Anatomy of a Storm – Tornadoes

The past two articles talked about the recent storm system that caused a blizzard in Wisconsin and heavy freezing rain in Illinois. The third and final article about this storm is about the southern end of the recent storm and a powerful tornado that devastated the town of Dumas, Arkansas.

What caused these tornadoes?
The cold front associated with low pressure system that causes a blizzard in Wisconsin and freezing rain in Illinois generated the formation of thunderstorms. The cold front brought in cold winter air from the northern US. This cold air combined with moist warm air to create updraft of air that formed the thunderstorm clouds. Once again, the currently strong jet stream over Arkansas played a big role. These upper levels winds enhanced spinning columns of air that are found in all thunderstorms. The updraft winds rotated these columns of air to a vertical position and this results in a rotating wall cloud.

As the storm becomes more powerful, heavy rainfall causes an area of air called the rear flank downdraft (RFD). The RFD’s rapid descent drags the rotating wall cloud close to the surface. At this point, a funnel cloud drops out of the funnel cloud and causes death and destruction on the ground.

Why does the funnel cloud form?
At this point, it remains unclear but many scientists are working on figuring this out. Stay tuned for more on this.

——
Posted by Tim Roth, author of the political blog Think Anew and Act Anew

Sources:
1. “Neccessary Ingredients for Thunderstorms”, NOAA’s JetStream – Online School for Weather
2. “Thunderstorm Hazards – Tornadoes”, NOAA’s JetStream – Online School for Weather
3. “Cyclogenesis”, Wikipedia entry