Storm Surge Estimate Calculator
Storm surge is the rise of the sea above the predicted tide during a storm. Two effects drive it: the low pressure under the storm lifts the sea by roughly 1 centimeter per hectopascal below standard (the inverse-barometer effect), and wind pushes water onto the coast (wind setup), usually the larger part. Wind setup has no universal formula, so this calculator computes the pressure component deterministically and takes the wind setup as your own input, then adds the predicted tide to give a total still-water level. Use official NOAA forecasts for any life-safety decision.
Surge estimate formula
Pressure rise = (reference - central) x 0.01 m per hPa
Estimated surge = pressure rise + wind setup
Total still-water level = surge + predicted tide
Feet = meters x 3.28084
The inverse-barometer rise is about 1 cm per hectopascal of pressure deficit. Wind setup, the dominant term, is a user input because it has no universal closed form and depends on local bathymetry and storm track.
Storm surge notes
- Wind setup usually dwarfs the pressure component for major coastal surge.
- Surge rides on top of the astronomical tide; timing relative to high tide matters.
- Wave run-up adds further height above the still-water level computed here.
- NOAA SLOSH and the National Hurricane Center provide authoritative forecasts.
- Follow official surge warnings and evacuation orders, not an estimate.
Storm surge: frequently asked questions
What is storm surge?
Storm surge is the abnormal rise of sea water above the predicted astronomical tide, driven by a storm. It is caused mainly by wind pushing water toward the shore and, to a lesser degree, by the low atmospheric pressure under the storm lifting the sea surface.
What is the inverse-barometer effect?
The inverse-barometer effect is the rise in sea level under low pressure: the sea surface lifts by roughly 1 centimeter for every 1 hectopascal that pressure falls below the standard 1,013 hectopascals. It accounts for a modest part of total surge; wind setup is usually the larger contributor.
Why is wind setup a user input here?
Wind setup depends on wind stress, fetch, water depth, coastline shape, and storm track in ways that have no single universal formula. Reliable surge prediction uses numerical models like NOAA SLOSH. Rather than fabricate a figure, this tool takes the wind-setup component as a clearly labelled user input.
How do I find total still-water level?
Add the estimated surge to the predicted astronomical tide at the time of landfall: total still-water level = tide + surge. Waves run up on top of this still-water level and add further height. Use official NOAA tide predictions for the tide value.
Where can I get authoritative surge forecasts?
The NOAA National Hurricane Center issues Potential Storm Surge Flooding maps and operates the SLOSH model for surge. Always rely on official forecasts and evacuation orders for life-safety decisions; this calculator is an educational estimate of the pressure and wind components only.
Official sources
- NOAA National Hurricane Center: Storm Surge.
- NOAA Tides and Currents: Tides and Currents.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.