Tropical Storm SAOLA Advisory Sun Jul 29

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 10W (SAOLA) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 10W (SAOLA), LOCATED APPROXIMATELY 340 NM
NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTH-NORTHWESTWARD AT
08 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE
IMAGERY DEPICTS AN ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC)
WITH TWO DISTINCT CIRCULATION CENTERS ROTATING ABOUT A CENTROID. THE
EASTERN CIRCULATION CENTER IS LOCATED NEAR 17.9N 126.6E AND THE
WESTERN CIRCULATION CENTER IS LOCATED NEAR 17.7N 125.2E. THE INITIAL
POSITION IS BASED ON THE CENTROID, WHICH IS BETWEEN THE TWO
CIRCULATION CENTERS. A 290057Z METOP-A IMAGE INDICATES THAT THE
PRIMARY CONVECTIVE BAND IS LOCATED OVER THE WESTERN PERIPHERY OF THE
LLCC WITH A WEAKER BAND OVER THE EASTERN PERIPHERY. A 290059Z ASCAT
IMAGE ALSO CONFIRMS THE ELONGATED NATURE OF THE LLCC WITH 30 TO 35
KNOT WINDS OVER THE SOUTHERN SEMI-CIRCLE. BASED ON THIS DATA, THERE
IS FAIR CONFIDENCE IN THE INITIAL POSITION. THE INITIAL INTENSITY IS
BASED ON THE ASCAT DATA AS WELL AS DVORAK ESTIMATES RANGING FROM 35
(PGTW, KNES) TO 55 KNOTS (RJTD). THE RJTD DVORAK ESTIMATE APPEARS
TOO HIGH CONSIDERING THE ASCAT DATA AND THE LLCC'S ELONGATED
SIGNATURE. ANIMATED WATER VAPOR IMAGERY INDICATES IMPROVED, NEAR-
RADIAL OUTFLOW. TS 10W IS CURRENTLY TRACKING NORTHWARD ALONG THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR). THE 28/12Z 500 MB
ANALYSIS DEPICTS A WEAK EASTERN STR AND A STRONG EAST-WEST ORIENTED
STR POSITIONED 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 TRACK SLOWLY NORTH-NORTHWESTWARD THROUGH
TAU 72 UNDER THE STEERING INFLUENCE OF THE EASTERN STR. DYNAMIC
MODEL GUIDANCE IS IN FAIR AGREEMENT WITH TWO DISTINCT GROUPINGS.
NOGAPS AND GFS REMAIN ON THE EASTERN EDGE OF THE ENVELOPE AND SHOW A
NORTH-NORTHEASTWARD TRACK THROUGH TAU 48, WHICH IS INCORRECT DUE TO
ERRONEOUS INTERACTION WITH ANOTHER SYSTEM DEVELOPING SOUTH OF JAPAN.
THE SECOND GROUPING OF MODELS (JGSM, ECMWF, UKMO AND WBAR) PRESENT A
MORE CONSISTENT FORECAST (AND TIGHT GROUPING) TOWARD TAIWAN WITHOUT
ANY INDICATIONS OF ERRONEOUS CYCLONE INTERACTION. TS 10W IS EXPECTED
TO INTENSIFY THROUGH THE FORECAST PERIOD TO A PEAK OF 95 KNOTS BY
TAU 72.
   C. IN THE EXTENDED TAUS, THERE IS LARGE SPREAD IN THE DYNAMIC
MODEL TRACKERS WITH NOGAPS AND GFS TRACKING THE SYSTEM NORTH OF
TAIWAN AND THE REMAINDER OF THE MODELS TRACKING THE SYSTEM OVER
TAIWAN. THERE IS LOW OVERALL CONFIDENCE IN THE FORECAST TRACK DUE TO
UNCERTAINTIES IN LOCATING THE SYSTEM CENTER AS WELL AS POTENTIAL
TRACK ERROR DUE TO THE WEAK STEERING INFLUENCE THROUGH TAU 72. AFTER
TAU 72, THERE IS INCREASED CONFIDENCE IN THE TRACK FORECAST AS THE
STEERING INFLUENCE TRANSITIONS TO THE STRONG STR POSITIONED OVER
CHINA AND JAPAN.//
NNNN
NNNN