WDPN31 PGTW 221500 MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR//JTWC// SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W WARNING NR 01// RMKS/ 1. FOR METEOROLOGISTS. 2. PROGNOSTIC REASONING FOR 221200Z7 TO 251200Z0 AUG 02. A. TROPICAL DEPRESSION (TD) 21W, LOCATED APPROXIMATELY 230 NM NORTH OF ENEWETAK ATOLL, HAS TRACKED NORTHWESTWARD AT 05 KNOTS OVER THE PAST 6 HOURS. THE WARNING POSITION IS BASED ON 221130Z9 ENHANCED INFRARED SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY ESTIMATES OF 25 AND 30 KNOTS. ANIMATED WATER VAPOR IMAGERY INDICATES IMPROVED ORGANIZATION AND POLEWARD OUTFLOW BEING ENHANCED BY AN UPPER LEVEL LOW NORTHEAST OF THE SYSTEM. A 221024Z1 SSM/I PASS DEPICTS A SYMMETRIC SYSTEM WITH MULTIPLE RAIN BANDS WRAPPING INTO THE LOW LEVEL CIRCULATION CENTER. B. THE LOW TO MID-LEVEL SUBTROPICAL RIDGE NORTH OF THE SYSTEM IS EXPECTED TO BUILD AND SLOWLY PROPAGATE WESTWARD. TD 21W IS FORECAST TO TRACK WEST-NORTHWESTWARD ALONG THIS SUBTROPICAL RIDGE THROUGH 72 HOURS. THE AVAILABLE DYNAMIC AIDS, CONSISTING OF NOGAPS, UKMET OFFICE (EGRR), AND THE JAPANESE GLOBAL MODEL (JGSM), ARE IN GOOD AGREEMENT WITH THE TRACK DIRECTION. THE MODELS DO NOT INITIALIZE THE SYSTEM WELL, KEEPING THE CIRCULATION BROAD AND WEAK FOR THE FIRST 24 TO 36 HOURS. SYNOPTIC OBSERVATIONS AND SATELLITE IMAGERY INDICATE A SECOND CIRCULATION WEST OF THE SYSTEM, NEAR 14.0N5 154.0E0. THE MODELS MERGE THE TWO CIRCULATIONS EARLY IN THE PERIOD, RESULTING IN A FASTER TRACK. OUR FORECAST IS BASED ON A BLEND PERSISTENCE AND ALL AVAILABLE DYNAMIC AIDS, WITH MORE EMPHASIS ON PERSISTENCE FOR THE FIRST 24 TO 36 HOURS. C. A WEAK UPPER LEVEL LOW NORTHEAST OF THE SYSTEM IS EXPECTED TO CONTINUE TO ENHANCE OUTFLOW OVER THE NEXT 12 TO 24 HOURS. THIS LOW IS EXPECTED TO FILL THROUGH THE FORECAST PERIOD, RESULTING TD 21W INTENSIFYING AT A LESS THAN CLIMATOLOGICAL RATE THROUGH 72 HOURS. D. THE FORECAST WIND RADII ARE BASED ON CLIMATOLOGY FOR AN AVERAGE-SIZED SYSTEM. FORECAST TEAM: WINGEART/LAM/KUMAGA/STATEN// NNNN