MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 09W (BAVI) WARNING NR 008// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 09W (BAVI), LOCATED APPROXIMATELY 548 NM SOUTH- SOUTHWEST OF CHINHAE, SOUTH KOREA, HAS TRACKED NORTHEASTWARD AT 07 KNOTS OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A COMPACT SYSTEM WITH FLARING CONVECTION WRAPPING INTO A TRANSIENT EYE. THE CONVECTION IN THE MSI LOOP HAS CONTINUED TO BUILD AND CONSOLIDATE OVER THE PAST 6 HOURS BUT REMAINS LIMITED OVER THE NORTHWESTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE EYE FEATURE PRESENT IN A 230506Z AMSR2 89GHZ IMAGE AND THE CIRCULATION PRESENT IN THE COMPOSITE RADAR LOOP. THE INITIAL INTENSITY OF 65 KTS IS PLACED WITH FAIR CONFIDENCE AND IS BASED ON A PGTW DVORAK CURRENT INTENSITY ESTIMATE OF T4.0 (65 KTS) AND FROM THE DATA PRESENT IN THE AMSR2 WIND FIELD PRODUCT. TY BAVI IS TRACKING NORTHEASTWARD ALONG AN EXTENSION OF A SUBTROPICAL RIDGE (STR) POSITIONED TO THE SOUTHEAST AND THROUGH AN ENVIRONMENT FAVORABLE FOR FURTHER INTENSIFICATION WITH VERY WARM (30-31 CELSIUS) SEA SURFACE TEMPERATURES, LOW (05-10 KNOTS) VERTICAL WIND SHEAR AND WELL-ESTABLISHED EQUATORWARD OUTFLOW IN THE UPPER LEVELS. 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 09W WILL CONTINUE TO TRACK GENERALLY NORTHEASTWARD THROUGH TAU 24 AS IT ROUNDS THE STR POSITIONED TO THE SOUTHEAST AND CONTINUED FAVORABLE VWS AND SSTS WILL ALLOW IT TO INTENSIFY TO 75 KTS BY THIS TIME. A SHORTWAVE TROUGH IN THE UPPER LEVELS WILL INDUCE A REORIENTATION OF THE STEERING RIDGE AFTER TAU 24 LEADING TO A GENERALLY NORTH TO NORTH-NORTHWESTWARD TRACK AND SLOWER TRACK SPEEDS BETWEEN TAU 24 AND TAU 48. SUFFICIENT OCEAN HEAT CONTENT, LOW VWS AND WARM SSTS WILL ALLOW THE SYSTEM TO REACH A PEAK INTENSITY OF 100 KTS BY TAU 48. BETWEEN TAU 48 AND TAU 72 TY BAVI WILL TRACK ALONG THE WESTERN PERIPHERY OF A BUILDING STR TO THE EAST AND BEGIN TO TRACK GENERALLY NORTHWARD. THE SYSTEM WILL WEAKEN SLIGHTLY TO AN INTENSITY OF 95 KTS BY TAU 72 DURING THIS TIME DUE TO SLIGHTLY INCREASED VWS AND DECREASING SSTS. THE CROSS TRACK SPREAD IN NUMERICAL MODELS SOLUTIONS PRESENTS A FAIR DEGREE OF CERTAINTY IN THE TRACK WITH A MAXIMUM 143NM SPREAD AT TAU 72, LENDING FAIR CONFIDENCE IN THE INITIAL PORTION OF THE JTWC FORECAST TRACK. C. AFTER TAU 72, STRONG (20-25 KTS) VWS AND COOLER (26-29 CELSIUS) SSTS WILL BEGIN TO WEAKEN TY BAVI AS IT CONTINUES TO TRACK NORTHWARD TOWARDS THE KOREAN PENINSULA. BETWEEN TAU 72 AND 96 THE SYSTEM WILL MAKE LANDFALL AND BEGIN TO DISSIPATE DUE TO LAND INTERACTION. AS IT TRACKS FURTHER INTO MAINLAND CHINA THE SYSTEM WILL DISSIPATE FURTHER DUE TO THE FRICTIONAL EFFECTS OF LAND AND FULLY DISSIPATE BY TAU 120. THERE IS A LARGE DEGREE OF UNCERTAINTY IN NUMERICAL MODEL SOLUTIONS DURING THIS PERIOD DUE TO THE TIMING OF THE SHORTWAVE TROUGH MOVEMENT, WITH A 352 NM SPREAD IN CROSS TRACK SPREAD BY TAU 96 WHICH INCREASES TO 592 NM BY TAU 120. THE HIGH DEGREE IN ACROSS TRACK MODEL SPREAD LENDS ONLY FAIR CONFIDENCE IN THE OVERALL JTWC FORECAST TRACK. NNNN NNNN