MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI// SUBJ/PROGNOSTIC REASONING FOR TYPHOON 24W (HALONG) WARNING NR 020// RMKS/ 1. FOR METEOROLOGISTS. 2. 6 HOUR SUMMARY AND ANALYSIS. TYPHOON (TY) 24W (HALONG), LOCATED APPROXIMATELY 142 NM WEST- SOUTHWEST OF MINAMI TORI SHIMA, JAPAN, HAS TRACKED NORTHEASTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A LARGE AREA OF EXPANDING DEEP CONVECTION PERSISTING OVER AND TO THE NORTH OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). A 070520Z SSMI 85GHZ MICROWAVE IMAGE INDICATES A PARTIALLY- EXPOSED LLCC WITH CURVED DEEP CONVECTIVE BANDING OVER THE NORTHERN SEMICIRCLE, WHICH SUPPORTS THE CURRENT POSITION WITH FAIR CONFIDENCE. UPPER-LEVEL ANALYSIS REVEALS A MARGINALLY-FAVORABLE ENVIRONMENT WITH LOW TO MODERATE (10 TO 20 KNOTS) SOUTHERLY VERTICAL WIND SHEAR (VWS) OFFSET BY ROBUST POLEWARD OUTFLOW. BASED ON THE WEAKENING CONVECTIVE STRUCTURE AND INCREASING VWS, THE CURRENT INTENSITY IS ASSESSED AT 90 KNOTS BASED ON THE LOWER END OF DVORAK CURRENT INTENSITY ESTIMATES RANGING FROM 5.0-5.5 (90-102 KNOTS). TY 24W IS TRACKING ALONG THE NORTHWESTERN PERIPHERY OF A DEEP-LAYERED SUBTROPICAL RIDGE (STR). 3. FORECAST REASONING. A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS PROGNOSTIC REASONING MESSAGE. B. TY 24W (HALONG) WILL ACCELERATE POLEWARD WHILE GRADUALLY TURNING NORTHEASTWARD TO EAST-NORTHEASTWARD. THE ENVIRONMENT WILL BECOME MORE UNFAVORABLE WITH INCREASING VWS AND COOLING SSTS, WHICH SUPPORTS THE WEAKENING TREND. BY TAU 24, THE SYSTEM WILL ENCOUNTER THE BAROCLINIC ZONE AND BEGIN EXTRA-TROPICAL TRANSITION (ETT). THESE COMBINED DYNAMICS WILL CONTRIBUTE TO ITS RAPID DECAY, AND BY TAU 48 WILL BE REDUCED TO A STORM-FORCE COLD CORE LOW WITH AN EXPANSIVE WIND FIELD AS IT COMPLETES ETT. THE NUMERICAL MODELS ARE IN GOOD AGREEMENT, LENDING FAIR CONFIDENCE IN THE JTWC TRACK FORECAST.// NNNN NNNN