Straight Line Winds and Hail: Colorado Severe Weather Awareness Week

Strong straight line winds and large hail are major weather threats in Colorado.

During this Severe Weather Awareness week in Colorado remember that threats from thunderstorms include tornados, straight line winds, hail, flooding and lightning.

Tornadoes are often the headline story, but damaging straight line winds can also injure and kill animals and humans. These winds are usually caused by an area of air within a storm which is quickly cooled by precipitation or the evaporation of precipitation.

This area of cooled air which is heavier than the surrounding air accelerates downward. As the cool air slams into the ground it spreads out from the area of impact. This process, in extreme cases, in result in wind speeds exceeding 100 MPH. Weather forecasters call these winds microbursts if they are less than 2.5 miles across and macrobursts if they are greater than 2.5 miles across.

These downbursts of cool air can be life threatening to pilots and can cause extensive damage, injuries and deaths at ground level. Try to get indoors during all storms because high winds can suddenly develop causing things on the ground to become swiftly moving missiles that can injure or kill.

Hail often occurs in Colorado. Hail forms within storms as liquid water and freezes in the cold mid and upper levels of the storms. The hailstones are kept aloft by strong updraft winds for a time and then cascade to the ground. In Colorado hailstones vary from pea size around 3/8 of an inch in diameter to softball size around 4 1/2 inches in diameter.

Hailstones can do tremendous damage to crops either as large hailstones or as a large volume of small hailstones that accumulate to a depth of several inches. Large hail damages vehicles and buildings and can be life threatening to animals and people.

The National Weather Service issues severe thunderstorm warnings for winds of 58 MPH or higher or for large hail one inch in diameter or larger. When you hear about a severe thunderstorm warning move to shelter.

When thunderstorms threaten you this severe weather season tune to NOAA all hazards weather radio. Wherever you are during threatening weather plan out the actions you would take if severe weather were to strike.

Guest blog written by Tom Magnuson, Warning Coordination Meteorologist, National Weather Service, Pueblo, Colorado.