The extra height a storm adds to the sea, found by subtracting the astronomical tide from the observed level. Onshore wind stress piles water against the coast and low pressure lifts the sea surface, with the effect amplified over wide, shallow shelves and in funnel-shaped bays. Surge can reach several metres in hurricanes and typhoons, and its timing relative to high tide decides how much flooding occurs.
Model has 1.5 metres of storm surge peaking near low water, so we may get away with it this time.
Surge figures sound dramatic, but what floods is the storm tide; always ask when the surge peaks relative to high water.
Also heard as
- surge
- positive surge
Do not mix it up with
- Storm tide: Storm surge is the extra water caused by the storm; storm tide is the total level, surge plus astronomical tide.
Related terms
Storm tide
The full water level reached in a storm: astronomical tide and storm surge added together.
Residual
The observed water level minus the predicted tide, showing the effect of weather, rivers and other non-tidal causes.
Inverse barometer effect
The rise of sea level under low air pressure and fall under high pressure, about 1 cm per hectopascal.
Set-down
A drop in water level below the predicted tide caused by winds blowing water away from the coast.