Tropical Storm SAOLA Advisory Mon Jul 30

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (SAOLA) WARNING NR
09//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 10W (SAOLA), LOCATED APPROXIMATELY 355 NM
SOUTH-SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED NORTH-NORTHWESTWARD
AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY AND A 292355Z SSMIS IMAGE DEPICT A WELL-DEFINED
LOW-LEVEL CIRCULATION CENTER WITH IMPROVED CONVECTIVE BANDING
WRAPPING TIGHTLY INTO THE CENTER. ANIMATED WATER VAPOR IMAGERY
DEPICTS RADIAL OUTFLOW WITH ENHANCED POLEWARD OUTFLOW ASSOCIATED
WITH THE TUTT. BASED ON THE IMPROVED ORGANIZATION AND SSMIS 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 PGTW, KNES 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 ERRONEOUS INTERACTION WITH TS 11W WITH NOGAPS, GFS, GFDN
AND JGSM INDICATING A MORE NORTHWARD TRACK (GREATER INTERACTION) AND
GFDN, UKMO, 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
BUT CONTINUES TO FAVOR ECMWF, WHICH HAS BEEN THE MOST CONSISTENT,
REALISTIC SOLUTION. 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 400 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 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 300NM 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 AND WILL BE
ABSORBED INTO 10W BY TAU 96. 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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