Predicting Forecast Error for the HRRR Using LSTM Neural Networks: A Comparative Study Using New York and Oklahoma State Mesonets

Long Short-Term Memory (LSTM) models are trained to predict forecast error for the High-Resolution Rapid Refresh (HRRR) model using the New York State Mesonet and Oklahoma State Mesonet near-surface weather observations as ground truth. Physical and dynamical mechanisms tied to LSTM performance are evaluated by comparing the New York domain to the Oklahoma domain. The contrasting geography and atmospheric dynamics of the two domains provide a compelling scientific foil. Evaluating them side by side highlights variations in LSTM prediction of forecast error that are closely linked to region-specific phenomena driven by both dynamics and geography. Using mean-absolute-error and percent improvement relative to HRRR, LSTMs predict precipitation error most accurately, followed by wind error and then temperature error. Precipitation errors exhibit an asymmetry, with overforecast precipitation detected more accurately than underforecast, while wind error predictions are consistent across over- and underforecast predictions. Temperature error predictions are relatively accurate but smoother, with respect to variance, than true observations. This paper describes an overview of LSTM performance with the expressed intent of providing forecasters with real-time predictions of forecast error at the point of use within the New York State and Oklahoma State Mesonets. This research demonstrates the potential of LSTM-based machine learning models to provide actionable, location-specific predictions of forecast error for high-resolution operational numerical weather prediction (NWP) systems.