Tropical Storm LEKIMA Advisory Wed Aug 07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (LEKIMA) WARNING NR
10//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 10W (LEKIMA), LOCATED APPROXIMATELY 449 NM
SOUTH OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD
AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY SHOWS A CONSOLIDATING SYSTEM WITH SHALLOW AND FRAGMENTED
RAIN BANDS TRAILING FROM THE SOUTHWEST. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON A FORMATIVE MICROWAVE EYE IN THE
060636Z SSMIS MICROWAVE IMAGE. THE INITIAL INTENSITY OF 50 KNOTS IS
AVERAGED FROM AGENCY DVORAK ESTIMATES RANGING FROM T3.0/45KTS TO
T3.5/55KTS. ENVIRONMENTAL ANALYSIS SHOWS THAT TS 10W IS UNDER
MODERATE (20 TO 25 KNOT) VERTICAL WIND SHEAR (VWS) THAT IS OFFSET BY
A STRONG EQUATORWARD OUTFLOW. SSTS ARE HIGHLY FAVORABLE AT 31
CELSIUS. THE CYCLONE IS IN A COL BETWEEN A SUBTROPICAL RIDGE (STR) TO
THE NORTHEAST AND A NEAR EQUATORIAL RIDGE (NER) TO THE SOUTH BUT
APPEARS TO BE MOVING SLOWLY NORTHWARD.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE OVERALL FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THE STR WILL SLOWLY ASSUME STEERING AND DRIVE TS 10W
NORTHWESTWARD TOWARD NORTHERN TAIWAN. THE VWS IS EXPECTED TO RELAX.
THIS PLUS IMPROVED RADIAL OUTFLOW AND WARM SSTS WILL PROMOTE STEADY
INTENSIFICATION TO A PEAK OF 75 KNOTS BY TAU 48. AFTERWARD, LAND
INTERACTION WILL REDUCE THE SYSTEM TO 65 KNOTS AFTER IT MAKES
LANDFALL JUST EAST OF TAIPEI. DYNAMIC MODEL GUIDANCE IS IN GOOD
AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THIS PORTION OF THE
JTWC FORECAST TRACK.
   C. BEYOND TAU 72, TS 10W WILL ROUND THE STR AXIS AND TRACK MORE
POLEWARD THROUGH THE TAIWAN STRAIT THEN DRAG ACROSS THE EASTERN
CHINESE COAST. LAND INTERACTION AND INCREASING VWS WILL GRADUALLY
ERODE THE SYSTEM DOWN TO 30 KNOTS BY TAU 120 AS IT APPROACHES
SHANGHAI. DYNAMIC MODEL GUIDANCE SPREADS OUT TO OVER 260 NM BY TAU
120 WITH NAVGEM ON THE EXTREME RIGHT OF THE ENVELOPE. THEREFORE,
THERE IS LOW CONFIDENCE IN THE EXTENDED PORTION OF THE JTWC FORECAST
TRACK THAT IS LAID JUST LEFT OF CONSENSUS TO OFFSET THE UNLIKELY
NAVGEM SOLUTION THAT DRIVES THE CYCLONE INTO THE STR.//
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