Met question - lenticular clouds

[FlyingForFun]

Last weekend I was talking to a couple of glider pilots about mountain flying. They said that it was easy to spot lift over a mountain because you can see "lenticular clouds stacked up above the mountain like plates".

Upon further discussion, none of us could explain why the lenticular clouds are stacked up - from the theory which we knew, we all thought there should be one, single, thicker cloud.

Can anyone explain this phenomenon?

FFF
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[OBK!]

Something to do with mountain waves?

I have the met book open here, I don't have a good understanding of met at all, I think it's crap! Hate the subject but all I can find about Lenticulars here....

"Lenticulars....usually associated with mountain waves"..

Why? I dunno, that's just what it says.:rolleyes:

[Speedbird252]

I guess the formations will also depend on the condition of the air that has been forced upwards. The relative humidity of each "parcel" will determine at what stage in the ascent it reaches its dew point, and subsequently condenses into visible droplets. Maybe this is why you get the cloud formations in a stack over the crest.

But im only guessing..........

Regards all,

Speedy

:cool: :confused: :cool:

Edited cos I carnt spell.

[FlyingForFun]

OBK, yes, we know the connection with mountain waves. The waves explain why you get lenticular cloud, but not why you get several of them stacked up.

Speedbird, that sounds almost plausible - all the thinking I'd been doing was based on a single airmass. But would you really get several airmasses within a fairly small vertical extent?

Seems like me and my friends aren't the only ones who don't completely understand this! Keep the ideas coming guys!

FFF
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[OBK!]

Geebas

I am sorry.

[FlyingForFun]

Oops - I think I missed a :D off my last post!

FFF
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[Wot No Engines]

FFF,

You can and do get several air masses that appear to be very close vertically, but are not. Wave normally forms in stable air masses (unless the wind speed is large enough).

As the wave system forms, a 10000' thick airmass will bend so that the top of it at a crest may be at 12000' and at a trough at 2000'. The bottom of the next airmass will now be at 2000' in the trough. The wavelength is typically only a few miles.

As the airmasses are stable, they don't mix. Hence the stacked up lenticulars much as Speedy suggested.

10 knot plus (1000' per min) climbs are regularly achieved - these are powerful systems. The rotor induced turbulence under a lenticular can be spectacular - often described as like being inside a wasing machine at maximum spin. Landing when this extends down to ground is interesting - no chance of a go around :eek:

[FlyingForFun]

Excellent - thanks, Wot No! I'll pass this info onto my glider-pilot friends. They did talk about the rotors, and how it's generally best to make sure you're moving fast enough to stay ahead of them!

FFF
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[Max Angle]

Mountain wave is indeed amazing stuff. On Febuary 17th 1986 Paul Harris, flying out of California City Airport, climbed in mountain wave generated by the Sierra Nevada mountains to 49009ft to claim the absolute altitude world record for a glider.

Well known (and very wealthy) aviation nut Steve Fosset is planning to break the record and eventually reach 100,000ft with his Perlan project. Check out:http://www.weatherextreme.com/perlan/
for more info.

[Wot No Engines]

Thanks MA,

Closer to home, Chris Rollings & Bryony Hicks managed to climb to about 38000' (11570m) over Scotland on 08/10/1995 in wave.

As for distance, Klaus Ohlmann flew over 2600km in wave in Argentina a few weeks ago in about 14 hours - this must have been close to VNE for the entire flight.

[bcpilot]

Living on both sides of the Rockies, I've noticed that quite often the lenticulars that i see and recognize are usually not stacked up. Just one, big lens shaped cloud over the mountain when it's windy. From the bottom, they're quite smooth, and a little ripply. If you google around for "lenticular clouds", you'll be able to find hundreds of pictures of them.
I've noticed something else on my internet journey today as well. I found a few sites that show the development of lenticulars as they form, and usually they seem to start as one large lens shaped cloud, and then become broken up into the layer plates afterward. This could be a mistaken interpretation of the pictures, too. I don't know. If this is what happens, then WHAT causes the breakup? I don't know. hmmm... And while we're on the subject, can somebody explain rotor and cap clouds please?