Ask the Meteorologist: Thunderstorms

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How can you tell if there will be a thunderstorm before hearing any thunder?

Nadine Clark

Ashland Middle School


There are three things that meteorologists need present in the atmosphere in order for thunderstorms to develop. These are all things that we can find by looking at weather models, or looking at something a little more in depth, known as a sounding. Soundings are produced from radiosondes, or weather balloons that the National Weather Service releases two times daily at stations across the country.

These radiosondes rise through our atmosphere and gather a bunch of data that then gets plotted on soundings and hodographs. This enables us to look at the vertical temperature profile of the atmosphere, the moisture content, and the winds! We can see the strength and direction of the winds through the different layers of the atmosphere.

Typically we need the air to be saturated in the mid levels, meaning the temperature and moisture profiles are close to one another and/or touching (clouds are then present). Clouds must be present in order for thunderstorms to develop obviously! We also look for veering winds with height, meaning the winds must turn clockwise with elevation. There are other parameters that can tell us how unstable the air mass in place is. This means, how much is the air rising? Are particles very buoyant? If CAPE values are high, over 1500 J/kg, we have an unstable air mass. This means there is a lot of warm, rising air. We also look at an index called the LI, Lifted Index. The more negative this is, the better. Negative values between -4 to -7 show signs of an unstable atmosphere.

There are many more parameters and tools that can be used to attest for the potential of thunderstorm activity, these are just a few!

Meteorologist Alyssa Caroprese