Predictions of Tropical Waves and Cyclogenesis at ECMWF

Predicting the evolution of tropical waves and whether they will develop into tropical cyclones remains a significant challenge. For developing and non-developing tropical waves in the Atlantic basin between 2020-24, insights into 0-10 day probabilistic predictions of genesis by the ECMWF Integrated Forecasting System (IFS) ensemble will be provided. Genesis cases of very low probability in the short range have been found to often correspond to waves that are either unusually weak or interacting with other features. The characteristics of selected tropical waves, including those during the CPEX-CV period in September 2022, will be illustrated.

For Atlantic tropical waves between 2023-24, the IFS control (“deterministic”) forecast is also compared against ECMWF’s new AI forecasting system (AIFS) using the same initial conditions. Attention is paid to the timing of genesis, the run-to-run consistency, and the physical structures of the waves and nascent tropical cyclones in the two forecasting systems.