tornado

A tornado is a violently rotating column of air that extends from a thunderstorm to the ground. It is often visible as a funnel cloud, though a funnel is not required for a tornado to exist. Tornadoes can cause severe damage along a narrow path of destruction, driven by intense winds and flying debris.

Most tornadoes form from supercell thunderstorms that possess a rotating updraft called a mesocyclone. Wind shear near the surface and aloft tilts horizontal rotation into a vertical orientation, which can intensify as the storm organizes. The tornado itself is a vortex of rapidly rotating air, whose contact with the ground concentrates wind and debris into a destructive corridor.

Structure and size vary widely. Diameters commonly range from tens to hundreds of meters, though they can be wider. Path lengths span from a few hundred meters to tens of kilometers. Lifespans are typically minutes, but some persist for an hour or more. Tornadoes are often accompanied by a debris cloud and a localized damage pattern.

Intensity and measurement: Modern assessments use the Enhanced Fujita scale, rated EF0 through EF5, based on observed damage. Wind estimates are inferred from destruction rather than direct speed measurements: EF0 corresponds to about 65–85 mph, EF5 to over 200 mph. Doppler radar helps detect rotation, while post-storm surveys refine estimates. Warnings and watches are issued by meteorological agencies to inform the public.

Geography and risk: Tornadoes occur worldwide but are most frequent in the United States, particularly in the region known as Tornado Alley, with higher incidence in spring and early summer. They also occur in Canada, Europe, Australia, and parts of Asia, with regional seasonal patterns.

Safety: If a tornado warning is issued, seek shelter immediately in a sturdy building, moving to a basement or interior room on the lowest floor, away from windows and heavy objects. In a mobile home, seek more solid shelter if possible. If outdoors, lie in a low area and cover the head; never seek shelter under overpasses.