Tropical Storm MEKKHALA Advisory Tue Aug 11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (MEKKHALA) WARNING
NR 004//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 07W (MEKKHALA), LOCATED APPROXIMATELY
332 NM SOUTH-SOUTHWEST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWARD
AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY EXPOSED LOW LEVEL
CIRCULATION CENTER (LLCC) WITH CONVECTIVE BANDING OVER THE
SOUTHERN SEMICIRCLE WRAPPING INTO THE CENTER. THE CURRENT
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE PARTIALLY
EXPOSED LLCC IN THE MSI LOOP AND THE LOW LEVEL CIRCULATION FEATURE
PRESENT IN A 100535Z AMSR2 89GHZ IMAGE. THE INTENSITY OF 35 KNOTS
IS PLACED WITH HIGH CONFIDENCE AND IS BASED ON MULTIAGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T2.0 (30 KTS, RJTD) AND T2.5 (35 KTS,
PGTW), A 100610Z ADVANCED DVORAK TECHNIQUE CURRENT INTENSITY ESTIMATE
OF T2.4 (34 KTS) AND A 100610Z SATCON ESTIMATE OF 36 KTS. TS MEKKHALA
IS TRACKING POLEWARD ALONG THE WESTERN PERIPHERY OF A SUBTROPICAL
STEERING RIDGE (STR) EXTENSION. THE SYSTEM IS SITUATED IN AN AREA OF
HIGH (25-30 KTS) VERTICAL WIND SHEAR AND VERY WARM (29-30C) SEA
SURFACE TEMPERATURES. UPPER-LEVEL DIFFLUENCE IS LIMITED, BUT AN
ANALYSIS OF SATELLITE-DERIVED ATMOSPHERIC MOTION VECTORS SUGGESTS THAT
EQUATORWARD OUTFLOW ALOFT CONTINUES TO STRENGTHEN.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 07W WILL CONTINUE TO TRACK POLEWARD ALONG THE STR THROUGH THE
ENTIRE 48 HOUR FORECAST PERIOD. THE SYSTEM WILL CONTINUE TO STEADILY
INTENSIFY TO 45 KTS BY TAU 12 DESPITE THE PERSISTENT HIGH VWS, LARGELY
DUE TO CONTINUED PASSAGE OVER VERY WARM WATER AND INCREASING POLEWARD
OUTFLOW AIDED BY AN UPPER-LEVEL TROUGH POSITIONED TO THE NORTHEAST. TS
MEKKHALA IS EXPECTED TO MAKE LANDFALL IN SOUTHEASTERN CHINA JUST PRIOR
TO TAU 48. AFTER THE SYSTEM MAKES LANDFALL IT WILL BEGIN TO WEAKEN DUE
TO THE FRICTIONAL EFFECTS OF LAND AND FULLY DISSIPATE OVER LAND BY TAU
48. NUMERICAL MODEL SOLUTIONS ARE IN FAIR AGREEMENT REGARDING THE OVERALL
FORECAST SCENARIO, BUT THERE IS SOME SPREAD IN THE EXACT POSITION OF
LANDFALL WITH A 60NM CROSS TRACK SPREAD IN SOLUTIONS AT TAU 48. OVERALL,
MODEL SOLUTIONS LEND FAIR CONFIDENCE IN JTWC TRACK FORECAST.//
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