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For the rest of you, lets continue. A number of readers of this blog have sent me emails the past few days about some strange looking clouds. Here is an example provided by Pam Keeley of Columbia City:
And our favorite high-definition time-lapse video provider, Dale Ireland of Silverdale, sent out this video yesterday showing the rapid formation of a similar phenomenon:
If you go to the second video, you will see another example of mammatus.
Both the still pictures and videos show evidence of sack-like protuberances extending below the cloud base---generally from base of the anvils of cumulonimbus clouds. Since they appear similar to female breasts (or udders if you know your way around cows), they are known as mammatus clouds. (that is about as racy as this blog is going to get).
Mammatus clouds can really look quite extraordinary....he is a particularly dramatic example:
So what is the origin of these other-worldly clouds?
As noted earlier, mammatus clouds tend to form under the anvils of cumulonimbus clouds. Here are some schematics of cumulonimbus clouds (thunderstorms) that show the positions of the mammatus.
There is some debate about the origin of these clouds, but the most frequently quoted explanation starts with the updraft sending lots of liquid water droplets or ice crystals in the anvil. The weight of all these particles results in negatively buoyant air (air denser that air around it) and this forces descent into the drier air below. This is just the opposite of normal convection you are used to, where warmer air rises to produce the turrets of convection. In this case, denser air descends producing downward-directed turrets. There are more details, of course, but you get the idea.
Just an amusing note to end. Some of use an IPHONE App by PointAbout, Inc. to view this blog. These folks produce all kinds of great weather apps (like IRADAR) and they did mine for free. For some reason, Apple gave this blog a rating of 9+ "Infrequent/Mild Mature/Suggestive Themes." I just can't imagine why!
Perhaps my talk about math education.....