WDPN33 PGTW 170900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (AMPIL) WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 37.2N 144.9E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 281 NM EAST-NORTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY ILLUSTRATES A
PROGRESSIVELY DEGRADING TYPHOON 08W (AMPIL). AS THE SYSTEM IS
RACING OFF THE COAST OFF JAPAN, THE SIGNIFICANT SHEAR IS
CONTRIBUTING TOWARDS AN INCREASING TILTED STRUCTURE AND WEAKENING
CONVECTIVE BANDING. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON EIR IMAGERY RESEMBLING EYE FEATURE REMNANTS, AS
WELL AS A 170611Z SSMIS 37 GHZ PASS, WHICH DEPICTS CLEAR LOW-LEVEL
CONVECTIVE BANDING, AS WELL AS FURTHER LACK OF CONVECTION SYMMETRY,
WITH MAJORITY OF IT PRESENT THROUGHOUT THE EASTERN HALF OF THE
TYPHOON. THE INITIAL INTENSITY OF 90 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON AN AVERAGE FROM A SUITE OF INTENSITY ESTIMATES,
INCLUDING AGENCY ESTIMATES AND AUTOMATED DVORAK FIXES, ALL
REFLECTIVE A 6 HOUR SYSTEM DEGRADATION.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP
SUBTROPICAL RIDGE

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   CIMSS SATCON: 84 KTS AT 170600Z
   CIMSS ADT: 72 KTS AT 170600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TY 08W (AMPIL) IF CURRENTLY FORECASTED TO
TRACK NORTHEASTWARD AT 11 KNOTS AND INCREASING IN SPEED THROUGHOUT
THE FORECAST PERIOD, WHILE RAPIDLY WEAKENING. AS THE SYSTEM WRAPS
AROUND THE NORTHERN PERIPHERY OF THE STR, THE ENVIRONMENTAL
CONDITIONS WILL CONTINUE TO ERODE IN TERMS OF TROPICAL CYCLONE
DEVELOPMENT, WITH COLD WATER AND VIRTUALLY NO OCEAN HEAT CONTENT.
BY TAU 24 THE SYSTEM IS EXPECTED TO BEGIN ITS EXTRATROPICAL
TRANSITION, AS IT REACHES THE BAROCLINIC ZONE, AS WELL AS GETS
EMBEDDED INTO THE JET MAXIMA. BY TAU 36 THE TRANSITION IS EXPECTED
TO BE COMPLETE AND TY AMPIL WILL BE CONSIDERED A COLD-CORE,
EXTRATROPICAL LOW.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN VERY
GOOD AGREEMENT, PARTICULARLY IN REGARDS TO TRACK, WITH ACROSS-TRACK
SPREAD OF 60 NM, AND ALONG-TRACK SPREAD OF 48 NM AT TAU 36.
THEREFORE THE JTWC FORECAST IS PLACED WITH HIGH CONFIDENCE, WITHIN
CLOSE PROXIMITY OF MULTI-MODEL CONSENSUS. IN REGARDS TO INTENSITY
GUIDANCE, ALL MODELS INDICATE STEADY AND RAPID WEAKENING, WITH THE
EXCEPTION OF THE CANADIAN MODEL, WHICH MAINTAINS THE INTENSITY AT A
SLOWER PACE OF DEGRADATION, AS WELL AS COAMPS-TC WHICH ESTIMATES A
HIGHER THAN AVERAGE PACE OF WEAKENING. ASIDE FROM THE TWO OUTLIERS,
THE MODEL GUIDANCE MAINTAINS A VERY TIGHT AGREEMENT THROUGHOUT TAU
36. JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE AND IS
TIGHTLY ALIGNED WITH THE ADJUSTED MULTI-MODEL INTENSITY CONSENSUS,
WITH EXPECTED INTENSITY OF 45 KNOTS, BY THE TIME TY AMPIL BECOMES
EXTRATROPICAL.

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