In this study we evaluate The European Centre for Medium-Range Weather Forecasts (ECMWF) model from the Subseasonal-to-Seasonal (S2S) database and the Navy Earth System Prediction Capability (ESPC) as part of the Subseasonal Experiment (SubX) on their ability to predict West Pacific TC activity using environmental fields (e.g., shear, humidity, low-level vorticity, upper-level velocity potential). To isolate the environmental signals associated with subseasonal variability of TC activity we examine events of anomalous accumulated cyclone energy (ACE) and TC days relative to each season. These events are used to create composites in ERA5 reanalysis fields of the environmental conditions related to West Pacific TC activity. These composites are used to select predictors to be fed into a statistical dynamical hybrid model. ECMWF and Navy-ESPC forecasts of these environmental predictors are combined and compared to model predictions of TC activity and MJO state to assess if an improvement in skill can be accomplished by considering these model forecasted environmental fields.

