Tropical Storm LEKIMA Advisory 09.08.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 10W (LEKIMA) WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 10W (LEKIMA), LOCATED APPROXIMATELY 236 NM WEST OF
KADENA AB, HAS TRACKED NORTHWESTWARD AT 14 KNOTS (KTS) OVER THE PAST
SIX HOURS. A 5-10 NM ROUND EYE IN ANIMATED MULTISPECTRAL SATELLITE
IMAGERY PROVIDES HIGH CONFIDENCE IN THE INITIAL POSITION. DESPITE
THE EYE REMAINING SMALL AND ROUND, ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY REVEALS THE SURROUNDING CONVECTION HAS BECOME
ASYMMETRIC WITH WARMER CLOUD TOP TEMPERATURES ON THE NORTHERN SIDE.
THE INITIAL INTENSITY OF 115 KTS IS BETWEEN CURRENT INTENSITY
ESTIMATES FROM T5.5-6.5 (102-127 KTS). THE ENVIRONMENT WITH GOOD
POLEWARD OUTFLOW, FAIR EQUATORWARD OUTFLOW, LOW (10-15 KT) VERTICAL
WIND SHEAR (VWS), AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURE
IS SUPPORTIVE BUT THERE DOES APPEAR TO BE SOME COMPARATIVELY DRY AIR
ENTRAINING IN FROM THE WEST THAT IS LIKELY CONTRIBUTING TO THE
WEAKENING SEEN OVER THE PAST 12 HOURS. 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. SHORTLY AFTER MAKING LANDFALL ABOUT 140 NM SOUTH OF SHANGHAI,
CHINA AROUND TAU 18, TY 10W WILL BEGIN TRACKING NORTHWARD AS THE STR
REORIENTS AND RECEDES SLIGHTLY TO THE EAST. THE SYSTEM SHOULD PASS
NEAR SHANGHAI ON A NORTHWARD TRACK AROUND TAU 40 AND PASS BRIEFLY
OVER THE YELLOW SEA ON A NORTH-NORTHWESTWARD TRACK BEFORE MAKING
SECOND LANDFALL NEAR QINGDAO, CHINA PRIOR TO TAU 72. LAND
INTERACTION IS EXPECTED TO WEAKEN THE SYSTEM TO 50 KNOTS BY TAU 72.
THE INTENSITY FORECAST IS VERY UNCERTAIN BECAUSE SMALL SHIFTS IN THE
TRACK COULD SIGNIFICANTLY IMPACT THE AMOUNT OF WEAKENING DUE TO LAND
INTERACTION. NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT FOR
THIS PORTION OF THE FORECAST, LENDING TO GOOD CONFIDENCE IN THE JTWC
TRACK FORECAST THROUGH TAU 72.
   C. BETWEEN TAU 72 AND 120, TY 10W IS EXPECTED TO CONTINUE
TRACKING NORTH-NORTHWESTWARD AND BEGIN ROUNDING THE STR AXIS. HIGH
VWS AND LAND INTERACTION ARE EXPECTED TO CONTINUE WEAKENING THE
SYSTEM, HOWEVER UNCERTAINTY IN THE INTENSITY FORECAST REMAINS HIGH
DUE TO UNCERTAINTY IN THE AMOUNT OF LAND INTERACTION. NUMERICAL
MODEL SPREAD INCREASES SIGNIFICANTLY AS SEVERAL MODELS (ECMWF,
GALWEM, UKMET) FOLLOW THE RECURVE SCENARIO WHILE THE OTHER MEMBERS
SHOW THE SYSTEM TURNING SOUTHWARD, POSSIBLY DUE TO DIRECT CYCLONE
INTERACTION WITH TY 11W. THE JTWC TRACK FORECAST FAVORS THE RECURVE
SCENARIO WITH LOW CONFIDENCE DUE TO MAJOR DIFFERENCES IN THE TRACK
BETWEEN THE TWO FEASIBLE FORECAST SCENARIOS.//
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