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.

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.

Cirrus Spissatus Cumulonimbogenitus (CH3)

After a blistering Friday afternoon, I dreaded the hot commute back home, but finally we got some relief in the form of afternoon thunderstorms. There were a few around with cool outflows, but limited areas of rain. Still, the thunderstorms do have another blessing: when they rain out, the Cirrus Spissatus helps keep the sky overcast for the rest of the evening. Specifically generated from Cumulonimbus Capillatus (CL9)(Your typical thunderstorm), this is called Cirrus Spissatus Cumulonimbogenitus (CH3). The downside, is that the cirrus also limits the diurnal heating necessary for further thunderstorm development and stabilizes the atmosphere to some extent.

The high clouds of the anvil separate from the mid and lower clouds and leave a nice veil over the sky. Unlike other cirrus, this is a bit darker and thicker in the middle, while more typical of cirrus around the edges.

These that I took, show the transition from CL9 to CH3.

Stratocumulus

Evening Sky

While walking Hank and Gus with Amanda this evening, we were treated to an active sky at sunset. Cumulus Fractus (CL1) in the foreground, with two Cumulonimbus (CL9) thunderstorms on the horizon (these were back towards Huntsville, AL!) and even some altocumulus castellanus (CM8). There were also some examples of altocumulus lenticularis, though I'm not sure I captured those well.

Eastern Colorado Mesocyclone

It is a very active night across the country's heartland with Tornado Warnings out in Montana, Colorado, Kansas, Indiana and Wisconsin. I found this monster on the radar in the plains of Eastern Colorado near the Kansas border. The Goodland, KS radar caught this excellent example of a Doppler tornado.

Lone Solstice Thunderstorm

Walking outside this evening to walk the dogs, I was treated to a beautiful thunderstorm in the distance, peaking over the trees and just tall enough to catch the last rays on the longest day of the year. The storm was one of the few to form over the Metro Atlanta area today, one with temperatures in the mid-90s. I love the contrast between the darkening evening sky and the bright cumulonimbus tower reaching over 25K feet. The pictures don't do it justice.

The Radar Image. The thunderstorm was to my Southwest and was moving quickly to the West.