Record Torrential Rainstorms on the Island of Hawaii, January–February 1979

Abstract

The heaviest and most extensive rainstorms in the history of weather records on the island of Hawaii occurred during the first two months of 1979. Nearly every rainfall record kept by the National Weather Service from the 45 min total through the monthly and two monthly totals was exceeded during January and February 1979. Only twice in the 90-year history of weather records at Hilo have rainfalls of similar magnitude occurred. The most significant characteristic of the 1979 storms is that the record rainfall was produced from warm clouds; clouds whose temperature is everywhere greater than 0°C. The February 1979 storm produced rainfalls of 78.2 mm in 1 h and 566.4 mm in 24 h at Hilo from storm clouds with tops below the freezing level. Such rainfall amounts and rates are customarily believed to occur only during thunderstorms, where the cloud tops extend considerably above the freezing level. Thunderstorm activity was absent during the 1979 rainstorms. An account of the January and February 1979 storms and a survey of past record rainfalls on the island of Hawaii are presented.