A shelf cloud is much different than a wall cloud. Shelf clouds do not rotate, and you would rarely see a tornado beneath one. (Gustnadoes are a different story for a different day.)
This picture was taken from the Haleyville SkyCam about 15 minutes ago as a very heavy storm was moving through Phil Campbell and Dime up in Franklin County. Storms like this look very scary, but the clouds stretched toward the ground are NOT tornadoes, funnel clouds, or wall clouds; they are actually “scud” clouds. Scud clouds are low cloud fragments caused by the thunderstorm’s downdraft, and they are harmless.
This is why we recommend storm spotter training. It can be tough to tell the difference, but training can help you distinguish the harmless from the life-threatening.
-Jason
On Twitter: @simpson3340
On Facebook: Jason Michael Simpson
–
