Tropical Storm LEKIMA Advisory 8月8日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (LEKIMA) WARNING NR 16//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (LEKIMA), LOCATED APPROXIMATELY 275 NM SOUTH-
SOUTHWEST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 07 KNOTS (KTS)
OVER THE PAST SIX HOURS. THERE IS HIGH CONFIDENCE IN THE INITIAL
POSITION BASED ON A 7 NM EYE IN ENHANCED INFRARED (EIR) SATELLITE
IMAGERY. ADDITIONALLY, THE EIR REVEALS A LONG RAIN BAND THAT EXTENDS
TO THE SOUTHWEST OF THE CENTER. THE INITIAL INTENSITY OF 110 KTS FALLS
BETWEEN MULTI-AGENCY DVORAK INTENSITIES OF T5.5-T6.0 (102-115 KTS).
FOR THE PAST 42 HOURS, TY 10W HAS RAPIDLY INTENSIFIED UNDER
FAVORABLE ENVIRONMENTAL CONDITIONS: RADIAL OUTFLOW, LOW (5-10 KT)
VERTICAL WIND SHEAR (VWS), AND WARM (29-30 CELSIUS) SEA SURFACE
TEMPERATURE (SST). TY 10W IS TRACKING ALONG THE SOUTHWEST PERIPHERY
OF A SUBTROPICAL RIDGE (STR).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 10W WILL CONTINUE ON ITS CURRENT NORTHWESTWARD TRACK UNDER
THE INFLUENCE OF THE STR, START TURNING MORE NORTHWARD AFTER TAU 36
AS THE STR SHIFTS TO THE EAST, AND MAKE LANDFALL SOUTH OF SHANGHAI
ON A NORTHWARD TRACK AROUND TAU 72. FAVORABLE CONDITIONS WILL ALLOW
FOR CONTINUED INTENSIFICATION THROUGH TAU 24. AFTERWARD, REDUCED
OUTFLOW AND LAND INTERACTION WILL WEAKEN TY 10W TO 85 KNOTS BY TAU
72. WITH THE CLOSE PROXIMITY OF TAIWAN AND CHINA TO THE FORECAST
TRACK, THERE IS HIGH UNCERTAINTY IN THE FORECAST INTENSITY DUE TO
THE IMPACT OF LAND INTERACTION. ALTHOUGH A BIFURCATION IN THE MODELS
BECOMES EVIDENT BY TAU 48, THERE IS FAIR CONFIDENCE IN THIS PORTION
OF THE FORECAST TRACK BECAUSE SPREAD IS 141 NM AT TAU 72.
   C. AFTER TAU 72, TY 10W WILL CONTINUE NORTHWARD ALONG THE WESTERN
PERIPHERY OF THE STR UNTIL TURNING NORTH-NORTHWESTWARD BY TAU 120 AS
WEAK RIDGE BUILDS TO THE NORTH. STEADY WEAKENING IS EXPECTED DUE
PRIMARILY TO LAND INTERACTION AS THE SYSTEM STRADDLES THE CHINESE
COAST. BY TAU 120, TY 10W SHOULD BE REDUCED TO 40 KTS OVER THE
YELLOW SEA. NUMERICAL MODELS BIFURCATE ABOUT TWO GROUPINGS, WITH
ECMWF, ECMWF ENSEMBLE MEAN, AND NAVGEM CLOSELY FOLLOWING THE JTWC
FORECAST TRACK AND THE REMAINING MEMBERS GROUPED ABOUT 170 NM TO THE
WEST BY TAU 120. IF THE STORM FOLLOWS THE WESTERN GROUPING OF
MODELS, IT WILL WEAKEN MORE RAPIDLY AND LIKELY DISSIPATE PRIOR TO
TAU 120. BASED ON THE BIFURCATION IN THE MODEL GUIDANCE, THERE IS
LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST TRACK.//
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