WDPN32 PGTW 060900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN)       
WARNING NR 041//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8N 130.1E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 319 NM SOUTH OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 36 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 06W HAS MAINTAINED INTENSITY AT 55 KNOTS OVER
THE PAST SIX HOURS WITH A SOMEWHAT ERRATIC TRACK OVER THE PAST 12
HOURS DUE TO THE PRESENCE OF MULTIPLE MESOVORTICES ROTATING WITHIN
A BROAD, EXPOSED CENTER. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) CONTINUES TO SHOW AN EXPOSED BUT DOMINANT LOW-LEVEL
CIRCULATION (LLC) WITH EXTENSIVE DEEP CONVECTIVE BANDING PERSISTING
OVER THE SOUTHERN SEMICIRCLE. A 060430Z AMSR2 89GHZ MICROWAVE IMAGE
REVEALS A NARROW BAND OF DEEP CONVECTION WRAPPING AROUND A VERY
BROAD, CONVECTION-FREE CENTER (APPROXIMATELY 200-225NM DIAMETER).
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE
MSI AND AMSR2 IMAGERY AS WELL AS JMA HOURLY RADAR FIXES.
ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE WITH
SIGNIFICANT DRY AIR IN THE MID- TO UPPER-LEVELS INDICATED IN THE
RECENT KAGOSHIMA AND NAZE SOUNDINGS. HOWEVER, THE DEEP CONVECTIVE
STRUCTURE HAS MAINTAINED DUE TO LOW VERTICAL WIND SHEAR (VWS), WARM
SST (29C) AND MODERATE EQUATORWARD VENTING. THERE IS HIGH CONFIDENCE 
IN THE INITIAL INTENSITY BASED ON THE 060430Z AMSR2 WINDSPEED DATA 
AND RANGE OF DVORAK ESTIMATES. 

INITIAL WIND RADII BASIS: SCATTEROMETER DATA AND AMSR2 DATA 

CURRENT STEERING MECHANISM: WEAK SUBTROPICAL RIDGE (STR) POSITIONED
TO THE EAST AND NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 45 KTS AT 060120Z
   CIMSS ADT: 30 KTS AT 060230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DUE TO THE PROLONGED TRACK OVER THE
KOREAN PENINSULA, THE FORECAST PHILOSOPHY HAS BEEN SWITCHED FROM
EXTRA-TROPICAL TRANSITION TO DISSIPATION.

FORECAST DISCUSSION: TS 06W IS WOBBLING SLOWLY EAST-NORTHEASTWARD
ALONG THE NORTHWESTERN PERIPHERY OF THE WEAK STR AND IS EXPECTED TO
SLOWLY TURN POLEWARD WITHIN THE NEXT 12 HOURS. TRACK SPEEDS REMAIN
SLOW DUE TO A DEVELOPING TROPICAL DISTURBANCE TO THE EAST, WHICH IS
DISRUPTING THE STR. THE SYSTEM'S SLOW TRACK MOTION IS RESULTING IN
PERSISTENT HEAVY RAINBANDS AND GALE-FORCE WINDS SUSTAINING OVER
OKINAWA. AFTER TAU 12, TS 06W WILL TURN NORTH-NORTHWESTWARD AND
GRADUALLY INTENSIFY DUE PRIMARILY TO IMPROVING POLEWARD OUTFLOW TO
A PEAK OF 65 TO 70 KNOTS BY TAU 72. AS THE LARGE (600NM DIAMETER)
SYSTEM TRACKS PARALLEL TO THE WESTERN COAST OF KYUSHU, IT WILL
GRADUALLY WEAKEN DUE TO FRICTIONAL EFFECTS WITH MORE SIGNIFICANT
WEAKENING AS IT APPROACHES THE BUSAN REGION WITH LANDFALL
ANTICIPATED NEAR TAU 96. AFTER TAU 96, TS KHANUN WILL TRACK ALONG
THE EASTERN PORTION OF THE KOREAN PENINSULA AND BEGIN INTERACTING
WITH THE LEADING EDGE OF A SUBTROPICAL SHORTWAVE TROUGH AND WEAK
BAROCLINIC ZONE. DESPITE THE BAROCLINIC INFLUENCE, THE SYSTEM IS
FORECAST TO DISSIPATE AS IT TRACKS INTO NORTH KOREA AND NORTHEAST
CHINA.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN FAIR AGREEMENT 
WITH A 150NM CROSS-TRACK SPREAD IN SOLUTIONS AT TAU 84 (NEAR SASEBO) 
DIVERGING TO 250NM AT TAU 96 (NEAR BUSAN). IN GENERAL, NUMERICAL 
GUIDANCE IS IN POOR AGREEMENT AFTER TAU 72 WITH LOW CONFIDENCE (HIGH 
UNCERTAINTY) IN THE JTWC FORECAST TRACK OVER THE KOREAN PENINSULA. 
THIS UNCERTAINTY IS ALSO REFLECTED IN THE 060000Z GEFS AND EPS 
PROBABILISTIC GUIDANCE. OVERALL, THERE IS MEDIUM CONFIDENCE IN THE 
JTWC INTENSITY FORECAST WITH THE 060000Z COAMPS-TC ENSEMBLE SHOWING 
AN 80 TO 100 PERCENT PROBABILITY OF REINTENSIFICATION THROUGH TAU 48.      

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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