Why do Cumulonimbus clouds swell so high?

Answer 1

It's been a while since I've taken that class, but I think it is because the unstable atmosphere allows the clouds to expand vertically.
If the atmosphere were stable, the clouds would stay flat because of a "cap".

Check this link out, too.
http://en.wikipedia.org/wiki/Cumulonimbus

Answer 2

The other answers are partially correct, but not entirely. A thunderstorm's updraft will continue to rise until instability ends. The instability inherent in a towering thunderstorm ceases at the equilibrium level. This level is often at about 30K to 45K feet. When the updraft reaches that level, it encounters "warmer" air (it's not really "warm", it's just warm enough that the expanding and cooling updraft is no longer WARMER than the air at that level). Since the updraft is no longer "warmer", there is no further impetus for it to continue rising any higher, and so it doesn't. That's where the flat top of an anvil is found.

It has nothing to do with the winds, other than the fact that the winds will determine how quickly that flat top will flow downstream, and in what direction.

Here's a couple more quick facts:

A strong updraft will "overshoot" the equilibrium level from the momentum and forcing from below. This is called an "overshooting top" or "dome". If you see a large overshooting top, you know for certain that the updraft, and hence instability, is very strong. This is paramount for the development of significant (large and violent) tornadoes.

Also, you can tell how strong the upper-level winds are by the way the anvil is blown downstream. If a storm has a circular "mushroom cloud" shape at the top, the upper level winds are weak, the storm will likely have a short life, and probably won't spawn any tornadoes. On the other hand, if the storm's anvil is vigorously blown downstream, the upper-level winds are strong, and that is conducive to tornadogenesis (if dozens of other parameters are also favorable).

Answer 3

All cumulus clouds have upcurrents. If the system is really big, or is generated by vastly differing weather systems (which is what creates violent storms - the interaction of cold and warm air), those upcurrents are violent enough to take the clouds up to where the jetstream winds flatten the cloud out into the characteristic anvil shape.

Answer 4

all unstable are rises.. depends on the temperature-- warm air goes up... depending on the amount of moisture in the air where the cloud starts... dry air high clouds

cumulonimbus clouds are in unstable air with lots of moisture when the air cools by touching other cooler air and also cools by expanding due to lower air pressure above

it will stop rising when it reaches the same temp as the air around it

Answer 5

It is due to the fact of the hot air rises and it pushes up the cloud with it. Once the hot air reaches the higher atmosphere it expands out causing the anvil shape.

Answer 6

Convection currents (updrafts) push and raise the tower into the air. Then it reaches the stratosphere, it can't go any higher so is spreads out making the anvil shape.