Share your favorite shelfies (photos or video of shelf clouds) to our /photos gallery, our Facebook page, or via Twitter MORE PHOTOS: 10 Spectacular Clouds | Earth's Highest Clouds | Hole-Punch Clouds) MORE ON WEATHER. The National Weather Service in Lubbock, Texas, documented a spectacular case of cold-frontal roll clouds in late September 2007. Either the gust front surged well away from the parent thunderstorm(s), or the thunderstorm(s) may have fizzled, leaving this remnant roll cloud.Īdvancing cold fronts have also triggered roll clouds on occasion. Unlike a shelf cloud, the roll cloud is detached from its parent thunderstorm(s). Wind gusts once the shelf cloud has passed may be quite strong, causing downed trees, tree limbs and power outages. When this warm, moist air condenses, you see the shelf cloud.Īs the shelf cloud passes, you feel an abrupt shift in wind direction and increased wind speed, followed within minutes by heavy rain or hail. Warmer, more moist air is lifted at the leading edge, or gust front, of this rain-cooled air. Rain-chilled air descends in a thunderstorm's downdraft, then spreads laterally when reaching Earth's surface. What you're seeing in a shelf cloud is the boundary between a downdraft and updraft of a thunderstorm or line of thunderstorms. ( PHOTOS: Scary Clouds That Are Not Tornadoes) While menacing in appearance, shelf clouds are not tornadoes or wall clouds. Wall clouds take on many shapes and sizes. The lowering denotes a storm's updraft where rapidly rising air causes lower pressure just below the main updraft, which enhances condensation and cloud formation just under the primary cloud base. Shelf clouds are typically seen at the leading edge of a thunderstorm or squall line of thunderstorms. Other interesting clouds: Wall Cloud: A localized lowering from the rain-free base of a strong thunderstorm. To understand how roll clouds form, we first must explain how shelf clouds develop. Both types of clouds can produce severe weather, including tornadoes. The first two photos in the slideshow from Lake Hendricks, Minnesota, on June 20, 2015, show a terrific example of a roll cloud. A shelf cloud is similar to a wall cloud, but it extends outward from the thunderstorm base. Based on their appearance, we certainly understand why.Ī more rare variety of this type of cloud, a roll cloud, resembles a giant rolling pin in the sky.

A shelf cloud, also known as an arcus or arc cloud, may be the most frequently submitted cloud photo to our photo gallery and Facebook page.

Wall cloud vs shelf cloud