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Clouds

Mike Calvert

Moderator
Staff member
#2
Ah, that good old topic :)

Was at the airfield at the weekend and got a nice informal lesson about lenticular clouds - or more correctly, a, singular, lenticular cloud - because of nearby hills, when the wind is from the south, it's quite normal apparently for just one to form right above our airfield, telling us there's lots of rotor underneath it.

In the books as I recall, lenticular clouds are often pictured as numerous rows, so it's good to understand they don't always appear in rows :)
 
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MadamBreakneck

Cross Country Pilot
#3
Standing wave clouds need (IIRC) a layer of stable air between two layers of unstable air. A hill (or some equivalent) kicks off a ripple in the stable layer - see your Cosgrove. Flying within that layer is extremely smooth, but as I discovered in my gliding days being on the wrong side of the wave can quickly bring you earthwards. Yes, the unstable layer can get interesting.

You've reminded me of an unusual phenomenon I noted in my gliding logbook back in the Spring of 1988 - see photo - in which we were able to soar a ridge in the 'wrong' wind direction.
PhoneCam004.jpg
When the rotor collapsed there was a mad dash by about half a dozen gliders landing all over the field. It was strange soaring the ridge while crabbing towards it.

For anybody interested, it was at the Long Mynd.
 

Vincent

Administrator
Staff member
#4
Hang gliding in the Yorkshire dales, particularly Wether Fell, had wave caused by the other site just upwind (name escapes me for now) and it was legendary when it was "on song" 5000 ft in perfect smooth conditions was not a problem apparently. Unfortunately, I never got to experience it myself.
 

ginge

Student Pilot
#5
Ahh a row of clouds in our neck of the woods, Essex, so not much in the way lumpy bits of ground, it often shows the edge of a sea breeze front. I recall one flight where having left an airfield near the coast with a lovely smooth tailwind when I encountered one of these. As I passed below the cloud it felt like being inside a washing machine and things were quite lively for a while. Then out from under it all went wonderfully smooth again, but now I was pushing into a pretty powerful headwind. The cloud stretched north to south as far as I could see, just an a line of unremarkable looking stuff, until you went under it that is.
 

randombloke

Cross Country Pilot
#6
Hang gliding in the Yorkshire dales, particularly Wether Fell, had wave caused by the other site just upwind (name escapes me for now) and it was legendary when it was "on song" 5000 ft in perfect smooth conditions was not a problem apparently. Unfortunately, I never got to experience it myself.
My best wave flying was at Merthyr Tydfil and Hay Bluff. Hay Bluff I got to the base of controlled airspace, 1,500ft above cloudbase...
 

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