If You See These Clouds, Be Careful...

One unique type of cloud can look like a tornado and in the second version, it forms at heights so low that it almost touches the ground. If you see this formation in the sky, it is a sign that severe weather is on the horizon. These are called Scud clouds and if you see them, you may soon be facing rain, hail, strong winds or lightning. Scud clouds do not pose any threat and are just a sign of bad weather to come.

How do Scud clouds come to life? Well, it's all about humidity. When it's raining, warm and moist air is pulled up into the sky. This is the fuel for a rainstorm. As the air rises, it cools to match the colder temperatures in the upper atmosphere. However, the moisture doesn't go anywhere and sticks around, leading to the formation of clouds through condensation. In some cases, the air does not wait until it reaches higher altitudes to condense so that it is saturated just above the ground, and the process of condensation begins at even lower altitudes than other clouds. As the air rises, it creates these cool vertically oriented scud clouds. They look wispy, ragged, and sometimes eerie. They can look like tornadoes, but they will never form into one. When scud clouds are caught in the downdraft area of a storm, they will travel faster than storm clouds. When scud clouds are in the updraft area, they tend to rise, and may show very limited to very strong side movement.

Another type of beautifully interesting cloud can be the Kelvin and Helmholtz clouds, named for Lord Kelvin (the discoverer of the Kelvin waves) and Hermann von Helmholtz (the physicist who first studied the physics behind them). They look just like ocean wave drawings, almost unreal. They both form when the upper layer of a cloud is moving faster than the lower one. The upper cloud is hotter than the lower one, so it's less dense and can move faster than the cooler, denser one below it. The instability at the boundary is what causes the upper edge to rise as the lower one moves forward, curling over like a wave breaking. So if you happen to hear the pilot mention “Kelvin-Holland clouds” on a flight, you can expect some turbulence.

Roll clouds are tubular, low-lying arcus clouds reaching hundreds of miles in diameter. Like Kelvin-helmholtz clouds they form when there is an inversion of warm air on top of cooler air, indicating instability. In this instance, the inversion is often caused by a thunderstorm.

Roll clouds are extremely rare and the only place where they are produced consistently is Australia's Cape York. They are called "Morning Glory clouds" and do not always coincide with storms. Why they are so consistent there is still a bit of an enigma. However, scientists believe it has something to do with the regular collision of the eastward moving sea breeze from the Bay of Carpentaria on the cape and the westward moving westward from the Coral Sea.

When an updraft develops during a thunderstorm, it rises, cools, and forms clouds. However, there is one point in the atmosphere where air cools as it rises: the tropopause. When an updraft reaches the tropopause, it can’t rise any higher. Instead, it begins to move laterally, creating a flat-top cloud known as an anvil cloud. The name incus comes from the Latin word incus, meaning “anvil.” On rare occasions, an anvil cloud will rise above the tropopause into the stratosphere. In this case, a cloud protrusion called an overshooting top will appear above the flat surface of the anvil. If you see an overshooting cloud, be prepared for a very bad storm. The clouds can tell us a lot about forecasting the weather, which is very useful for us humans. However, there remains lots of mystery about what's actually up there in the clouds that we have yet to discover...