Time-Series Analysis and Statistical Forecasting of Daily Rainfall in Kupang, East Nusa Tenggara, Indonesia: A Pilot Study

This study introduces a statistical time-series approach to analyze daily rainfall in Kupang, Indonesia. Using the piecewise cubic Hermite interpolation, missing data were filled, and the continuous wavelet transform (CWT) identified a strong annual rainfall pattern. The Rainfall Anomaly Index (RAI) was used to assess wet/dry conditions, with time-series modeling predicting future RAI values. The Prophet model showed an RMSE of 0.84 and effectively captured increasing drought trends and seasonal wet/dry patterns.