WDPN33 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (AMPIL) WARNING NR 021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 37.8N 147.3E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 396 NM EAST-NORTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 19 KTS
   SIGNIFICANT WAVE HEIGHT: 44 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A FURTHER 
WEAKENING TYPHOON 08W (AMPIL), WITH PROGRESSING DEVELOPMENT OF THE 
VERTICAL TILT, DUE TO INCREASING SHEAR. WHILE THE INTENSITY OF THE 
SYSTEM DECREASED, 170805Z RCM-2 SAR PASS REVEALED AN EXPANDING WIND 
FIELD. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON 
THE EXTRAPOLATION OF THE SAR POSITION, AS WELL AS A 171147Z MTB ASCAT 
IMAGE. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE SAR DATA, AS WELL AS A SUITE OF INTENSITY 
ESTIMATES, INCLUDING AGENCY ESTIMATES AND AUTOMATED DVORAK FIXES. 

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP
SUBTROPICAL RIDGE

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 87 KTS AT 171200Z
   CIMSS ADT: 57 KTS AT 171200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TY 08W (AMPIL) IS CURRENTLY FORECASTED TO 
CONTINUE TRACKING NORTHEASTWARD AT 19 KNOTS AND INCREASE IN SPEED 
THROUGHOUT THE FORECAST PERIOD, WHILE RAPIDLY WEAKENING. THE SYSTEM IS 
CURRENTLY TRANSITING OVER COLDER WATER OF 25 DEGREES CELSIUS, AS WELL 
AS NO REMAINING OCEAN HEAT CONTENT COMBINED, WHILE BEING EXPOSED TO 
SHEAR OF 25 KNOTS, MAKING IT A CLEARLY UNFAVORABLE ENVIRONMENT FOR ANY 
TROPICAL REDEVELOPMENT. HOWEVER, AS THE SYSTEM BEGINS ITS 
EXTRATROPICAL TRANSITION, IT WILL BECOME EMBEDDED IN THE JET MAXIMA, 
ALLOWING IT FOR A POTENTIAL BAROCLINIC INTENSIFICATION. TY AMPIL IS 
CURRENTLY FORECASTED TO WEAKEN DOWN TO TROPICAL STORM STRENGTH OF 50 
KTS BY TAU 24 AND RETAIN THAT INTENSITY, WHILE IT COMPLETES THE 
EXTRATROPICAL TRANSITION.

MODEL DISCUSSION: NUMERICAL MODEL PREDICTION REMAINS IN VERY TIGHT 
AGREEMENT IN REGARDS TO TRACK FORECAST, WITH CROSS-TRACK SPREAD OF 52 
NM, AND ALONG-TRACK SPREAD OF 56 NM AT TAU 36. JTWC FORECAST IS PLACED 
WITH HIGH CONFIDENCE TIGHTLY POSITIONED NEAR MULTI-MODEL CONSENSUS. 
INTENSITY ESTIMATES AND MODELS ARE ALSO IN GOOD AGREEMENT WITH ONLY 
THE COAMPS-TC PREDICTING A QUICKER AND SHARPER WEAKENING. MAJORITY OF 
THE REMAINING MODELS DEPICT A STEADY AND RAPID WEAKENING UNTIL TAU 24, 
WITH POTENTIAL IMPACT FROM A STRONG BAROCLINIC ZONE BY TAU 36 ALLOWING 
THE SYSTEM TO RETAIN ITS INTENSITY AT THAT STAGE.  

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