A user asked this question and it may be useful information for other users:

"For the UK Met Office seasonal forecast single level dataset on the CDS, there are three systems (12, 13 and 14) which one should I use?

For example the system 12 has forecast years between 2017-2018 whilst system 14 only for the year 2019.

If I want the whole time series of hindcasts and 2017-2019 forecasts should I combine the systems or they are different?"

Thanks,

Kevin