Climate Matters: Record early spring warmth fuels severe weather

Temperatures between 15 and 30 degrees above normal are forecast across the Central and Southern United States tomorrow, bringing an enhanced risk of severe thunderstorms to the Midwest.

Columbia already broke its record high on Monday, reaching 82 degrees at 4 p.m. local time, which topped the previous record of 80 degrees set on March 9, 1986.

The highest potential for severe weather on March 10 is expected in northeastern Missouri, central Illinois, and northwestern Indiana during the afternoon and evening.

Warm surface temperatures in the region contribute to atmospheric instability, which supports thunderstorm development when combined with moisture and strong winds aloft.

These conditions are driven in part by an increase in Convective Available Potential Energy, or CAPE, which measures the atmospheric energy available for thunderstorms. Global warming has caused CAPE values to rise, especially in the eastern U.S.

Severe weather potential is currently highest in the spring, and data suggests it is increasing. A Climate Central analysis of CAPE trends from 1979 to 2021 found that parts of the Ohio Valley, Kentucky, and Tennessee have experienced 10 to 15 more days with high CAPE values during spring. In summer, some areas of the Northeast have seen an increase of 10 to 15 or more days with CAPE above 1,000 joules per kilogram since 1979.

Overall, days with higher CAPE in the eastern U.S. have become more frequent, while they’ve decreased in the West.

While CAPE quantifies air instability, forecasters note that it is only one factor in the formation of severe weather. Other ingredients, such as the wind shear required to generate tornado spin, have an unclear relationship with rising temperatures.

Despite these complexities, the frequency of storm-producing weather conditions is trending upward. Research also shows that the number of tornadoes occurring in large outbreaks has increased.

The Enhanced Risk for severe thunderstorms is expected to peak tomorrow afternoon and evening. Residents in the affected regions of Missouri, Ill. and Indiana are advised to monitor local forecasts as the storm system moves through the Central and Southern United States.