WDPN33 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (AMPIL) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.8N 143.0E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 164 NM EAST-NORTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A ROBUST
TYPHOON STRENGTH CIRCULATION WITH A 9NM WIDE EYE SURROUNDED BY DEEP
CONVECTION. OVER THE PAST SEVERAL HOUR, PERSISTENT
NORTH-NORTHWESTERLY DEEP LAYER SHEAR HAS ERODED MOST OF THE BANDING
FEATURES IN THE NORTHWESTERN QUADRANT OF 08W. THE INITIAL POSITION
IS PLACED WITH HIGH CONFIDENCE BASED ON THE SMALL EYE FEATURE IN
EIR IMAGERY. THE INITIAL INTENSITY OF 100 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE PREPONDERANCE OF INTENSITY ESTIMATE
INCLUDING AGENCY DVORAKS, CIMSS ADT, AIDT, DPRINT AND DMINT ALL
SUPPORTING 100KTS WITH NEGLIGIBLE DEVIATION.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHARY OF A DEEP
LAYERED SUBTROPICAL RIDGE ENTRENCHED TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T6.0 - 115 KTS
   CIMSS SATCON: 102 KTS AT 1700Z
   CIMSS ADT: 92 KTS AT 1830Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE DUAL-CHANNEL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: 08W (AMPIL) IS FORECASTED TO CONTINUE TRACKING
ALONG THE NORTHWESTERN PERIPHERY OF THE STR WHICH WILL GUIDE THE
SYSTEM NORTHEASTWARD THROUGH THE FORECAST PERIOD. AS THE SYSTEM
CONTINUES TO TRACK POLEWARD AND EASTWARD, ITS ENVIRONMENT WILL
CONTINUE TO WORSEN. OVER THE PAST FEW HOURS, THE NORTHWESTERN
PERIPHERY OF 08W HAS BEGUN TO ERODE UNDER PERSISTENT NORTHERLY
FLOW. NEAR TAU 24, 08W WILL TRACK POLEWARD OF THE 26C ISOTHERM
WHICH WILL FURTHER EXACERBATE THE WEAKENING TREND. NEAR TAU 36, THE
SYSTEM INCREASES ITS INTERACTION WITH THE STRONG BAROCLINIC ZONE
ASSOCIATED WITH THE JET MAXIMA, THEREBY INITIATING EXTRATROPICAL
TRANSITION. THIS TRANSITION WILL BE SWIFT, BY TAU 48, AS 08W IS
RAPIDLY INCORPORATED INTO AND POLEWARD OF THE SUBTROPICAL JET,
BECOMING A COLD CORE BAROCLINIC LOW, DEVOID OF ANY SUBTROPICAL
CHARACTERISTIC.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN EXCELLENT AGREEMENT,
SHOWING A 31NM CROSS TRACK SPREADING AT TAU 24 THAT BECOMES 89NM AT
TAU 48. FOR THIS REASON, THE JTWC FORECAST TRACK IS PLACED WITH
HIGH CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS ALSO IN TIGHT
AGREEMENT WITH ALL MEMBERS INDICATING A STEADY WEAKENING TREND
THROUGH THE FORECAST PERIOD WITH MINIMAL DEVIATION. FOR THIS
REASON, THE JTWC INTENSITY FORECAST IS ALSO PLACED WITH HIGH
CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: ---
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: ---//
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