WDPN31 PGTW 301500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SONGDA) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.5N 124.1E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 239 NM SOUTH-SOUTHWEST OF KUNSAN AB, S.
KOREA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT SYSTEM THAT IS STRUGGLING TO CONSOLIDATE WITH FORMATIVE 
CONVECTIVE BANDING FROM THE NORTH AND SOUTH FEEDING INTO A PARTIALLY-
EXPOSED LOW-LEVEL CIRCULATION (LLC). THE INITIAL POSITION IS PLACED 
WITH MEDIUM CONFIDENCE BASED ON THE PARTIALLY-EXPOSED LLC. THE 
INITIAL INTENSITY IS ALSO PLACED WITH MEDIUM CONFIDENCE BASED ON 
OVERALL ASSESSMENT OF AGENCY AND AUTOMATED DVORAK ESTIMATES AND IS
CONSISTENT WITH THE CONVECTIVE SIGNATURE. ENVIRONMENTAL CONDITIONS
ARE MARGINALLY FAVORABLE WITH MODERATE POLEWARD OUTFLOW AND WARM
SST OFFSET BY MODERATE VERTICAL WIND SHEAR.

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

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A LOW- TO
MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTHEAST CENTERED OVER
CENTRAL JAPAN.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 45 KTS AT 300915Z
   CIMSS ADT: 33 KTS AT 301150Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 06W WILL TRACK MORE NORTHWESTWARD THROUGH
TAU 12 THEN TURN NORTHWARD AS IT ROUNDS THE WESTERN PERIPHERY OF
THE STR WHICH IS EXPECTED TO ERODE WITH THE APPROACH OF A
MIDLATITUDE SHORTWAVE TROUGH. AFTER TAU 24, THE CYCLONE WILL
ACCELERATE NORTH-NORTHEASTWARD ON THE POLEWARD SIDE OF THE STR,
MAKING LANDFALL OVER THE WEST COAST OF NORTH KOREA JUST AFTER TAU
60. THE MARGINALLY FAVORABLE CONDITIONS WILL FUEL A SLIGHT
INTENSIFICATION TO A PEAK OF 35KTS BY TAU 12. AFTERWARD, INCREASING
VWS AND COOLING SST WILL LEAD TO A STEADY WEAKENING TO 25KTS PRIOR
TO LANDFALL AND DISSIPATION BY TAU 72 AS LAND INTERACTION SPEEDS UP
THE EROSION.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH THE MAIN PACK GRADUALLY SPREADING TO JUST 50NM AT TAU 72. JGSM
IS THE SOLE LEFT-OF-TRACK OUTLIER OFFERING A DUE NORTHWARD
TRAJECTORY. IN VIEW OF THIS, THERE IS ONLY MEDIUM CONFIDENCE IN THE
JTWC TRACK FORECAST. 


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