Straight line winds can be as damaging as a tornado. This
image is from a park in Tennessee. (NWS)
During the spring and summer months in Colorado, a wide array of severe weather can strike. Tornadoes may grab all the headlines, but straight line winds and hail can do a great amount of damage in their own right - and they are more common.
Straight line winds are winds out of a thunderstorm and are classified as severe when they hit 58 mph. These winds can reach tornado and hurricane force and as a result, cause property damage and can injure and even kill animals and humans. These winds are usually the result of air cooling rapidly due to precipitation or evaporation. As the cooler air is heavier than the surrounding warmer air, it rushes downward, accelerating toward the ground and spreads out as it hits, much like pancake batter being poured onto a griddle.
These winds can exceed 100 mph which obviously present a danger to life and property. Flying debris picked up by the winds can wreak havoc. Airports and pilots need to be aware of these conditions and precautions are usually taken when these conditions exist.
Microbursts can be particularly hazardous to airports. (NASA)
One term many of you may have heard is microburst - this is a straight line wind less than 2 ½ miles across. If it is more than 2 ½ miles across, it is called a macroburst.
Because these winds are so strong, the damage from them can oftentimes be mistaken as a result of a tornado. When the National Weather Service inspects such damage, they look for telltale signs to determine what the real cause is. A tornado due to its rotating nature will throw debris in a circle and haphazardly. Straight line winds are just as the name implies - straight - so the damage will be in a straight pattern out from where it initially strikes the ground. The image at the top right depicts just this situation when an 80mph straight line wind struck a park in Tennessee.
Another thunderstorm threat that almost everyone in Colorado is familiar with is hail. Hail is quite simply frozen water that is held aloft by the updraft winds of a thunderstorm, going up and down, getting bigger and bigger until it simply weighs too much to stay in the air. Small, pea-sized hail is pretty common in Colorado but softball sized can and does happen.
This is the largest recorded hail stone which is more than 7
inches in diameter and fell in Nebraska in 2003. (NOAA)
Oftentimes clouds will exhibit a green color cast when hail is present and small hail can be the harbinger of bigger stones to come so it is always wise to seek shelter when hail if falling, even if it doesn’t seem that bad. The bigger hailstones provide a great risk for crops, property and can result in injury and death.
How big can hail get? On June 22, 2003 in the south central Nebraska town of Aurora, the world’s largest hailstone fell. This stone measured a whopping 7 inches in diameter and over 18 inches in circumference! See the picture at right or click here for more information.
The National Weather Service issues severe thunderstorm warnings for winds of 58 mph or higher and for large hail 3/4 of an inch in diameter or larger. Realize that some storms are capable of much larger hail and much higher wind so when you hear about a severe thunderstorm warning, seek shelter.
This is the third in a five part series on Colorado’s severe weather as part of Colorado Severe Weather Awareness Week.
Comments
Hey, learned a new term: "Straight line winds" Thanks, Tony. We actually had hail this morning here in Mathews County, VA.
I'd not heard of straight line winds either.
We've had microbursts here, often the media will call them "mini tornadoes".
The hail in that video was incredibly forceful.
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