What are Thunderstorms ?

A thunderstorm is a cumulonimbus cloud that produces thunder and lightning. Many times heavy rainfall and gusty winds accompany thunderstorms. Thunderstorms can occur any time of year, although they are most common during spring and summer.

What causes thunderstorms ?

Thunderstorms are generated by instability in the lower atmosphere. Usually warm moist air is forced to rise rapidly to form cumulonimbus clouds. The warm moist air at low levels of the atmosphere can be forced aloft by a front, mountain or daytime heating. If a jet stream disturbance with its cold air pool higher aloft crosses overtop this unstable air, explosive cloud growth can occur. This is usually what happens when severe thunderstorms form. Sometimes the atmosphere is "capped". That means that a warm layer of air exists above the lower unstable air. If this warm layer is strong enough, it will keep thunderstorms from forming.

Where do thunderstorms form ?

Thunderstorms can form at location where sufficient instabitily exists to produce a cumulomimbus cloud. Thunderstorms are rare in the arctic regions due to the lack of warm moist air. They are most common in the tropics where there is an abundance of instability. Severe thunderstorms are most common in the mid-latitudes where the combination of warm moist air and jet stream energy coincide.

Thunderstorm Safety

Severe Thunderstorm Warning - A severe thunderstorm has been observed or has been indicated on radar. Quarter sized hail ( hail at least 1 inch in diameter) or winds 58 mph or stronger have been observed or estimated by weather authorities. Severe Thunderstorm Watch - Conditions are favorable for the formation of severe thunderstorm including large hail, damaging winds, and isolated tornadoes. Stay vigilant.

For more on answers to your questions about weather, check our weather page. Join our weather message board to interact about the latest topics about weather and hurricanes!