Tornadoes
... Tornadoes form from cumulonimbus clouds. Tornadoes are either “weak,” “strong,” or “violent.” About 70% of all tornadoes are “weak,” meaning their wind speeds are no greater than 110 MPH. “Weak tornadoes usually have a thin, rope-like shape. “Strong” tornadoes are usually “classic,” funnel-shaped clouds, while “violent” tornadoes are very large. ... Tornadoes form in the uprising of air into a thunderstorm. ... The conditions that cause tornadoes are frequent among the southern US in the early spring.