Abstract

In this paper, a revised method for typhoon precipitation probability forecast, based on the frequency-matching method, is developed by combining the screening and the neighborhood methods. The frequency of the high-resolution precipitation forecasts is used as the reference frequency, and the frequency of the low-resolution ensemble forecasts is used as the forecast frequency.

Based on frequency–matching method, the frequency of rainfall above the rainstorm magnitude increases. The forecast members are then selected by using the typhoon tracks of the short-term predictions, and the precipitation probability is calculated for each member using a combination of the neighbor and the traditional probability statistical methods. Moreover, four landfalling typhoons (i.e., STY Lekima and STS Bailu in 2019, and TY Hagupit and Higos in 2020) were chose to test the rainfall probability forecast.

The results show that the method performs well with respect to the forecast rainfall area and magnitude for the four typhoons. The Brier and Brier skill scores are almost entirely positive for the probability forecast of 0.1–250 mm rainfall during Bailu, Hagupit and Higos (except for 0.1mm of Hagupit), and for<100 mm rainfall (except for 25 mm) during Lekima.