Thunderstorm!

Last night we had a fairly long-lasting Prairie thunderstorm. It was one of those days were you can feel it coming...in my case, quite literally, as I developed a headache as the storm approached.

Conditions were perfect: hot, unstable air, moisture (to form clouds and rain) and lift (a front). I was not terribly excited about the storm, as it was just another Prairie thunderstorm. However, I got excited in a hurry when I saw cumulonimbus mammatus clouds forming. To the best of my knowledge, they're fairly rare, and I haven't seen them here before.

I grabbed my point and shoot camera and snapped a few photos before they disintegrated. It was getting pretty dark, so they can be hard to see, but they would have been spectacular if the sunlight had lasted just a little bit longer...

They are named "mammatus" due to their shape, which is somewhat udder-like. The interesting thing about them is that they are a rare example of clouds forming in stable (sinking) air.

They are poorly understood, but I have heard they are formed like this:
- the temperature of the subsiding air increases as as the air descends (adiabatic warming)

- this temperature increase is offset by the energy required to evaporate the precipitation particles

- if more energy is required for evaporation than is generated by the subsidence, the sinking air will be cooler than its surroundings and will continue to sink downward (as stable air does).

Over time, the cloud droplets do eventually evaporate and the mammatus dissolve, which took about 10 or 15 minutes.

Overall, they were pretty impressive. And then after it got dark, the lightning and thunder started in earnest. I was out on my balcony and I took a few shots (but I missed MANY spectacular pictures of lightning).

This was pretty cool - the whole sky was streaked with lightning, and this just shows the tail end (or my reflexes wouldn't have caught anything!).