The data is currently based on:
Live wind farm generation data is taken from the Elexon downloads. This data is also easily viewable on the excellent Gridwatch site, which is where I was originally directed to Elezon. I aim to download the live data on the hour. This will normally take the output from the previous 5 minute point. So 12:00 will show 11:55.
Forecast data is based on the met office 5 day downloads. Each of the almost 10,000 major wind turbines, all those over 0.5MW and wind farms over the same amount are matched to the nearest weather station along with the individual wind turbine specs to estimate the likely output from that turbine.
At the moment the best way of looking at this is to spot trends. The data isn't yet modified to make it fit, however if there is a good trend I will aim to include additional curves to try to predict real output.
I believe this is the only source of wind output forecasting based on individual turbines and weather stations. Along with the above,