WDPN31 PGTW 310300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SONGDA) 
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 33.4N 122.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 240 NM SOUTHWEST OF KUNSAN AB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH RAPIDLY
DECAYING DEEP CONVECTION FLARING OVER THE NORTHERN QUADRANT. A
302302Z GMI 89GHZ COLOR COMPOSITE MICROWAVE IMAGE REVEALS DEFINED
SHALLOW BANDING WRAPPING INTO THE LLCC WITH A LINEAR BAND OF DEEP
CONVECTION OVER THE NORTHERN QUADRANT. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE MSI AND MICROWAVE IMAGERY.
TROPICAL DEPRESSION 06W IS LOCATED WITHIN A MARGINAL ENVIRONMENT
UNDER STRONG SOUTHERLY FLOW ASSOCIATED WITH AN UPPER-LEVEL TROUGH
OVER NORTHEAST CHINA. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON RECENT ASCAT DATA AND THE RJTD DVORAK
ESTIMATE.

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

CURRENT STEERING MECHANISM: THE SYSTEM IS STEERING ALONG THE
WESTERN PERIPHERY OF A STRONG SUBTROPICAL RIDGE CENTERED SOUTH OF
CENTRAL JAPAN.


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 302350Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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 IS FORECAST TO TRACK POLEWARD ALONG THE
WESTERN PERIPHERY OF THE LOW-LEVEL SUBTROPICAL RIDGE (STR) THROUGH
TAU 24. AFTER TAU 24, THE SYSTEM WILL RECURVE NORTH-NORTHEASTWARD
AS IT ROUNDS THE NORTHWEST PERIPHERY OF THE STR. ENVIRONMENTAL
CONDITIONS WILL DEGRADE THROUGH THE FORECAST PERIOD WITH INCREASING
VERTICAL WIND SHEAR AND DRY AIR ENTRAINMENT, THEREFORE, THE SYSTEM
WILL WEAKEN AND DISSIPATE PRIOR TO MAKING LANDFALL ALONG THE
SOUTHWESTERN COAST OF NORTH KOREA.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT
WITH THE BULK OF THE GUIDANCE SUPPORTING THE JTWC FORECAST TRACK.
THERE IS SOME UNCERTAINTY IN THE TIMING OF THE NORTH-NORTHEAST TURN
WITH MEDIUM CONFIDENCE OVERALL. OVERALL, THERE IS HIGH CONFIDENCE
IN THE JTWC INTENSITY FORECAST WITH RELIABLE INTENSITY
GUIDANCE INDICATING A STEADY DECREASE IN INTENSITY THROUGH THE
FORECAST PERIOD. 

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