Tropical Storm LEKIMA Advisory Thu Aug 08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (LEKIMA) WARNING NR 14//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (LEKIMA), LOCATED APPROXIMATELY 336 NM SOUTH OF
KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHWESTWARD AT 08 KNOTS OVER
THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY SHOWS
THE SYSTEM HAS DEVELOPED A WELL-DEFINED 10-NM EYE AS IT BECAME MORE
COMPACT AND CONSOLIDATED. THE SYSTEM STILL TRAILS A LARGE RAIN BAND
TO THE SOUTHWEST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EYE FEATURE THAT LINED UP PERFECTLY WITH A SHARPLY
OUTLINED MICROWAVE EYE IN THE 070453Z 36GHZ AMSR2 IMAGE. THE INITIAL
INTENSITY OF 85 KNOTS IS BASED ON AN OVERALL ASSESSMENT OF TIGHTLY
CLUSTERED AGENCY DVORAK FIXES RANGING FROM T4.5/77KTS TO T5.0/90KTS.
ENVIRONMENTAL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH
NEAR-RADIAL OUTFLOW, LOW VERTICAL WIND SHEAR AND WARM SST (30C). TY
10W IS TRACKING ALONG THE SOUTHWEST PERIPHERY OF A SUBTROPICAL RIDGE
(STR) TO THE NORTHEAST.
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, PASSING JUST TO THE NORTH OF TAIWAN NEAR
TAU 48 BEFORE TURNING MORE POLEWARD. THE FAVORABLE CONDITIONS WILL
FUEL GRADUAL TO RAPID INTENSIFICATION TO A PEAK OF 125 KNOTS BY TAU
48. AFTERWARD, INCREASING VWS AND LAND INTERACTION WILL WEAKEN IT TO
100 KNOTS BY TAU 72 AS IT APPROACHES THE CHINESE COAST. NUMERICAL
MODEL  GUIDANCE IS IN GOOD AGREEMENT WITH A 155NM SPREAD IN SOLUTIONS
AT  TAU 48 NEAR TAIWAN, LENDING FAIR CONFIDENCE IN THIS PORTION OF
THE JTWC FORECAST TRACK.
   C. AFTER TAU 72, TY 10W WILL TURN NORTHWARD AS THE STR REORIENTS
IN A NORTH-SOUTH CONFIGURATION TO THE EAST. STEADY WEAKENING IS
EXPECTED PRIMARILY DUE TO INCREASING VWS AND LAND INTERACTION AS THE
SYSTEM STRADDLES THE EASTERN CHINESE COAST. BY TAU 120, TY 10W
WILL BE REDUCED TO 60 KNOTS AFTER IT PASSES JUST TO THE EAST OF
SHANGHAI. NUMERICAL MODELS SIGNIFICANTLY DIVERGE WITH AFUM ON THE
LEFT AND NAVGEM ON THE RIGHT MARGIN OF THE ENVELOPE, SPANNING A SWATH
OF OVER 650NM. THEREFORE, THERE IS LOW CONFIDENCE IN THE EXTENDED
PORTION OF THE JTWC FORECAST TRACK THAT IS LAID TO THE LEFT OF
CONSENSUS TO OFFSET THE UNLIKELY NAVGEM SOLUTION DRIVING THE CYCLONE
STRAIGHT INTO THE STR. SINCE THE EVENTUAL TRACK AFFECTS THE PROJECTED
INTENSITY, THERE IS ALSO LOW CONFIDENCE IN THE INTENSITY FORECAST AT
THE EXTENDED TAUS.//
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