HEAVY RAIN EVENTS OVER THE SOUTH-FACING SLOPES OF HAWAII - ATTENDANT CONDITIONS

Heavy rain events (>100 mm day(-1)) over the southeast flank of Mauna Loa volcano on the island of Hawaii are examined using surface, rawins onde, rain gauge, and satellite data. The events occur in the presence of four types of synoptic-scale disturbances that include Kona storms , cold fronts, upper-tropospheric troughs, and tropical systems. The h eaviest rainfall occurs at elevations above 0.5 km over the volcano sl opes facing the prevailing low-level flow with the leeside slopes expe riencing considerably smaller amounts. Rainfall duration and patterns demonstrate that the rains and Bash floods are the result of more than one convective cell. Soundings prior to the heavy rain events show on ly modest instability, with only the K index serving as a useful predi ctor for heavy rain among the standard stability indices. There is an increase in both the moisture content of the midlevels (750-450 mb) an d the onshore Bow normal to the terrain gradient prior to the heavy ra in. The lack of the trade winds and the attendant inversion is a signi ficant signal considering the persistence of these features over the H awaiian Islands throughout the year. Possible roles for midlevel moist ure in lessening the detrimental effects of entrainment on updraft buo yancy and suppressing cold outflow formation and thus storm movement a re also discussed.