WDPN33 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 08W (AMPIL) WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.6N 141.0E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 289 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON 08W
(AMPIL) WITH A LARGE RAGGED EYE AND A SYMMETRIC CENTRAL DENSE
OVERCAST (CDO) OUTLINING THE EYE. THE EYE HAS BECOME INCREASINGLY
MORE WELL-DEFINED OVER THE PAST 6 HOURS THOUGH AS THE SYSTEM
CONTINUES ITS TRACK NORTHWARD. ENVIRONMENTAL ANALYSIS INDICATES
THAT 08W IS IN A HIGHLY FAVORABLE ENVIRONMENT FOR FURTHER
INTENSIFICATION CHARACTERIZED BY STRONG RADIAL OUTFLOW ALOFT, VERY
LOW VERTICAL WIND SHEAR, AND WARM (30-31C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE ANIMATED MSI AND A 150618Z GMI 37 GHZ MICROWAVE IMAGE
REVEALING A DEFINED EYE FEATURE. THE INITIAL INTENSITY OF 90 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK
INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG RADIAL

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 ALONG THE
WESTERN PERIPHERY OF THE STR TO THE EAST THROUGH TAU 24. NEAR TAU
24, THE SYSTEM IS FORECAST TO BEGIN A TURN NORTHEASTWARD ABOUT 75
NM SOUTHEAST OF YOKOSUKA AS IT ROUNDS THE STR. AFTER TAU 24, 08W IS
EXPECTED TO CONTINUE TRACKING ALONG THE NORTHWESTERN AND NORTHERN
PERIPHERIES OF THE STR THROUGH THE REMAINDER OF THE FORECAST PERIOD
AS IT MAKES ITS WAY INTO THE BAROCLINIC ZONE. EXTRATROPICAL
TRANSITION IS FORECAST TO START AROUND TAU 72 WITH COMPLETION BY TAU
96. REGARDING THE INTENSITY FORECAST, 08W IS FORECAST TO RAPIDLY
INTENSIFY THROUGH TAU 24 WITH A PEAK INTENSITY OF 120 KTS IN
RESPONSE TO THE HIGHLY CONDUCIVE ENVIRONMENT. AFTER TAU 24, VERTICAL
WIND SHEAR IS EXPECTED TO INCREASE TO AROUND 15-20 KTS AND SEA
SURFACE TEMPERATURES ARE EXPECTED TO QUICKLY DROP. THIS WILL
INITIATE THE WEAKENING TREND, WHICH WILL PERSIST THROUGH THE
REMAINDER OF THE FORECAST PERIOD. AROUND TAU 60, SEA SURFACE
TEMPERATURES WILL DROP BELOW 25 C AND 08W WILL RAPIDLY DEGRADE IN
RESPONSE. AN INTENSITY OF 45 KTS IS FORECASTED AS EXTRATROPICAL
TRANSITION COMPLETES NEAR THE TAU 96 MARK. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN VERY GOOD
AGREEMENT THROUGH TAU WITH A CROSS-TRACK SPREAD OF JUST 30 NM AT
TAU 24 AS IT PASSES BY THE BOSO PENINSULA. GEFS AND ECENS MEMBERS
ARE VERY CLOSE TO THE ENSEMBLE MEAN AS WELL. THIS LENDS HIGH
CONFIDENCE TO THE JTWC TRACK FORECAST THOUGH TAU 72, AND MEDIUM
THEREAFTER. INTENSITY GUIDANCE IS IN SLIGHTLY WORSE AGREEMENT. MANY
RAPID INTENSIFICATION (RI) AIDS CONTINUE TO TRIGGER AND DEPICT A
PEAK INTENSITY RANGING FROM 115-125 KTS. NON-RI AIDS ARE SLIGHTLY
SPLIT, WITH HAFS-A AND HWRF BOTH DEPICTING A PEAK INTENSITY OF
AROUND 105 KTS AT TAU 24 WHILE GFS AND THE STATISTICAL DYNAMICAL
MODELS SHOWING A PEAK OF 95 KTS AROUND TAU 24. ALL GUIDANCE AGREES
ON WEAKENING AFTER TAU 24 THOUGH. THE JTWC INTENSITY FORECAST IS
PLACED WITHIN THE RI RANGE THROUGH TAU 24 AND CLOSE TO THE
CONSENSUS AFTERWARDS. 

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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