Reading path: Coastal water observation →
Storm effects and the tide
A storm can affect coastal water level through several processes. Wind may push water toward or away from shore, and lower atmospheric pressure can allow sea level to rise relative to the surrounding air pressure. Waves also run up beaches and over structures, creating short-lived water movement that is different from a sustained change in the underlying level.
The astronomical tide continues during a storm. The level observed at a coast therefore reflects the tide combined with weather effects and local geography. Shallow bays, harbors, and open coasts can respond differently to similar winds. A high-water observation during a storm is not enough to tell which contribution was largest.
Compare observations with predictions
Use a fixed, safe reference such as a marked public gauge or a stable shoreline feature viewed from a safe position. Record the time and observed level, and compare it with the tide prediction for the closest relevant station. NOAA Tides and Currents provides official U.S. tide predictions and, at selected locations, water-level observations and coastal condition information. Check that the station actually represents your site.
For example, if the observed level is higher than predicted around the same tidal phase over several readings, storm-related effects may be contributing. A single difference could also reflect an imperfect station match, wave runup, timing error, or local setup. Keep the predicted value and observed value separate in your notes rather than calling one “the storm level.”
Include wind and pressure context
Record wind direction and strength from a reliable nearby observation when available, along with pressure trends and the time of any storm passage. Onshore winds may pile water against some coastlines, while offshore winds can have a different effect. The response depends on coastline orientation, bay shape, and water depth, so a direction that raises levels at one site may not do so elsewhere.
Distinguish a sustained water level from waves reaching farther up the shore. A wave crest can briefly cross a reference point even if the still-water level has changed little. If a gauge is available, its time series is more useful for this comparison than occasional visual checks. Do not approach flooded, exposed, or wave-washed areas to gather observations.
Describe local variability
Compare several storm periods or compare a storm interval with calm days at similar tide stages. Note the station, method, prediction source, wind, and pressure context. NOAA’s coastal inundation information covers selected areas; availability and representativeness vary by location, so treat it as contextual evidence rather than a universal coastal record.
A careful summary might read: “Observed water levels exceeded the nearby prediction during the onshore-wind interval; the gauge is several kilometres from the beach, so local setup may differ.” This states the evidence and its limits. A consistent record can clarify how storms and tides combine at one coastline without assuming that another shore will respond in the same way.
Sources & further reading
Have a correction or a source to suggest? Send a note →