Wednesday, July 28, 2010

Wal-Mart Clouds

I'm constantly looking at the sky, quizzing myself about cloud types-usually I can't remember the exact name of the cloud. The other day we rounded the corner into Wal-Mart and were greeted with a perfect example of Amanda's favorite cloud, Cirrus Spissatus Cumulonimbogenitus. (It's her favorite because she's heard me ask her a thousand times to identify these guys and she usually says, "That really long-named cloud.")

Anyway, I pulled out the new phone and snapped a few pictures. The scenario was a typical hot day in Metro Atlanta, with surface temperatures in the mid 90's. This particular thunderstorm was to our south, just below the City of Atlanta- we were 30 miles to the north in Woodstock. The thunderstorm, like many slow-moving summer giants, rained itself out. The relatively cold rain and cold downdrafts neutralized the fuel: heat. As the surface cooled, there was no longer any convection and thus, very little rising air. Unlike springtime thunderstorms that usually have a steering mechanism keeping them moving along a boundary, constantly fed with more unstable, warm, rising air, summertime thunderstorms are slow-movers with little to direct their general movement.

As you can see below the clouds in the upper atmosphere are overtaken by strong winds at that level. The lack of convection and strong vertical circulation within the storm led to the clouds being sheered and whisped away in dramatic fashion. The anvil of this thunderstorm becomes elongated and misshapened. As the evening progresses, these clouds can dominate the sky, with only a triangle-like shape as a reminder of its past.












Thursday, July 8, 2010

Evening Cirrus

Cirrus clouds represent the large group of high clouds (CHx). Because they are so high, they often catch the sun's light well after the sun has fallen below the horizon, offering beautiful contrasts of reds, oranges and yellows against a dark blue evening sky. Tonight, I found a large amount of CH2 clouds (Cirrus Floccus) and CH4 clouds (Cirrus Fibratus).

Cirrus Floccus is categorized as CH2, which also includes Cirrus Spissatus and Cirrus Castellanus. Cirrus Floccus is defined as cirrus in cumuliform tufts. Spissatus is typically smoothed fan-like cirrus that is progressively dense. Castellanus often have associated virga with small turrets.

The picture below shows Cirrus Floccus for the most part.

Cirrus Fibratus (CH4) is described as cirrus with filaments and is often arranged in parallel lines, as seen below.

Cirrus Floccus


Cirrus Floccus and Fibratus

Cirrus Floccus should be distinguished from Cirrocumulus Floccus (CH9) which are much higher, rarer and form at low temperatures.