Retrospective Sub-Seasonal Forecasts of Extreme Precipitation Events In The Arabian Peninsula Using Convective-Permitting Modeling
byC. B. Risanto, H. -I. Chang, T. Luong, C. L. Castro, H. P. Dasari, I. Hoteit
This paper is to demonstrate the potential of extreme cool-season precipitation forecasts in the Arabian Peninsula (AP) at sub-seasonal time scales, identify the region and periods of forecast opportunity, and investigate the predictability of synoptic-scale forcing at sub-seasonal time scales. To this end, we simulate 18 extreme precipitation events using the convective-permitting weather research and forecasting (CP-WRF) model with lateral boundary forcing from the European Centre of Medium-range Weather Forecasts sub-seasonal to seasonal reforecasts (ECMWF S2S reforecasts). The simulations are initiated at one-, two-, and three-week lead times. At all lead times, the CP-WRF improved the mean accumulated precipitation in the extratropical synoptic regimes over the west coastal and central AP and the central Red Sea. Based on categorical statistics with a threshold of 20-mm accumulated precipitation over 7 days, the CP-WRF accurately forecasted the precipitation over Jeddah, the west coast of AP, and the central Red Sea up to three weeks lead time. The relative operating characteristic curve reconfirmed the high forecasting skill of the CP-WRF, with an area under the curve above 0.5 in most of the events at all lead times. Finally, the correlation coefficients between the ECMWF and ECMWF reanalysis interim 500-hPa geopotential heights were higher in the events associated with the extratropical synoptic regime than in those associated with the tropical synoptic regime, regardless of lead time. Therefore, the convective-permitting model can potentially improve the accuracy of extreme winter precipitation forecasts at two-and three-week lead times over Jeddah, the west coast of AP, and the central Red Sea in the extratropical synoptic regime.