Basically, the clouds need to be overhead, but there needs to be a gap in the cloud cover to the west (possibly even beyond the horizon).
This gap lets sunlight in from below the clouds, so that it can shine up on the bottom of them. If you look carefully, you can see that the illuminated parts of the clouds are the ones facing west and down.
That’s why the sunset only looks this brilliant occasionally. Conditions have to be perfect for it. It’s most common after a heavy rain, because the evaporating water tends to create the perfect array of clouds. But the timing has to be just right too. Too soon, and there’s no gap for the sun to peak through; too late and the clouds scatter.
It depends on the position of the clouds.
Basically, the clouds need to be overhead, but there needs to be a gap in the cloud cover to the west (possibly even beyond the horizon).
This gap lets sunlight in from below the clouds, so that it can shine up on the bottom of them. If you look carefully, you can see that the illuminated parts of the clouds are the ones facing west and down.
That’s why the sunset only looks this brilliant occasionally. Conditions have to be perfect for it. It’s most common after a heavy rain, because the evaporating water tends to create the perfect array of clouds. But the timing has to be just right too. Too soon, and there’s no gap for the sun to peak through; too late and the clouds scatter.