Tropical Storm RAMMASUN Advisory Sat Jul 19

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 09W (RAMMASUN) WARNING
NR 32//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON 09W (RAMMASUN), LOCATED APPROXIMATELY 220 NM
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. AS THE DVORAK INTENSITY
ESTIMATES HAVE INCREASED OVER THE PAST SIX HOURS AND THERE IS
EVIDENCE OF IMPROVEMENTS IN THE STRUCTURE, THE INTENSITY HAS BEEN
INCREASED TO 135 KNOTS. UPPER LEVEL ANALYSIS SHOWS A FAVORABLE
ENVIRONMENT CHARACTERIZED BY STRONG EQUATORWARD OUTFLOW AND MODERATE
(15 TO 20 KNOTS) VERTICAL WIND SHEAR. THE INITIAL POSITION IS BASED
UPON THE DEFINED EYE FEATURE IN THE MSI LOOP WITH HIGH CONFIDENCE.
STY 09W IS STEADILY TRACKING WEST-NORTHWEST ALONG THE SOUTHWESTERN
PERIPHERY OF THE SUBTROPICAL RIDGE (STR) EXTENDING OVER EASTERN
CHINA.
3. FORECAST REASONING.
   A. NO CHANGE TO FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC
REASONING MESSAGE.
   B. STY 09W IS FORECAST TO REMAIN ON A GENERALLY WEST-
NORTHWESTWARD TRACK AS THE STR PERSISTS TO INFLUENCE THE TRACK FOR
THE REMAINDER OF THE FORECAST. STY 09W IS EXPECTED TO BEGIN TO
WEAKEN AS THE STORM CONTINUES TO TRACK ACROSS HAINAN AND THE LUICHOW
PENINSULA OVER THE NEXT 6 HOURS. BETWEEN TAU 12 AND 24, STY
RAMMASUN WILL MAKE FINAL LANDFALL IN NORTHERN VIETNAM, WHICH WILL
CAUSE RAPID WEAKENING DUE TO FRICTIONAL EFFECTS OF THE NORTHERN
MIDLANDS AND MOUNTAINOUS REGION WITH COMPLETE DISSIPATION OF THE
SYSTEM IS EXPECTED BY TAU 48. NUMERIC MODEL GUIDANCE IS IN VERY
TIGHT AGREEMENT WITH THE TRACK FORECAST, WHICH IS POSITIONED WITH
HIGH CONFIDENCE.//
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