It does look like the chart resets at midnight, and the "Click here to view yesterday's output" leads to a different graph which has "Small Hydro, Biogas, Biomass, Geothermal" added to the bottom. I would judge that one as showing a low end even smaller than you state, less than 30% of a 1000MW tick, so perhaps 250MW. It says the highest end is 3592MW at midnight (higher than the 2600 at midnight this morning). That is a ratio of 14.4:1 actually, higher than you claim.
However the chart does show that the output is pretty predictable. Some of the contrarian posters here seem to think it varies every minute, which may be why they seem to avoid posting otherwise informative charts like this. I personally doubt land-based wind is going to ever be anything more than a trivial amount of our energy. Offshore is much higher and perhaps more consistent, but solar or nuclear is really what will work.