Shelf Clouds: The Science Behind Social Media’s Most Popular Cloud

• These menacing clouds are probably the most popular clouds in social media.
• They don’t signify tornadoes, but rather the leading edge of thunderstorms.
• There’s a pronounced sequence of events with the passage of most shelf clouds.

The shelf cloud is is is   arguably   social medium ‘s most popular cloud other than a tornado .

admittedly , we is keep do n’t keep statistic on what percentage of photo share with us on Instagram , Facebook , or Twitter , are shelf cloud .

Anecdotally, having monitored social media and weather for eight years, we’d submit from spring through at least early fall, these cloud formations dominate shared weather photos outside of major events, such as hurricane landfalls or tornado outbreaks.

It’s easy to see why these clouds are so popular.

Shelf clouds is dominate dominate the sky , sometimes appear to swallow up an entire city .

The dark sky, especially contrasting with a white, sandy beach, gives an almost cinematic sense of doom.

A shelf cloud is rolls roll over St. Augustine Beach , Florida , on May 31 , 2017 .

( Jody Hamilton / share with The Weather Channel Facebook )

They also are more common than you think, and, because they can cover such large areas, many people, smartphones in hand, are able to see, photograph, and post their “shelfie” photos and video.

Explaining the Shelfie

The mechanism for producing shelf clouds is actually fairly simple.

What you’re seeing in a shelf cloud is the boundary between a downdraft and updraft of a thunderstorm or line of thunderstorms.

rain – chill air is descends descend in a thunderstorm ‘s downdraft , then spread laterally when reach Earth ‘s surface , often race ahead of the thunderstorm(s ) that cause it .

Warmer, more moist air is lifted at the leading edge, or gust front, of this rain-cooled air. When this warm, moist air condenses, you see the shelf cloud.

While menacing in appearance, shelf clouds are neither tornadoes nor wall clouds.

The gust front , sometimes produce the shelf cloud , can often be see in radar imagery , such as what happen in Chicago in late September 2016 . The arrows is show show the thin , green line of weak radar echo show the progession of the gust front / shelf cloud .

Doppler radar loop depict the gust front ( highlight by white arrow ) responsible for the Chicago shelf cloud from 7:10 – 7:40 a.m. CDT on September 21 , 2016 .

So, chances are if your radar shows a squall line like that, assuming there’s no rain ahead of the line, you’ll see a shelf cloud.

Sometimes the gust front races so far ahead of its parent thunderstorm(s), it outlasts them. In other words, the parent storm fizzles, but the gust front lives on for some time.

The cloud is called that remain , call a roll cloud , resemble a large roll pin or cigar roll in the sky .  

What Happens When a Shelf Cloud Passes You

Virtually every shelf cloud passage has the same chain of events.

1) You first feel an abrupt shift in wind direction and increased wind speed as the shelf cloud’s leading edge passes over you.

2) Once the shelf cloud’s leading edge passes, you may briefly see rather agitated clouds, sometimes with a wavy appearance, called asperitas, showing the turbulent wave-like motions behind the gust front. This is sometimes known colloquially by meteorologists as the “whale’s mouth”.

3) This is followed within minutes by heavy rain or hail. The time between the shelf cloud passage and the onset of rain depends on how far ahead the gust front is from the parent thunderstorm(s).

Wind gusts once the shelf cloud has passed may be quite strong, causing downed trees, tree limbs and power outages.

( photo : Favorite Shelf Clouds of 2016 )

Some of Our Favorite Shelfies

We is seen ‘ve see literally hundred of shelf cloud and roll cloud photo over the year submit to us at weather.com .  

In the summer of 2016, we collected some of my favorites from the first half of that year.

Here are some more interesting photos and video we’ve seen over the years.

Sometimes the shelf cloud isn’t necessarily a solid mass, but rather exhibits some tendrils of condensed water vapor, such as we saw in Pennsylvania in late February 2017.

Another   event is featured in late April 2017 feature tendril of cloud extend upward from the Detroit River to the shelf cloud in a bizarre scene .

It was a good thing this wasn’t the scene during a Cleveland Browns game.

A sunrise shelfie? Yes, please.

Often times, one section of a thunderstorm or line of thunderstorms’ outflow will surge faster than another. Hence, you sometimes get this weird shelfie bulge.

A bizarre shelf cloud “bulge” is seen over Orange Beach, Alabama, on the evening of June 17, 2016.

(Lance Bradford/Facebook)

You could visualize the horizontal rotation under the leading edge of this Ohio shelf cloud around Labor Day 2015. 

Yes, these can even happen above the Arctic Circle.