WDPN31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (CIMARON) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
 
SUMMARY:
   INITIAL POSITION: 27.8N 133.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 556 NM SOUTHWEST OF YOKOSUKA, JAPAN
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET
 
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
INCREASINGLY PROMINENT POLEWARD OUTFLOW CHANNEL FLOWING
NORTHEASTWARD DUE TO THE PROXIMITY OF SOUTHWESTERLY JETSTREAM WINDS
IN THE UPPER LEVELS. DESPITE THE IMPROVED OUTFLOW, THE SYSTEM HAS
BEEN STRUGGLING TO REMAIN ORGANIZED AFTER IT DECOUPLED OVER 12 HOURS
AGO. SINCE THEN, THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS BEEN
FULLY EXPOSED WHILE MEANDERING SOUTHWESTWARD, APART FROM THE MAIN
AREAS OF CONVECTION DISPLACED TO THE EAST. ISOLATED AREAS OF 
CONVECTION CONTINUE TO FLARE THROUGHOUT THE EASTERN SEMICIRCLE WITH 
ANVILS SHEARING TO THE EAST. THE INITIAL INTENSITY OF 30 KTS IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON CIMSS CURRENT INTENSITY 
ESTIMATES ADT AND DRPINT, WHICH ARE AT 31 KTS, AND DUE TO THE ONGOING
DECOUPLED STRUCTURE WEAKENING THE SYSTEM. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE FULLY EXPOSED LLCC.
 
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
 
CURRENT STEERING MECHANISM: WEAK STEERING DUE TO A COL BETWEEN
SUBTROPICAL RIDGES TO THE WEST AND EAST.
 
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   RCTP: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 251130Z
 
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
 
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE
 
3. FORECAST REASONING.
 
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
 
FORECAST DISCUSSION: WEAK DIFFLUENCE ALOFT, LOW-TO-MODERATE
VERTICAL WIND SHEAR, AND WARM SEA SURFACE TEMPERATURES WILL ALLOW
THE SYSTEM TO MAINTAIN A RELATIVELY STEADY INTENSITY WHILE IN ITS
CURRENTLY STALLED POSITION. THE WEAK ENVIRONMENTAL STEERING FLOW
HAS LED TO A SLOW AND ERRATIC DRIFTING MOTION IN THE SHORT TERM
UNTIL THE SUBTROPICAL RIDGE TO THE EAST BEGINS TO GAIN INFLUENCE
BETWEEN TAU 12 AND TAU 24. AS THE SUBTROPICAL RIDGE TAKES CONTROL
OF THE SYSTEM'S ENVIRONMENT, 18W WILL ACCELERATE NORTHEASTWARD
TOWARDS CENTRAL HONSHU. UNLESS IT CAN REGAIN A MORE
VERTICALLY-ALIGNED STRUCTURE, THERE IS A GOOD POSSIBILITY THE
SYSTEM MAY DISSIPATE AFTER TAU 36. ASSUMING THE SYSTEM CAN MAINTAIN
ITS ORGANIZATION, IT IS EXPECTED TO BECOME INCREASINGLY ELONGATED
AFTER TAU 36. THIS WILL ALLOW FOR SIGNIFICANT DRY AIR TO BE DRAWN
INTO THE CORE FROM THE WEST BY TAU 48, FURTHER INCREASING THE
CHANCES OF DISSIPATION, AND OTHERWISE LEADING TO EXTRATROPICAL
TRANSITION. ANY REMAINING ELEMENTS OF 18W WILL BECOME FULLY
EXTRATROPICAL BY TAU 72, AND THE ASSOCIATED WIND FIELD WILL
STRENGTHEN DUE TO BAROCLINIC CYCLOGENESIS PROCESSES.
 
MODEL DISCUSSION: TRACK GUIDANCE SHARES IMPROVING AND TIGHT
AGREEMENT REGARDING AN INITIALLY QUASI-STATIONARY MOTION TURNING
POLEWARD AND CURVING TO THE NORTHEAST AT ACCELERATING SPEEDS. THE
INTENSITY GUIDANCE, HOWEVER, REMAINS CHALLENGED BY UNCERTAINTIES
REGARDING TWO POSSIBLE OUTCOMES OF 18W, INDICATING A POTENTIAL
RE-INTENSIFICATION DURING THE TRANSITION TO AN EXTRATROPICAL LOW OR
A COMPLETE DISSIPATION OF THE SYSTEM PRIOR TO TRANSITION. THE JTWC
FORECAST IS WEIGHTED BELOW THE BULK OF THE INTENSITY GUIDANCE,
BASED ON THE METEOROLOGICAL ANALYSIS THAT THE ENVIRONMENT WILL
BECOME INCREASINGLY UNFAVORABLE IN THE MIDDLE TAUS. THE SLIGHT
STRENGTHENING PREDICTED AT TAU 72 REFLECTS CONDITIONS ASSOCIATED
WITH A DEVELOPING EXTRATROPICAL LOW AND IS MOST CLOSELY MATCHED TO
THE GFS INTENSITY AID.
 
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH//
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