WDPN32 PGTW 150300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (EIGHT) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.4N 140.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 355 NM SOUTH OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 22 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY
EXPOSED, FAST MOVING LOW-LEVEL CIRCULATION (LLCC) OF TROPICAL STORM
(TS) 08W. THE INITIAL POSITION IS THEREFORE PLACED WITH HIGH
CONFIDENCE BASED ON THE SATELLITE IMAGERY ASSESSMENT, CORROBORATED
WITH THE ANALYSIS OF A 150011Z METOP-C ASCAT PASS. GALE FORCE WINDS
ARE LIMITED TO THE EASTERN SEMICIRCLE OF THE SYSTEM, AS IS THE DEEP
CONVECTION PERSISTING OVER THE LAST 6 HOURS. TS 08W IS TRANSITING
NORTHWARD, IN THE WAKE OF TS 06W, WITH TRANSLATION SPEEDS AS HIGH
AS 22 KTS. ENVIRONMENTAL ANALYSIS REVEALS LOW TO MODERATE VERTICAL 
WIND SHEAR (VWS), WARM (27-28 C) SEA SURFACE TEMPERATURES (SST) AND 
MODERATE EQUATORWARD OUTFLOW ENHANCED BY A TROPICAL UPPER TROPOSPHERIC 
TROUGH (TUTT) CELL TO THE SOUTHEAST. THE INITIAL INTENSITY OF 35 KTS IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED ASCAT PASS, 
AS WELL AS THE JTWC DVORAK FIX AND A 22 KTS DPRINT ESTIMATE.

INITIAL WIND RADII BASIS: A 150011 METOP-C ASCAT

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS D-PRINT: 22 KTS AT 150000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: THE VORTEX BELONGING TO TS 08W IS TRANSITING
NORTHWARD AT AN IMPRESSIVE RATE AND IS EXPECTED TO APPROACH THE COAST 
OF JAPAN WITHIN THE NEXT 12 HOURS. IT IS CURRENTLY STEERED BY A LARGE, 
DEEP-LAYER STR CENTERED TO THE NORTHEAST, AHEAD OF A LONGWAVE TROUGH 
TO THE WEST. AS THE SYSTEM APPROACHES SOUTHERN HONSHU, NEAR THE BOSO 
PENINSULA, THE STR IS EXPECTED TO REORIENT SLIGHTLY, RESULTING IN TS 
08W ROUNDING ITS AXIS. AFTERWARD, THE SYSTEM WILL BEGIN TRACKING 
NORTHEASTWARD, WHILE BEING EXPOSED TO INCREASING VERTICAL WIND SHEAR 
AND IMPACTS OF LAND INTERACTION. AS A RESULT, TS 08W IS EXPECTED TO 
BEGIN WEAKENING, WITH FULL DISSIPATION EXPECTED BY TAU 36.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN FAIR AGREEMENT, 
ALBEIT LIMITED, AS NOT ALL MODELS ARE PICKING UP ON THIS CIRCULATION. 
HOWEVER, AMONG THE AVAILABLE CONSENSUS MEMBERS, CROSS-TRACK SPREAD IS 
AT THE LEVEL OF 20 NM BY LANDFALL, INDICATING STRONG CONCURRENCE. OF 
NOTE, TRACK GUIDANCE BECOMES MORE DIVERGENT AROUND THE TIME OF 
DISSIPATION, AS WITNESSED BY CROSS-TRACK SPREAD INCREASING TO 245 NM 
BY TAU 36. THEREFORE JTWC TRACK FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE. INTENSITY GUIDANCE IS ALSO ASSESSED WITH MEDIUM CONFIDENCE 
BASED ON NEARLY ALL MODELS INDICATING POTENTIAL FOR SLIGHT UPTICK IN 
INTENSITY OVER THE NEXT 12 HOURS, FOLLOWED BY RAPID WEAKENING DRIVEN 
BY THE IMPACTS OF LAND INTERACTION AND INCREASING VERTICAL WIND SHEAR. 
THE ONLY OUTLIER AT THE MOMENT IS HAFS, WHICH PREDICTS IMMEDIATE 
WEAKENING.

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