Severe Storm Lingo

Severe Storm Terminology


A supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. Supercells are typically also classified as severe thunderstorms, and tornadoes most commonly form from these kinds of storms.

Severe Thunderstorm

A very strong thunderstorm in which at least one of the following is present:

  • Hail 3/4 of an inch or greater
  • Winds greater than 58 mph
  • A tornado

A rotating column of air that stretches from the base of a thunderstorm. Upon impact with the ground, strong winds associated with a tornado can kick up dust and debris, and cause great damage.

Straight-line Winds

Strong winds that aren't associated with a tornado, but cause considerable damage.


A frozen form of precipitation consisting of individual balls or lumps of ice called hail stones, produced from cumulonimbus or thunderstorm clouds. A bigger hail stone signifies a longer lifespan within the cloud, which also signifies a strong thunderstorm with strong updrafts. Hail can cause significant damage.

Watches, Warnings, and Advisories

Severe Thunderstorm Watch

A severe thunderstorm watch is issued when there is a possibility that thunderstorms in and near the watch box area may produce the following severe weather conditions:

  • Hail 3/4 of an inch or greater
  • Winds greater than 58 mph
Severe Thunderstorm Warning

A severe thunderstorm warning is issued when a storm with any of these severe weather criteria is approaching the warning area:

  • Hail 3/4 of an inch or greater
  • Winds greater than 58 mph

Severe thunderstorms can and do produce tornadoes.

Tornado Watch

Tornadoes are possible. Remain alert for approaching storms. Watch the sky and stay tuned to NOAA Weather Radio, commercial radio or television for information.

Tornado Warning

A tornado has been sighted or indicated by weather radar. Take shelter immediately.

Prepare For the Extreme

By the time severe weather hits, it's already too late. Disaster preparedness is about having an established safety plan. Whether it's preparedness for floods, earthquakes, hurricanes, or fires, the key to survival in disasters is planning. Use our preparedness section to stay informed, make a plan, and most importantly—remain safe in an emergency.