The National Weather Service issues different types of alerts to communicate varying levels of tornado threat. Distinguishing between a tornado watch and a tornado warning is crucial, as each alert signifies a different situation and requires specific actions. Being informed about these distinctions allows individuals to respond appropriately.
Tornado Watch Explained
A tornado watch is issued when atmospheric conditions are favorable for tornadoes to develop in or near a specified area. This means that while no tornado has been sighted, the ingredients for tornado formation, such as strong thunderstorms with rotating updrafts, are present. The Storm Prediction Center (SPC) typically issues these watches, which can cover a large geographical area, sometimes spanning multiple counties or even several states.
These watches usually remain in effect for several hours, often between four to eight hours, allowing time for conditions to evolve. The presence of strong thunderstorms, large hail, or rapidly changing wind directions at different altitudes can indicate the potential for tornadoes, leading to a watch being issued.
Tornado Warning Explained
In contrast, a tornado warning signifies that a tornado has been sighted or indicated by weather radar, posing an imminent threat to life and property in a specific area. These warnings are issued by local National Weather Service (NWS) forecast offices when there is confirmed evidence of a tornado. This evidence can include a visual sighting from trained storm spotters or law enforcement, or distinct radar signatures such as a hook echo or debris ball, which suggest a tornado is occurring or about to form.
Tornado warnings cover a much smaller, more localized area, typically a city or a single county, and are usually in effect for a shorter duration, often around 30 minutes to an hour.
Knowing the Difference and Staying Safe
The fundamental difference between a tornado watch and a tornado warning lies in the immediacy of the threat. A tornado watch indicates that tornadoes are possible, urging preparedness and monitoring of weather conditions. During a tornado watch, it is advisable to review emergency plans, gather necessary supplies, and identify the safest shelter locations within your home or workplace. Staying informed through local news or a NOAA Weather Radio is also important.
Conversely, a tornado warning means a tornado is imminent or already occurring, demanding immediate action. Upon receiving a tornado warning, individuals should immediately seek shelter in the lowest level of a sturdy building, such as a basement or an interior room away from windows. Mobile homes and vehicles are particularly unsafe during a tornado warning, and occupants should seek more substantial shelter. If caught outdoors with no sturdy shelter nearby, lying flat in a ditch or low-lying area, covering your head, can offer some protection. Alerts are commonly disseminated through NOAA Weather Radio, Wireless Emergency Alerts (WEA) on mobile phones, local television and radio broadcasts, and community sirens.