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Posted at 11:15 AM ET, 07/29/2009

Summer: A Good Time to Watch Clouds

By Ann Posegate

Wx and the City

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What kind of clouds are these? Find out after the jump. Photo courtesy UCAR.

Summer is a great time for cloud-watching. This summer (now that it feels like summer), while you're sitting at the beach, camping in a nearby park or taking a stroll down a city street, try to take some time to watch the sky and identify the clouds that go by.

One of the first things weather enthusiasts usually learn is how to identify clouds. Another fun activity -- especially with kids -- is finding images in the clouds, such as objects or animals. The great thing about cloud-watching is that anyone can do it, from anywhere. It's instant entertainment, not to mention a connection to the natural world. (Yesterday, I overheard a coworker retelling her experience from a recent thunderstorm. Afterward, she exclaimed, "I can't imagine living somewhere with no weather ... I just love watching the clouds!")

Here are a few of my favorite cloud types that can be seen above the D.C. area in the summer -- some are common, some are rare and a treat to see, and some warn of severe weather.

Keep reading for pictures and explanations of some common and rare cloud types...

Common or somewhat common:

Altocumulus -- mid-level clouds; great clouds to find images in

Courtesy UCAR

Cumulus Congestus -- also called towering cumulus; can develop into cumulonimbus and turn into thunderstorms

Courtesy UCAR

Cumulonimbus -- very tall, often with an anvil-shaped top; produce thunderstorms; also known as thunderheads

Courtesy UCAR

Cirrus -- high clouds; can often look like horse's tails or paint brush strokes

Courtesy UCAR

Contrails -- man-made clouds; common over the city from planes and jets flying overhead

Courtesy UCAR

Rare or somewhat rare:

Lenticular -- formed above and nearby mountains; can look like flying saucers

Courtesy UCAR

Mammatus -- can occur after severe thunderstorms; often seen during sunrise or sunset

Courtesy UCAR

Kelvin-Helmholtz -- can occasionally be seen in this area, usually among cirrus

Courtesy UCAR

Iridescent Clouds -- an optical effect caused by the diffraction of sunlight around water droplets in thin clouds, often in altocumulus, cirrocumulus, cirrus or lenticular clouds

Courtesy UCAR

It's also fun to watch how cloud cover progresses over several hours. Certain patterns are associated with approaching fronts, so by watching the clouds you can learn to make your own short-term forecasts. Here are two helpful diagrams that display clouds in a typical cold front and warm front to help you get started. In addition, here's a great online cloud guide from Plymouth State University's meteorology program, and another from the University of Illinois.

Look up: there's more to the sky than meets the eye!

By Ann Posegate  | July 29, 2009; 11:15 AM ET
Categories:  Posegate, Wx and the City  
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I can't recall ever having seen a true Kelvin-Helmholtz formation, either here or in Wisconsin...they seem to be extremely rare. Would recognize one if I saw it. Altocumulus standing lenticular is a lot more common, and I've seen quite a few mammatus formations, especially in the Midwest. Sometimes a mammatus-like formation develops when moist air sinks into a drier layer underneath; the mammatus is generally indicative of downward "reverse convection".

Castellanus and floccus clouds are rather common...these altocumulus clouds tend to look like a high-based cumulus congestus when well-developed...they can portend thunderstorms, especially on hot, humid mornings.

Rare clouds around here include the extremely high-altitude nacreous and noctilucent clouds, which generally form in polar latitudes. It's possible that water vapor at these altitudes may be the biggest greenhouse gas in the atmosphere. Space shuttle exhaust has been confirmed as a source of artificial noctilucent clouds.

Posted by: Bombo47jea | July 29, 2009 12:34 PM | Report abuse

@ Bombo - On a warm partly-cloudy day last fall, I noticed a small K-H formation in the distance while in NW DC. I did a triple-take, not believing what I was seeing. I went inside to get my camera, but couldn't see it by the time I got back outside. Up until then, I had only seen these clouds once (when I lived in the mountains, where they are most common) and never before around the D.C. area.

However, I have never seen noctilucent clouds, at least as far as I know. Have you seen them around here? Around sunset? I've heard that nowadays they are being seen at more southern latitudes. Here's a fun video about them produced by NASA, complete with an a cappella choir of scientists singing the background music. :)

Posted by: Ann-CapitalWeatherGang | July 29, 2009 3:18 PM | Report abuse

Thanks for this post! As you say, I am a weather enthusiast with little "real" knowledge of weather (though reading CW has certainly helped that), and I am always trying to identify the clouds around here.

My husband is now determined to see mammatus clouds, since they appeared in NYC (and, consequently, all over the blogosphere).

Posted by: dinermail | July 29, 2009 5:03 PM | Report abuse

@dinermail - Great to hear! Clouds are a fun introduction to weather, and summer is a good time to keep a lookout for them. Around here, Mammatus might occur before or after thunderstorms, especially during sunset when the colors highlight the "bumps" in the clouds. For example, I saw them the night after Tropical Storm Hanna last year, after the storms ended. They glowed orange and pink with the sunset.

Posted by: Ann-CapitalWeatherGang | July 29, 2009 6:20 PM | Report abuse

K-H are probably a mountain-induced wave-type formation...the lenticular formations are far more common.

I can't admit to ever having seen a nacreous or noctilucent cloud, though I hear a lot more about them these days. I believe the difference is that nacreous clouds are in the stratosphere, while noctilucent clouds appear at even higher levels. These types are the only clouds generally found above the troposphere.

One cloud reference I've always found valuable, but may be out of print today is the small book "Instant weather forecasting" by Alan Watts. This book was originally published in 1968 in the UK but was reprinted in 1976 by Dodd Mead. The same author also wrote two books on weather forecasting for recreational boaters. Detailed cloud books of note include the Roger Tory Peterson "Field Guide to the Atmosphere", and the National Audubon Society's "Field Guide to North American Weather".

Posted by: Bombo47jea | July 29, 2009 8:04 PM | Report abuse

wow, ann, those are amazing photos. all i know about clouds is what i taught at disco creek summer camp last summer - using tomie depaola's "clouds" book. it was great to try to recap different types and hear 4-6-year olds yell "serious clouds!!!" (instead of cirrus). don't you miss teaching? :)

Posted by: grace515 | July 29, 2009 9:55 PM | Report abuse

One of the best sites for photgraphs of every cloud type known is that of the Cloud Appreciation Society.

The Society is also exploring whether the photograph here is a
new type of cloud. The link there for more dramatic photos of this kind seems to be down. However, you'll find more examples on the 8th page. What do you think - a new cloud type or ..."

Posted by: SteveT-CapitalWeatherGang | July 29, 2009 10:08 PM | Report abuse

That really was a fun video! I'm still humming it..."Noctilucent cloud..."

Posted by: --sg | July 29, 2009 10:55 PM | Report abuse

@ Steve - a new cloud type or ... Photoshop? If those are real, they are amazing. I've never seen anything like them. Sort of like wave and mammatus traits combined.

@ Grace515 - Yes, I do. That's a cute story! Tomie DePaola's cloud book is a great one for getting young children interested in clouds.

@ sg - I still can't get it out of my head, even today!

Posted by: Ann-CapitalWeatherGang | July 30, 2009 12:19 PM | Report abuse

Thanks, Ann and Steve, for the banquet of clouds.

I love this blog. For weather fans, it's cloud nine.

Posted by: jhbyer | August 1, 2009 9:03 PM | Report abuse

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