Nebraska is a state that experiences a significant number of tornadoes each year, firmly placing it within the region of the central United States known colloquially as Tornado Alley. The state’s location makes it a frequent target for severe weather systems that produce these rotating columns of air. Understanding the nature of this threat, including the frequency and meteorological factors involved, is a necessary part of living in or traveling through the Great Plains. Systems are in place to monitor, warn, and mitigate the potential danger they represent.
Confirmation and Annual Frequency
Nebraska averages between 40 to 50 tornadoes annually, although this figure can fluctuate significantly from year to year depending on atmospheric patterns. The highest concentration of activity tends to occur in the central and eastern portions of the state, where the necessary atmospheric ingredients frequently converge. The peak months for tornado activity fall during May and June, coinciding with the most favorable clash of air masses.
To classify the strength of these events, meteorologists use the Enhanced Fujita (EF) Scale, which rates a tornado from EF0 to EF5 based on the damage it causes. An EF0 tornado causes light damage, while an EF5 tornado is capable of causing incredible destruction, leveling well-built homes. The scale estimates the wind speed based on 28 different damage indicators. Since the rating is based on damage, it is often not assigned until a post-storm survey is completed by National Weather Service personnel.
Factors Contributing to Nebraska’s Tornado Risk
Nebraska’s high tornado frequency is due to its geographic position, which facilitates the collision of three distinct air masses. Warm, moist air flows northward from the Gulf of Mexico, providing the necessary fuel and instability for powerful storms. This moisture then collides with cool, dry air moving eastward from the Rocky Mountains, creating a boundary known as a dry line. A third element, hot, dry air from the high deserts of the Southwest, sometimes moves over the top of the moist air, creating a strong temperature inversion that traps heat and increases instability.
This layering of air masses, combined with changing wind speed and direction with height, known as wind shear, creates the rotational energy needed for supercell thunderstorms. The flat topography of the Great Plains offers an unobstructed path for these air masses to meet. This expansive, open environment allows supercells—large, long-lived thunderstorms with a deeply rotating updraft—to maintain their structure and produce tornadoes.
Safety Protocols and Warning Systems
Public safety relies on two distinct alert levels: a Tornado Watch and a Tornado Warning. A Watch means conditions are favorable for tornadoes to develop, requiring residents to monitor the weather and be prepared to act. A Warning is issued when a tornado has been sighted visually or indicated by Doppler radar, signaling that immediate action is required to seek shelter.
When a Tornado Warning is issued, residents must immediately move to the lowest level of a building, such as a basement or a storm cellar. If an underground shelter is unavailable, the safest location is a small, interior room or hallway on the ground floor, away from all windows. The goal is to put as many walls as possible between occupants and the outside, and to shelter under something sturdy to protect against falling debris.
The public receives alerts through a variety of systems:
- NOAA Weather Radio, which can be programmed to alert for specific counties.
- Outdoor warning sirens, utilized by local communities for a Tornado Warning or confirmed funnel cloud sighting.
- The Emergency Alert System (EAS), which delivers information via television and radio.
- Wireless Emergency Alerts (WEA), which send direct text messages to cell phones.