WDPN31 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SONGDA) 
WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.9N 123.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 206 NM SOUTHWEST OF KUNSAN AB, S. KOREA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS  A
SEMI-EXPOSED LOW LEVEL CIRCULATION (LLC) WITH RAPIDLY ERODING DEEP
CONVECTION STRETCHED POLEWARD FROM THE NORTHERN HALF. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MSI LLC
FEATURE. THE INITIAL INTENSITY IS PLACED WITH MEDIUM CONFIDENCE
BASED ON AN OVERALL ASSESSMENT OF AGENCY DVORAK ESTIMATES AND
NEARBY SURFACE OBSERVATIONS AND REFLECTS THE DEGRADED CONVECTIVE
STRUCTURE. AUTOMATED DVORAK VALUES APPEAR TO BE OVER-ESTIMATED. TD
06W IS NOW IN AN UNFAVORABLE ENVIRONMENT WITH STRONG POLEWARD
OUTFLOW GREATLY OFFSET BY MODERATE TO STRONG (20-25KTS) VWS AND
COOLING (27-26C) SSTS IN THE YELLOW SEA.

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

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A STRONG
SUBTROPICAL RIDGE (STR) CENTERED SOUTH OF
CENTRAL JAPAN.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 44 KTS AT 310504Z
   CIMSS ADT: 37 KTS AT 310550Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG 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: TD SONGDA WILL TRACK NORTH-NORTHEASTWARD ALONG
THE WESTERN PERIPHERY OF THE STR. THE UNFAVORABLE ENVIRONMENT WILL
CONTINUE TO ERODE THE SYSTEM AND CAUSE ITS DISSIPATION BY TAU 36,
POSSIBLY SOONER, IN THE YELLOW SEA.

MODEL DISCUSSION: NUMERICAL MODELS ARE GENERALLY IN AGREEMENT WITH 
SEVERAL MEMBERS BECOMING MORE ERRATIC ACROSS- AND ALONG-TRACK, AN
INDICATION OF A WEAK VORTEX. IN VIEW OF THIS, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS.

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