When we were driving down to Loweswater, Blake Fell was clear. When we arrived, the mist had settled high on the sunny side of the fell. It was a still day and got me thinking. My hypothesis is that the rising sun started to increase the evaporation on the sunny side which increased the humidity. That then took the amount of water vapour in the air above the amount needed for saturation at that temperature. Then it cleared at lunchtime, probably because the air temperature had risen and was no longer at the saturation level.
We looked across to Grasmoor in the afternoon. There was a cloud stubbornly lingering in the high corrie to the right of the summit. It stayed there all afternoon. So I came up with a hypothesis that the lack of wind inside the corrie would allow the humidity to remain high enough by not shifting the water vapour. The horizontal wisp of cloud half way up the cliffs was another interesting feature. It also persisted at exactly that level. Could that be to do with the temperature decreasing as you go up to be low enough for saturation at that altitude? I'm not sure how true all of this is but I have had a great time coming up with theories and thinking about them.
