Research Briefs

Modeling study captures deadly tornado outbreak

NCAR scientists have performed one of the most detailed simulations ever of a massive tornado outbreak

Satellite image of southeastern U.S. with swirling storms.

The deadliest tornado outbreak in the United States since 1974 occurred over April 27–28. This image, from NASA's GOES satellite, shows the storms on April 27 at 1:45 p.m. Central Daylight Time. (Image courtesy NASA.)

NCAR scientists have performed one of the most detailed simulations ever of a massive tornado outbreak.

In late April 2011, an extremely violent spate of tornadoes, dubbed the Super Outbreak, tore a path of destruction through the southern and eastern parts of the United States, making April 27 the deadliest U.S. tornado day since 1925. Especially hard hit was Alabama, where a series of supercell storms and accompanying tornadoes resulted in 239 deaths.

The research team, led by Wanli Wu and Yubao Liu, used an advanced weather forecasting system built on the NCAR-based Weather Research and Forecasting model. They simulated two waves of tornadic storms that occurred on April 27 in Alabama. The experiment tested the model’s ability for fine-resolution precision forecasting.

The model successfully captured the severe storm system that moved through the study area, the supercell vortices that spun off some of the tornadoes, and the waves of tornado-like damaging winds. Whereas many past tornado studies have targeted individual tornadoes, this one simulated the widespread, massive collection of tornadoes observed in both the morning and evening hours. Although predicting the precise timing and locations of individual tornadoes remains a challenge, the model’s fine resolution of 300 meters (328 yards) captured many tornadogenesis processes and features, such as strong updrafts and downdrafts, along with the overall storm system.