Tropical Storm LEKIMA Advisory 8月10日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (LEKIMA) WARNING NR 24//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (LEKIMA), LOCATED APPROXIMATELY 168 NM SOUTH OF
SHANGHAI, CHINA, HAS TRACKED NORTH-NORTHWESTWARD AT 10 KNOTS OVER
THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY
DEPICTS A SLIGHT WEAKENING TREND WITH A COMPACT CENTRAL DENSE
OVERCAST FEATURE. A 091446Z GMI 89GHZ IMAGE AND RADAR IMAGERY
INDICATE CONCENTRIC EYEWALLS WITH SPIRAL BANDING. OVERALL, THERE IS
GOOD CONFIDENCE IN THE INITIAL POSITION. CURRENTLY, THERE ARE NO
SURFACE OBSERVATIONS AVAILABLE NEAR THE CENTER, HOWEVER, A 09/15Z
OBSERVATION FROM DACHEN DAO, APPROXIMATELY 25NM EAST OF THE CENTER,
INDICATED 070/33 KNOTS WITH SLP NEAR 968.6MB. UPPER-LEVEL ANALYSIS
REVEALS LOW VERTICAL WIND SHEAR AND ROBUST POLEWARD OUTFLOW ENHANCED
BY A SHORTWAVE TROUGH TO THE NORTHWEST. THEREFORE, INTERACTION WITH
LAND / FRICTIONAL EFFECTS ARE THE PRIMARY WEAKENING MECHANISM. TY
10W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 10W IS FORECAST TO TRACK NORTHWARD THROUGH TAU 72 ALONG THE
WESTERN PERIPHERY OF THE STR, WHICH REORIENTS NORTH-SOUTH. THE
SYSTEM IS FORECAST TO RAPIDLY WEAKEN AS IT TRACKS OVER THE EASTERN
COAST OF CHINA. NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT,
THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE JTWC
FORECAST TRACK.
   C. AFTER TAU 72, TY 10W WILL TRACK UNDER STRONG SOUTHWESTERLY
FLOW ASSOCIATED WITH A DEEP SHORTWAVE TROUGH OVER NORTHEAST CHINA,
WHICH WILL FURTHER WEAKEN THE SYSTEM DUE TO INCREASING VERTICAL WIND
SHEAR AND CONVERGENCE ALOFT. NUMERICAL MODEL GUIDANCE DIVERGES WITH
SEVERAL MODELS JUMPING ERRONEOUSLY TO MIDLATITUDE VORTICITY CENTERS.
THE REMAINDER OF THE GUIDANCE INDICATES A SLOW NORTHEASTWARD TRACK
OVER THE GULF OF POHAI. TY 10W IS FORECAST TO DISSIPATE BY TAU 96 AS
IT TRACKS CLOSE TO THE UPPER-LEVEL JET. OVERALL, TRACK CONFIDENCE
REMAINS HIGH.//
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