WDPN35 PGTW 281500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 15W (JONGDARI) WARNING NR 27//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 15W (JONGDARI), LOCATED APPROXIMATELY 95 NM 
SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 19 
KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY DEPICTS GRADUAL WEAKENING OF CORE CONVECTION AS THE SYSTEM 
TRACKS ALONG THE SOUTHERN COAST OF HONSHU, HOWEVER, A WEAK, 
TRANSIENT EYE IS EVIDENT. RADAR IMAGERY CONFIRMS THE PRESENCE OF AN 
EYE FEATURE WITH A PARTIAL EYEWALL AND SPIRAL BANDING. OVERALL, 
THERE IS GOOD CONFIDENCE IN THE INITIAL POSITION BASED ON THE RADAR 
IMAGERY AND FIXES. SURFACE OBSERVATIONS FROM IROZAKI (47666), 
APPROXIMATELY 31NM NORTH AT 28/11Z, INDICATE MAXIMUM SUSTAINED (10-
MINUTE AVERAGE) WINDS 080/59 KNOTS. THE INITIAL INTENSITY IS 
ASSESSED AT 70 KNOTS BASED ON THE SURFACE OBSERVATIONS FROM IROZAKI 
AS WELL AS PGTW, RJTD DVORAK ESTIMATES OF 4.0/4.5 (65/77 KNOTS). 
UPPER-LEVEL ANALYSIS INDICATES A MARGINALLY FAVORABLE ENVIRONMENT 
WITH MODERATE TO STRONG VERTICAL WIND SHEAR (VWS) OFFSET BY GOOD 
POLEWARD OUTFLOW. TY 15W IS TRACKING QUICKLY WEST-NORTHWESTWARD 
BETWEEN THE NORTHERN PERIPHERY OF A BROAD LOW AND THE SUBTROPICAL 
RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE. 
   B. THE SYSTEM WILL CONTINUE TO TRACK ON A WEST-NORTHWESTWARD TO 
WESTWARD TRAJECTORY AROUND THE PERIPHERY OF THE BROAD LOW WITH THE 
STR MAINTAINING TO THE NORTH THROUGH TAU 12. AFTER TAU 12, TY 15W 
WILL TURN WEST-SOUTHWESTWARD TO SOUTHWESTWARD AS IT STEERS ALONG THE 
NORTHWEST PERIPHERY OF THE BROAD LOW WITH THE WESTERN EXTENSION OF 
THE STR POSITIONED TO THE NORTH. TY 15W WILL MAKE LANDFALL ALONG THE 
SOUTHERN COAST OF HONSHU IN THE NEXT 4-6 HOURS AND IS FORECAST TO 
TRACK ACROSS WESTERN HONSHU THROUGH TAU 24, WHICH WILL LEAD TO 
SIGNIFICANT WEAKENING DUE TO FRICTIONAL EFFECTS OF LAND. INCREASING 
VWS AFTER TAU 48 SHOULD CONTINUE TO WEAKEN THE SYSTEM WITH 
DISSIPATION EXPECTED BY TAU 72. THERE IS SOME POTENTIAL FOR THE 
SYSTEM TO REGENERATE AFTER TAU 72 AND TRACK WESTWARD TOWARD THE 
COAST OF CHINA. NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT ONLY 
THROUGH TAU 24. AFTER TAU 24, THE PRESENCE OF THE STRONG UPPER LOW 
OVER WESTERN JAPAN WILL WORSEN AN ALREADY COMPLEX SYNOPTIC 
ENVIRONMENT. GFS AND NAVGEM RAPIDLY WEAKEN TY 15W AND MERGE THE 
REMNANT SYSTEM WITH THE LOW-LEVEL REFLECTION OF THE UPPER LOW AS 
EVIDENT IN THE 850MB VORTICITY FIELDS, WHICH SHOW TWO DISTINCT 
VORTICITY CENTERS ROTATING CYCLONICALLY AND EVENTUALLY COALESCING. 
THE JTWC FORECAST FAVORS THE ECMF, CTCX AND EEMN SOLUTIONS WHICH 
MAINTAIN A MORE REALISTIC TRACK WITHOUT MERGER. DUE TO THE MODEL 
DEGRADATION AFTER TAU 24, THERE IS LOW CONFIDENCE IN THE JTWC 
FORECAST TRACK.//
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