WDPN31 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 12W (YAGI) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 113.0E
   INITIAL INTENSITY: 130 KTS
   GEOGRAPHIC REFERENCE: 414 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 47 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) DEPICTS A WELL
ORGANIZED SUPER TYPHOON 12W (YAGI). THE INITIAL POSITION IS PLACED
WITH HIGH CONFIDENCE BASED ON A CLEARLY VISIBLE 15NM, ROUND EYE
FEATURE. ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH STRONG RADIAL
OUTFLOW, LOW VERTICAL WIND SHEAR AND HIGH SEA SURFACE TEMPERATURES.
SYSTEM IS CURRENTLY TRACKING WESTWARD, WITH A TROCHOIDAL MOTION AND
BRIEF PERIODS OF SOUTHWESTWARD COMPONENT. BEING STEERED BY A DEEP-
LAYER SUBTROPICAL RIDGE (STR) TO THE NORTH. THE EYE TEMPERATURE COOLED 
6 DEGREES CELSIUS SINCE THE LAST WARNING, DOWN TO 7 DEGREES CELSIUS, 
INDICATING SLIGHT WEAKENING TREND. THE INITIAL INTENSITY OF 130 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE MAJORITY OF AGENCY AND 
OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   RJTD: T7.0 - 140 KTS 
   RCTP: T7.0 - 140 KTS 
   KNES: T6.0 - 115 KTS
   DEMS: T7.0 - 140 KTS 
   CIMSS SATCON: 134 KTS AT 051800Z
   CIMSS ADT: 132 KTS AT 051730Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: FOLLOWING THE EYEWALL REPLACEMENT CYCLE (ERC)
THE SYSTEM RETAINED ITS MAXIMUM INTENSITY OF 120 KTS AND IS HEADING
TOWARDS THE ISLAND OF HAINAN. THE CURRENT TRACK TAKES IT OVER THE
NORTHERN PORTION OF THE ISLAND, GRAZING THE SOUTHERN TIP OF THE
LEIZHOU (LUICHOW) PENINSULA, BY WHICH TIME IS EXPECTED TO WEAKEN
DUE TO INTERACTION WITH LAND. AS THE STY YAGI ENTERS THE GULF OF
TONKIN, IT WILL ENCOUNTER SIMILARLY FAVORABLE ENVIRONMENT TO THAT
OF SOUTH CHINA SEA, WITH EVEN HIGHER AVAILABLE OCEAN HEAT CONTENT,
OFFSET HOWEVER BY A WEAKER UPPER LEVEL DIVERGENCE. THEREFORE THERE
IS A POTENTIAL FOR SLIGHT RE-INTENSIFICATION OVER THE WARM WATERS
OF THE GULF, CONTINGENT ON STY 12W SPEED OVER WATER, AS WELL AS THE
IMPACT OF TERRAIN ON THE OUTER BANDS OF CONVECTION. BY TAU 36 STY
YAGI IS FORECAST TO REACH NORTHERN VIETNAM, BY WHICH TIME IT WILL
BEGIN TO RAPIDLY WEAKEN DUE TO INTERACTION WITH THE TERRAIN,
PARTICULARLY THE NORTHERN EXTENT OF THE ANNAMITE MOUNTAIN RANGE.


MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE REMAINS IN GOOD
AGREEMENT WITH CROSS-TRACK SPREAD OF 35 NM AT TAU 36, WITH ONLY A
COUPLE MODELS TRACKING THE SYSTEM SLIGHTLY FURTHER SOUTH THAN THE
JTWC TRACK AND THE MULTI-MODEL CONSENSUS. ENSEMBLE MODEL TRACK
GUIDANCE ALSO REMAINS IN TIGHT AGREEMENT. SIMILARLY, THERE IS A
STRONG AGREEMENT IN TERMS OF INTENSITY FORECAST ACROSS ALL MODEL
GUIDANCE WITH THE EXCEPTION ON CANADIAN MODEL, WHICH REFLECTS MUCH
SLOWER WEAKENING TREND THAN THE JTWC ESTIMATE. STY YAGI IS FORECAST
TO COMPLETE DISSIPATION OVER LAND BY TAU 72.


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