Verification of the 2019 GloSea5 Seasonal Tropical Cyclone Landfall Forecast for East China

A prototype climate service was developed and trialled in early 2019 to provide a seasonal forecast of June–July–August (JJA) tropical cyclone (TC) landfall risk for the East China region ahead of the forthcoming typhoon season. Test forecasts were produced in both March and April 2019 and a final forecast released to the China Meteorological Administration (CMA) on 1 May 2019. The trial service was produced by using the Met Office Global Seasonal forecast system (GloSea5): a forecast of the Western Pacific Subtropical High (WPSH) index was used to infer landfall risk based on a simple linear regression between historical model WPSH indices and observed TC landfalls in East China. The forecast method shows significant skill for forecasting JJA landfall risk in East China with up to three months lead time, with the greatest skill for predictions initialised in May. The 2019 forecast provided good guidance of the near-average TC activity observed in East China in JJA 2019. The success of the forecast adds confidence to an improved climate service ahead of the 2020 typhoon season.