Tropical Storm TRAMI Advisory Mon Sep 24

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (TRAMI)
WARNING NR 11//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 28W (TRAMI), LOCATED APPROXIMATELY 660 NM SOUTHEAST
OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 09
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE
IMAGERY DEPICTS A 130NM DIAMETER CENTRAL DENSE OVERCAST FEATURE WITH
A 10NM RAGGED EYE. A 230438Z AMSR2 89GHZ IMAGE INDICATES A RAPIDLY
CONSOLIDATING SYSTEM WITH SPIRAL BANDING WRAPPING INTO A COMPACT
EYEWALL AND MICROWAVE EYE FEATURE, WHICH SUPPORTS THE CURRENT
POSITION WITH HIGH CONFIDENCE. TY TRAMI HAS RAPIDLY INTENSIFIED 45
KNOTS OVER THE PAST 24 HOURS FROM 50 KNOTS TO THE CURRENT INTENSITY
OF 95 KNOTS, WHICH IS BASED ON AN AVERAGE OF DVORAK ESTIMATES
RANGING FROM T5.0 (90 KNOTS) TO T5.5 (102 KNOTS). UPPER-LEVEL
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH NEAR-RADIAL
OUTFLOW, ENHANCED BY A TUTT CELL TO THE NORTHEAST, AND LOW VERTICAL
WIND SHEAR. TY 28W IS TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHERN
PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR) ENTRENCHED TO
THE NORTH.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. THE INITIAL 34-KNOT WIND
RADII HAVE BEEN ADJUSTED BASED ON A DETAILED ANALYSIS OF THE 230017Z
ASCAT IMAGE.
   B. TS TRAMI IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE AFOREMENTIONED STR THROUGH TAU 36. AFTER
TAU 36, A MIDLATITUDE SHORTWAVE TROUGH WILL DEEPEN OVER
THE EAST CHINA SEA AND WESTERN JAPAN CREATING A BROAD, PERSISTENT
BREAK IN THE STR. THIS WILL RESULT IN A SLIGHT POLEWARD TURN AND
SIGNIFICANT DECREASE IN TRACK SPEEDS AS THE STEERING INFLUENCE
ERODES QUICKLY. TRACK SPEEDS ARE EXPECTED TO REMAIN SLOW THROUGH TAU
72 AS THE STR SLOWLY REBUILDS TO THE NORTH AND THE SYSTEM RETURNS TO
A WEST-NORTHWESTWARD COURSE. WITH THE EXCEPTION OF HWRF AND GFS,
NUMERICAL MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH A 120NM
SPREAD IN SOLUTIONS AT TAU 72, HOWEVER, THERE IS SIGNIFICANT
UNCERTAINTY IN THE TRACK / TRACK SPEEDS DURING THE TAU 48 TO TAU 72
PERIOD WITH AN ERRATIC TRACK POSSIBLE. THE SYSTEM IS EXPECTED TO
INTENSIFY TO SUPER TYPHOON STRENGTH BY TAU 36 UNDER VERY FAVORABLE
CONDITIONS WITH A PEAK INTENSITY OF 140 KNOTS ANTICIPATED BY TAU 72.
   C. AFTER TAU 72, NUMERICAL MODEL GUIDANCE INDICATES INCREASING
SPREAD AND GREATER UNCERTAINTY IN THE EXACT FORECAST TRACK WITH A
330NM SPREAD IN SOLUTIONS AT TAU 120 (EXCLUDING THE HWRF AND GFS
OUTLIERS). THE GFS AND HWRF SOLUTIONS SHOW A SHARP NORTHWARD TRACK
TOWARD THE RYUKYU ISLANDS IN THE EXTENDED PERIOD WHICH IS DEEMED
UNLIKELY DUE TO EXCESSIVE INTERACTION WITH THE MIDLATITUDE SHORTWAVE
TROUGH. THE JTWC OFFICIAL FORECAST FAVORS A SLOW, WEST-NORTHWESTWARD
TRACK TOWARD TAIWAN AND ISHIGAKI-JIMA AS SUPPORTED BY THE BULK OF
THE MODEL GUIDANCE. TY 28W IS FORECAST TO WEAKEN SLIGHTLY AFTER TAU
72 AS ENVIRONMENTAL CONDITIONS DEGRADE. OVERALL, THERE IS LOW
CONFIDENCE IN THE JTWC TRACK DUE TO THE LARGE SPREAD IN SOLUTIONS
AFTER TAU 72.//
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