Recent study shows energy in the atmosphere needed for thunderstorms has increased over the years in central Illinois

Published: Sep. 23, 2022 at 7:06 PM CDT
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PEORIA (25 News Now) - As we enter the fall season, we essentially enter our second severe weather season. This map shows the number of total tornadoes that occurred in September, October, and November from 1950 through 2021. One study from Climate Central shows that the potential for thunderstorm development over the years has increased across central Illinois. The way this study evaluated this was by a parameter called CAPE. CAPE is an acronym for Convective, Available, Potential Energy (to help explain, you can replace the word CAPE for “thunderstorm fuel”).

Total through September, October, and November is 59.
Total through September, October, and November is 59.(25 News First Alert Weather Team)

It is a parameter used by meteorologists to determine the potential for thunderstorm development in a given day. Ed Shimon, Warning Coordinator Meteorologist from the National Weather Service, explained it as “The measure of the difference in temperature and moisture between the ground level and the temperatures aloft.” So the more drastic the temperature and moisture difference between the surface and the upper atmosphere, the higher the CAPE. The higher the CAPE leads to, “The higher the potential of severe weather is there. It’s one of the parameters that definitely is a major portion of our determination of whether severe weather can occur” said Shimon.

The study shows that we are having more days with this CAPE parameter being present, which means our daily chances for thunderstorm development is increasing. This is because as our climate warms, warmer air can hold more moisture. So the air at the surface is getting warmer and more humid, so comparing this to the upper atmosphere, the difference can become more drastic leading to more CAPE (the upper atmosphere is colder and drier).

Credit to Climate Central 2022
Credit to Climate Central 2022(Climate Central 2022)

In regard to the picture, “1000 J/kg” is a CAPE value that thunderstorms typically have and it is measured in Joules per kilogram (energy per 1 kg mass of air). Dr. Robert Trapp, a professor of atmospheric science at the University of Illinois Champaign-Urbana and national expert listed on the study, said “The future will tend to be accompanied by an increase in severe weather, an increase in frequency of severe weather for certain parts of the country including central Illinois.”

Summer is our most active severe weather season, but no matter the season, severe weather can happen anytime. Heading into fall and winter, trends have shown a jump in severe weather in November and December, especially over the past 10 years. Shimon added, “Our fall season does not mean severe weather will go to the way side, actually quite the contrary. We have a secondary bump of severe weather occurrences in November and December.”

Tornadoes are most common between May and August, but there has been an increase in November...
Tornadoes are most common between May and August, but there has been an increase in November and December.(National Weather Service Lincoln, IL)

It’s important to keep in mind, the increase in these days according to climate models is small. Dr. Trapp explained, “A day per year of an increase, so it’s not like in ten years were going to see severe weather on every day during the winter season.” But these days do hold weight, and have the potential to develop large severe weather outbreaks like we saw on December 10th, 2021.

Always be ready for severe weather no matter the season because the central Illinois climate allows for it to happen at any time throughout the year. Also, make sure you have a safety plan heading into fall and winter, whether it’s for damage to your house from strong winds, flood coverage, or knowing where to take shelter from a tornado.