Severe Weather / Tornado
The National Weather Service defines a Severe Thunderstorm as a thunderstorm that
(1) produces a tornado,
(2) has winds of at least 58 mph (50 knots or ~93 km/h), and/or
(3) has hail at least 1 inch (quarter sized) in diameter.
Structural wind damage may imply the occurrence of a severe thunderstorm. A thunderstorm wind equal to or greater than 40 mph (35 knots or ~64 km/h) and/or hail of at least ½ inch is defined as approaching severe.
A tornado is a violently rotating column of air that extends from a thunderstorm to the ground and is often—although not always—visible as a funnel cloud. Lightning and hail are common in thunderstorms that produce tornadoes. Tornadoes cause extensive damage to structures and can disrupt transportation, power, water, gas, communications, and other services in its direct path and in neighboring areas. Related thunderstorms can cause heavy rains, flash flooding, and hail.
About 1,200 tornadoes hit the United States every year, approximately 3-5 per year in Maryland, but every state is at risk. Most tornadoes in the United States occur east of the Rocky Mountains with concentrations in the central and southern plains, the Gulf Coast, and Florida.
Tornadoes can strike in any season, but occur most often in the spring and summer months. They can occur at all hours of the day and night, but are most likely to occur between 3 p.m. and 9 p.m.
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