PERSISTENCY OF RAIN AND NO-RAIN PERIODS DURING THE WINTER AT SAN FRANCISCO

Abstract

A 20-year record of winter precipitation data for San Francisco is used to determine frequencies of periods of rain and no-rain of various lengths and the frequencies of periods of a given type of weather followed by the same type of weather. The observed frequencies are compared with those expected on chance and are examined for evidence of persistence of rain and no-rain. The use of persistency as a forecasting aid is discussed and its skill determined.