WDPN32 PGTW 071500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (KHANUN)      
WARNING NR 046//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.4N 131.2E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 292 NM SOUTH-SOUTHEAST OF SASEBO, JAPAN
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 34 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXYVIS SATELLITE IMAGERY DEPICTS DEEP CONVECTIVE BANDING 
WRAPPING INTO A BROAD, EXPOSED CENTER WITH MULTIPLE MESOVORTICES 
ROTATING CYCLONICALLY AROUND A DEFINED CENTROID. ANIMATED RADAR 
IMAGERY REVEALS CONVECTIVE BANDING WRAPPING INTO A BROAD, ILL-DEFINED 
CENTER. A 070847Z SMAP IMAGE SHOWS A LARGE, SYMMETRIC CORE OF WEAK 
WINDS, ABOUT 90 NM DIAMETER, WITH A REGION OF 55-60 KNOT WINDS (1-
MINUTE AVERAGE) OVER THE EAST AND SOUTH QUADRANTS. DUE TO THE BROAD 
NATURE OF THE CENTER, THERE IS MEDIUM CONFIDENCE IN THE INITIAL 
POSITION. OVER THE PAST SIX HOURS, THE TRACK MOTION HAS REMAINED SLOW 
TOWARD THE NORTH. A 070917Z SSMIS 37 GHZ COLOR COMPOSITE IMAGE 
SUGGESTS SLIGHTLY IMPROVED CONVECTIVE STRUCTURE WITH BANDING WRAPPING 
INTO A DEFINED CENTER. ENVIRONMENTAL CONDITIONS HAVE IMPROVED WITH 
EXPANDING RADIAL OUTFLOW, LOW VERTICAL WIND SHEAR AND WARM SST (29C). 
HOWEVER, MID-LEVEL TO UPPER-LEVEL DRY AIR ENTRAINMENT IS LIKELY 
HINDERING DEVELOPMENT AT THIS TIME. THE INITIAL INTENSITY IS BASED ON 
THE RECENT SMAP DATA HEDGED CLOSER TO THE RJTD CURRENT INTENSITY 
ESTIMATE OF 55 KNOTS. A 070907Z RCM-2 SAR IMAGE INDICATES MAXIMUM 
WINDS OF 69 KNOTS BUT APPEARS TO BE TOO HIGH. 

INITIAL WIND RADII BASIS: SMAP DATA ADJUSTED WITH SURFACE
OBSERVATIONS OVER THE RYUKYU ISLANDS. 

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: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 47 KTS AT 071034Z
   CIMSS ADT: 39 KTS AT 071140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 06W IS DRIFTING SLOWLY POLEWARD BASED ON A 
SERIES OF RECENT JMA RADAR FIXES AND IS FORECAST TO TRACK SLOWLY 
NORTHWARD TO NORTH-NORTHWESTWARD OVER THE NEXT 48 HOURS WHILE
STEADILY INTENSIFYING TO 65-70 KNOTS NEAR SASEBO DUE TO IMPROVING, 
ROBUST POLEWARD OUTFLOW AND WARM SST VALUES. THE SYSTEM IS FORECAST 
TO GRADUALLY RE-MOISTEN, WHICH WILL ALSO AID IN THE REINTENSIFICATION 
PHASE. AFTER TAU 72, TS KHANUN WILL ACCELERATE OVER 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 GUIDANCE HAS SHIFTED FURTHER WEST OVER 
THE WESTERN KOREAN PENINSULA AND WEST SEA. CONSEQUENTLY, THE JTWC 
TRACK FORECAST WAS SHIFTED SLIGHTLY WEST OF THE PREVIOUS WARNING. DUE 
TO THE BROAD CENTER AND UNCERTAINTY IN THE INITIAL POSITION AND TRACK 
MOTION, THE JTWC TRACK FORECAST IS POSITIONED ALONG THE EASTERN EDGE 
OF THE AIDS ENVELOPE CLOSE TO THE ECMWF TRACK. SEVERAL MODELS 
INCLUDING GFS, UKMET AND NAVGEM TRACK THE SYSTEM NORTH-NORTHWESTWARD 
OVER THE WEST SEA INTO THE UPPER LEVEL WESTERLIES, WHICH APPEARS 
UNLIKELY. HOWEVER, THE 070600Z GEFS AND EPS PROBABILISTIC GUIDANCE 
SHOWS INCREASING UNCERTAINTY WITH A LARGE SPREAD AFTER TAU 48. 
OVERALL, THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST 
WITH THE 070000Z COAMPS-TC ENSEMBLE SHOWING AN 80 TO 100 PERCENT 
PROBABILITY OF MODERATE INTENSIFICATION THROUGH TAU 24 DECREASING TO 
40 PERCENT PROBABILITY THROUGH TAU 48.

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