cb and anvil

[pax anglia]

It is Donkey's Years since I did Met and I really should know this,but......
Can anyone tell me at what altitude cb's normally top out into an "anvil" please? If I recall correctly they reach a point where vertical development is no longer possible (tropopause ?) and they therefore flatten out.Well worth avoiding I know, but a mightily impressive sight all the same.

['%MAC']

Quite correct, the tropopause acts as a top to the boiling cloud mass and tries to vertically constrain the building cu, as the saturated air is constrained in the vertical direction it spreads out horizontally, forming an anvil. Large, powerful cells may be able to penetrate the trop in what is referred to as an overshooting top (creative name). This top may reach 45,000 to 70,000 feet, when it collapses it does so with a great amount of velocity, being on the order of 41 m/sec (92mph). This is in a near vertical direction. Don’t know of many aircraft that wouldn’t find this a difficult environmental variable at such height. Another reason to stay well clear.

The tropopause acts as a lid because the temperature does not change with height, it is thus absolutely stable (i.e. the environmental lapse rate has a steeper slope then the dry or saturated lapse rates). In a stable atmosphere vertical development is inhibited. There are many ways to measure stability in the atmosphere, the Lifted index, the K index, the Showalter index; each one with its particular advantages. Just so JT doesn’t yell at me again for being too simplistic....

The K index requires only upper air data and gives the area or probability of a thunderstorm, but its reliability decreases for non-airmass thunderstorms. The Lifted index indicates the severity rather then the probability of a thunderstorm, and the Showalter index indicates the possibility of thunderstorms. In every case stability is a function of temperature lapse rate and moisture content.

[pax anglia]

%MAC

Many thanks for that comprehensive response ! I am very grateful to you. I was prompted to ask as last summer there was a COLOSSAL Cb near where I work,a real textbook job,huge Cauliflower base,massive anvil and steel grey curtains of rain teeming down from the overhang.In the interests of polite conversation and from a visual spectacle point of view,I asked a work colleague had she noticed this display? I might have known the answer would be "No" but how could anyone miss it ?
I see you are located in CO-I hope you haven't been affected by the forest fires.

Thanks again
PA

['%MAC']

Clouds are pictures in the sky
They stir the soul, they please the eye
They bless the thirsty earth with rain,
which nurtures life from cell to brain –
But no! They’re demons, dark and dire,
hurling hail, wind, flood, and fire
Killing, scarring, cruel masters
Of destruction and disasters
Clouds have such diversity –
Now blessed, now cursed,
the best, the worst
But where would life without them be?
(Vollie Cotton)


Well it was my pleasure Pax Anglia, and thanks for the concern, my little hobbit hole is deep within the mountains, no threat for now. :)