WDPN31 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (YAGI) WARNING NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 115.1E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 193 NM SOUTH-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 49 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER AN IMPRESSIVE PERIOD OF EXTREMELY RAPID INTENSIFICATION,
TYPHOON 12W HAS WEAKENED WHILE UNDERGOING AN EYEWALL REPLACEMENT
CYCLE (ERC) AS PREDICTED BY THE CIMSS M-PERC PRODUCT. ANIMATED
ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 15NM ROUND EYE,
WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE.
EIR IMAGERY, HOWEVER, DOES SHOW A CLEAR WEAKENING TREND WITH EROSION
OF THE EYEWALL OVER THE NORTHWESTERN QUADRANT AND WARMING CLOUD TOP
TEMPERATURES. A 050546Z ATMS 88.2GHZ MICROWAVE IMAGE REVEALS A
COMPACT EYEWALL WITH A BREAK IN THE EYEWALL OVER THE NORTHWESTERN
QUADRANT, WITH FRAGMENTED SPIRAL BANDING. ENVIRONMENTAL CONDITIONS
REMAIN FAVORABLE WITH RADIAL OUTFLOW AND LOW VERTICAL WIND SHEAR
THUS, THE CURRENT WEAKENING TREND IS SOLELY ATTRIBUTED TO THE ERC.
THE INITIAL INTENSITY OF 125 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON AGENCY CURRENT INTENSITY ESTIMATES, WITH OBJECTIVE
ESTIMATES RANGING FROM 117 TO 124 KNOTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND SAR DATA 

CURRENT STEERING MECHANISM: STRONG SUBTROPICAL RIDGE (STR)
ENTRENCHED OVER CENTRAL AND EASTERN CHINA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T7.0 - 140 KTS 
   RCTP: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   DEMS: T6.5 - 127 KTS
   CIMSS SATCON: 119 KTS AT 050600Z
   CIMSS ADT: 124 KTS AT 050600Z
   CIMSS AIDT: 117 KTS AT 050600Z
   CIMSS DPRINT: 122 KTS AT 050600Z
   CIMSS DMINT: 118 KTS AT 050454Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

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: TYPHOON 12W PEAKED AT ABOUT 135-140 KNOTS NEAR
042100Z AS REFLECTED IN EARLIER SAR DATA BUT HAS SUBSEQUENTLY
WEAKENED DUE TO THE ONGOING ERC. WHILE ENVIRONMENTAL CONDITIONS
REMAIN FAVORABLE OVER THE NEXT 12 HOURS, SOME RE-INTENSIFICATION IS
POSSIBLE AFTER THE ERC COMPLETES. AFTER TAU 12, THE SYSTEM WILL
TRACK WESTWARD APPROACHING HAINAN ISLAND, WITH A MORE PRONOUNCED
WEAKENING TREND DUE TO INTERACTION WITH LAND. AFTER TAU 24, RAPID
WEAKENING WILL OCCUR AS THE SYSTEM TRACKS OVER SOUTHERN CHINA AND
NORTHERN VIETNAM, WITH LANDFALL EXPECTED NEAR TAU 48. AS THE SYSTEM
TRACKS INTO THE RUGGED TERRAIN OF NORTHERN VIETNAM, IT WILL
DISSIPATE BY TAU 72. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE USED IN THE JTWC
CONSENSUS (CONW) REMAINS IN TIGHT AGREEMENT WITH A 45-50NM
CROSS-TRACK SPREAD FROM TAU 36 TO TAU 48. PROBABILISTIC GUIDANCE
FROM THE ECMWF (EPS) AND GFS (GEFS) ENSEMBLES ALSO REMAINS IN TIGHT
AGREEMENT SUPPORTING THE JTWC TRACK FORECAST WITH HIGH CONFIDENCE.
RELIABLE INTENSITY GUIDANCE IS ALSO IN VERY GOOD AGREEMENT
SUPPORTING THE RAPID WEAKENING PHASE EXPECTED AFTER TAU 24.   

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