Some days, especially in summer, the clouds of central Colorado present a spectacular skyscape constantly changing and shifting from puffy cotton balls to ominous thunderclouds to occasional bright blue skies of the American West. One such day was last Sunday and the following time-lapse video captured the scene:
A brief aside, if you like Madeleine Peyroux‘s music, you can buy her “Careless Love” album at:
Why the clouds?
The Rocky Mountains, as with all imposing mountain chains, affect weather and climate in a number of significant ways. Summertime heating of the mountain slopes causes one of the more majestic effects, the regular, almost daily, development of thundershowers over the higher terrain.
The Rockies in central Colorado reach elevations just above 14,000 ft (4267 m), about one-third of the way up into the troposphere (the layer in the earth’s atmosphere closest to the ground where most of our weather and clouds form). When the sun warms a high-elevation mountainside during the day in summer, that heat is quickly transferred to the atmosphere. Putting a heat source at 14,000 ft up in the troposphere, a level where the atmosphere is usually chilly, causes convection, the rising of air due to heating. Even on relatively dry days with only a meager amount of moisture in the troposphere, the convection caused by the elevated heat source of the mountains is so strong clouds can still form. If there is enough moisture, those clouds will become showers and thundershowers.
Ah, summer! (Well, in the Northern Hemisphere, that is.) Aside from ice cream, beaches, flowers, vacations, and sunburns, summer also means impressive thunderclouds (cumulonimbus clouds). Over the mountains of central Colorado, we usually don’t get the massive “supercell” thunderstorms that occur over the Great Plains of North America, but picturesque convective clouds still form almost daily. Here are just a few examples from the last couple of weeks:
Yesterday was an active weather day along Colorado’s Front Range. A relatively cool springtime weather system from the Pacific, which had moved through the Pacific Northwest on Memorial Day Monday (even affecting San Francisco with a bit of light rain), made it to the central Rockies yesterday morning. Bands of thundershowers formed ahead of the system and moved out of the mountains into the Denver area during the late morning. From a park in Littleton, I took a few photos of one of the approaching lines of storms. The silhouetted darkness of the distant foothills and the angry look of the sky contrasted vividly with the green spring grass in the foreground. I used Aperture to modify some of the images to discover how different enhancements changed the photographic mood of the morning. The results follow…
And, just what did this menacing line of storms look like from above? Fluffy white, and relatively disorganized, as this image from NASA’s Aqua satellite shows (taken a couple hours after the ground-based images; Denver is near the center of the image):
Ever since I learned about the Cloud Appreciation Society (CAS) a few years ago, I became an instant fan and, as quickly as international post would allow, I became a life-long member. Not only does the society have a wonderful collection of cloud pictures and videos from its 32,000+ members (not to mention cloud music, art, and poetry), but they (we) also encourage learning about clouds through a mix of solid science and a bit of whimsy. After all, learning while laughing definitely speeds learning, no matter what the subject—especially, if it is about something as ephemeral as clouds.
Given my enthusiasm for the Society, it’s no big surprise that I have managed to convince a few wise members of my friends and family clan to appreciate clouds with me and join the CAS. There is at least one very important member of the family, though, who I missed. And, she made it quite obvious to me today that she, too, has as strong an appreciation for clouds as anyone else. Meet Olive, the cloud-spotter feline of the household:
Just what has attracted her attention, you ask? It is a picture of one of several thunderstorms which moved over the Boulder, Denver, and Colorado Springs metro areas today. I took the thunderstorm picture earlier in the day thinking it would be a nice contrast to the winter weather pictures I took last week during our late-season snowfall (Last week was winter, this week is spring; extrapolation predicts summer soon). While cropping the image on the computer, Olive the cloud-spotter feline spotted it. She was mesmerized, quite unusual for her capricious personality. In fact, she was mesmerized to the point where she remained still long enough for this, and a few other, cute cat pictures. To keep her purring, I promised to remit her lifetime membership fee for the Cloud Appreciation Society as soon as possible. They already have a dog who is a member, but I think Olive would be the first cat.
To complete the story, here’s the thunderstorm image that so intrigued Olive:
With this storm and the showers that followed it, we received about 0.5 inch (12 mm) of rain today. Any rain (or snow, for that matter) this spring is a big help for us because we are still trying to get out of long-term drought.
During this transitional season from winter to summer, as the sun travels higher in the sky each day and hints of summer’s warmth become more frequent, the weather responds to the nature of the season as well. Often, here in the central Rockies of Colorado, there are days when still-chilly northwesterly winds are accompanied by frequent snow showers in the unstable atmosphere of spring—unstable because the atmosphere retains its cold memory from winter, while the land rapidly warms from the relatively strong springtime sun. The following timelapse animation shows an example of this, with daytime heating causing snow showers to form and spread southeastward pushed by strong, cold winds from the northwest:
The timelapse compresses about 3 hours of midday weather into 33 seconds of video. It was taken yesterday (29 March), and the camera was pointed to the south-southeast. The images used in the animation were taken once every 20 seconds. The location was just west of the Continental Divide in the Colorado Rockies.