A tornado is a violently rotating column of air extending from a thunderstorm down to the Earth’s surface. These destructive weather phenomena develop rapidly, often forming within minutes, making quick detection and immediate action crucial for survival. While intense tornadoes can exceed 250 miles per hour, even weaker ones cause significant harm. Preparedness requires understanding the systems and signs designed to alert the public to imminent danger.
Reliable Warning Systems
Official warnings are primarily issued by the National Weather Service (NWS) and disseminated through layered technology.
The NOAA Weather Radio All Hazards (NWR) is a highly reliable method, broadcasting continuous weather information directly from the NWS office. Many NWR receivers feature Specific Area Message Encoding (SAME) technology, allowing them to automatically alert users for warnings specific to their county, even while they are sleeping.
The Wireless Emergency Alert (WEA) service is another widely used system. It sends geolocated, text-like messages directly to all compatible cell phones within a defined threat area. These alerts are broadcast from cell towers and provide near-instantaneous notification of a serious threat without requiring a subscription or tracking specific user locations.
Communities also utilize outdoor warning sirens, activated during a Tornado Warning to alert people who are outside. These sirens are specifically engineered to be heard outdoors and are not designed to penetrate the walls of a home or business. Relying solely on sirens while inside is insufficient, underscoring the need for multiple alert sources like NWR or WEA.
Physical Signs of an Approaching Tornado
A person’s senses can provide crucial, immediate indicators that a tornado is forming or nearby.
One common visual cue is the presence of a wall cloud, a localized lowering of the rain-free base of a thunderstorm. If this lowered cloud base begins to visibly rotate, it signals a heightened risk of a tornado forming within the next 10 to 20 minutes.
The most obvious sign is the funnel cloud, a rotating column of air extending from the cloud but not yet touching the ground. When this column makes contact with the ground, it officially becomes a tornado, often made visible by a swirling cloud of debris and dust at its base. This debris cloud signals an active tornado even if the condensation funnel is obscured by rain or low-hanging clouds.
The sky can take on unusual coloration, sometimes appearing dark green or yellow, likely caused by light scattering through large hailstones within the storm. An approaching tornado is frequently preceded by large hail and a sudden shift in the atmosphere. Auditory warnings are distinct; the continuous, low-pitched sound of a fully formed tornado is often compared to the loud roar of a freight train or jet engine.
Distinguishing Between a Tornado Watch and Warning
The NWS uses two primary terms to communicate the level of tornado threat, and understanding the distinction dictates the appropriate response.
A Tornado Watch means that conditions are favorable for tornadoes to develop in or near the watch area over the next few hours. This is the time for preparation, such as gathering emergency supplies, identifying a safe room, and monitoring official weather sources.
A Tornado Warning is a far more serious alert, meaning a tornado has been sighted by human spotters or indicated by Doppler radar. This signifies imminent danger to life and property and covers a much smaller, more specific area than a Watch. Warnings typically last around 30 minutes and demand immediate protective action. Upon receiving a Tornado Warning, you must seek shelter immediately.