Tropical Storm RAMMASUN Advisory Fri Jul 11

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (NINE) WARNING NR
05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 09W (NINE), LOCATED APPROXIMATELY 82 NM EAST-
SOUTHEAST OF ANDERSEN AFB, GUAM HAS TRACKED WEST-NORTHWESTWARD
AT 15 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
(EIR) SATELLITE IMAGERY DEPICTS FORMATIVE DEEP CONVECTIVE BANDING
SURROUNDING A SMALL, TIGHTLY COMPACT LOW-LEVEL CIRCULATION CENTER
(LLCC). A 111132Z METOP-A MICROWAVE IMAGE REVEALS THE CONSOLIDATED
STRUCTURE OF THE TIGHTLY WRAPPED LLCC WITH BANDING FEATURES WRAPPING
TO THE CENTER. THE INITIAL POSITION IS BASED ON THE EIR ANIMATION
AND ABOVE MICROWAVE IMAGE WITH FAIR CONFIDENCE. THE INITIAL
INTENSITY HAS REMAINED AT 35 KNOTS BASED ON CURRENT STRUCTURE AS
WELL AS DVORAK INTENSITY ESTIMATE ASSESSMENT FROM ALL REPORTING
AGENCIES. UPPER-LEVEL ANALYSIS CONTINUES TO INDICATE A FAVORABLE
ENVIRONMENT CHARACTERIZED BY WEAK (05 TO 10 KNOTS) VERTICAL WIND
SHEAR AND STRONG RADIAL OUTFLOW, AS EVIDENT IN THE WATER VAPOR
IMAGERY. TS 09W IS CURRENTLY TRACKING WEST-NORTHWESTWARD ALONG THE
SOUTHERN PERIPHERY OF THE DEEP-LAYER SUBTROPICAL RIDGE (STR)
ANCHORED TO THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST TRACK
PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. HOWEVER,
THE INTENSITY FORECAST HAS SLIGHTLY DECREASED DUE TO THE SLOW
ORGANIZATION AND AN OVERALL DECREASE IN OBJECTIVE AID INTENSITY
GUIDANCE.
   B. TS 09W IS FORECAST TO CONTINUE TRACKING WEST-NORTHWEST THROUGH
THE NEXT 72 HOURS ALONG THE SOUTHERN PERIPHERY OF THE STR. FAVORABLE
CONDITIONS OF LOW VWS, WARM SEA SURFACE TEMPERATURE, AND STRONG
OUTFLOW ARE EXPECTED TO PERSIST THROUGH THE FORECAST PERIOD. THE
SYSTEM IS FORECAST TO INTENSIFY TO TYPHOON STRENGTH AT TAU 36.
   C. AFTER TAU 72, A MID-LATITUDE SHORTWAVE TROUGH IS FORECAST TO
DIG IN FROM EASTERN CHINA AND MODIFY THE STEERING RIDGE. THIS
MODIFICATION OF THE RIDGE WILL SLOW TS 09W AND BEGIN TO SLOWLY DRIVE
THE SYSTEM POLEWARD. THE COMBINED EFFECTS OF FAVORABLE SST AND UPPER-
LEVEL CONDITIONS WILL ENHANCE FURTHER INTENSIFICATION FOR THE
REMAINDER OF THE FORECAST. THE AVAILABLE MODEL GUIDANCE IS IN GOOD
AGREEMENT; HOWEVER, DUE TO THE INITIAL POSITIONING AND TRACK SPEEDS
UNCERTAINTY, THERE IS OVERALL LOW CONFIDENCE IN THE JTWC FORECAST.//
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