05/06/2024
~Weather Classroom: SCUD Clouds and Funnel Clouds~ I wanted to share two *fantastic* shots of the strong storm on Saturday, along with some general weather knowledge - y'all know how much I love sharing what I know about the weather with you!
The first picture was taken by Gavin Graves in Portage, and the second is from official weather spotter Kat Seiber in Lowell. The third picture is one I've snagged off of Google to give you a good reference for the information I'm sharing today, where I talk about the differences between wall and shelf clouds, as well as the differences between SCUD clouds and funnel clouds! Visual aids are always good things, I think!
What you're looking at is an absolutely beautiful shelf cloud formation. Shelf clouds form when the downdrafts in a strong-to-severe storm brings down air that's cooler than the rest of the storm, which then displaces the warm air out ahead of the storm, lifting the warmer air up which causes it to condense at the boundary of cool and warm air. These usually indicate a solid line of storms rather than a broken line, with winds striking ahead of the storm and then the shelf cloud will typically bring very heavy rain and sometimes hail from that warm air rising and cooling over and over until it forms ice.
Shelf clouds may also appear to rotate horizontally, which can sometimes cause weak and very short lived QLCS/Squall Line tornadoes.
It's important to note that shelf clouds are very different animals from wall clouds, although some can mistake the shelves for walls.
When rotation occurs with wall clouds, they will always rotate vertically, and will be smaller and more compact than shelves, whereas shelf clouds will be very wide and look a lot like the motherships breaking through the atmosphere in Independence Day (it's what I always think of LOL!)
Wall clouds are always the result of supercell storms, and these clouds will often have a solid and very tall anvil shape at their top from the extreme updrafts in the storm (these anvil-shaped clouds are called cumulonimbus clouds, and are considered the 'king of clouds!')
A common misconception with wall clouds as well is that they always produce tornadoes; but less than half of them do! However ALL wall clouds indicate a supercell storm and particularly dangerous severe weather.
Wall clouds will usually have what's commonly known as a tail cloud, properly called a flumen - you can see it on the left side of the image of the wall cloud. These are often mistaken for funnels as they can be quite long and funnel-like in appearance, however these tails are typically hanging horizontally off of the wall cloud and are caused by warm air and moisture flowing into the wall cloud. Tail clouds don't rotate, however the presence of a tail cloud is indicative of tornadic risk.
There's also another trickster that's often mistaken for a funnel cloud that's commonly seen with wall clouds known as SCUD clouds (the name itself is an acronym: Scattered Cumulus Under Deck.) SCUD clouds can strongly resemble a funnel as they can extend in a funnel shape down toward the ground. Unlike funnels, however, these clouds can look wispy and will often be broken up, and will almost always have jagged edges. SCUD clouds will NOT rotate.
SCUD clouds also often detach from the bottom of the storm cloud itself, which funnels never will. SCUD clouds are actually harmless and do not cause severe weather, although they are often found with severe storms. However, this isn't always true - any storm can produce SCUD clouds, and they can also be seen with shelf clouds, not just wall clouds!
Funnel clouds are much more solid and condensed, and are almost always smooth edged as the funnel begins to descend. They will always be rotating, and this rotation will be visible at close range (in which case, run) or at a distance if you've got good eyes, or zoom in a camera or utilize a pair of binoculars. ALWAYS seek shelter in the presence of a funnel cloud. It may not head your way, but the debris from tornadoes can scatter for miles, and it's always better to have yourself under cover in case any of it flies your way.
If that funnel IS headed your way and you don't have a basement or storm cellar to shelter in, go to the most interior room in your house; if this happens to be a bathroom, hunker down in the bathtub! I also recommend sheltering under some sort of solid object wherever you seek shelter, but if this isn't possible, then cover yourself with a blanket to help protect against cuts and glancing blows from objects, and keep your arms wrapped around and over your head as best you can to protect against solid objects. Better to have fractured arms than fractured skulls!
I hope this post was really informative for you all, and thanks again to Gavin and Kat for these great snapshots of that beautiful shelf!
