What are some warning signs of a tornado?

April 30, 2012 Print Friendly and PDF

While tornadoes can happen in any state in the nation, and at any time of the day or night, the greater likelihood for tornadoes to occur is on a hot, sticky day during the summertime. It is these conditions, along with daily sunshine, that causes daytime heating to create unstable conditions and massive convective wind currents building vertically into the atmosphere. These vertical wind currents develop into towering cumulus clouds and thunderstorms. While not all thunderstorms are severe, all thunderstorms are dangerous and can develop tornadoes.

Tornadoes may develop from thunderstorms when warm, moist air is in advance of eastward-moving cold fronts. Watch for skies that turn suddenly dark and greenish (a phenomenon caused by hail) and increasing wind speeds. Keep a particular lookout for the formation of funnel clouds.

  • Large Hail
    Tornadoes are spawned from powerful thunderstorms that often produce large hail.
  • Calm before the Storm
    Often just prior to tornado touchdowns, the winds may die down and the air may become very still; clear, sunlit skies are not uncommon behind a tornado.
  • Clouds of Debris
    Approaching debris clouds can mark a tornado’s location, even if a funnel is not visible.
  • Funnel Clouds
    A visible rotating extension of the cloud base is a sign that a tornado may develop. Tornadoes are evident when one or more clouds turn a greenish color and a dark funnel descends.
  • Roaring Noise
    High winds can cause a roaring sound often compared with a passing freight train.

More information about the science of tornadoes is available from the National Weather Service.

Related frequently asked questions:

What is a tornado?

What should I do during a tornado watch?

What is the Fujita Scale for tornadoes?

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