Tropical Storm SAOLA Advisory Tue Jul 31

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (SAOLA) WARNING NR
13//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 10W (SAOLA), LOCATED APPROXIMATELY 285 NM SOUTH-
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 02
KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY (MSI) SHOWS THE LOW LEVEL CIRCULATION CENTER (LLCC) HAS
BECOME QUASI-STATIONARY OVER THE PAST 12 HOURS. THE NEAR EQUATORIAL
RIDGE (NER) THAT HAS BEEN STEERING THE SYSTEM IS NOW COMPETING WITH
THE SUBTROPICAL RIDGE TO THE NORTH. THE CURRENT INTENSITY IS BASED
ON DVORAK ESTIMATES FROM PGTW, RJTD AND KNES RANGING FROM 55 TO 65
KNOTS. BASED ON THE ORGANIZATION AND STRUCTURE OF THE LLCC, THE
INTENSITY WAS KEPT ON THE LOWER SIDE OF THE ESTIMATES. UPPER LEVEL
ANALYSIS INDICATES TS 10W IS BEGINNING TO LOSE OUTFLOW SUPPORT FROM
THE TROPICAL UPPER TROPOSPHERIC TROUGH CELL LOCATED OVER EASTERN
CHINA. EQUATORWARD OUTFLOW REMAINS WELL DEFINED AND IS HELPING TO
SUSTAIN THE CURRENT INTENSITY.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING.
   B. TS 10W IS FORECAST TO SLOWLY DRIFT IN A GENERAL NORTHWESTWARD
DIRECTION UNDER THE INFLUENCE OF COMPETING STEERING MECHANISMS. BY
TAU 36 THE STR TO THE NORTH IS EXPECTED TO OVERCOME THE NER AS THE
DOMINANT STEERING INFLUENCE CAUSING AN INCREASE IN TRACK SPEED. GOOD
UPPER LEVEL SUPPORT IN COMBINATION WITH FAVORABLE SURFACE CONDITIONS
WILL ALLOW A STEADY INTENSITY INCREASE TO A MAXIMUM OF 100 KNOTS BY
TAU 72.
   C. IN THE EXTENDED TAUS, TS 10W IS EXPECTED TO MAKE LANDFALL BY
TAU 84, WITH A STEADY WEAKENING TREND THEREAFTER, LEADING TO
COMPLETE DISSIPATION BY TAU 120. MODEL GUIDANCE IS REMAINS
WIDESPREAD ON THE TIMING OF THE TURN WESTWARD AND WITH THE TIMING OF
LANDFALL. THIS FORECAST FAVORS THE ECMWF SOLUTION WITH A CLOSE TRACK
OVER TAIWAN. THERE IS LOW CONFIDENCE IN THE
EXTENDED FORECAST TRACK DUE TO THE TIMING OF THE SHIFT FROM QUASI-
STATIONARY MOTION TO A TRACK ALONG THE SOUTHERN BOUNDARY OF THE
STR.//
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