Met World Frenzy

[CoffmanStarter]

Paging our resident PPRuNe Met Officer ... Mr Langleybaston ;)

It would seem the Met World is getting a bit excited with this supposed new cloud type/formation "Undulatus Asperatus". Apparently the proposed new classification hasn't been formally recognised yet by the World Meteorological Organisation (WMO).

Apparently these clouds occur when enough atmospheric instability, or rising air, is available to create widespread cloud cover, as well as wind shear and turbulence, which creates the wavy, rough sea-like visual effect ... nothing particularly new there then :8

Should we hold off amending AP3307 just yet :}

[goudie]

Beautiful but some are quite scary:eek:



MjUDGtAzN8w

[Basil]

God: "That lot are getting a bit uppity; lets scare the b'stads!"

Looks similar to mammatus but in rows.
Mammatus porcus anyone? :E

[CoffmanStarter]

I'd 'support' that Basil :}

[langleybaston]

Its a trick of the light I tell you! If it's not in the forecasts it didn't happen!

These are both beautiful and "a little bit frightening", apocalyptic even ...... fairly frequently seen Vale of York in my Leeming Topcliffe Church Fenton days.

Essentially I think they are created by lee waves in very very moist air ..... the usual lenticular shape of lee wave cloud "dries out" hence no cloud in the temporarily descending bit, and then, on the next bounce, another cloud forms in the next bounce. Here though we see no, or negligible drying out. This explanation will do for reasonably large separations of the wave shapes, but for short separations we are probably looking at Kelvin-Helmholtz waves, a mechanism for sorting out the atmospheric stresses in strong vertical shear. [and also associated with severe CAT in dry air]. Such shears occur in similar conditions to lee waves so we may even be looking at multiple causes.
The drama is increased by low sun angles and little clear bits of sky of course.
Back to retirement ..............

[CoffmanStarter]

Many thanks LB ... Glad to hear the World isn't coming to an end just yet ;)

[Shaft109]

I've got a picture taken facing south from work that's pretty much identical to the sky at about 0:30 in the clip - but now I've noticed it I 'see' it quite often, although sometimes in quite localised areas of the sky.

It reminds me of the 'twix' adverts where they pour caramel and move the biscuit leaving a rug effect - do dry and wet airmasses have differing viscosity?

[langleybaston]

Viscosity. Oh! dear!, outside my field of knowledge so I speak as a layman. Probably not different to any significance, but what does matter is density and vertical motion in a sheared layer.
To think that I used to teach this stuff ....................

[uffington sb]

That's what those chemtrails do to clouds.
I bet they're full of fake snow:E