Tropical Storm SAOLA Advisory Pzt, 30.07.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (SAOLA) WARNING NR
08//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 10W (SAOLA), LOCATED APPROXIMATELY 390 NM
SOUTH-SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTHWESTWARD AT 08
KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY
INDICATES THAT THE LOW-LEVEL CIRCULATION CENTER (LLCC) HAS
CONSOLIDATED WITH IMPROVED CONVECTIVE BANDING WRAPPING INTO THE
CENTER. ANIMATED WATER VAPOR IMAGERY DEPICTS RADIAL OUTFLOW WITH
ENHANCED POLEWARD OUTFLOW ASSOCIATED WITH THE TUTT. A 291822Z AMSU
IMAGE SHOWS STRONG BANDING OVER THE SOUTHERN SEMI-CIRCLE WITH
WEAKER, FRAGMENTED BANDING OVER THE NORTHERN SEMI-CIRCLE. A 291548Z
OCEANSAT IMAGE PROVIDES GOOD EVIDENCE THAT THE PREVIOUSLY ELONGATED
LLCC HAS STRENGTHENED AND BECOME MORE SYMMETRIC OVER THE PAST 12
HOURS. BASED ON THE IMPROVED ORGANIZATION AND THE OCEANSAT IMAGE,
THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION AND RECENT TRACK
MOTION. THE INITIAL INTENSITY OF 55 KNOTS IS BASED ON SUBJECTIVE
DVORAK ESTIMATES OF 55 KNOTS FROM BOTH PGTW AND RJTD AND IS IN
AGREEMENT WITH OBJECTIVE INTENSITY ESTIMATES, WHICH RANGE FROM 50-55
KNOTS. TS 10W IS CURRENTLY TRACKING SLOWLY NORTH-NORTHWESTWARD ALONG
THE WESTERN PERIPHERY OF A WEAK STEERING RIDGE POSITIONED TO THE
EAST-SOUTHEAST. THE 29/12Z 500MB ANALYSIS INDICATES THAT THE
SUBTROPICAL RIDGE (STR) REMAINS ENTRENCHED OVER EASTERN CHINA AND
JAPAN.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM
THE PREVIOUS PROGNOSTIC REASONING.
   B. TS 10W IS FORECAST TO CONTINUE TRACKING SLOWLY NORTH-
NORTHWESTWARD THROUGH TAU 72 UNDER THE STEERING INFLUENCE OF THE
EASTERN STEERING RIDGE. DYNAMIC MODEL GUIDANCE REMAINS IN FAIR
AGREEMENT. THE PRIMARY DIFFERENCE BETWEEN THE DYNAMIC MODELS IS THE
DEGREE OF INTERACTION WITH TS 11W WITH NOGAPS, GFS, UKMO AND JGSM
INDICATING A MORE NORTHWARD TRACK (GREATER INTERACTION) AND GFDN,
WBAR AND ECMWF INDICATING A MORE NORTHWESTWARD TRACK (LESSER
INTERACTION). IN GENERAL, THE JTWC FORECAST HAS SHIFTED SLIGHTLY
POLEWARD WITH THE BULK OF THE MODELS ALSO TRENDING POLEWARD OVER THE
PAST 24 HOURS. THE JTWC FORECAST TRACK IS POSITIONED CLOSE TO THE
MODEL CONSENSUS AND FAVORS A SLOW, COMPLEX TRACK THROUGH TAU 72 WITH
WEAK INTERACTION WITH TS 11W BETWEEN TAU 48 AND TAU 72. AT THIS
TIME, THE TWO SYSTEM CENTERS WILL APPROACH WITHIN 500 NM POSSIBLY
PRODUCING A SHORT-TERM SLOW-DOWN OR ERRATIC TRACK EAST OF TAIWAN;
HOWEVER, IT IS UNLIKELY THAT 10W WILL BE AFFECTED SIGNIFICANTLY BY
THE MUCH WEAKER 11W. TS 10W IS EXPECTED TO INTENSIFY TO A PEAK
INTENSITY OF 100 KNOTS BY TAU 72 DUE TO THE FAVORABLE ENVIRONMENT.
   C. IN THE EXTENDED TAUS, TS 10W WILL TURN WESTWARD OVER OR JUST
TO THE NORTH OF TAIWAN AS IT TRANSITIONS TO THE STEERING INFLUENCE
OF THE STR OVER EASTERN CHINA AND JAPAN. TS 10W AND TS 11W ARE
EXPECTED TO APPROACH WITHIN 350-400NM DURING THIS PERIOD BUT 10W AS
THE LARGER, MORE POWERFUL SYSTEM, AGAIN, SHOULD SEE MINIMAL
INFLUENCES. TS 11W, HOWEVER, IS EXPECTED TO WEAKEN RAPIDLY AS IT
ENCOUNTERS INCREASING VERTICAL WIND SHEAR ASSOCIATED WITH 10W'S
OUTFLOW. THERE IS LOW OVERALL CONFIDENCE IN THE FORECAST TRACK DUE
TO THE WEAK STEERING ENVIRONMENT THROUGH TAU 72 AND POSSIBLE WEAK
INTERACTION WITH 11W. AFTER TAU 72, THERE IS INCREASED CONFIDENCE IN
THE FORECAST TRACK AS THE STEERING INFLUENCE TRANSITIONS TO THE
STRONG STR POSITIONED OVER CHINA AND JAPAN.//
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