MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 15W (FIFTEEN) WARNING NR 002// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL DEPRESSION (TD) 15W (FIFTEEN), LOCATED APPROXIMATELY 447 NM WEST OF WAKE ISLAND, HAS TRACKED NORTHWESTWARD AT 08 KNOTS (KTS) OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTION OVER THE SOUTHERN AND EASTERN SEMICIRCLES WITH FORMATIVE BANDING WRAPPING INTO THE CONSOLIDATING LOW LEVEL CIRCULATION CENTER (LLCC). A 262323Z METOP-C PARTIAL ASCAT IMAGE REVEALS A SWATH OF 30 KT WINDS WRAPPING AROUND THE EASTERN SEMICIRCLE OF THE SYSTEM. THE INITIAL POSITION IS PLACED WITH GOOD CONFIDENCE BASED ON THE ASCAT IMAGE AND A 262229Z MHS 89 GHZ MICROWAVE IMAGE WHICH SHOWS CONVECTIVE BANDING ALONG THE EASTERN SEMICIRCLE. AN UPPER LEVEL LOW TO THE NORTHWEST CONTINUES TO HINDER THE DEVELOPMENT OF DEEP CONVECTION OVER THE NORTHWESTERN QUADRANT AS OBSERVED IN THE MSI. THE INITIAL INTENSITY IS SET AT 30 KTS, HEDGED SLIGHTLY HIGHER THAN MULTI- AGENCY DVORAK CURRENT INTENSITY ESTIMATES OF T1.5 (25 KTS) AND SUPPORTED BY A 270001Z ADVANCED DVORAK TECHNIQUE ESTIMATE OF T2.0 (30 KTS) AND THE AFOREMENTIONED ASCAT DATA. TD 15W REMAINS IN A MODERATELY CONDUCIVE ENVIRONMENT FOR DEVELOPMENT, CHARACTERIZED BY LOW (<15 KT) VERTICAL WIND SHEAR (VWS) AND WARM (29-30 CELSIUS) SEA SURFACE TEMPERATURES (SST). THE EFFECTS OF THE UPPER LEVEL LOW ARE BEING OFFSET BY THE POINT SOURCE LOCATED OVER THE SYSTEM WHICH IS ENHANCING DIFFLUENCE ALOFT. TD 15W IS TRACKING NORTHWESTWARD UNDER THE STEERING INFLUENCE OF A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TD 15W IS FORECAST TO TRACK NORTH-NORTHWESTWARD THROUGH TAU 36 AS IT STEADILY INTENSIFIES DUE TO CONTINUED CONDUCIVE SST AND LOW VWS. AROUND TAU 36, TD 15W WILL BEGIN TO ROUND THE STR AXIS WITH THE APPROACH OF A DEEP MIDLATITUDE TROUGH, TURNING FIRST NORTHWARD THROUGH TAU 48 AND THEN NORTH-NORTHEASTWARD THROUGH TAU 72. NUMERICAL MODEL GUIDANCE IN IS TIGHT AGREEMENT REGARDING THE TIMING OF THE RECURVE WITH A CROSS-TRACK SPREAD OF 100 NM AT TAU 36. AFTER TD 15W ROUNDS THE STR AXIS, IT WILL BEGIN EXTRATROPICAL TRANSITION (ETT) AS IT INTERACTS WITH THE BAROCLINIC ZONE AROUND TAU 60. THE SYSTEM IS FORECAST TO INTENSIFY TO A PEAK INTENSITY OF 75 KTS BY TAU 72. HOWEVER, THE SYSTEM?S PEAK INTENSITY MAY OCCUR EARLIER, AROUND TAU 60. DUE TO THE LOW MODEL SPREAD, THERE IS GOOD CONFIDENCE IN THE NEAR TERM JTWC TRACK FORECAST. C. AFTER TAU 72, INCREASING VERTICAL WIND SHEAR AND RAPIDLY COOLING (<26 CELSIUS) SST WILL CAUSE THE SYSTEM TO QUICKLY WEAKEN THROUGH THE REMAINDER OF THE FORECAST PERIOD. TD 15W WILL TURN TO AN EAST- NORTHEASTWARD TRACK ALONG THE PERIPHERY OF THE AFOREMENTIONED STR. BY TAU 96, THE SYSTEM GAIN FRONTAL CHARACTERISTICS AS IT COMPLETES ETT AND BECOMES EMBEDDED IN THE JET FLOW. NUMERICAL MODEL GUIDANCE IS IN EXCELLENT AGREEMENT THROUGH THE EXTENDED FORECAST WITH A 106 NM SPREAD AT TAU 72. FURTHERMORE, THE 26/18Z ECMWF ENSEMBLE SOLUTIONS ARE IN GOOD AGREEMENT THROUGHOUT THE FORECAST PERIOD. THUS, THERE IS OVERALL HIGH CONFIDENCE IN THE JTWC FORECAST TRACK.// NNNN NNNN