MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 06W (DANAS) WARNING NR 09// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 06W (DANAS), LOCATED APPROXIMATELY 200 NM WEST-SOUTHWEST OF KADENA AB, HAS TRACKED NORTHWARD AT 18 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION (LLC) WITH DEEP CONVECTION CONFINED TO THE EASTERN SEMICIRCLE. RECENT MSI (18/06- 08Z) INDICATES THE LLC MAY BE DECOUPLING AND DRIFTING NORTH- NORTHWESTWARD, WHICH ADDS SOME UNCERTAINTY TO THE EARLY PHASE OF THE FORECAST TRACK. A 180723Z SSMIS 91GHZ IMAGE ALSO INDICATES A PARTIALLY-EXPOSED LLC WITH EXTENSIVE DEEP CONVECTIVE BANDING OVER THE EAST AND SOUTHEAST QUADRANTS. A 180158Z ASCAT IMAGE CONTINUES TO SHOW A HIGHLY ASYMMETRICAL WIND FIELD WITH AN EXTENSIVE SWATH OF 30 TO 40 KNOT WINDS OVER THE EASTERN SEMICIRCLE, WHICH EXTEND 180-200NM EAST. OVERALL, THERE IS GOOD CONFIDENCE IN THE 18/06Z POSITION BASED ON RADAR IMAGERY, SURFACE OBSERVATIONS AND MSI. THE INITIAL INTENSITY IS ASSESSED AT 40 KNOTS, HEDGED ABOVE DVORAK INTENSITY ESTIMATES OF T2.5 (35 KNOTS) BASED ON THE AFOREMENTIONED ASCAT DATA. UPPER-LEVEL ANALYSIS DEPICTS A GENERALLY FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR AND FAIR OUTFLOW. TS 06W IS TRACKING NORTHWARD ALONG THE WESTERN PERIPHERY OF A NORTH-SOUTH ORIENTED SUBTROPICAL RIDGE. 3. FORECAST REASONING. A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. FORECAST WIND RADII ARE BASED ON THE WIND RADII CONSENSUS (RVCN). B. TS 06W IS FORECAST TO TRACK NORTHWARD TO NORTH-NORTHEASTWARD THROUGH TAU 48 ALONG THE NORTHWEST PERIPHERY OF THE SUBTROPICAL RIDGE (STR). AFTER TAU 48, THE SYSTEM WILL BEGIN TO ROUND THE STR AND WILL BEGIN TO INTERACT WITH RELATIVELY WEAK MIDLATITUDE WESTERLIES OVER THE KOREAN PENINSULA. THERE IS MODERATE UNCERTAINTY IN THE FORECAST TRACK DUE TO THE ASYMMETRIC NATURE OF THE SYSTEM WITH POTENTIAL FOR A WESTWARD TRACK SHIFT AND LANDFALL ALONG THE SOUTHWEST COAST OF KOREA IF THE SYSTEM REMAINS DECOUPLED. FURTHERMORE, THE EXPANSIVE GALE FORCE WINDS OVER THE EASTERN SEMICIRCLE ARE EXPECTED TO PERSIST DUE TO AN ENHANCED GRADIENT WITH A STRONG HIGH TO THE EAST. TS 06W IS FORECAST TO INTENSIFY SLIGHTLY TO A PEAK OF 45 KNOTS BUT SHOULD WEAKEN STEADILY THROUGH TAU 48. AFTER LANDFALL, THE SYSTEM WILL WEAKEN RAPIDLY OVER THE MOUNTAINOUS TERRAIN OF KOREA AND SHOULD DISSIPATE BY TAU 72. OVERALL, THERE IS MODERATE CONFIDENCE IN THE JTWC FORECAST TRACK WITH A SPREAD OF 200NM AT TAU 48.// NNNN NNNN