WDPN31 PGTW 151500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 15W (CHOI-WAN)/
WARNING NR 15//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
    A. SUPER TYPHOON (STY) 15W (CHOI-WAN), LOCATED APPROXIMATELY 175
NM NORTH-NORTHWEST OF SAIPAN, HAS TRACKED WEST-NORTHWESTWARD AT 08
KNOTS OVER THE LAST 06 HOURS. ANIMATED INFRARED SATELLITE IMAGERY
SHOWS THAT STY 15W HAS SEEN A MARKEDLY IMPROVED CONVECTIVE SIGNATURE
NEAR AN EXPANDING EYEWALL, WITH DVORAK ESTIMATES OF 7.0 FROM PGTW AND
RJTD AT THE LATEST POSITION. STY 15W HAS TRACKED ALONG THE
SOUTHWESTERN PERIPHERY OF A MID-LEVEL SUBTROPICAL RIDGE (STR) THAT
EXTENDS FROM NORTHEAST OF 15W INTO THE VICINITY OF IWO TO. TRACK
SPEEDS HAVE REMAINED FAIRLY CONSISTENT OVER THE PAST 12 HOURS,
RANGING FROM 08 TO 10 KNOTS. AN UPPER LEVEL TROPICAL TROPOSPHERIC
TROUGH (TUTT) CELL TO THE NORTHEAST HAS CONTINUED TO PROVIDE GOOD
EASTWARD OUTFLOW, IN ADDITION TO AN UPPER LEVEL POINT SOURCE
ANTICYCLONE OVER STY 15W THAT HAS BEEN PROVIDING STRONG RADIAL
OUTFLOW OVER THE PAST 24 HOURS. THE MULTIPLE OUTFLOW MECHANISMS IN
CONCERT WITH HIGH VALUES OF OCEAN HEAT CONTENT (OHC) AND SEA SURFACE
TEMPERATURES (SST) HAVE ALLOWED FOR STY 15W TO INTENSIFY FURTHER OVER
THE PAST 12 HOURS. 
3. FORECAST REASONING.
    A. THE FORECAST PHILOSOPHY HAS CHANGED SLIGHTLY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE, WITH OHC AND SST VALUES
FORECAST TO REMAIN FAVORABLE THROUGH THE ENTIRE FORECAST PERIOD.
    B. STY CHOI-WAN WILL TRACK NORTHWESTWARD THROUGH TAU 48 UNDER THE
INFLUENCE OF THE STR DESCRIBED IN PARA 2.A. THE SYSTEM WILL SLOWLY
INTENSIFY OVER THE NEXT 12 TO 24 HOURS AND THEN MAINTAIN THE SUPER
TYPHOON INTENSITY THROUGH TAU 72 WITH MULTIPLE UPPER LEVEL OUTFLOW
CHANNELS SUPPORTING THE STRONG INFLOW OVER REGIONS OF HIGH OHC AND
SST VALUES. BY TAU 36 STY 15W WILL REACH THE WESTERN EXTENT OF THE
STR AND BEGIN TO TRACK MORE NORTHWARD AROUND THE RIDGE AXIS. BY TAU
72 STY 15W WILL BEGIN TO RECURVE NORTHEASTWARD.
     C. BEYOND TAU 72, CHOI-WAN WILL MAINTAIN A NORTHEASTWARD TRACK
TOWARDS AN APPROACHING MID-LATITUDE TROUGH, WITH A STEADY INCREASE IN
TRACK SPEED THROUGH TAU 120. THE NUMERICAL MODELS ARE IN FAIR
AGREEMENT WITH TRACK, HOWEVER HAVE SIGNIFICANT INCONSISTENCIES WITH
SPEED. THIS FORECAST FAVORS THE MODEL CONSENSUS WITH REGARDS TO
TRACK, BUT IS SLOWER THAN CONSENSUS TO ACCOUNT FOR DIFFERENCES IN
DYNAMIC MODEL GUIDANCE ON SPEED.//
NNNN