What is a storm surge?

A storm surge occurs when a powerful storm, such as a hurricane or typhoon, drives ocean water toward the coast, raising sea levels far above the normal tide. It is caused mainly by strong onshore winds piling water against the shore, with a smaller contribution from the storm low air pressure allowing the sea to bulge upward. When a surge coincides with high tide, the combined water level, called the storm tide, can be especially destructive. Storm surges are frequently the deadliest aspect of tropical cyclones, flooding low-lying coastal areas rapidly and sweeping away buildings. The severity depends on the storm strength, size, speed, and the shape and depth of the coastline.