Interesting local weather phenomena

[Graham Easterling]

When there is an ENE wind alingned with the peninsula you'd expect some convergence along the spine of Cornwall.

However, days like today it is not enough to generate cloud, but what often happens is as the airflow down the English and Bristol Channels converge off Lands End, the resultant cloud can effect Scilly.

Satellite 2:30 & 4:00 PM

Basically cloudless over Cornwall, but on Scilly, well away from the more typical land based convectional cloud.

Absolutely glorious in Penzance today. Maximum of 20.2C yesterday, 20.1C today.

Graham

Penzance

[Len]

Does something similar in terms of convergence of 2 airstreams downwind of Devon and Cornwall be happening again today?

Even some billows (undulatus) in the stratus today.

Len

[Graham Easterling]

Yes, I think it is happening again. 

Up to 21.3C today, warmest day since 22.2C on 12th August (15th August reached 21.2C) Dropped backed a degree or so around 2:30 pm as a weak sea breeze set in. Looks like you got above 22C.

MetO forecasting 23C for Penzance tomorrow, they have been fairly accurate of late.

Graham

Penzance

[Len]

Yes, max 22.7C today in my garden,

Min 13.2C

No sea breeze here. ENEasterl too strong.

Len

Wembury

[jack.h...@gmail.com]

On Wednesday 18 September 2024 at 22:45:16 UTC+1 Len wrote:

No sea breeze here. ENEasterl too strong.

When doing my weatherjack gliding forecasts, I used a rule of thumb about sea breezes.  I had picked it up in from a very competent met man in the Air Force.  It was just that - a rule of thumb.

Significant sea breezes (not just puffs on the beach) only develop if the depth of convection (including any cloud) is between 5,000 and 10,000 feet.  Hence, a hot blue day with very limited depth of convection (one reason it is hot - the heat is trapped) OR a day with towering cumulus, is unlikely to have a sea breeze.  There is of course the gradient wind to consider, to which any sea breeze component would need to be added.

I have little idea of the science behind this rule of thumb.  But the fact is, IT WORKS.

Jack