Severe weather types

Severe weather takes many forms. Some of the most common include damaging winds, large hail, and tornadoes. Each can have devastating impacts.

Hail stones comes in many shapes and sizes, depending on the strength of the thunderstorm. The size of the hail is directly related to the strength of a thunderstorm’s updraft of warm, moist air. As super-cooled water droplets begin to collect and freeze onto an ice pellet thousands of feet above the ground, it will start falling toward the surface as gravity takes over. If that aforementioned updraft of air is stronger than gravity’s pull, the newly-formed, small hailstone will be tossed upward into the subfreezing thunderstorm over and over again. As it’s tossed upward, it will collect more and more water, which keeps refreezing, eventually creating a larger stone. This process continues until the stone’s weight becomes too heavy for the updraft and it falls toward the ground. Sometimes hail can be as big as golf balls, baseballs, or even grapefruit. The largest hail stone ever reported in our area was 4.5″ in diameter. That’s the size of a softball! It happened in Hartford City back in April 2001.

Another damaging form of severe weather is a microburst. Microbursts create a path of damage with strong wind gusts, some as high as 160 mph (EF-4 tornado strength)! As precipitation falls from a thunderstorm, rain-cooled air can collect above the surface. This building pool of cold air can rapidly fall toward the surface because it is much more dense than the warm air underneath it. When this rapidly accelerating air hits the ground, it fans out in all directions and damaging winds occur.

And of course, there are tornadoes. These violent, but natural, forces of nature often damage, injury, and even death. For tornadoes to develop, you need 3 key ingredients: 1) lots of instability in the atmosphere, 2) increasing wind speed with height, and 3) changing wind direction with height. The most favorable conditions for tornadoes often feature winds at the surface out of the south or southeast. Winds thousands of feet above us should be stronger and out of a more westerly direction. This change in wind speed and direction with height will then cause a column of horizontally rotating air. Inside a severe thunderstorm’s strong updraft, this rotating column can then be tilted vertically. As this column of air spins faster, rain and hail can cause the end to tilt back down. If it touches the ground, then you have a tornado. If it doesn’t reach the ground, it would just be classified as a funnel cloud. Tornadoes are such small-scale features that it’s impossible for computer models to show exactly where they will be. But, we can determine if and when all the ingredients are in place and where tornadoes may be possible.

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