WDPN31 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (YAGI) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.7N 111.3E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 314 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 51 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS INDICATED IN ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY,
TYPHOON (TY) 12W IS BEGINNING TO WEAKEN AS IT MAKES LANDFALL OVER 
NORTHERN HAINAN ISLAND. HOWEVER, EIR IMAGERY AND RADAR IMAGERY 
CONTINUE TO SHOW A ROUND 21NM EYE WITH A NEAR COMPLETE EYEWALL AND 
SPIRAL BANDING OVER THE SOUTHERN SEMICIRCLE. ALTHOUGH THE EYEWALL IS 
BEGINNING TO ERODE OVER THE WESTERN QUADRANT, THE OVERALL STRUCTURE 
REMAINS WELL-ORGANIZED WITH EXTENSIVE SPIRAL BANDING OVER ALL 
QUADRANTS. SURFACE OBSERVATIONS AT HAIKOU (ZJHK), OVER NORTHERN HAINAN 
ISLAND, HAVE INCREASED QUICKLY TO 52 KNOTS SUSTAINED (10-MINUTE 
AVERAGE) GUSTING TO 8O KNOTS, WITH SLP NEAR 970MB. OVERALL, THERE IS 
HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON THE EIR IMAGERY. THE 
INITIAL INTENSITY IS ASSESSED AT 125 KNOTS BASED ON THE LOWER END OF 
THE AGENCY DVORAK CURRENT INTENSITY ESTIMATES AND OBJECTIVE INTENSITY 
ESTIMATES RANGING FROM 116 TO 132 KNOTS.   

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   DEMS: T7.0 - 140 KTS 
   CIMSS ADT: 132 KTS AT 060600Z
   CIMSS AIDT: 123 KTS AT 060600Z
   CIMSS DPRINT: 116 KTS AT 060600Z
   CIMSS DMINT: 127 KTS AT 060551Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: LAND INTERACTION

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: TY 12W IS FORECAST TO TRACK WESTWARD TO WEST-
NORTHWESTWARD THROUGH THE FORECAST PERIOD. AS THE SYSTEM TRACKS OVER 
HAINAN ISLAND, RAPID WEAKENING WILL COMMENCE DUE TO INTERACTION
WITH THE RUGGED TERRAIN. AFTER TAU 12, TY 12W WILL WEAKEN FURTHER AS 
IT TRACKS ACROSS THE GULF OF TONKIN, WITH LANDFALL OVER NORTHERN 
VIETNAM EXPECTED NEAR TAU 24. AS THE SYSTEM TRACKS INTO NORTHERN 
VIETNAM, IT WILL WEAKEN RAPIDLY AND DISSIPATE BY TAU 72. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE USED IN THE JTWC
CONSENSUS (CONW) REMAINS IN TIGHT AGREEMENT WITH A 40NM CROSS-TRACK
SPREAD AT TAU 24. 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 12.

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