When severe weather is forecast, the National Weather Service (NWS) uses specific alerts to communicate the level of threat to the public. Understanding these terms is essential for safety and minimizing risk. Alerts like the Tornado Watch are designed to give people a head start on preparing for potentially dangerous conditions.
Defining a Tornado Watch
A Tornado Watch is an alert issued by the Storm Prediction Center (SPC) of the National Weather Service when atmospheric conditions are favorable for the development of tornadoes in a designated area. This means that while a tornado is possible, one has not yet been sighted or indicated by radar. The watch area typically covers a large region, often encompassing numerous counties or even multiple states, accounting for the broad potential for severe storm development.
The issuance of a watch is a signal to “Be Prepared,” indicating that the ingredients needed for tornadic thunderstorms—such as sufficient moisture, atmospheric instability, and wind shear—are present. Watches are generally issued well in advance of any severe weather, typically lasting between four to eight hours. This timeframe provides the public with several hours of lead time to finalize safety plans before the severe weather is expected to begin.
Watch vs. Warning: Understanding the Difference
The primary confusion point for the public lies in the distinction between a Tornado Watch and a Tornado Warning, which is based on immediacy and threat level. A Tornado Watch means that tornadoes are possible in the area, advising residents to review their safety plans and remain vigilant. It is a heads-up that conditions are conducive for severe weather to form, but the danger is not imminent.
In contrast, a Tornado Warning means that a tornado has been sighted by trained spotters or indicated by Doppler weather radar, signifying imminent danger. Warnings are issued by the local NWS office and cover a much smaller, specific area, often lasting for only about 30 minutes. The action required shifts from “Be Prepared” during a watch to “Take Action” during a warning, demanding that people immediately seek safe shelter.
Preparation and Action Steps During a Watch
When a Tornado Watch is issued, the main goal is to use the lead time to prepare for the possibility of a warning being issued later. Immediate steps should include monitoring weather information through multiple reliable sources, such as a NOAA Weather Radio with a battery backup or local media broadcasts. This ensures you can receive a warning immediately if the situation escalates.
Families should use the watch period to review their emergency plan and confirm the location of their safe room, such as a basement, storm cellar, or an interior, windowless room on the lowest floor. Important supplies should be gathered and placed in or near the shelter location, including a first aid kit, water, non-perishable food, and flashlights.
It is also advisable to ensure that all mobile devices and power banks are fully charged in case of power outages later in the storm. Proactively securing outdoor items that could become projectiles in high winds, such as patio furniture, should also be completed during the watch. Having a bicycle or motorcycle helmet readily available is a simple, effective measure to protect the head from flying debris should a warning be issued.