WDPN31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (TRAMI) 
WARNING NR 12//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 28W (TRAMI), LOCATED APPROXIMATELY 618 NM SOUTH-
SOUTHEAST OF KADENA AB, OKINAWA, JAPAN, HAS TRACKED WESTWARD AT 11 
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY CLEARLY INDICATES TROCHOIDAL MOTION WITH A CENTRAL DENSE 
OVERCAST FEATURE AND A SMALL 7NM ROUND EYE, WHICH SUPPORTS THE 
CURRENT POSITION WITH HIGH CONFIDENCE. A 231204Z MHS 89GHZ IMAGE AND 
A 230848Z SSMIS 91GHZ IMAGE (AS WELL AS THE UW-CIMSS P-ERC PRODUCT) 
INDICATE AN ONGOING EYEWALL REPLACEMENT CYCLE WITH CONCENTRIC 
EYEWALLS AND A MOAT FEATURE EVIDENT. TY TRAMI HAS RAPIDLY 
INTENSIFIED 60 KNOTS OVER THE PAST 24 HOURS FROM 55 KNOTS TO THE 
CURRENT INTENSITY OF 115 KNOTS, WHICH IS BASED ON A PGTW DVORAK 
ESTIMATE OF T6.0 (115 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 WESTWARD 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. 
   B. TY TRAMI IS FORECAST TO TRACK WEST-NORTHWESTWARD UNDER THE 
STEERING INFLUENCE OF THE AFOREMENTIONED STR THROUGH TAU 24. AFTER 
TAU 24, 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, GFS AND THE GFS 
ENSEMBLE MEAN (GEFS), NUMERICAL MODEL GUIDANCE REMAINS IN GOOD 
AGREEMENT WITH A 65NM SPREAD IN SOLUTIONS AT TAU 72, HOWEVER, THERE 
IS SIGNIFICANT UNCERTAINTY IN THE TRACK / TRACK SPEEDS DURING THE 
TAU 36 TO TAU 72 PERIOD WITH AN ERRATIC TRACK POSSIBLE. THE SYSTEM 
IS EXPECTED TO INTENSIFY TO SUPER TYPHOON STRENGTH BY TAU 12 UNDER 
VERY FAVORABLE CONDITIONS WITH A PEAK INTENSITY OF 145 KNOTS 
ANTICIPATED BY TAU 36.
   C. AFTER TAU 72, NUMERICAL MODEL GUIDANCE INDICATES INCREASING 
SPREAD AND GREATER UNCERTAINTY IN THE EXACT FORECAST TRACK WITH A 
290NM SPREAD IN SOLUTIONS AT TAU 120 (EXCLUDING THE HWRF, GFS AND 
GEFS OUTLIERS). THE GFS, GEFS 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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