Dynamical Seasonal Prediction of Tropical Cyclone Activity Using the FGOALS-f2 Ensemble Prediction System

There is a distinct gap between tropical cyclone (TC) prediction skill and the societal demand for accurate predictions, especially in the western Pacific (WP) and North Atlantic (NA) basins, where densely populated areas are frequently affected by intense TC events. In this study, seasonal prediction skill for TC activity in the WP and NA of the fully coupled FGOALS-f2 V1.0 dynamical prediction system is evaluated. In total, 36 years of monthly hindcasts from 1981 to 2016 were completed with 24 ensemble members. The FGOALS-f2 V1.0 system has been used for real-time predictions since June 2017 with 35 ensemble members, and has been operationally used in the two operational prediction centers of China. Our evaluation indicates that FGOALS-f2 V1.0 can reasonably reproduce the density of TC genesis locations and tracks in the WP and NA. The model shows significant skill in terms of the TC number correlation in the WP (0.60) and the NA (0.61) from 1981 to 2015; however, the model underestimates accumulated cyclone energy. When the number of ensemble members was increased from 2 to 24, the correlation coefficients clearly increased (from 0.21 to 0.60 in the WP, and from 0.18 to 0.61 in the NA). FGOALS-f2 V1.0 also successfully reproduces the genesis potential index pattern and the relationship between El Nino-Southern Oscillation and TC activity, which is one of the dominant contributors to TC seasonal prediction skill. However, the biases in large-scale factors are barriers to the improvement of the seasonal prediction skill, e.g., larger wind shear, higher relative humidity, and weaker potential intensity of TCs. For real-time predictions in the WP, FGOALS-f2 V1.0 demonstrates a skillful prediction for track density in terms of landfalling TCs, and the model successfully forecasts the correct sign of seasonal anomalies of landfalling TCs for various regions in China. SIGNIFICANCE STATEMENT: Skillful prediction of tropical cyclone (TC) activity on a seasonal time scale is a reference for preventing and reducing disasters, but there is a distinct gap between TC prediction skill and the societal demand for accurate predictions, especially in the western Pacific and North Atlantic basins. The seasonal prediction of TCs using a global dynamical prediction system is potentially a useful tool for disaster prevention and mitigation. FGOALS-f2 V1.0 is a dynamical global ensemble prediction system, which has the ability to make seasonal predictions of global TCs. Here we evaluate the prediction skill for TCs in FGOALS-f2 V1.0 and then give possible reason(s) for the demonstrated levels of skill. The skillful prediction of TCs predicted by FGOALS-f2 V1.0 is shown in this study, especially in the western Pacific (WP) and the North Atlantic (NA), e.g., genesis location and TC number correlation (r = 0.60 in WP; r = 0.61 in NA), which will contribute to disaster prevention and mitigation.