Tropical Storm SONGDA Advisory 7月31日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SONGDA)
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 33.5N 123.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 206 NM SOUTHWEST OF KUNSAN AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER A BRIEF PERIOD OF FAVORABLE CONDITIONS, ENVIRONMENTAL
CONDITIONS ARE DEGRADING WITH MODERATE TO HIGH VERTICAL WIND SHEAR
ASSOCIATED WITH STRONG SOUTHERLY FLOW AHEAD OF AN UPPER-LEVEL
TROUGH OVER NORTHEAST CHINA. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS A LINEAR BAND OF DEEP CONVECTION SHEARING
POLEWARD WITH A COMPACT, PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION
(LLCC) POSITIONED ALONG THE SOUTHERN EDGE OF THE DEEP CONVECTION. A
301942Z SSMIS 91GHZ MICROWAVE IMAGE ALSO REVEALS A LINE OF
DISORGANIZED DEEP CONVECTION WITH SHALLOW BANDING WRAPPING INTO THE
CENTER. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON ANIMATED EIR. 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: T1.0 - 25 KTS
   RJTD: T2.0 - 30 KTS
   CIMSS SATCON: 47 KTS AT 301746Z
   CIMSS ADT: 35 KTS AT 301750Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 36. AFTER TAU 36, 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//
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