A tornado is arguably one of the most violent weather forces in nature and on average claim 70  lives in the United States per year. As we have seen recently, they develop FAST and leave as fast as they can develop.

Truth: Tornadoes are sometimes vary hard to see! There are low rain content storms (mainly tornadoes seen over the central plains) and high rainfall content storms that make detecting rotating winds and tornadoes very hard to see. This is more often the type of tornado that affects the Southeast.

A Tornado is a rotating column of air that comes down from a thunderstorm. A funnel cloud is a tornado that hasn’t reached the surface.

Tornadoes DO require a violent thunderstorm before they can exist. A tornado needs many ingredients, at many layers of the atmosphere before they can exist: typically but not always they require a front at the surface with warm moist air in front and cold dry air behind. These collide at the surface because they are coming from  almost oposite directions. In the lower level jet stream warm moist air is necessary (around 3,000-5,500ft.) to provide a bouyancy mechanism to the developing storm.

But it still needs more. Another layer up there needs to be another layer of wind, typically coming in from the southwest but colder due to it’s height. This layer is heavier than the moist bouyant air and acts as a temporary lid to the growing thunderstorm beneath it. The dynamics below this lid must be strong enough to eventually penetrate the cold air above it. If the CAPE, (Convective Available Potential Energy) is large enough to break this lid then the warmer bouyant air can interact with the cold unstable air above it and create rotating winds.

Still, we’re not quite there. Once the wind breaks through the cold lid, it must have a strong upper level wind at the highest level (the jet stream) to pick it up and pull the unstable air further up. This helps move the storm, and strengthen it’s travel speed.

When a thunderstorm becomes this violent with horizontal rotating winds, an updraft (strong burst of vertical air pulls the rotating column of air up vertically which produces what we see (or sometimes do not see) as a tornado.

The Gulf Coast (Including AL, GA & the Panhandle) typically has its most favorable months for tornadoes in Febuary and March because we are so much warmer than inland areas. We have the influence of the Gulf of Mexico as a huge factor in our storms and it’s one of the reason SE AL doesn’t get typically near as cold or as often as N. AL. Storms along fronts drop down across the plains during the winter and bring very cold, fast moving upper level winds. If you have the right right conditions with this all at the surface and right winds, temps etc. it becomes a highly volatile environment. The later we get into spring the less these plains storms can make it down to the south, the contrast isn’t as strong. The threat gradually retreats to the Northern part of AL, then the plains, then eventually in late summer up to the Northern plains, great lakes region.

We typically see two severe seasons here, early Spring and late Fall, but the Spring severe season usually proves the stronger of the two. Hope this helps clear some things up!

About these ads