WDPN31 PGTW 061500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 02W (NEPARTAK)
WARNING NR 15//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON 02W (NEPARTAK), LOCATED APPROXIMATELY 419 NM
SOUTHEAST OF TAIPEI, TAIWAN, HAS TRACKED WEST-NORTHWESTWARD AT 16
KNOTS OVER THE PAST SIX HOURS. THE CURRENT POSITION IS BASED ON
RECENT SATELLITE EYE FIXES FROM PGTW AND RJTD AND A 061001Z SSMIS
IMAGE, WITH HIGH CONFIDENCE. THE INTENSITY OF 150 KNOTS IS
CONSISTENT WITH SUBJECTIVE DVORAK INTENSITY ESTIMATES FROM MULTIPLE
REPORTING AGENCIES AS WELL AS RECENT OBJECTIVE SATELLITE INTENSITY
CONSENSUS DATA. STY 02W HAS MAINTAINED INTENSITY OVER THE PAST
SIX HOURS, AIDED BY LOW VERTICAL WIND SHEAR, PASSAGE OVER VERY WARM
WATER, AND VIGOROUS DUAL-CHANNEL OUTFLOW ALOFT. THE CONVECTIVE
STRUCTURE NOW RESEMBLES AN ANNULAR CYCLONE, WITH A STRONG CORE OF
CONVECTION AND MINIMAL CONVECTIVE BANDING EVIDENT IN RECENT INFRARED
SATELLITE IMAGERY. STY 02W CONTINUES TO TRACK QUICKLY WEST-
NORTHWESTWARD ALONG THE PERIPHERY OF A DEEP-LAYERED SUBTROPICAL
STEERING RIDGE.
3. FORECAST REASONING.
   A. THE FORECAST TRACK HAS SHIFTED VERY SLIGHTLY TO THE SOUTH AND
WEST OF THE PREVIOUS FORECAST BASED ON TRENDS IN NUMERICAL MODEL
TRACK FORECAST GUIDANCE AND CURRENT ANALYSIS OF THE STEERING RIDGE
ORIENTATION. MORE RAPID WEAKENING IS EXPECTED IN THE EXTENDED
FORECAST PERIOD, LEADING TO DISSIPATION BY TAU 96.
   B. STY 02W WILL CONTINUE TRACKING GENERALLY WEST-NORTHWESTWARD
TOWARD CENTRAL TAIWAN ALONG THE PERIPHERY OF THE CURRENT STEERING
RIDGE OVER THE NEXT 24 TO 36 HOURS. WHILE NUMERICAL GUIDANCE
SUGGESTS A SMALL DIP IN INTENSITY OVER THE NEXT DAY OR SO, FAVORABLE
ENVIRONMENTAL CONDITIONS AND THE PRESENTLY-OBSERVED ANNULAR
CONVECTIVE STRUCTURE WILL LIMIT THE POTENTIAL FOR SIGNIFICANT
WEAKENING PRIOR TO LANDFALL. HOWEVER, THE SYSTEM WILL WEAKEN RAPIDLY
AS IT CROSSES TAIWAN BETWEEN TAU 36 AND TAU 48, AND AGAIN AS IT
PROGRESSES INTO MAINLAND CHINA AFTER TAU 48. THE CIRCULATION IS
EXPECTED TO TURN POLEWARD AND MOVE FURTHER INLAND AS IT ROUNDS THE
STEERING RIDGE AXIS AFTER TAU 48. WHILE NUMERICAL MODEL GUIDANCE HAS
SHIFTED SLIGHTLY, IT IS IN GOOD OVERALL AGREEMENT IN THE NEAR-TERM,
LENDING HIGH CONFIDENCE TO THAT PORTION OF THE TRACK FORECAST.
   C. IN THE EXTENDED PERIOD, STY 02W WILL CONTINUE TRACKING OVER
LAND AS IT ROUNDS THE STEERING RIDGE AXIS. DISSIPATION IS NOW
EXPECTED TO OCCUR BY TAU 96. NUMERICAL MODELS CONTINUE TO DIFFER
REGARDING THE SPEED AND TIGHTNESS OF THE POLEWARD TURN BUT HAVE
CONVERGED SUFFICIENTLY TO LEND HIGH CONFIDENCE TO THE EXTENDED
FORECAST TRACK.//