|A multi-vortex tornado in Oklahoma two years ago.|
Another severe outbreak seems destined to develop this coming weekend.
I noted something interesting in some of the inevitable tornado videos on YouTube that came out of this latest severe weather outbreak. Some of the videos were dramatic examples of multi vortex tornadoes.
You can see some of the videos of this month's and past multi vortex tornadoes at the bottom of this post. Really fascinating.
Multi vortex tornadoes feature smaller sized tornadoes swirling within the main circulation of a larger tornado. They're especially prevalent in stronger tornadoes.
Suction vortices create little narrow paths of much stronger winds within an already destructive tornado The suction vortices can add more than 100 mph to the wind speed in parts of a tornado circulation, says NOAA's Storm Prediction Center.
Often, four, five, six or sometimes more suction vortices are swirling around the main tornado circulation like square dancers at a Texas hoedown.
The suction vortices are why you see such weird but sadly familiar damage patterns after a tornado. One house is totally destroyed, while the house right next door just has minor damage. The trashed house was probably hit by a suction vortice, the house next door wasn't. Luck of the draw.
More often than not, you don't see the suction vortices in a multi vortex tornado. The dense funnel of the main tornado doesn't let you see them.
Sometimes, though, the main tornado funnel doesn't condense into a dense cloud. So you see the suction vortices dancing around, like in the past couple of days in Iowa and Texas.
They change and whirl and rotate around each other, always changing their form and picking up stuff from the ground and flinging it high into the air.
One such tornado hit the area around Lake City, Iowa on Sunday. Jacob Dickey - you can find him on Twitter @Jacob_Dickey caught the vortices swirling about and sadly causing damage. Fascinating, though:
Chasers with TVNWeather.com caught another multi vortex tornado near Denton, Texas late last week.
TVNWeather.com also filmed perhaps my favorite video of a multi-vortex tornado, this one near Woonsocket, South Dakota last June. The suction vortices are lit up bright white by the sun, and they are mesmerizing: