Tropical Storm RAMMASUN Advisory Mon Jul 14

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (RAMMASUN) WARNING
NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM 09W (RAMMASUN), LOCATED APPROXIMATELY 583 NM EAST
OF MANILA, PHILIPPINES, HAS TRACKED WESTWARD AT 15 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS
THE DEEP CENTRALIZED CONVECTION HAS PERSISTED OVER THE PAST FEW HOURS
WITH INCREASING OUTFLOW TO THE SOUTHWESTERN QUADRANT. THE CURRENT
INTENSITY HAS BEEN INCREASED TO 50 KNOTS BASED ON THE BETTER OBSERVED
ORGANIZATION IN MSI WITH DVORAK ESTIMATES FROM PGTW AND RJTD
INCREASING IN THE PAST SIX HOURS. TS 09W HAS SLOWED SLIGHTLY AS THE
SYSTEM HAS STARTED TO DEVELOP VERTICALLY WITH DECREASING VERTICAL
WIND SHEAR (VWS) (5 TO 10 KNOTS). TS 09W REMAINS ON A WESTWARD TRACK
ALONG THE SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE (STR) ANCHORED
TO THE NORTH OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS
PROGNOSTIC REASONING MESSAGE.
   B. TS 09W IS FORECAST TO CONTINUE WESTWARD FOR THE NEXT 36 HOURS
ALONG THE SOUTHERN PERIPHERY OF THE ENTRENCHED STR. IMPROVING UPPER
LEVEL SUPPORT AND FAVORABLE SEA SURFACE TEMPERATURES (SST) WILL
PROVIDE FOR FURTHER INTENSIFICATION THROUGH LANDFALL INTO THE CENTRAL
PHILIPPINES SLIGHTLY AFTER TAU 24. AS THE SYSTEM TRACKS OVER LAND, A
SLIGHT WEAKENING TREND IS ANTICIPATED THROUGH TAU 48. AS THE CIRCU-
LATION CROSSES OVER SOUTHERN LUZON INTO THE SOUTH CHINA SEA, AN
IMPROVING ENVIRONMENT IN THE LOW LEVEL FLOW, WITH IMPROVING UPPER
LEVEL SUPPORT WILL CAUSE TS 09W TO START INTENSIFYING BY TAU 72. THE
TRACK WILL SHIFT TO A MORE WEST-NORTHWESTWARD DIRECTION AS THE STR
WEAKENS SLIGHTLY UNDER THE INFLUENCE OF A DIGGING MID-LATITUDE TROUGH
OVER EASTERN CHINA.
   C. IN THE EXTENDED TAUS, TS RAMMASUN IS FORECAST TO TRACK WEST-
NORTHWESTWARD ACROSS THE SOUTH CHINA SEA TOWARDS NORTHERN HAINAN
ISLAND, MAKING LANDFALL AROUND TAU 108 INTO THE LUICHOW PENINSULA.
WARM SSTS, DECREASED VWS, AND INCREASED OUTFLOW IN THE SOUTH CHINA
SEA WILL ALLOW FOR INTENSIFICATION, REACHING A MAXIMUM OF 85 KNOTS
PRIOR TO LANDFALL. MODEL GUIDANCE IS IN GOOD AGREEMENT WITH SOME
DIFFERENCES IN TRACK SPEED BUT IS OTHERWISE TIGHTLY GROUPED. DUE TO
THE LOW CONFIDENCE IN THE INITIAL POSITION AND THE UNCERTAINTY IN
THE TRANSLATIONAL SPEED, THE CONFIDENCE IN THE FORECAST REMAINS
LOW.//
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