Tag: Weather

Like wall clouds, shelf clouds also form underneath thunderstorm clouds. As you can imagine, this fact doesn’t help observers differentiate between the two. While one is easily mistaken for the other to the untrained eye, cloud spotters know that a shelf cloud is associated with thunderstorm outflow (not inflow like wall clouds) and can be found in the storm’s precipitation area (not rain-free area like walls clouds).  Another hack to telling a shelf cloud and wall cloud apart is to think of rain “sitting” on the shelf and a tornado funnel “coming down” from the wall.  Link Source: Means, Tiffany. “Clouds That…

Wall Clouds Wall clouds form under the rain-free base (bottom) of cumulonimbus clouds. It takes its name from the fact that it resembles a dark gray wall (sometimes rotating) that lowers down from the base of the parent storm cloud, usually just before a tornado is about to form. In other words, it is the cloud from which a tornado spins.     Wall clouds form as the thunderstorm updraft draws in air near the ground from several miles around, including from the nearby rain shaft. This rain-cooled air is very humid and the moisture within it quickly condenses below the rain-free base to create the wall cloud. …

Whoever first exclaimed “The sky is falling!” must have seen mammatus clouds overhead. Mammatus appear as bubble-like pouches that hang on the underside of clouds. As odd as they look, mammatus aren’t dangerous — they simply signal that a storm may be nearby.  When seen in association with thunderstorm clouds, they’re typically found on the underside of anvils. Link Source: Means, Tiffany. “Clouds That Spell Severe Weather.” ThoughtCo, Aug. 1, 2021, thoughtco.com/clouds-that-spell-severe-weather-4089934.

An anvil cloud isn’t a stand-alone cloud, but more of a feature that forms at the top of a cumulonimbus cloud.  The anvil top of a cumulonimbus cloud is actually caused by it hitting the top of the stratosphere — the second layer of the atmosphere. Since this layer acts as a “cap” to convection (the cooler temperatures at its top discourage thunderstorms), the tops of storm clouds have nowhere to go but outward. Strong winds high up fan this cloud moisture (so high up that it takes the form of ice particles) out over great distances, which is why anvils can extend outward for hundreds of miles…

Cumulonimbus clouds are thunderstorm clouds. They develop from convection — the transport of heat and moisture upward into the atmosphere. But, whereas other clouds form when air currents rise several thousand feet and then condense where those currents stop, the convective air currents that create cumulonimbus are so powerful, their air rises tens of thousands of feet, condensing rapidly, and often while still journeying upward. The result is a cloud tower with bulging upper portions (that look something like cauliflower).  If you see a cumulonimbus, you can be sure there’s a nearby threat of severe weather, including bursts of rainfall, hail, and possibly even tornadoes. Generally, the taller the cumulonimbus cloud, the more…