How severe weather happens

Each spring we start talking about severe weather almost daily here in Colorado. This is a 9NEWS special report on severe weather in Colorado.

KUSA - As the days get longer, they also get warmer - giving the key ingredient to fuel thunderstorms.

Like clockwork from April through September between noon and sunset, these storms form when surface temperatures are highest. Thunderstorms typically form in warm and moist air and need three basic ingredients to form: moisture, unstable air that is warm and can rise rapidly, and a lifting mechanism, like a front.

“Much like when you heat water on a stove you start to see the bubbles, that's what happens when the surface of the Earth is heated so convection forms. Sometimes that convection can be strong enough to produce severe weather,” said Paul Schlatter, meteorologist with National Weather Service in Boulder.

A typical Colorado thunderstorm is less than 20 miles in diameter and produces wind gusts to 50 mph, hail up to half an inch in diameter, with frequent lightning and a rainfall rate of 3/4 of an inch per hour.

Most thunderstorms can form and then dissipate in about 60 minutes and that's the typical garden variety thunderstorm in Colorado. But certain conditions are more favorable for thunderstorms that can last much longer say for several hours.

“Storms that become severe are ones that are the most unstable, where the warmest air is beneath the coldest air. That instability forms a strong updraft where the warm air rises. and the stronger the updraft the better the ability for a storm to generate hail, and lightning, and those types of things,” Schlatter said.

A severe thunderstorm is considered to have hail up to an inch in diameter or larger, winds with gusts of 58 mph or greater or a tornado. We also have a unique characteristic to northern Colorado from the Denver metro area north into Weld County that we call the Denver Cyclone.

“It's a broad circulation and when you get surface heating on top of that boundary convection can form. Storms can form right on top of that boundary and sometimes we can get tornadoes that form as the storm grows. As the storm is going up it has a quick spin up tornado that we call a non-super cell tornado,” Schlatter said.

Lightning. Hail. Tornadoes. Flooding. Are you ready for this severe weather? Make a preparedness plan to keep your family and property safe when extreme weather strikes.  

© 2017 KUSA-TV


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