Tropical Storm LEKIMA Advisory Tue Aug 06

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (LEKIMA) WARNING NR
06//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 10W (LEKIMA), LOCATED APPROXIMATELY 456 NM
SOUTH-SOUTHEAST OF KADENA AB, HAS TRACKED NORTHWESTWARD AT 05 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) REVEALS AN EXPOSED, BROAD LOW LEVEL CIRCULATION (LLC) WITH DEEP
CONVECTION WRAPPING INTO THE CENTER FROM THE SOUTH. THERE IS FAIR
CONFIDENCE IN THE INITIAL POSITION PLACED USING THE MSI AND SHALLOW
BANDING IN A 050649Z SSMIS 91 GHZ MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 35 KTS IS CONSISTENT WITH MULTI-AGENCY DVORAK ESTIMATES
OF T2.5 (35 KTS). THE ENVIRONMENT IS FAVORABLE WITH RADIAL OUTFLOW,
WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE, AND MODERATE (15-20 KT)
VERTICAL WIND SHEAR (VWS). TS 10W IS TRACKING SLOWLY ALONG THE
SOUTHWEST PERIPHERY OF A SUBTROPICAL RIDGE (STR) THAT IS BEING
DISTORTED BY TS 09W.
3. FORECAST REASONING.
   A. RIDGING BUILDING IN FROM THE NORTHEAST LATE IN THE FORECAST HAS
BECOME THE DOMINANT STEERING FEATURE, PULLING THE EXTENDED TRACK
SIGNIFICANTLY FURTHER WEST OVER EASTERN CHINA.
   B. THROUGH TAU 48, TS 10W IS EXPECTED TO CONTINUE TRACKING
NORTHWESTWARD AND SLOWLY ACCELERATE AS TS 09W MOVES AWAY AND THE STR
BUILDS BEHIND IT. THE FAVORABLE ENVIRONMENT SHOULD SUPPORT STEADY
INTENSIFICATION TO 65 KTS BY TAU 72. UNCERTAINTY IN THE MODEL TRACK
GUIDANCE FOR THIS PORTION OF THE FORECAST IS HIGH AS THERE IS A 220NM
SPREAD AT TAU 72 WITH THE MOST SIGNIFICANT VARIABILITY BETWEEN NVGM
AND JGSI TRACKS.
   C. BEYOND TAU 72, TS 10W IS EXPECTED TO GRADUALLY TURN MORE
POLEWARD AS IT ROUNDS THE STR AXIS AROUND TAU 96. ASSUMING THE SYSTEM
FOLLOWS THE FORECAST TRACK, THE ENVIRONMENT WILL REMAIN FAVORABLE
UNTIL LAND INTERACTION EFFECTS ARE INTRODUCED AS IT BEGINS TRACKING
OVER TAIWAN AROUND TAU 90. TRACK SPREAD AT TAU 120 HAS BEEN
SIGNIFICANTLY REDUCED WITH UNCERTAINTY BETWEEN POSITION OVER COASTAL
CHINA OR FURTHER INLAND. THE HIGH UNCERTAINTY IN THE TRACK GUIDANCE
COULD GREATLY AFFECT THE ENVIRONMENTAL AND LAND INTERACTION EFFECTS,
RESULTING IN HIGH UNCERTAINTY IN THE INTENSITY FORECAST. BASED ON THE
HIGH SPREAD IN THE MODEL GUIDANCE, THERE IS LOW CONFIDENCE IN THE
JTWC TRACK FORECAST.//
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