MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (MEARI) WARNING NR 17// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 26W (MEARI), LOCATED APPROXIMATELY 243 NM EAST OF IWO TO, HAS TRACKED NORTH-NORTHEASTWARD AT 20 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS AN ASYMMETRIC AREA OF DEEP CONVECTION SHEARING NORTHWARD DUE TO STRONG (40-60 KNOTS) SOUTHWESTERLY VERTICAL WIND SHEAR (VWS) ASSOCIATED WITH THE LEADING EDGE OF A DEEP MIDLATITUDE SHORTWAVE TROUGH. A 061734Z SSMI 37GHZ COLOR COMPOSITE IMAGE SHOWS A PARTIALLY-EXPOSED, BROADENING LOW-LEVEL CIRCULATION CENTER POSITIONED ON THE SOUTHERN EDGE OF THE AFOREMENTIONED AREA OF DEEP CONVECTION. THE INITIAL INTENSITY IS ASSESSED AT 80 KNOTS BASED ON DVORAK INTENSITY ESTIMATES RANGING FROM 65 TO 90 KNOTS. VIGOROUS POLEWARD OUTFLOW CONTINUES TO SUSTAIN THE CURRENT CONVECTION. TY 26W IS TRACKING NORTH-NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY MEARI IS EXPECTED TO CONTINUE TRACKING NORTHEASTWARD TO NORTH-NORTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE STEERING STR. TY 26W IS UNDERGOING EXTRA-TROPICAL TRANSITION (ETT) AS IT BEGINS TO INTERACT WITH THE MIDLATITUDE TROUGH AND BAROCLINIC ZONE AND IS FORECAST TO RAPIDLY WEAKEN AS VWS INCREASES. THE TYPHOON WILL GAIN FRONTAL CHARACTERISTICS AND COMPLETE ETT BY TAU 18 AS A STRONG COLD- CORE LOW. DYNAMIC MODEL GUIDANCE REMAINS IN TIGHT AGREEMENT, THEREFORE, THERE IS HIGH CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN