Sunday, January 15, 2012

Couple Of Questions

Sarah Truebe asked:

...Can you direct me to a resource on mammatus clouds? I noticed them yesterday, and I think I've only ever seen them before under anvil clouds of thunderstorms. Why do they form in other contexts? Thanks!

Sarah, mammatus can form on clouds that are not associated with thunderstorms, as they did yesterday. Usually, though they are associated with deep convection and thunderstorms. Yesterday there was instability in middle-to-upper levels and there was convection aloft with fairly high cloud bases, but with no lightning or thunder, and, eventually, just  a few sprinkles. Such events are fairly common here in southeastern Arizona.

The question of why they form is much more difficult. You can find any number of simple explanations on the internet, but these are usually not very accurate. The real answer is that we're not really sure of what exactly causes mammatus clouds.        http://journals.ametsoc.org/doi/pdf/10.1175/JAS3758.1
The preceding link is to a technical paper on mammatus (written by 11 authors and mentioning discussions with 19 other atmospheric scientists). They conclude that there is no definite answer as to causes, but there are a number of possible mechanisms, as well as "...more research is needed."

Chuck Doswell asked:  Is that your bluebird photo?

No, Chuck, I grabbed it from an internet site. I did know what kind of bird it was though, thanks to my field guide. I don't take very great photos with my little, simple digital camera. Yesterday was even more frustrating than usual. Batteries slowly faded and I lost six or so photos, which were undoubtedly my best shots. I had taken photos of sevral spectacular live oaks down in the gullies and lost every one of them.

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