Strong winds from a storm push seawater toward the coast, raising the water level far above the predicted tide. This abnormal rise is storm surge. It is often the most destructive aspect of a landfalling hurricane or intense extratropical cyclone.

Surge height depends on wind speed, storm size, forward speed, angle of approach, and the shape of the coastline and seafloor. Shallow continental shelves and funnel-shaped bays amplify the surge. Waves on top of the elevated water add further destruction. Historical disasters such as the 1900 Galveston hurricane and Hurricane Katrina demonstrated the lethal potential of storm surge.

Forecast models combine meteorological predictions with coastal bathymetry to estimate surge. Evacuation decisions for low-lying areas rest heavily on these forecasts. Climate-driven sea-level rise is increasing the baseline upon which surge builds, so that future storms will produce higher water levels even if the storms themselves do not intensify.

• Abnormal sea-level rise driven by storm winds
• Major cause of coastal flooding and damage
• Amplified by shallow shelves and coastal geometry
• Forecasted to guide evacuations