  The Yangtze River has been subject to heavy flooding throughout history, and
in recent times severe floods such as those in 1998 have resulted in heavy loss
of life and livelihoods. Dams along the river help to manage flood waters, and
are important sources of electricity for the region. Being able to forecast
high-impact events at long lead times therefore has enormous potential benefit.
Recent improvements in seasonal forecasting mean that dynamical climate models
can start to be used directly for operational services. The teleconnection from
El Ni\~no to Yangtze River basin rainfall meant that the strong El Ni\~no in
winter 2015/2016 provided a valuable opportunity to test the application of a
dynamical forecast system.
  This paper therefore presents a case study of a real time seasonal forecast
for the Yangtze River basin, building on previous work demonstrating the
retrospective skill of such a forecast. A simple forecasting methodology is
presented, in which the forecast probabilities are derived from the historical
relationship between hindcast and observations. Its performance for 2016 is
discussed. The heavy rainfall in the May-June-July period was correctly
forecast well in advance. August saw anomalously low rainfall, and the
forecasts for the June-July-August period correctly showed closer to average
levels. The forecasts contributed to the confidence of decision-makers across
the Yangtze River basin. Trials of climate services such as this help to
promote appropriate use of seasonal forecasts, and highlight areas for future
improvements.
