Tropical Storm TRAMI Advisory Tue Sep 25

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 28W (TRAMI)
WARNING NR 15//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 28W (TRAMI), LOCATED APPROXIMATELY 478 NM
SOUTH-SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED
NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY DEPICTS A SYMMETRIC EYEWALL
SURROUNDING A 30NM ROUND EYE. A 240558Z SSMI 85GHZ IMAGE REVEALS
EXCELLENT SPIRAL BANDING WRAPPING INTO A 110NM DIAMETER CORE.
CONSEQUENTLY, THERE IS HIGH CONFIDENCE IN THE CURRENT POSITION. STY
28W HAS RAPIDLY INTENSIFIED (35 KNOTS) OVER THE PAST 24 HOURS FROM
95 KNOTS TO THE CURRENT INTENSITY OF 130 KNOTS, WHICH IS BASED ON
PGTW/RJTD DVORAK INTENSITY ESTIMATES OF T6.5 (127 KNOTS). RECENT EIR
BRIEFLY INDICATED DVORAK INTENSITY ESTIMATES OF T7.0. THEREFORE, THE
CURRENT INTENSITY IS HEDGED ABOVE THE DVORAK INTENSITY ESTIMATES AT
SUPER TYPHOON STRENGTH. DESPITE WEAKENING OUTFLOW INTO A TUTT CELL
POSITIONED TO THE EAST, UPPER-LEVEL OUTFLOW REMAINS ROBUST WITH A
STRONG POLEWARD CHANNEL ASSOCIATED WITH A DEEP UPPER-LEVEL SHORTWAVE
TROUGH OVER THE EAST CHINA SEA. STY 28W IS TRACKING NORTHWESTWARD
ALONG THE SOUTHWESTERN 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.
   B. STY TRAMI IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE
STEERING INFLUENCE OF THE AFOREMENTIONED STR THROUGH TAU 12. AFTER
TAU 12, THE 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
NORTHWESTWARD COURSE. NUMERICAL MODEL GUIDANCE REMAINS IN MARGINAL
AGREEMENT THROUGH TAU 72 WITH A 140NM SPREAD IN SOLUTIONS AT TAU 72,
HOWEVER, TRACKERS VARY FROM A WEST-NORTHWESTWARD TRACK TO A NORTH-
NORTHEASTWARD TRACK. CONSEQUENTLY, THERE IS SIGNIFICANT UNCERTAINTY
IN THE TRACK / TRACK SPEEDS DURING THE TAU 12 TO TAU 72 PERIOD WITH
AN ERRATIC TRACK POSSIBLE. THE SYSTEM IS EXPECTED TO MAINTAIN SUPER
TYPHOON STRENGTH THROUGH TAU 72 WITH A PEAK INTENSITY OF 145 KNOTS
ANTICIPATED BY TAU 24.
   C. AFTER TAU 72, NUMERICAL MODEL GUIDANCE INDICATES INCREASING
SPREAD AND GREATER UNCERTAINTY IN THE EXACT FORECAST TRACK WITH A
510NM SPREAD IN SOLUTIONS AT TAU 120. IN GENERAL, THE GLOBAL MODELS
DEPICT A SIMILAR SYNOPTIC ENVIRONMENT WITH A WEAK EXTENSION OF THE
STR TO THE NORTH SUPPORTED BY A MIDLATITUDE SHORTWAVE RIDGE,
HOWEVER, EACH MODEL INDICATES SIGNIFICANTLY DIFFERENT TRACK
FORECASTS FROM TAIWAN TO OKINAWA. THE JTWC OFFICIAL FORECAST FAVORS
A NORTHWESTWARD TRACK TOWARD ISHIGAKI-JIMA AS SUPPORTED BY THE MULTI-
MODEL CONSENSUS. STY 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 DEGREE OF UNCERTAINTY
THROUGH THE ENTIRE FORECAST TRACK.//
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