WDPN33 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (NEPARTAK) WARNING 
NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.1N 150.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 304 NM NORTHWEST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A
DISORGANIZED SUBTROPICAL SYSTEM WITH THE DEEP CONVECTION SHEARED
NORTHEASTWARD PARTIALLY EXPOSING A RAGGED, LARGE, AND ELONGATED LOW
LEVEL CIRCULATION. THE INITIAL POSITION IS PLACED WITH LOW
CONFIDENCE BASED ON THE EIR LOOP. THE INITIAL INTENSITY IS BASED ON
THE PGTW DVORAK FIX AND THE ADT ESTIMATE.

INITIAL WIND RADII BASIS: RECENT SCATTEROMETER DATA.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 241740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST INTENSITIES HAVE BEEN
REDUCED, OTHERWISE, TRACK PHILOSOPHY REMAINS THE SAME. 

FORECAST DISCUSSION: SUBTROPICAL SYSTEM 11W WILL CONTINUE ON ITS
CURRENT TRACK THEN TURN MORE NORHTWESTWARD AFTER TAU 12 UNDER THE
STR. THE MARGINAL ENVIRONMENT WILL SUSTAIN THE CURRENT INTENSITY
FOR 12HRS AS STRONG OUTFLOW AND WARM SSTS OFFSET THE STRONG VWS.
AFTERWARD, THE CYCLONE WILL WEAKEN TO TROPICAL DEPRESSION INTENSITY
AND STRUGGLE TO MAINTAIN CORE INTENSITY AS THE LARGE LLC BECOMES
IRREGULAR AND UNWIELDY. ADDITIONALLY, AN UPPER LEVEL LOW WILL STACK
OVER THE SYSTEM AFTER TAU 48 AND CAUSE SUBSIDENCE ALOFT AND STREAM
COLD DRY AIR IN THE LOWER LEVELS. SHOULD 11W MAINTAIN A CORE, IT
WILL MAKE LANDFALL OVER HONSHU AFTER TAU 72 IN THE VICINITY OF
IWAKI AND CROSS INTO THE SEA OF JAPAN (SOJ) AFTER TAU 96. THE
UNUSUALLY WARM SOJ MAY REVIVE IT 30KTS.

MODEL DISCUSSION: NUMERICAL MODELS HAVE DIVERGED SIGNIFICANTLY
ACROSS- AND ALONG-TRACK WITH NVGM ON THE LEFT MARGIN OF THE
ENVELOPE TRACKING THE VORTEX OVER TOKYO, ACROSS HONSHU, THEN
DEFLECTING IT WEST-SOUTHWESTWARD TOWARD SOUTH KOREA. GFS OFFERS A
NORTH-NORTHEASTWARD TRAJECTORY THAT IS TRUNCATED TO 36HRS ON THE
RIGHT MARGIN. AFUM AND ECMF ALSO OFFER TRUNCATED SOLUTIONS BETWEEN
THE MARGINS. BY TAU 120, THE MODELS SPREAD OUT TO OVER 750NM. THESE
VARYING SOLUTIONS INDICATE THE MODELS ARE TRACKING MULTIPLE WEAK
VORTICES.    

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