Tornado warning: what it means and how much time you have
A tornado warning means a tornado is happening or about to happen inside the area the warning covers. Go to shelter when it is issued. Don't wait to see or hear it.
Who issues it, and for where
Your local National Weather Service office issues it when radar shows rotation that is likely producing a tornado, or when spotters, police or the public report one. The warning is a shape drawn along the storm's path, usually covering the next 30 to 45 minutes of travel. Counties and towns listed in the text are the ones the shape touches, but only the area inside the shape is warned.
The words in the warning
- Radar indicated: radar shows strong rotation; nobody has confirmed a tornado yet. Plenty of these do produce tornadoes, often hidden in rain or darkness.
- Observed: someone has seen the tornado, or radar shows debris lofted into the air. It is on the ground.
- Damage threat considerable: forecasters expect a strong tornado. You may hear this called a particularly dangerous situation (PDS) warning.
- Damage threat catastrophic: a tornado emergency. A large, violent tornado is confirmed and headed for a populated place. This is rare.
How much time you have
Less than most people think. The average time between a tornado warning and the tornado reaching a place has been under about ten minutes in recent years (Brooks and Correia, "Long-term performance metrics for National Weather Service tornado warnings", Weather and Forecasting, 2018), and some tornadoes form with no warning at all. Nighttime and rain-wrapped tornadoes are the hardest to see coming. That is why the warning is the signal to move, not the sight of a funnel.
The minutes for your own address depend on where you sit in the warning shape. Someone at the far end of a 40-minute warning has much longer than someone at the near edge. TornadoTrack draws each storm cell's projected path with clock times every 15 minutes, and tells you how long you have before you need to start moving, given how long you say it takes you to get to shelter.
What to do
- Go to your shelter now: a basement or storm shelter, or an interior room on the lowest floor with no windows. Where to shelter has the details, including mobile homes and cars.
- Bring your phone, shoes and something to protect your head.
- Stay there until the warning expires or is cancelled for your area. A storm can carry more than one tornado.
- Outdoor sirens are meant for people outdoors. Don't count on hearing them inside.