Tropical Storm FUNG-WONG Advisory Thu Sep 18

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (FUNG-WONG) WARNING
NR 05//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 16W (FUNG-WONG), LOCATED APPROXIMATELY 284 NM
EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED WEST-
NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY (EIR) DEPICTS DEEP CONVECTIVE BANDING
ACROSS THE WESTERN SEMI-CIRCLE OF A LOW LEVEL CIRCULATION CENTER
(LLCC) THAT IS PARTIALLY EXPOSED AND HAS BUILDING CENTRAL
CONVECTION. THE CURRENT POSITION IS BASED ON THE EIR LOOP WITH GOOD
CONFIDENCE DUE TO THE EXPOSED NATURE OF THE LLCC. THE INITIAL
INTENSITY REMAINS ASSESSED AT 35 KNOTS BASED ON PERSISTENCE FROM A
PREVIOUS ASCAT PASS AS DVORAK INTENSITY ESTIMATES RANGE FROM 30 TO
35 KNOTS. UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY CONDUCIVE
ENVIRONMENT AS VERTICAL WIND SHEAR (VWS) HAS INCREASED TO MODERATE
LEVELS (10 TO 20 KNOTS) AND EQUATORWARD OUTFLOW REMAINS STRONG. TS
FUNG-WONG IS CURRENTLY TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF
THE SUBTROPICAL RIDGE (STR) THAT IS POSITIONED TO THE NORTHEAST OF
THE SYSTEM.
3. FORECAST REASONING.
   A. THE TRACK HAS BEEN SIGNIFICANTLY SLOWED IN THE EXTENDED
PORTION OF THE FORECAST AS MODELS HAVE COME INTO A BETTER AGREEMENT
IN THE ESTABLISHMENT OF THE SUBTROPICAL RIDGE.
   B. THROUGH THE NEXT DAY, TS 16W WILL CONTINUE TO TRACK TO THE
NORTHWEST UNDER THE INFLUENCE OF THE STR THAT IS EXPECTED TO WEAKEN
AND BREAK AS A SUBTROPICAL TROUGH DEEPENS TO THE NORTH. AS THE STR
BREAKS DOWN, THE SYSTEM WILL SLOW DOWN UNDER THE SIGNIFICANTLY
WEAKER RIDGE. WHILE THERE IS THE POSSIBILITY OF INTENSIFICATION AS
THE SYSTEM TRACKS INTO A MORE FAVORABLE UPPER-LEVEL ENVIRONMENT, THE
PROXIMITY OF TS 16W TO THE NORTHEAST COAST OF LUZON WILL POTENTIALLY
LIMIT INTENSIFICATION. ALSO, THROUGH TAU 48 AND 72, THE PROXIMITY TO
THE TAIWANESE COAST COULD ALSO LIMIT INTENSIFICATION. MODELS ARE IN
GOOD AGREEMENT ON THE TRACK THROUGH TAU 72 WITH ALL SHOWING THE
SYSTEM ENTERING THE BREAK IN THE RIDGE AND PROCEEDING POLEWARD,
ALTHOUGH AT A SLOWER TRANSLATIONAL SPEED.
   C. IN THE EXTENDED FORECAST, THE AFOREMENTIONED TROUGH WILL RE-
ORIENT THE STR DRIVING FUNG-WONG NORTHEASTWARD AS IT APPROACHES THE
BAROCLINIC ZONE AND BEGINS EXTRA-TROPICAL TRANSITION BY THE END OF
THE FORECAST PERIOD. SLIGHT INTENSIFICATION IS EXPECTED AS THE
SYSTEM GAINS POLEWARD OUTFLOW AND TRACKS OVER FAVORABLE SEA SURFACE
TEMPERATURES. MODEL GUIDANCE HAS BECOME BETTER ALIGNED WITH MOST
SHOWING A BROAD RECURVE SCENARIO ALTHOUGH THERE REMAINS A LARGE
VARIANCE IN TRANSLATIONAL SPEED AFTER TAU 72 AS MODELS DISAGREE ON
HOW DEEP THE TROUGH DEVELOPS AND HOW THE TROUGH AFFECTS THE STR.
NAVGEM AND GFDN REMAIN OUTLIERS AS THEY AMPLIFY THE RIDGE AND DRIVE
THE SYSTEM TOWARDS MAINLAND CHINA. DUE TO THE SIGNIFICANT
DIFFERENCES IN THE SPEED OF THE TRACK IN THE EXTENDED TAUS DUE TO
THE ORIENTATION OF THE STR AND HOW DEEP THE TROUGH DEVELOPS, THERE
IS OVERALL LOW CONFIDENCE IN THE FORECAST.//
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