WDPN33 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (AMPIL) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 26.9N 140.7E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 507 NM SOUTH OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 26 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT
CORE OF WITH SPIRAL BANDS OF DEEP CONVECTION PRESENT TO THE NORTH,
EAST AND SOUTH OF THE SYSTEM, WHILE THE NORTHWEST QUADRANT SHOWS A
MASS OF DRY AIR PROTRUDING INTO THE CORE OF THE SYSTEM. THE
PRESENCE OF DRY MID-LEVEL AIR IS REVEALED BY THE LACK OF
SIGNIFICANT CONVECTION TO THE WEST, WITH THE LOW-LEVEL CLOUD BANDS
CLEARLY EVIDENT IN THE CLEAR DRY AIR. A 140353Z AMSR2 MICROWAVE
PASS SHOWED A WELL-DEFINED MICROWAVE EYE FEATURE IN THE 36GHZ BAND,
WHILE THE 89GHZ BAND REVEALED THE HIGHLY ASYMMETRIC NATURE OF THE
CONVECTIVE STRUCTURE, SOME CONTINUED EASTERLY VORTEX TILT AND THE
DRY AIR ON THE WEST SIDE. THE INITIAL POSITION IS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON THE OBSCURED LLCC, AND EXTRAPOLATION FO
THE AMSR2 MICROWAVE EYE FEATURE. THE INITIAL INTENSITY OF 60 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A MIX OF AGENCY ESTIMATES
OF T4.0 AND OBJECTIVE INTENSITY AIDS OF 45 TO 63 KTS, AS WELL AS
ENVIRONMENTAL IMPACTS LEADING TO THE ARRESTED, BUT STEADY
DEVELOPMENT OF THE SYSTEM. THE ENVIRONMENT REMAINS FAVORABLE
OVERALL, WITH LOW SHEAR, IMPROVING POLEWARD OUTFLOW INTO A
TUTT-CELL TO THE NORTH, AND WARM SSTS. HOWEVER, THE PRESENCE OF THE
DRY AIR IS HINDERING THE SYSTEM FOR THE TIME BEING AND DISRUPTING
CORE SYMMETRIZATION.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 62 KTS AT 130600Z
   CIMSS ADT: 47 KTS AT 130600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 08W (AMPIL) IS CURRENTLY
TRACKING NORTH-NORTHEAST UNDER THE INFLUENCE OF THE NEAR-EQUATORIAL
RIDGE TO THE SOUTHEAST, BUT IS EXPECTED TO START TRANSITIONING INTO
A MORE NORTHWARD TRACK, WHILE GUIDED BY THE DEEP-LAYER SUBTROPICAL
RIDGE EAST OF JAPAN. CONTINUING NORTH, TS AMPIL WILL BE KEPT ON A
NORTHERLY TRACK BY THE PASSAGE OF TD 09W, WHICH IS ALSO TRACKING
NORTH, ALONG THE WESTERN PERIPHERY OF THE STR. WHILE THE MAJORITY
OF THE DYNAMICAL MODELS SUGGEST KEEPING THE TRACK OFF THE SHORE OF
JAPAN, THE MOST RECENT RUN OF THE GFS ENSEMBLE HAS MOVED THE TRACK
SLIGHTLY TO THE WEST AGAIN, BUT KEEPS THE CENTER OFFSHORE OF THE
CHIBA PENINSULA. IN ADDITION, THE ACTUAL CPA TO JAPAN MAY BE CLOSER
THAN IT APPEARS ON THE GRAPHIC, DUE TO INTERPOLATION OF THE TRACK
BETWEEN TAUS 48 AND 72. IN REGARDS TO THE INTENSITY FORECAST, THERE
IS STILL MODERATE DRY AIR INTRUSION INTO THE SYSTEM FORECASTED OVER
THE NEXT 12-18 HOURS. BY TAU 24, THE DRY AIR WILL NO LONGER BE AN
ISSUE, ALLOWING FOR MUCH MORE RAPID DEVELOPMENT, INVOLVING LOWER
SHEAR, 30-31 DEGREE CELSIUS SSTS AND IMPROVED DUAL CHANNEL OUTFLOW.
TS AMPIL IS EXPECTED TO ACHIEVE PEAK INTENSITY OF 110 KTS JUST
PRIOR TO CPA TO JAPAN. TS 08W IS EXPECTED TO STEADILY WEAKEN
FOLLOWING THE CPA TO JAPAN, BEGINS EXTRATROPICAL TRANSITION (ETT)
BY TAU 96 WITH TRANSITION TO A STORM-FORCE EXTRATROPICAL LOW TAU
120.

MODEL DISCUSSION: MODEL GUIDANCE HAS BEEN IN CLOSE CONSENSUS
PARTICULARLY IN REGARDS TO THE TS 08W TRACK, WITH MINOR VARIATIONS
IN REGARDS TO THE CPA DISTANCE. THE MAJORITY OF THE DETERMINISTIC
AND ENSEMBLE MODELS STILL TAKE THE SYSTEM ON THE OFFSHORE TRACK. OF
NOTE, SOME OF THE GFS ENSEMBLE MEMBERS ARE STILL HAVING THE VORTEX
CENTER CROSSING INTO THE TOKYO AREA PRIOR TO THE NORTHEASTWARD
TURN. JTWC FORECAST REMAINS BELOW THE MOST AGGRESSIVE INTENSITY
MODEL RUNS LIKE HAFS-A AND COAMPS-TC, BUT IN CLOSE PROXIMITY TO THE
MULTI-MODEL CONSENSUS DURING THE INTENSIFICATION PHASE, WHILE
REMAINING ON THE HIGHER END DURING THE WEAKENING STAGE.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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