WDPN32 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (EIGHT) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.7N 140.7E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 164 NM SOUTH-SOUTHEAST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 33 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS A FURTHER
ACCELERATING, NOW NEARLY FULLY OBSCURED LOW-LEVEL CIRCULATION
CENTER (LLCC) ASSOCIATED WITH TROPICAL STORM (TS) 08W. THE INITIAL
POSITION IS DETERMINED WITH MEDIUM CONFIDENCE BASED ON THE
LOW-LEVEL CLOUD TRACING, PARTICULARLY THE EXTRAPOLATION OF NORTHERN
SEMICIRCLE CONVECTIVE BANDING LOCATION. THE INITIAL INTENSITY
ESTIMATE OF 40 KTS IS ALSO ASSIGNED MEDIUM CONFIDENCE BASED ON
PERSISTING TRAIL OF CENTRAL CONVECTION PRESENT IN THE MSI, AS WELL
AS THE LATEST AGENCY DVORAK AND THE AUTOMATED INTENSITY ESTIMATES
LISTED BELOW. TS 08W HAS ACCELERATED SIGNIFICANTLY SINCE THE LAST
WARNING AND IS ASSESSED TO BE TRANSITING NORTH AT 33 KTS, STILL
FOLLOWING THE SYNOPTIC TRAIL OF TS 06W. ENVIRONMENTAL ANALYSIS
INDICATES A MARGINAL THERMODYNAMIC AND DYNAMIC REGIME, CHARACTERIZED 
BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), SUFFICIENTLY WARM SEA 
SURFACE TEMPERATURES (SST) RANGING FROM 27 TO 28 C, AND MODERATE 
EQUATORWARD UPPER-LEVEL OUTFLOW ENHANCED BY A TROPICAL UPPER 
TROPOSPHERIC TROUGH (TUTT) CELL LOCATED TO THE SOUTHEAST.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: STRONG SUBTROPICAL RIDGE (STR) TO THE
EAST-NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 37 KTS AT 150600Z
   CIMSS AIDT: 41 KTS AT 150700Z
   CIMSS D-PRINT: 28 KTS AT 150700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE 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: THE VORTEX OF TS 08W IS TRACKING NORTHWARD AT
VERY HIGH TRANSLATIONAL VELOCITY AND IS EXPECTED TO MAKE PROXIMAL
APPROACH TO THE JAPANESE COAST WITHIN THE NEXT 6-12 HOURS. CURRENT
MOTION IS DICTATED BY STEERING FLOW ASSOCIATED WITH A BROAD,
DEEP-LAYER SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST-NORTHEAST,
POSITIONED AHEAD OF A MID-LATITUDE LONGWAVE TROUGH OVER SOUTH
KOREA. CURRENT TRACK GUIDANCE INDICATES THAT TS 08W WILL TRANSIT
JUST EAST OF SOUTHERN HONSHU, IN THE VICINITY OF THE BOSO
PENINSULA. SIMULTANEOUSLY, A SLIGHT REORIENTATION OF THE STR AXIS
IS EXPECTED TO INDUCE A NORTHEASTWARD TRACK ALONG THE NORTHWESTERN
PERIPHERY OF THE STR. TRACK GUIDANCE ALSO INDICATES LANDFALL OVER 
NORTHEASTERN HONSHU TO OCCUR AROUND TAU 12, PRIOR TO SECONDARY
LANDFALL OVER SOUTHERN CENTRAL HOKKAIDO. OF NOTE, NEARLY ALL OF THE 
GALE FORCE WINDS ARE LOCATED THROUGHOUT THE EASTERN SEMICIRCLE OF THE 
STORM, AS WITNESSED BY RELATIVELY CALM (10-15 KTS) WINDS REPORTED AT 
HACHIJOJIMA WMO STATION, JUST WEST OF THE TRACK. IN TERMS OF 
INTENSITY, TS 08W IS CURRENTLY APPROACHING OR HAS ALREADY REACHED ITS 
PEAK OF APPROXIMATELY 40 KTS AND AS ITS WIND FIELD BEGINS TO INTERACT 
WITH LAND, IT IS FORECAST TO START WEAKENING. ADDITIONALLY, THE SYSTEM 
WILL ENCOUNTER RAPIDLY DETERIORATING ENVIRONMENTAL CONDITIONS, 
INCLUDING ENHANCED VWS AND RAPIDLY COOLING SST. DISSIPATION OF THE 
LOW-LEVEL VORTEX IS EXPECTED BETWEEN TAUS 24 AND 36.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE EXHIBITS FAIR AGREEMENT
IN THE NEAR TERM, THOUGH NOT ALL DYNAMIC MODELS HAVE FULLY
INITIALIZED THE LLCC. AMONG THE AVAILABLE GUIDANCE, CROSS-TRACK
SPREAD IS RELATIVELY MINIMAL (APPROXIMATELY 20 NM AT LANDFALL),
REFLECTING HIGH AGREEMENT ON THE SHORT-TERM TRACK. HOWEVER, MODEL
DIVERGENCE INCREASES SUBSTANTIALLY IN THE POST-LANDFALL PERIOD,
WITH CROSS-TRACK SPREAD EXPANDING TO OVER 300 NM BY TAU 36. THE
JTWC TRACK FORECAST IS THEREFORE ASSESSED WITH MEDIUM CONFIDENCE.
INTENSITY GUIDANCE ALSO SUPPORTS A MEDIUM CONFIDENCE LEVEL, AS ALL
AVAILABLE GUIDANCE INDICATES MORE OR LESS ABRUPT WEAKENING DUE TO
STRONG SHEAR AND LAND INTERACTION. TIMELINE OF THE DISSIPATION
REMAINS UNCERTAIN, BUT IT IS CONTAINED WITHIN THE 24-36
HOUR ENVELOPE AMONG ALL AVAILABLE GUIDANCE.

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