Inland Sailing Wind Conditions

On fine settled days, especially in summer, it is common for mornings to be still and a light breeze to fill in something around 10:30 or 11:00. This is because radiative cooling of the ground overnight causes a temperature inversion that prevents mixing of the air at ground level and a few 10s of metres up where the gradient breeze is stronger. As the sun heats the ground, the inversion breaks down, mixing begins and the breeze fills in. This is exactly the same reason why in the same conditions, you get a clear sky first thing in the morning but fluffy cumulus clouds start appearing from mid-morning onwards.

In terms of sea-breeze moving inland, I live around 30 miles from the south coast and a few times a year, an obvious sea breeze arrives around 18:00 in the evening. The fluffy cumulus clouds disappear and a noticeably cool breeze suddenly fills in from the south-west. I used to fly gliders from a nearby airfield and once enjoyed a late afternoon soaring in the rising curtain of air as the sea breeze arrived - a very noticeable and obvious effect. But conditions have to be perfect for the sea-breeze to get this far inland. 

I've sailed at Grafham for 30 years! 

During the summer, we SOMETIMES get a wind increase at around 5-7PM on summer days.  It has happened every summer I can remmeber, but it NOT predictable, but local weather did not predict it.  Maybe something to do with wind circulations as a result of sea winds.  I read something a while back that suggested you can get these kind of effects a fair way inland in certain conditions.....

Grafham is however a LONG way from the sea!!!

I plan to be at the club on Sunday and hopefully Wednesday next week,