This is often seen but yesterday I got a good photo on a flight EGKA-LFMT. The correspondence of the cloud and the land is perfect.
Does anyone know the mechanism?
There is the theory behind but it’s always impressive when you see low clouds stopping dead on land-sea interface
Nice picture!
Flew yesterday, Rocheter [EGTO] to Calais [LFAC], and witnessed exactly the same beautiful phenomenon. It was a perfect layer about 1000’ thick between 1400’ – 2300’ which made ‘VFR on top’ very enjoyable.
It compensated me for my disappointing Shopping Trip: I had forgotten that Armistice Day was a Public Holiday in France and all the shops were closed!
@Peter all cumuliform clouds need (or make themselves) upwards directed movement in the air in order that water condenses. This is typically obtained from obstacles on ground, such as the shoreline or hills. On water there is no such obstacle.
However obstacles such as hills/mountains close to the sea may shift the position where air starts to lift far out to the sea. On the northern coast of Spain, for example, I observe this practically every time I fly there. There are mountains close to the coast, so when winds are strong, the stratocumulus may extend several 10 miles or even more than 100 miles out over the sea, but often enough clouds stop at the shoreline. So I just fly over the sea to descent there.
It’s not that temp over ground is cooler after night and moist air is reaching dev point then ?
Peter wrote:
Does anyone know the mechanism?
I don’t know the weather situation, but if I may guess. The night before was clear and cooling of the land caused radiation fog and an inversion to form. During the day the fog lifted to make a thin layer of stratus. Do you know the cloud base?
Exactly. Looks like lifted fog. It can be also artificial fog to show everyone how cool is to be seaplane pilot ;)
Yes; could be. This was prob99 fog which just earlier lifted off to something like OVC001
2 typical effects mainly:
1.a. If there’s a cliff at the coast, mechanical lifting of the airmass coming from the ocean. Air goes up, cools down, water condenses to clouds.
1.b. even if it’s a flat coast, land creates increased friction, the boundary layer (which is a lack of flow) thickens. The airmass keeps coming from the ocean, has no place to go but up. Air goes up, cools down, water condenses to clouds.
2. The ocean surface is dark, does not heat up the airmass. The land surface is still warm, especially this fall. Classic convection somewhat inland.
Lifted fog needs an “entry point”, or it will keep the sun away and the ground will not heat to lift it. Typical fall OVC002.
