WDPN33 PGTW 161500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (AMPIL) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 35.0N 142.0E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 114 NM EAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TYPHOON
08W (AMPIL) WITH AN APPEARANCE THAT HAS DEGRADED OVER THE PAST 6
HOURS. THE NORTHERN SECTOR OF THE EYEWELL HAS THINNED OUT AND HAS
BECOME INCREASINGLY RAGGED. THE CENTRAL DENSE OVERCAST (CDO) TOPS
HAVE WARMED AND BECOME MUCH LESS SYMMETRIC WITH A LARGER BULK OF
THE CONVECTION CONFINED IN THE SOUTHERN SEMICIRCLE. DESPITE THE
RECENT DEGRADATION, 08W CONTINUES TO HAVE AN INTENSE APPEARANCE
OVERALL WITH TIGHTLY WRAPPED BANDING AND IMPRESSIVE CIRRUS
FILAMENTS EXTENDING OUTWARD FROM THE SYSTEM. ENVIRONMENTAL ANALYSIS
INDICATES THAT 08W IS IN A FAVORABLE ENVIRONMENT FOR FURTHER
DEVELOPMENT CHARACTERIZED BY STRONG OUTFLOW ALOFT, SLIGHTLY
ELEVATED NORTHEASTERLY SHEAR (AROUND 10 KTS), AND WARM (29-30 C)
SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE ANIMATED EIR IMAGERY AND THE PRESENCE OF
THE EYE FEATURE. THE INITIAL INTENSITY OF 105 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK ESTIMATES LISTED
BELOW.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: 08W IS FORECAST TO CONTINUE TRACKING
NORTHEASTWARD AS IT ROUNDS THE AXIS OF THE STR TO THE EAST OVER THE
NEXT 12 HOURS. AFTER TAU 12, 08W WILL HAVE MADE ITS WAY TO THE
NORTHERN PERIPHRY OF THE STR AND IS EXPECTED TO TRACK MORE
EAST-NORTHEASTERLY AS IT BEGINS TO HEAD TOWARD THE BAROCLINIC ZONE.
EXTRATROPICAL TRANSITION IS FORECAST TO BEGIN AROUND TAU 36 AND
COMPLETE BY TAU 48. 08W HAS BEGUN ITS WEAKENING TREND AS VERTICAL
WIND SHEAR STARTS TO INCREASE WITH VALUES AROUND 25 KTS AT TAU 24.
SEA SURFACE TEMPERATURES WILL ALSO QUICKLY DROP TO BELOW 25 C NEAR
THE SAME TIME. AS A RESULT, 08W IS FORECAST TO DROP TO 85 KTS BY
TAU 24 AND TO 55 KTS AS IT COMPLETES EXTRATROPICAL TRANSITION. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN
EXTREMELY TIGHT AGREEMENT REGARDING THE TRACK OF 08W WITH A MERE 35
NM CROSS-TRACK SPREAD AT TAU 24 WHICH INCREASES TO JUST 71 NM AT
TAU 48. THIS LENDS HIGH CONFIDENCE TO THE JTWC TRACK FORECAST. THE
INTENSITY GUIDANCE IS IN OVERALL GOOD AGREEMENT WITH A SIMILAR
WEAKENING TREND AS DEPICTED BY THE JTWC FORECAST. COAMPS-TC AND GFS
SUGGEST A SLIGHTLY QUICKER WEAKENING TREND, TO AROUND 70 KTS AT TAU
24, WHILE HAFS-A AND HWRF HAVE MORE GRADUAL TREND OF AROUND 90 KTS
AT TAU 24. AFTER TAU 24, GUIDANCE CLOSES IN AND AGREES MORE
CLOSELY. THE JTWC INTENSITY FORECAST IS PLACED SLIGHTLY MORE IN
LINE WITH THE HAFS-A AND HWRF DEPICTION IN THE NEAR TERM AND CLOSE
TO CONSENSUS THEREAFTER WITH MEDIUM CONFIDENCE.

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