On Sunday, 23 July 2017 20:45:38 UTC+3, firsys wrote:
Yesterday, close to my home field, after I had given up( 2500 ft cloudbase)
I noticed lennie like clouds lining up across the light NW wind.

I have flown thermal wave often in the past, but nothing in the last ten years.
Missed this one but probably too weak to use.

These systems can difficult to get into but extensive and rewarding if you can do it.

Has anyone any idea of the met conditions for development of T.W?

Here are a couple:

Weak convection in the lower layer with light winds.

An upper wind of 15+ kts above an inversion, rising with height.

But there must be something else or I would see this more frequently.

John Firth
Ottawa

They are pretty common everywhere in flatlands but obviously hard to spot as wave is almost always above cloudbase level and often weak. Wave occurs in stable atmosphere, so inversion above convective layer is common, preferable with strong wind shear. Approaching fronts usually create wave patterns..