Evaluation of Subseasonal to Seasonal (S2S) Precipitation Forecast Performance from NMME-2 Model over Indonesia
Dwina Nugraha (a), Muhammad Ridho Syahputra, S.Si., M.Si. (b), Dr. Muhammad Rais Abdillah, S.Si., M.Sc. (b)

a) Department of Meteorology, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, 40132, Indonesia
b) Atmospheric Sciences Research Group, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, 40132, Indonesia

Abstract

Subseasonal to Seasonal (S2S) precipitation forecast as a bridge for the gap between weather and seasonal forecast, can be utilized as supporting information for decision-making related to hydrometeorological disaster mitigation activities in Indonesia. However, uncertainty in global models caused forecast performance can be different across regions and time periods. Therefore, it is important to evaluate forecast performance before utilizing the prediction result. In this study, performance of probabilistic precipitation forecast from Multi-model Ensemble (MME) of three models in The North American Multi-Model Ensemble phase 2 (NMME-2) project was evaluated using evaluation metrics Continuous Ranked Probability Score (CRPS) and reliability diagram. The evaluation was conducted during the Boreal Summer (May-October) and Boreal Winter (November-April) periods, as well as during the active period of subseasonal climate variability phenomenon Madden-Julian Oscillation (MJO). The results show, S2S precipitation forecast from MME of three models in NMME-2 project are sufficiently accurate and reliable during the Boreal Summer period for Central Sumatra, Southern Sumatra, Southern Kalimantan, Java, Southern Sulawesi, and Southern Papua regions, with a range of CRPS values between 4-16 mm/7 days and a ^perfect^ reliability category. There is no significant difference in the performance of S2S precipitation forecast between the active and inactive events of the Madden-Julian Oscillation (MJO). The difference in CRPS values between these two periods is only around 0.8-1.2 mm/7 days, and there is no difference in reliability categories across Indonesia as a whole, nor significant spatial pattern differences.

Keywords: Forecast performance, Precipitation, Subseasonal to Seasonal (S2S), NMME-2.

Topic: Ocean-Atmosphere Dynamics