WDPN31 PGTW 041500 MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W (MAWAR) WARNING NR 16// RMKS// 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON 04W (MAWAR), LOCATED APPROXIMATELY 185 NM SOUTH OF KADENA AB, OKINAWA, HAS TRACKED NORTHEASTWARD AT 10 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS DEEP CONVECTION ALONG THE NORTHWESTERN QUADRANT HAS SLOWLY DIMINISHED OVER THE PAST SIX HOURS. IT ALSO INDICATES THE SYSTEM IS BEGINNING TO ELONGATE TO THE NORTHEAST AS A MID-LATITUDE TROUGH, LOCATED OVER EASTERN ASIA, MOVES INTO THE EAST CHINA SEA. INCREASING INTERACTION WITH THE MID-LATITUDES HAVE STARTED TO IMPACT THE OVERALL STRUCTURE OF TY 04W. THE EYE HAS BROKEN DOWN INTO TIGHT SPIRAL BANDING AND THE BANDS ALONG THE SOUTHERN HALF OF THE SYSTEM HAVE ALSO WEAKENED CONSIDERABLY OVER THE PAST SIX HOURS. THE INITIAL POSITION IS BASED ON THE EIR IMAGERY AND THE POSITION FIX FROM PGTW WITH HIGH CONFIDENCE. THE CURRENT INTENSITY IS BASED ON 4.5/5.5 DVORAK ESTIMATE FROM PGTW AND REFLECTS THE RECENT WEAKENING TREND OBSERVED IN EIR. UPPER LEVEL ANALYSIS INDICATES THAT THE SYSTEM IS MAINTAINING ITS SELF-INDUCED MESO-ANTICYCLONE, WHICH IS PROVIDING FOR WEAK VERTICAL WIND SHEAR (VWS) (05-10 KNOTS) OVER THE LOW LEVEL CIRCULATION CENTER (LLCC). A SHARP GRADIENT OF MODERATE TO STRONG VWS (20 KNOTS AND GREATER) ASSOCIATED WITH THE UPPER-LEVEL WESTERLIES EXISTS POLEWARD OF 25N. ANIMATED WATER VAPOR IMAGERY DEPICTS A ZONAL PATTERN IN THE MID-LATITUDES, HOWEVER THE POLEWARD OUTFLOW CHANNEL CONTINUES TO TAP INTO THE ZONAL FLOW HELPING TO KEEP THE SYSTEM AS A STRONG TYPHOON. TY 04W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO THE EAST OF THE SYSTEM. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 04W IS EXPECTED TO TRACK ALONG THE WESTERN PERIPHERY OF THE STEERING STR FOR APPROXIMATELY THE NEXT 12 TO 24 HOURS. DURING THIS THE TIME INTENSITY SHOULD GRADUALLY DECREASE AS THE SYSTEM ENTERS INCREASINGLY HOSTILE VWS AND DECREASING SEA SURFACE TEMPERATURES (SST) (24-26 DEGREES CELSIUS). DURING TAUS 36-72, TY MAWAR WILL STEER INTO THE MID-LATITUDES ALONG THE NORTHWESTERN PERIPHERY OF THE STEERING STR, FURTHER WEAKENING DUE TO THE STRONG WESTERLY VWS AND EVEN COOLER SST VALUES. A MID-LATITUDE TROUGH, CURRENTLY OVER EASTERN ASIA, WILL TRACK OUT OVER JAPAN AND AID IN THE EVENTUAL CAPTURE OF THE LLCC INTO THE MID-LATITUDE WESTERLIES. THE SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION DURING TAU 48 AND COMPLETE IT BY TAU 72. THERE CONTINUES TO BE HIGH CONFIDENCE IN THE TRACK FORECAST DUE TO THE TIGHT ENVELOPE OF NUMERICAL MODEL GUIDANCE. THE CPA TO KADENA AB IS CURRENTLY 121 NM AT 042200Z.// NNNN