WDPN31 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 18W (CIMARON) 
WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.2N 131.8E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 236 NM EAST-NORTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 18W (CIMARON) WITH AN INCREASINGLY DISORGANIZED, EXPOSED
LOW-LEVEL CIRCULATION CENTER. THE LLCC HAS BECOME ELONGATED OVER
THE PAST 6 HOURS AS THE FRONTAL BOUNDARY EXTENDS DOWN TO THE SYSTEM.
FLARING CONVECTION CAN BE SEEN RUNNING ALONG THE NORTHEASTERN
PERIPHERY, DISPLACED AWAY FROM THE CENTER, ALONG THE CONVERGENT
FLOW. ENVIRONMENTAL ANALYSIS INDICATES THAT 18W IS IN AN
UNFAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD OUTFLOW
ALOFT, MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR, AND THE
PRESENCE OF DRY AIR ALONG THE WESTERN SEMICIRCLE OF THE CIRCULATION.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLCC IN THE ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF
25 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE LOW AGENCY
DVORAK AND RAGGED OVERALL APPEARANCE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: PLACED WITHIN A WEAK STEERING PATTERN
BETWEEN TWO SUBTROPICAL RIDGES POSITIONED TO THE EAST AND WEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS DPRINT: 26 KTS AT 261800Z
   CIMSS DMINT: 26 KTS AT 261638Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 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: 18W IS FORECAST TO BEGIN TRACKING
NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE
TO THE EAST AND ALONG THE ENHANCED GRADIENT WITHIN THE FRONTAL
BOUNDARY RUNNING PARALLEL TO THE COAST OF JAPAN. THIS TRACK IS
EXPECTED TO BE MAINTAINED THROUGH TAU 24 AS THE VORTEX BECOMES
INCREASINGLY ELONGATED AND RIPPED APART DUE TO HIGH VERTICAL WIND
SHEAR ALONG THE FRONTAL BOUNDARY. DISSIPATION OVER WATER IS
EXPECTED TO OCCUR NEAR TAU 24 SOUTHEAST OF KYUSHU.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO HAVE
DIFFICULTY TRACKING THE VORTEX OF 18W DUE TO ITS PLACEMENT NEAR THE
FRONTAL BOUNDARY. THE ECMWF ENSEMBLE MEAN CONTINUES TO SHOW A VERY
QUICK DISSIPATION, WHICH SEEMS LIKELY DUE TO THE LLCC APPEARING TO
ERODE OVER THE PAST 6 HOURS. THE GFS ENSEMBLE MEAN HOLDS ON TO THE
VORTEX FOR SLIGHTLY LONGER BUT STILL DISSIPATES WITHIN 36 HOURS.
DETERMINISTIC MODEL TRACKERS UNREALISTICALLY TRACK 18W VERY QUICKLY
ALONG THE COAST OF JAPAN, POSSIBLY JUMPING VORTICIES. THE JTWC
TRACK FORECAST DEVIATES FROM THE DETERMINISTIC TRACKERS AND IS MORE
IN LINE WITH THE ENSEMBLES WITH LOW CONFIDENCE. INTENSITY GUIDANCE
IS IN GOOD AGREEMENT THAT 18W WILL REMAIN WEAK AS IT DISSIPATES AND
LENDS HIGH CONFIDENCE TO THE JTWC INTENSITY FORECAST. 

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