Next the persistence component of the CLIPER is determined. Various tests based on maximizing the pattern correlation (correlation coefficient computed for all stations) between CLIPER forecast rain and observed value on the persistence duration indicate that a 3-h period is optimal to project a reasonable short-range rainfall estimate. Since convective timescale is sometimes as short as an order of 2–3 h, application of a longer persistence amount even degrades some of the forecasts. Thus the 3-h persistence duration is applied to all of the 365 main-island rain stations (i.e., persistence is average rain in the 3 h before initial forecast time). Then experiments are performed to determine the relative contributions from climatology and persistence in the final rainfall prediction. Evaluation is again based on pattern correlation in 3-h periods up to 24 h. It is found that the optimal pattern correlation is realized when the ratio of climatology to persistence is 4/6 (7/3) in the 0–3-h (3–6-h) time period, and then only climatology is used after 6 h. That is, the CLIPER model can be stated mathematically as ×climatology+(1−)× persistence, in which =0.4 (=0.7) in the 0–3-h (3–6-h) forecast period and equals to one otherwise.