Britain's wind farms promised 2.8 GW off Lincolnshire. Then the wind stopped.

Storms that shut turbines down are well known. Sudden lulls are not. I found 448 of them in two years, mapped seven, and watched how NESO filled the gap each time.

Last month I wrote about the North Sea mystery behind Britain's emergency call to France. On the evening of Friday 9 October, the wind farms off the Suffolk coast lost more than half their output in about an hour. A front had crossed the coast with a lull behind it, and the farms had told NESO they would be running near full. Frequency fell below 49.8 Hz and NESO took 270 MW of Emergency Assistance from France.

That raised an obvious question: was Suffolk a one-off? Weather forecasters will tell you it was not. Small, fast-moving features such as fronts, squall lines and the calm patches behind them are exactly what a weather model struggles to place to the nearest hour and the nearest 20 km. When one passes over a cluster of wind farms, the farms can all fall short of their own forecasts at once.

So I went looking. This piece covers what I found: how often it happens, where, and what NESO does about it.