MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 18W (MALAKAS) WARNING NR 06// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TROPICAL STORM (TS) 18W (MALAKAS), LOCATED APPROXIMATELY 289 NM NORTH OF YAP, HAS TRACKED WESTWARD AT 12 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS SOME IMPROVED ORGANIZATION AND STRENGTHENING IN THE CONVECTIVE STRUCTURE. A 130111Z GPM 89GHZ MICROWAVE IMAGE SHOWS DEEP CONVECTIVE BANDING WRAPPING INTO AN IMPROVED LOW LEVEL CIRCULATION CENTER (LLCC). THE CURRENT POSITION IS BASED ON THE LLCC IN THE GPM IMAGE WITH GOOD CONFIDENCE. THE INTENSITY HAS BEEN INCREASED BASED ON THE IMPROVED STRUCTURE OF ALL IMAGERY AND IS SUPPORTED BY A DVORAK INTENSITY ESTIMATE OF T3.0 (45 KNOTS) FROM PGTW. ENVIRONMENTAL ANALYSIS REVEALS A MARGINAL ENVIRONMENT DUE TO THE NEGATIVE IMPACTS OF THE OUTFLOW FROM STY 16W PRODUCING MODERATE (15-20 KNOTS) VWS AND RESTRICTED POLEWARD OUTFLOW. HOWEVER, WATER VAPOR IMAGERY SHOWS A TUTT CELL LOCATED TO THE NORTHEAST PRODUCING ENHANCED EASTERLY OUTFLOW WHICH IS PROVIDING SUFFICIENT VENTILATION FOR THE INCREASED CONVECTION. SEA SURFACE TEMPERATURES REMAIN FAVORABLE NEAR 29 CELSIUS. TS 18W IS TRACKING ALONG THE SOUTHERN PERIPHERY OF THE DEEP- LAYERED SUBTROPICAL RIDGE (STR) TO THE NORTH. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TS 18W IS FORECAST TO TRACK WEST-NORTHWESTWARD THEN NORTHWESTWARD THROUGH TAU 72. TS MALAKAS WILL GRADUALLY INTENSIFY OVER THE NEXT 24 HOURS, BUT AT A SLOW RATE, DUE TO THE CONTINUED NEGATIVE EFFECTS FROM THE OUTFLOW OF STY 16W. BY TAU 36, STY 16W WILL MOVE WEST OF TAIWAN WHICH WILL ALLOW FOR INCREASED INTENSIFICATION OF TS 18W AS THE VWS DECREASES AND THE OUTFLOW GREATLY IMPROVES. DYNAMIC MODEL GUIDANCE IS IN BETTER AGREEMENT DURING THIS PORTION OF THE FORECAST WITH THE BULK OF GUIDANCE SUPPORTING THE CURRENT TRACK. EGRR IS AN OUTLIER TO THE WEST TAKING THE CYCLONE OVER TAIWAN. GFS AND ITS ENSEMBLE CONTINUE TO SHOW AN EARLIER RECURVE TO THE EAST OF THE CURRENT TRACK. C. IN THE EXTENDED FORECAST, TS 18W WILL REACH THE WESTERN EXTENT OF THE STEERING STR AND TURN POLEWARD INTO THE MID-LATITUDE WESTERLIES. THE STRONG ZONAL FLOW WILL RAPIDLY INCREASE THE VWS CREATING ADVERSE EFFECTS FOR THE STORM. THE SYSTEM WILL CONTINUE TO WEAKEN AS IT APPROACHES KYUSHU. DUE TO THE SPREAD IN MODEL GUIDANCE SHOWING MULTIPLE SOLUTIONS, ESPECIALLY AFTER TAU 48, THERE IS LOW CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN