Seasonal ARIMA Modeling and Forecasting of Rainfall in Warri Town, Nigeria

Abstract

We obtained historical data of rainfall in Warri Town for the period 2003-2012 for the purpose of model identification and those of 2013 for forecast validation of the identified model. Model identification was by visual inspection of both the sample ACF and sample PACF to postulate many possible models and then use the model selection criterion of Residual Sum of Square (RSS), Akaike’s Information Criterion (AIC) complemented by the Schwartz’s Bayesian Criterion (SBC), to choose the best model. The chosen model was the Seasonal ARIMA (1, 1, 1) (0, 1, 1) process which met the criterion of model parsimony with RSS value of 81.098,773, AIC value of 281.312,35 and SBC value of 289.330,84. Model adequacy checks showed that the model was appropriate. We used the model to forecast rainfall for 2013 and the result compared very well with the observed empirical data for 2013.