WDPN31 PGTW 042100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (YAGI) WARNING NR 014//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.2N 116.3E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 161 NM SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A WELL
VISIBLE, SLIGHTLY RUGGED EYE FEATURE TRACKING WESTWARD, WITH A
TROCHOIDAL WOBBLE MOTION. FOLLOWING THE LAST 18 HOURS OF RAPID
INTENSIFICATION AND ENABLED BY STRONG UPPER LEVEL DIVERGENCE, THE
SYSTEM IS CURRENTLY EXHIBITING A STRONG, RADIAL OUTFLOW. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE EYE 
FEATURE IN THE ANIMATED INFRARED IMAGERY AND LINED UP WITH THE 041025 
RCM-2 SYNTHETIC APERTURE RADAR (SAR) IMAGE. THE INITIAL INTENSITY OF 
120 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON AFOREMENTIONED SAR 
PASS, AS WELL AS OBJECTIVE AND AGENCY INTENSITY ESTIMATES LISTED 
BELOW.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T6.5 - 127 KTS
   CIMSS SATCON: 105 KTS AT 041200Z
   CIMSS ADT: 127 KTS AT 041800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 31-32 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: TYPHOON (TY) 12W (YAGI) IS FORECAST TO TRACK
WEST-NORTHWESTWARD, PASSING THROUGH THE LEIZHOU (LUICHOW)
PENINSULA, JUST NORTH OF HAINAN BETWEEN TAU 36 AND 48, FOLLOWED BY
TRANSIT THROUGH THE GULF OF TONKIN AND LANDFALL OVER NORTHERN
VIETNAM. CURRENT TRACK PLACES THE TY YAGI JUST NORTH OF HANOI. THE
MAIN STEERING MECHANISM FOR THE TYPHOON 12W REMAINS A BROAD
SUBTROPICAL RIDGE (STR) TO THE NORTH OF THE SYSTEM. OVER THE NEXT
36 HOURS, TY YAGI IS FORECAST TO REMAIN INFLUENCED BY HIGHLY
FAVORABLE ENVIRONMENT, CONSISTING OF LOW VERTICAL WIND SHEAR (5-10 
KTS), WARM SEA SURFACE TEMPERATURES (30-31 DEGREES CELSIUS), AS WELL 
AS HIGH OCEAN HEAT CONTENT AND UPPER LEVEL DIVERGENCE VALUES. 
THEREFORE, TY 12W IS EXPECTED TO CONTINUE INTENSIFYING TO SUPER 
TYPHOON STRENGTH (130 KTS), WITH A POTENTIAL OF HIGHER MAXIMUM 
INTENSITY BETWEEN TAUS 24-36. TY YAGI IS FORECAST TO BEGIN WEAKENING 
AFTERWARD DUE TO DAMPENED OUTFLOW, AS WELL AS SLOWLY INCREASING VWS. 
UPON MAKING LANDFALL, THE SYSTEM IS EXPECTED TO RAPIDLY WEAKEN, 
PARTICULARLY IN RESPONSE TO THE INTERACTION WITH THE NORTHERN EXTENT 
OF THE ANNAMITE MOUNTAIN RANGE.

MODEL DISCUSSION: MODEL GUIDANCE REMAINS IN GOOD AGREEMENT, WITH
ALL MODELS TRACKING THE SYSTEM ACROSS THE LEIZHOU (LUICHOW)
PENINSULA INTO THE NORTHERN VIETNAM. JTWC FORECAST IS PLACED CLOSE
TO THE CONSENSUS, WITH HIGH CONFIDENCE OUT TO TAU 72. FOLLOWING TAU
72 SOME UNCERTAINTY REMAINS IN TERMS OF THE INTERACTION BETWEEN THE
IMPACT OF STR AND THE TERRAIN. AS FAR AS INTENSITY GUIDANCE,
MAJORITY OF THE MODELS REFLECT POTENTIAL FOR CONTINUOUS
INTENSIFICATION AT LEAST TILL TAU 24, WITH RAPID DECLINE IN
INTENSITY AFTER TAU 36. THE INTENSITY MODEL OUTLIERS - HAFS-A, HWRF
- PREDICT INITIAL WEAKENING, WHILE GFS SHOWS RAPID WEAKENING OVER
THE NEXT 12 HOURS FOLLOWED BY INTENSIFICATION OUT TO TAU 36. THE
GUIDANCE OF ALL THREE MODELS DOES NOT CORRESPOND WELL WITH THE
CURRENT ENVIRONMENTAL CONDITIONS, THEREFORE JTWC INTENSITY GUIDANCE
IS ASSESSED SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS, TO ACCOUNT
FOR THE IMPACTS OF THE HAFS-A, HWRF AND GFS.

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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