PARTIALLY OBSCURED
LLCC. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A 051330Z SCATTEROMETRY IMAGE SHOWING 30KTS IN
THE EASTERN PERIPHERY, WITH 25 KTS IN THE SOUTHERN PERIPHERY.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) POSITIONED TO
THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 27 KTS AT 051730Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) YUN-YEUNG (12W) IS
FORECAST TO TRACK NORTHEASTWARD TO NORTH-NORTHEASTWARD ALONG THE
WESTERN PERIPHERY OF THE STR TO THE EAST THROUGH TAU 96 THEN TURN
EASTWARD AND SLOW AS IT ROUNDS THE STR AXIS THROUGH TAU 120. THE
SYSTEM IS ANTICIPATED TO GRADUALLY INCREASE IN INTENSITY TO A PEAK
OF NEAR 55KTS BY TAU 48, INFLUENCED BY WARM SSTS (29 TO 30 DEGREES
CELSIUS) AND MODERATE TO LOW VWS (5 TO 20 KTS). ADDITIONALLY, A MID-
LATITUDE SHORTWAVE TROUGH PASSES NORTH OF 12W AROUND TAU 36, BRIEFLY
ENHANCING POLEWARD OUTFLOW ALOFT AND CONTRIBUTING TO STORM
DEVELOPMENT AND INTENSITY.  AFTER TAU 48, THE SYSTEM IS EXPECTED TO
EXPERIENCE SIGNIFICANT DRY AIR ENTRAINMENT ALONG THE WESTERN
PERIPHERY AND SLOWLY WEAKEN THROUGH TAU 120.  DISSIPATION OVER
WATER IS EXPECTED AFTER TAU 120.

MODEL DISCUSSION: WITH THE EXCEPTION OF JAPAN METEOROLOGICAL
AGENCY'S GLOBAL SPECTRUM MODEL (GSM) TRACKING THE SYSTEM ACROSS THE
KANSAI REGION OF JAPAN NEAR TAU 54, NUMERICAL DETERMINISTIC AND
PROBABILISTIC GUIDANCE IS IN MODERATE AGREEMENT (CROSS-TRACK SPREAD
OF 160NM AT TAU 72) THAT TD YUN-YEUNG WILL REMAIN OVER WATER EAST OF 
JAPAN THROUGHOUT THE FORECAST PERIOD TO TAU 120. BOTH THE GFS AND 
ECMWF ENSEMBLES SHOW 10 TO 20 ENSEMBLE MEMBERS HAVING FAIRLY ERRATIC
TRACKS POST TAU 72 AS THE SYSTEM WEAKENS, LENDING TO A MEDIUM TRACK
CONFIDENCE FOR THE LATER INTERVAL.

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