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Mural in Motion

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:
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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.


Convective Compositions

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:

Small cumulonimbus cloud forming

Mad Hatter

Mammatus Clouds

Angry Mammatus Clouds from Severe Storm to the West

Cumulonimbus in the distance

Cumulonimbus in the Distance over the Rockies

Rain falling out of small thunderstorm

Rain Falling From Small Convective Cloud

Thunderstorm in the distance

Thunderstorm Moving Away

Approaching Thunder

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):


A Snow Shower in May

Often in May, with the air still retaining some winter chill, and the land warming rapidly from near-summer sunshine, convective showers of snow and hail form over the Rockies and adorn the sky-scape.  This happened over the weekend and I caught this image showing a beautifully picturesque shower as it was passing by to the east.  The fibrous texture of the cloud’s top results from ice crystals formed as the shower cell bubbles skyward due to the heating below.  Grayish snow and soft-hail can be seen falling out of the cloud obscuring the land surface underneath it.  Surface temperatures were in the low 50s°F (12°C) in the sunshine, dropping to about 40°F (4°C) when one of these showers passed overhead.  The snow and soft hail would whiten the ground, briefly providing a wintertime look to the May landscape and angering the nesting robins chilled by the sudden squall.

A Springtime Snow Shower over the Rockies

A Springtime Snow Shower over the Rockies

An Appreciative Cat

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:

Wide-angle view of approaching thunderstorm; dark clouds in foreground, streaks of rain in background

Approaching thunderstorm

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.

May it snow?

Central Colorado had a very snowy April—for instance, Boulder, CO set a record for April snowfall measuring more than four feet (122 cm) of snow during the month…and most of that fell during a two-week span in the middle of the month. May has continued the pattern with an all-day snowfall today along the Front Range of the central Rockies. What does a mid-spring snow day look like? Much like a mid-winter snow day except for the perturbed robin and the confused buds…

A collage of 4 pictures showing snowy scenes from May Day 2013, in central Colorado

Snowy scenes from May Day 2013

“You are getting sleepy…very sleepy…”

Here’s a second interesting view of Isaac, now well inland over northern Louisiana.  This time it’s an animation of the surface wind field around Isaac at 11:00 a.m. CDT.  The creative and wonderfully imaginative people at Google’s Big Picture data visualization group created the surface wind visualization site ( which was the source for this animation.  The hypnotic swirl is mesmerizing.

Hurricane Isaac Crosses the Coast

Here’s an interesting 22-hour radar loop from the New Orleans NEXRAD site (the National Weather Service’s weather radar site) showing hurricane Isaac very slowly crossing the coast and heading inland:

Today’s Stream of Consciousness

Today, I’m making my first attempt to create a blog entry on my iPad using the much-loveblogsy_icond blogsy app. The result: So far, so good. Intuitive (I haven’t looked at their tutorial videos yet), easy to use, designed for iPad’s touch-n-swipe interface. And, even better, a lot less frustrating compared to my initial experience with the WordPress app (which is fine for simple stuff, but is not very feature-rich…although the price is right!) [Update, January 28, 2016: Blogsy is no longer with us. Sigh.]

And, now for the abrupt change of subject (befitting the stream of consciousness)—

As the 11-year solar sunspot cycle continues to heat up…

…the effects of another impressive solar flare are headed towards Earth in the next 24 sxi_20120306_235815165_ba_15hours. Updates about expected impacts on radio transmissions, auroral activity, etc. are issued by NOAA’s Space Weather Prediction Center and posted here. It doesn’t look like the auroral activity will be seen this far south (40°N), but it really doesn’t matter because we’ll be covered in clouds through tonight.

Temperature at KDEN, past 2 days

And, just why is it so cloudy in Colorado? Because of a cold front which moved rapidly down the Front Range of the central Rockies last night. We went from 73°F yesterday (just 2°F shy of the record high temperature for March 6) to a current temperature of 27°F—a 45°F drop!

Hmmm…just ran across an oddity in blogsy. I wanted to use the degree symbol (HTML code: ° or °, but when I went into the HTML editor side of blogsy and put in the code, then returned to the rich text editor side (with a real-time preview of the blog entry), no degree symbol…just the actual HTML code is shown. We’ll see what happens after I post this to the WordPress site…
Update after my post: While blogsy does not show the degree symbol in its rich text editor, the degree symbol shows up just fine (as I had hoped) on the WordPress site. Good. Blogsy passes the test!

Snowless Winter? Not entirely snowless, but certainly snowstarved

There have been many headlines about the lack of snow over the conterminous U.S. this winter particularly because the northeastern U.S., a major source region for headlines, has experienced an unusually mild winter.  For instance:

Outdoor Enthusiasts Adapting to Snowless Winter West of Boston
Festival has Near Meltdown
Towns Save Money in Snowless Winter
Home Depot Given Warm Winter Boost

The less than normal snow extent also affects many parts of the western U.S. including where I live in Colorado.  It was visually evident during the President’s Day weekend when I noticed I could see most of my two-foot tall snow stake at our house at the 8300-ft level in the Colorado mountains:

Snow on the ground, Feb. 2012

That contrasted with the conditions of a year ago which were much different.  Just how different?  This picture from last year’s President’s Day weekend shows the same snow stake at the same location:

Snow on the ground, Feb. 2011

Ah yes!  What a difference a year makes.  Even more striking is the difference in the amount of water contained in the central Colorado snowpack this year as opposed to last.SWE in central Colorado, 21 February 2012  The graph to the right shows the snow water equivalent (SWE), the amount of water in the snowpack measured in inches, for a location not too far from the snow stake comparing Jan 1-Feb 21 of last year with the same period this year (last year=blue, this year=red).  Again, what a difference a year makes!  Last year the snowpack contained more than 3″ of water (if you were to melt all the snow in a column); this year the pack has about ¾”, just 25% of last year’s amount.

The dearth of snow in the Central Rockies is not confined to the area just around my snow stake.Colorado snowpack, 21 February 2012  This next map, from the Natural Resources Conservation Service (NRCS—a part of the U.S. Dept. of Agriculture), shows all of Colorado having a below average snow season this year. The NRCS collects data about the snowpack (snow depth, water content, etc.), both remotely and in-situ, and produces a variety of maps depicting the condition of the wintertime snow cover. Their Colorado map set can be accessed from here.

Snowpack over the western U.S., 21 February 2012
To the right is an even bigger picture view, again from the Natural Resources Conservation Service.  Most of the western U.S. except the far northern regions and a few spots in the southern Rockies have had a snowstarved winter.  If you are interested in monitoring changes in the snowpack across the western U.S., here’s where you can access daily updates to this map.

Much of this winter’s snowlessness across the U.S. is related to the location of the jet stream.250 mb average jet stream winds 24Nov11 to 21Feb12  Winter storms generally follow the path of the jet stream (Storms develop along thermal boundaries between cold air to the north and warm air to the south, in the Northern Hemisphere.  The jet stream is created by these same thermal differences.) Generally, cold air and snow will be more prevalent along and on the poleward side of the jet stream’s location.  This winter, on average, the jet stream has been farther north than normal especially over the western U.S. as this map shows (magenta arrows show average position of the jet stream).  Usually, those magenta arrows would be hundreds of miles farther south and the northward bulge over western North America would not be as pronounced.  This is a pattern which is often seen during La Niña conditions (cold water over the central Pacific Ocean) like what we have this winter—although this year the jet stream is even farther north than in typical La Niña years.

And, as with all things weather, by the time I post this missive it will be old news.  In the past few days the jet stream has shifted south and west (as shown by this satellite picture and wind speed map from today).
Jet Stream Over the U.S. 22 Feb. 2012It now enters the U.S. over the Pacific Northwest and dives down into the central Rockies.  Meanwhile over the eastern U.S., it’s farther south as well (and, not surprisingly, Richmond, VA had a few inches of snow this past weekend). For Colorado, this has meant a return to snowy conditions for our mountains with fresh powder at the ski resorts being measured in feet rather than inches.  This is good news for the western watersheds (but bad news for my snow stake).  And for the next 10 days, at least, it looks like the jet stream will remain closer to its normal position across the western U.S. leading to more normal wintertime weather.

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