WDPN32 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 08W (HIGOS) WARNING NR 
013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.2N 135.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 507 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS THE
LOW-LEVEL CIRCULATION CENTER OF TROPICAL STORM (TS) 08W (HIGOS)
FULLY OBSCURED BENEATH A SHALLOW, BUT PERSISTENT, ELONGATED CENTRAL
DENSE OVERCAST. ADDITIONALLY, ANIMATED EIR DEPICTS DRIER AIR
SURROUNDING THE SYSTEM, IDENTIFIABLE BY THE COMPLETE LACK OF
CONVECTION OUTSIDE THE IMMEDIATE VICINITY OF THE STORM. A 25120Z
PARTIAL METOP-B ASCAT PASS REVEALS THE HIGHEST WIND SPEEDS MEASURED
BY THE SWATH ARE CONFINED TO THE SOUTHEASTERN QUADRANT.
ENVIRONMENTAL ANALYSIS REVEALS A MARGINALLY FAVORABLE ENVIRONMENT,
CHARACTERIZED BY LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), WARM
(29-30 C) SEA SURFACE TEMPERATURES, OFFSET BY WEAK EQUATORWARD
OUTFLOW AND THE RELATIVELY DRIER SURROUNDING ENVIRONMENT.

INITIAL WIND RADII BASIS: ADJUSTED THE EASTERN WIND RADII USING THE
251201Z PARTIAL ASCAT PASS.

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 55 KTS AT 251340Z
   CIMSS AIDT: 46 KTS AT 251340Z
   CIMSS D-PRINT: 37 KTS AT 251340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 08W IS FORECASTED TO CONTINUE TRACKING TO
THE NORTH-NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF THE STR
POSITIONED TO THE NORTHEAST AND CROSS THE RIDGE AXIS PRIOR TO TAU
12, BEFORE TRACKING NORTH-NORTHEASTWARD UNTIL TAU 36. AT AROUND TAU
12, 08W WILL ENCOUNTER AN INCREASINGLY HOSTILE ENVIRONMENT THAT
WILL INITIATE A QUICK EXTRATROPICAL TRANSITION (ETT) AS THE SYSTEM 
BECOMES FULLY EMBEDDED IN THE MID-LATITUDE WESTERLIES. INCREASED
UPPER-LEVEL SUPPORT WILL ASSIST IN SUSTAINING SURFACE INTENSITIES
NEAR 45 KTS BY TAU 36 AS TS 08W BECOMES A VERY SHALLOW, SYMMETRIC
COLD-CORE LOW. THE POSSIBILITY FOR THE SURFACE CIRCULATION TO FILL
INTO AN OPEN TROUGH PERSISTS; HOWEVER, ELEVATED SURFACE 
INTENSITIES ARE FORECASTED TO REMAIN UNTIL THE END OF THE FORECAST
PERIOD REGARDLESS OF THE ULTIMATE FATE OF HIGOS. ADDITIONALLY, TS
08W MAY INTERACT WITH TS 07W (MEKKHALA) AS THE TWO STORMS APPROACH
EACH OTHER OFF THE COAST OF MAINLAND JAPAN; HOWEVER, IT IS NOT
EXPECTED THAT THE TWO STORMS WILL MERGE.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT FROM TAU 0-12, BUT IS IN MODERATE AGREEMENT THEREAFTER.
SEVERAL MODELS ARE UNABLE TO TRACK A VORTEX PAST TAU 12 (GSM,
ECMWF DETERMINISTIC, AND EXPERIMENTAL AI), WHILE NAVGEM LOSES THE
CIRCULATION AT TAU 24. AS A RESULT, THE JTWC TRACK FORECAST HAS
BEEN PLACED WITH LOW CONFIDENCE DUE TO UNCERTAINTIES WITH THE
EXPECTED QUICK EXTRATROPICAL TRANSITION OR COMPLETE DISSIPATION
INTO AN OPEN TROUGH. RELIABLE INTENSITY GUIDANCE REMAINS IN
MODERATE AGREEMENT, BUT GENERALLY, RELIABLE MODELS AGREE IN A
SLIGHT INTENSIFICATION PHASE FOLLOWED BY TERMINAL WEAKENING. AS A
RESULT, THE JTWC INTENSITY FORECAST IS ASSESSED WITH MEDIUM
CONFIDENCE.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: LOW
   INTENSITY 00-72 HR: MEDIUM//
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