Tropical Storm RAMMASUN Advisory vie, 18-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (RAMMASUN) WARNING NR 31//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 09W (RAMMASUN), LOCATED APPROXIMATELY 220 NM SOUTH-
SOUTHWEST OF HONG KONG, HAS TRACKED WEST-NORTHWESTWARD AT 12 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL (MSI) AND ENHANCED
INFRARED SATELLITE IMAGERY SHOW THE EYE HAS IMPROVED ORGANIZATION
WITH A SMALL INCREASE IN COLD CLOUD TOPS. DVORAKS HAVE BEEN STEADY
OVER THE PAST SIX HOURS BUT DUE TO THE SLIGHT IMPROVEMENTS, THE
CURRENT INTENSITY HAS BEEN INCREASED TO 125 KNOTS. UPPER LEVEL
ANALYSIS SHOWS A FAVORABLE ENVIRONMENT CHARACTERIZED BY VIGOROUS
EQUATORWARD OUTFLOW AND LOW (05 TO 10 KNOTS) VERTICAL WIND SHEAR.
THE INITIAL POSITION IS BASED UPON THE DEFINED EYE FEATURE IN THE
MSI LOOP WITH HIGH CONFIDENCE. TY 09W IS STEADILY TRACKING WEST-
NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE
(STR) NORTHEAST OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. TY 09W IS FORECAST TO REMAIN ON A GENERALLY WEST-NORTHWESTWARD
TRACK THROUGH THE REMAINDER OF THE FORECAST AS THE STR PERSISTS TO
THE NORTHWEST OF THE SYSTEM. TY 09W IS EXPECTED TO STRENGTHEN FOR
THE NEXT SIX HOURS BEFORE THE FRICTIONAL EFFECTS OF HAINAN ISLAND
BEGIN TO WEAKEN THE SYSTEM. WEAKENING WILL PERSIST AFTER TRACKING
OVER THE NORTHERN HALF OF HAINAN ISLAND AND AS THE SYSTEM BEGINS TO
INTERACT WITH THE LUICHOW PENINSULA. ONCE TY 09W MAKES LANDFALL IN
THE BORDER REGION OF NORTHERN VIETNAM AND SOUTHERN CHINA, A RAPID
WEAKENING WITH COMPLETE DISSIPATION OF THE TROPICAL SYSTEM IS
EXPECTED BY TAU 48. NUMERIC MODEL GUIDANCE IS IN VERY TIGHT AGREEMENT
WITH THE TRACK FORECAST, WHICH IS POSITIONED WITH HIGH CONFIDENCE,
CLOSE TO THE MULTI-MODEL CONSENSUS.//
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