Why is TN peak tornado season in the spring months?

NASHVILLE, Tenn. (WKRN) — Tennessee is prone to tornadoes at any time of the year, but the spring months are the most likely time for tornadoes to occur. They are also more common in the colder months when the warm and cold air masses clash.

WKRN tornadoes by month
Tornadoes by month since 1811. Data from NWS Nashville.

Most tornadoes occur in March, April, and May. But, the secondary severe weather season is just as important (November to February).

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WKRN severe weather overall setup
WKRN severe weather overall setup

For major severe and tornadic storms, there usually needs to be defined areas of warm moist air and cold dry air. This is separated by the jet stream, and typically peaks in the spring months. This type of setup also occurs in the fall and winter months, when the clash of warmer air and colder air can collide.

WKRN severe weather ingredients
WKRN severe weather ingredients

The severe weather ingredients

Four major components are needed for severe thunderstorms, and they occur very often in the Spring season.

1. Instability
Also known as the increase of solar radiation. This allows air to rise and potentially aid in the development of storms.

2. Moisture
For our region that is the Gulf of Mexico. Moisture is measured in the form of dew points, and how humid or dry it feels to your skin.

3. Lift
That’s defined by either a warm front or a cold front. As one of these fronts lifts over our region, that can allow for thunderstorm development.

4. Wind Shear
Wind shear is a change in wind direction AND speed with respect to height. When there is greater shear in the atmosphere, it can allow for the thunderstorm to tilt, separating the updraft of rising air from the downdraft of the rain and hail. And right in between these two areas is where you can get tornado formation.

WKRN general thunderstorm versus a wind shear driven thunderstorm

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Note the image above to see the differences between a general thunderstorm and a severe thunderstorm. A general storm has a thunderstorm updraft and downdraft altogether. There is no separation, meaning wind shear is weak. A severe thunderstorm will have a separate updraft and downdraft region, allowing for the storm to maintain itself and tilt into the atmosphere.

When all the severe weather ingredients are combined, the weather is set to potentially make the perfect recipe for severe thunderstorms and tornadoes in the spring season.

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