DULUTH, MN– Severe Weather Awareness week continues Tuesday with the topics of lightning, hail and damaging winds.
There are certain criteria that need to be met in order to have a thunderstorm be classified as severe:
-Wind gusts in excess of 58 mph
-Hail size of 1″ in diameter (the size of a Quarter)
Not all thunderstorms become severe, but all thunderstorms produce lightning. Each year, an average of 47 people are killed each year, with several hundred more injured. It is important to know the following tips if thunderstorms are approaching your area:
-No place outside is safe, so seek shelter inside a sturdy structure or vehicle if you hear thunder
-If you hear thunder, you are close enough to be struck by lightning
-After you hear the last crack of thunder, stay inside your safe shelter for at least 30 minutes
If you are caught outdoors and can’t reach a sturdy structure or vehicle, here are some ways that can reduce your risk of being struck:
-Get off any higher elevated areas
-Never lie completely flat on the ground
-Never seek shelter under trees that are isolated, near bodies of water or any objects that conduct electricity, such as power lines or barbed-wire fences
If you seek shelter inside, that’s a great place to be, but you can still be struck indoors if you are not careful. If indoors:
-Stay away from windows and doors
-Don’t use any objects that are corded or plugged into an electrical outlet
-Avoid using any plumbing, such as the shower, toilet and sinks
Thunderstorms can be strong enough to produce hail. According to the National Weather Service (NWS), hail is formed when updrafts within the thunderstorm carry raindrops up into the higher levels of the atmosphere, where it is extremely cold, and the drops form into balls of ice. The hail can grow in size and that is dependent on the strength of the updraft, as it can continue to lift the drops higher up in the cloud if the updraft is strong enough. Once it becomes heavy enough to overcome the strength of said updraft, that’s when the hail falls to the ground.
On average, hail has caused upwards of a billion dollars per year in property damage.
While most hailstones are rather small, usually about the size of a pea or marble (0.25″-0.50″ in diameter), hail can be as big as baseball or even up to softball size. The largest hailstone ever recorded was in Vivian, South Dakota on June 23, 2010, where a piece of hail measured 8″ in diameter!
The bigger sized hailstones can fall over 100 mph, and those are the hailstones that can injure, or even kill people.
For the NWS to issue a severe thunderstorm warning, hail needs to be at least 1″ in diameter, which is the size of a quarter.
Some thunderstorms can produce damaging, straight-line winds instead of hail, but can be just as destructive as hail.
Winds need to be in excess of 58 mph for it to become severe. In cases where you have a line of severe thunderstorms and the storms begin to “bow out”, you can get the straight line winds that can approach 70, 80, OR even up to 100 mph. In these cases, treat the damaging winds as you would a tornado and seek shelter.
Downbursts can occur when rain-cooled air accelerates to the ground, and can produce damaging winds.
Wednesday’s topic will be on flooding.