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
03//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 09W (NINE), LOCATED APPROXIMATELY 224 NM EAST-
SOUTHEAST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-NORTHWESTWARD AT 13
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS CENTRAL CONVECTION HAS FURTHER DEEPENED AS
THE SYSTEM FORMED NEW BANDS THAT WRAPPED TIGHTER INTO THE LOW LEVEL
CIRCULATION CENTER THAT REMAINS OBSCURED BY CLOUD COVER. THE INITIAL
POSITION IS BASED ON THE EIR LOOP AND EXTRAPOLATED FROM A NOTCH
FEATURE ON A 102339Z METOP-B MICROWAVE PASS. THE INITIAL INTENSITY IS
ASSESSED SLIGHTLY HIGHER THAN AGENCY DVORAK ESTIMATES TO REFLECT THE
DEEPENED CONVECTION AND IMPROVED BANDING OVER THE LAST SIX HOURS.
UPPER-LEVEL ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH DUAL
OUTFLOW: ONE ENHANCED BY A TUTT CELL TO THE NORTHEAST AND A WESTWARD
OUTFLOW CHANNEL INDUCED BY THE STRONG EASTERLY WINDS ALONG THE
SOUTHERN PERIPHERY OF THE STEERING SUBTROPICAL RIDGE (STR) TO THE
NORTH. ADDITIONALLY, LIGHT VERTICAL WIND SHEAR (VWS) VALUES AT 05-10
KNOTS, AND WARM SEA SURFACE TEMPERATURES (28-30 DEGREES CELSIUS) ARE
CONDUCIVE FOR FURTHER DEVELOPMENT.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST TRACK PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING BULLETIN.
   B. TS 09W IS EXPECTED TO CONTINUE TRACKING GENERALLY
WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE DEEP-LAYERED
STR ANCHORED TO THE NORTH THROUGHOUT THE FORECAST PERIOD. FAVORABLE
CONDITIONS MENTIONED IN PARA 2 ARE ALSO EXPECTED TO PERSIST, ALLOWING
THE SYSTEM TO GRADUALLY INTENSIFY. BY TAU 36, THE CYCLONE WILL BE A
FULL-FLEDGED TYPHOON AND WILL REACH 85 KNOTS BY TAU 72.
   C. AFTER TAU 72, TS 09W WILL DRIFT INTO AN EVEN WARMER POOL OF
WATER (32 DEGREES CELSIUS) IN THE PHILIPPINE SEA. THIS, IN ADDITION
TO SUSTAINED FAVORABLE UPPER LEVEL CONDITIONS WILL LEAD TO RAPID
INTENSIFICATION. BY THE END OF THE FORECAST PERIOD, THE SYSTEM WILL
BE A VERY STRONG TYPHOON AT 110 KNOTS. THE AVAILABLE NUMERIC MODEL
GUIDANCE IS IN GOOD AGREEMENT AND LENDS FAIR CONFIDENCE TO THE JTWC
TRACK FORECAST.//
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