Severe Weather In The Northland

By KBJR News 1

August 4, 2010 Updated Aug 4, 2010 at 11:47 AM CDT

The Northland's weather is often extreme, especially in the winter but we also see our fair share in the warmer months as well.

The last few summers have been quiet, but the fact remains...we are in a part of the country that is vulnerable to hail, high winds, and tornadoes.

George Kessler takes a look at what it takes to push a typical northland summer day into the "danger zone."

Severe weather can have devastating consequences so understanding the conditions that can lead us into danger is critical.

The most common severe weather patterns include thunderstorms, high winds and, of course, tornadoes.

The ingredients in these weather patterns generally include straight-line wind gusts in excess of 70mph, hail exceeding 3/4 of an inch or funnel clouds.

When those three conditions combine in the Northland we're in for a bumpy ride. Most severe weather begins with a thunderstorm,

At their basic level, thunderstorms are created when warm, humid air is lifted into the colder reaches of the upper atmosphere.

That generally happens due to a developing cold front.

Chilly air has a greater density than warm air, so when a front approaches it acts like a giant scoop, lifting the warm air up and out of its way.

But what conditions allow a garden-variety rumbler to grow into a potentially lethal monster?

How big a storm gets depends on how much fuel it has available and how big a motor it has.

Storms are fueled through heat and humidity.

A storm's motor is the strength of the front.

The more powerful they are, the faster the heat and humidity is lifted and converted into rain, lightning, hail and wind.

Hail can be one of the by-products of this weather pattern. It can form when warm, humid air rises quickly.

The rising air is so strong, that rain drops go up, instead of down, freezing solid in the upper parts of the atmosphere.

Another by-product of this weather pattern can be dangerous straight line winds.

Rain-cooled air forms a downward moving column beneath the storm.

The high-speed winds in the upper reaches then get pulled down by the falling air and are directed at the ground.

These winds aren't spinning, but that doesn't mean they aren't powerful.

In some cases they exceed 100 mph, and act like the blade of a bulldozer crossing the countryside.

Last and most complicated is the tornado.

Carol Christenson with the National Weather Service says, "In order to get rotation inside the storm we have to have winds that are turning as you go up into the atmosphere. Not only are the winds turning, but they're also increasing in speed, and that helps make the rotation."

The severe ingredients linked to a tornado include temperatures in excess of 80 degrees, dew points in excess of 60, and either a strong front or strong upper level system arriving when the heat and humidity is present.

It's not uncommon to have one or two of those ingredients present on a summer afternoon, but when they combine its time to grab your weather radio and seek shelter.

The NNC's meteorology staff is always on high alert for a combination of these ingredients and will alert you when there's danger in the air so you can be prepared well in advance.