Tropical Storm RAMMASUN Advisory Fri Jul 18

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (RAMMASUN) WARNING NR 29//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 09W (RAMMASUN), LOCATED APPROXIMATELY 288 NM SOUTH OF
HONG KONG, HAS TRACKED NORTHWESTWARD AT 10 KNOTS OVER THE PAST
SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) SHOWS
TY RAMMASUN HAS CONTINUED TO STRENGTHEN AS A CONCENTRIC EYEWALL HAS
BUILT IN WHILE CONVECTIVE BANDING HAS DEEPENED AND A DEFINED 16 NM
EYE HAS FORMED. A RECENT 171150Z SSMIS MICROWAVE IMAGE ALSO DEPICTS
INCREASED STRENGTHENING AS BANDING HAS INCREASED IN ALL QUADRANTS
AND THE CONVECTION AROUND THE EYEWALL HAS DEEPENED AND BECOME MORE
SYMMETRIC. 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 EIR LOOP WITH HIGH CONFIDENCE. THE
INITIAL INTENSITY IS ASSESSED AT 95 KNOTS BASED UPON DVORAK
INTENSITY ESTIMATES THAT RANGE FROM 90 TO 102 KNOTS. TY 09W IS
STEADILY TRACKING WEST-NORTHWEST ALONG THE SOUTHWESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE (STR) NORTHEAST OF THE SYSTEM.
3. FORECAST REASONING.
   A. THE INITIAL INTENSITY AND FORECAST INTENSITIES HAVE BEEN
GREATLY INCREASED DUE TO THE RECENT IMPROVEMENT IN THE SYSTEM AND AS
THE JOINT TYPHOON WARNING CENTER HAS RECOVERED FROM A CONTINUITY OF
OPERATIONS EXERCISE WHICH USED THE JMA FORECAST THAT IS BASED ON
LOWER 10 MINUTE AVERAGE WINDS.
   B. TY 09W IS FORECAST TO CONTINUE ON A GENERALLY WEST-
NORTHWESTWARD TRACK THROUGH THE REMAINDER OF THE FORECAST AS THE STR
REMAINS NORTHWEST OF THE SYSTEM. THE SYSTEM IS EXPECTED TO CONTINUE
TO STRENGTHEN FOR THE NEXT 18 HOURS BEFORE THE FRICTIONAL EFFECTS OF
HAINAN ISLAND BEGIN TO WEAKEN THE SYSTEM BY TAU 24. AFTER LANDFALL
ACROSS HAINAN ISLAND, A WEAKENING TREND IS FORECAST, WHICH WILL
BECOME MORE RAPID AS THE SYSTEM MAKES LANDFALL AGAIN ACROSS THE
CHINESE/VIETNAMESE BORDER WHICH WILL DISSIPATE THE SYSTEM BY TAU 72
AS IT TRACKS FURTHER INLAND. 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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