MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (BOLAVEN) WARNING NR 04// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 16W (BOLAVEN), LOCATED APPROXIMATELY 410 NM SOUTH OF IWO TO, JAPAN, HAS TRACKED WEST-NORTHWESTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A MORE TIGHTLY WRAPPED LOW-LEVEL CIRCULATION CENTER (LLCC). A 201741Z SSMI 89GHZ IMAGE DEPICTS THE DEEP CONVECTION IS STILL MOSTLY CONFINED TO THE SOUTHERN SEMI-CIRCLE AND A 1729Z TRMM 37GHZ IMAGE STILL DEPICTS A TIGHTLY WRAPPED LLCC WITH SHALLOW CONVECTIVE BANDING. THE INITIAL INTENSITY OF 45 KNOTS IS BASED ON DVORAK ESTIMATES OF 45 KNOTS FROM ALL AGENCIES (PGTW,KNES, AND RJTD). THE INITIAL POSITION IS BASED ON RECENT EIR ANIMATION AS WELL AS THE AFOREMENTIONED IMAGERY WITH FAIR CONFIDENCE. UPPER- LEVEL ANALYSIS CONTINUES TO SHOW A FAVORABLE ENVIRONMENT WITH IMPROVED RADIAL OUTFLOW, ALTHOUGH THE OUTFLOW CHANNEL INTO THE TUTT TO THE NORTHEST HAS WEAKENED AS THE TUTT HAS FILLED. TS 16W IS SLOWLY TRACKING WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL STEERING RIDGE TO THE NORTHEAST. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 16W IS FORECAST TO CONTINUE WEST-NORTHWESTWARD AND PICK UP SPEED IN THE NEXT 24 HOURS AS THE SUBTROPICAL RIDGE (STR) SOUTH OF JAPAN AMPLIFIES AND BECOMES THE DOMINANT STEERING INFLUENCE WHILE A LONGWAVE TROUGH THAT IS CURRENTLY OVER CHINA WEAKENS AND MOVES OUT. DYNAMIC MODEL GUIDANCE IS IN FAIRLY TIGHT AGREEMENT WITH NGPS AND GFDN SHOWING A SLOWER MORE SOUTHERN TRACK WHICH SEEMS UNLIKELY DUE TO THE STR ALREADY WELL-ESTABLISHED AS SUPPORTED BY UPPER AIR OBSERVATIONS IN THE REGION. TS 16W WILL CONTINUE TO INTENSIFY AS ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE. C. AFTER TAU 72, TS 16W IS FORECAST TO CONTINUE TO TRACK WEST- NORTHWESTWARD BUT SHOULD SLOW AS ANOTHER MIDLATITUDE TROUGH DIGS IN FROM EASTERN CHINA, WEAKENING THE STEERING STR. DYNAMIC MODEL GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 72 WITH THE SIGNIFICANT DIFFERENCES BEING IN TRACK SPEED WHICH MAY AFFECT THE INTENSITY. AFTER TAU 72, THERE IS A SPREAD OF MODELS WITH NGPS AND GFDN SHOWING A SLOWDOWN AS THE SYSTEM INTERACTS WITH THE AFOREMENTIONED MIDLATITUDE TROUGH AND A POSSIBLE NORTHERLY TURN WHILE GFS, JGSM, AND EGRR SHOW A FASTER TRACK NORTHWESTWARD WITH NO WEAKENING OF THE SUBTROPICAL RIDGE. THERE IS HIGH CONFIDENCE UP TO TAU 72, BUT AFTERWARDS, THE CONFIDENCE IS LOW DUE TO THE TIMING AND EFFECT OF THE MIDLATITUDE TROUGH ON THE STR.// NNNN NNNN