The United States uses a system of weather alerts to communicate the potential for dangerous atmospheric conditions. These alerts provide time for preparation and action when severe weather, such as tornadoes, is possible or imminent. Understanding the difference between advisories is essential, as each one signals a different level of threat and requires a distinct response. The most common alerts related to tornadic activity are the Watch and the Warning, which represent two separate phases of a developing severe weather event.
Defining a Tornado Watch
A Tornado Watch is an alert issued when atmospheric conditions are favorable for tornadoes to develop in a specified area. This does not mean a tornado has been spotted or is actively occurring, but that the ingredients for severe weather are present. This determination is made by the Storm Prediction Center (SPC), a branch of the National Weather Service (NWS), which analyzes meteorological data for the entire country. The SPC looks for signs of instability, wind shear, and moisture that can fuel powerful supercell thunderstorms.
The geographical area covered by a Watch is typically large, often encompassing numerous counties or multiple states. These alerts are generally issued well in advance of severe weather forming and are usually in effect for several hours, often lasting between four and eight hours. The issuance of a Tornado Watch signals a “Be Prepared” phase, giving people time to review safety plans before any immediate danger exists.
The Difference Between a Watch and a Warning
The distinction between a Tornado Watch and a Tornado Warning centers on the difference between potential and actuality. A Watch signifies that conditions are possible for a tornado to occur, prompting preparation. This alert is issued by the centralized Storm Prediction Center using broad-scale meteorological models and forecast data.
A Tornado Warning is an urgent alert signaling that a tornado is either imminent or already occurring, representing an immediate danger to life and property. This alert is issued by local NWS forecast offices when a tornado has been sighted by trained spotters or indicated by Doppler radar. Warnings cover a much smaller area, usually the size of a city or small county, and typically last around 30 minutes. The public response shifts from preparation to immediate action and taking shelter when a Warning is issued.
Immediate Actions to Take When a Watch is Issued
When a Tornado Watch is issued for your area, the focus should be on proactive preparation and heightened vigilance. This is the time to gather information and ensure everything is ready should the threat escalate to a Warning.
Preparation Checklist
When a Watch is issued, take the following steps:
- Check multiple sources for weather updates, such as a NOAA weather radio, local news broadcasts, or reliable weather apps.
- Identify the safest place in your home, typically a basement, storm cellar, or a small, interior room on the lowest floor away from windows.
- Gather emergency supplies, including water, a flashlight, a first-aid kit, and protective items like a bicycle helmet or heavy blankets, and keep them easily accessible.
- Secure any loose objects outside, such as patio furniture or garbage cans, which could become hazardous flying debris in high winds.