Forecasting of Rainfall in Central Java using Hybrid GSTAR-NN-PSO Model Hasbi Yasin, Budi Warsito, Rukun Santoso and Arief Rachman Hakim E3S Web Conf., 125 (2019) 23015 Published online: 28 October 2019 DOI: 10.1051/e3sconf/201912523015