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These distinctions are not merely technical. Each hazard requires different preparations. A coastal community threatened by a tropical cyclone may need to consider storm surge and evacuation routes. A neighborhood under a tornado warning needs immediate access to a suitable shelter. A city facing flash flooding must avoid low-lying roads and move away from rapidly rising water.
Tornadoes: small in footprint, potentially devastating in impact
Tornadoes can form when particular combinations of atmospheric instability and wind shear support organized rotation within a thunderstorm. The development process is complex, and forecasters cannot always predict precisely where an individual tornado will touch down.
Some tornadoes are relatively weak and short-lived. Others are violent enough to destroy well-built structures and carry debris over substantial distances. Their paths can be narrow compared with the areas affected by the surrounding storm, but the damage along those paths can be catastrophic.
A tornado warning should prompt immediate action. People should move to a basement or a small interior room on the lowest floor of a sturdy building, away from windows. If no basement is available, a bathroom, hallway, or other interior space may provide a safer option, depending on the building layout.
Protect the head and neck with arms, a helmet, a mattress, or thick blankets if available. Avoid large open rooms with wide roof spans when a safer interior space exists. Mobile homes and vehicles generally offer poor protection from tornadoes; people should follow local emergency instructions to reach a designated shelter when a tornado threat is identified