Tornado watch vs warning: How is a tornado watch different from a warning - terms explained as destructive tornadoes batter US states

A tornado watch is in effect for parts of northern Alabama, eastern Kentucky, northern Mississippi and central Tennessee until 6 a.m. C.T. Thursday, according to the Storm Prediction Center. Nearly 6 million people are impacted by the watch, which includes Nashville, Tennessee, and Tupelo, Mississippi.

Meanwhile multiple “large and extremely dangerous” tornadoes impacted parts of eastern Arkansas last night (Wednesday 2 April), according to the National Weather Service. One of these tornadoes triggered a rare tornado emergency.

Last night there were nearly two dozen tornado warnings in effect in the central US just after 6 p.m. CDT. But what’s the difference between a tornado watch and warning? Here’s everything you need to know.

Tornado watch vs warning

When weather authorities, mainly the National Weather Service, issue a tornado watch, be prepared. These alerts mean tornadoes are possible in the area under the watch.

Watches mean the conditions favour thunderstorms that can whip up tornadoes and are usually issued for hours at a time. Tornadoes extend from thunderstorms when instability leads to wind variations that support rotation, according to NWS.

This instability comes from warm moist air at ground level mixing with cooler dry air above. Combine this with wind shear, and strong updrafts can start the rotations. These conditions are perfect for a tornado, and when meteorologists detect them, will issue a watch.

When a warning is issued, take action. This means tornado conditions are imminent and have been spotted either by someone on the ground or by radar. Warning areas are typically smaller than those within a watch and are issued for a shorter time period, typically about 15 minutes.