Tides and Tide Prediction

This tide and tide prediction resource directory links to online tide predictors, tide observations/sea level measurements, tide prediction software you install to generate tide predictions on demand, and general information on tides and tide prediction. Before computers and software, machines, like the one at left, generated tide predictions.

Tides are the alternating rise and fall of sea level with respect to land, as influenced by the gravitational attraction of the moon and sun. Other factors influence tides; coastline configuration, local water depth, seafloor topography, winds, and weather alter the arrival times of tides, their range, and the interval between high and low water. A tide prediction can differ from the actual sea level that will be observed as a result of the tide. Predicted tidal heights are those expected under average weather conditions. When weather conditions differ from what is considered average, corresponding differences between predicted levels and those actually observed will occur. Generally, prolonged onshore winds (wind towards the land) or a low barometric pressure can produce higher sea levels than predicted, while offshore winds (wind away from the land) and high barometric pressure can result in lower sea levels than predicted. Thus mariners need to take local conditions into account when considering critical activities with tide prediction information.

When looking at tide predictions, watch out for daylight savings time if applicable locally to the site of the predictions. Do the tide predictions adjust for daylight savings time? Some play out their predictions only in standard time, so be sure to adjust accordingly if applicable. In the U.S., daylight savings starts 2nd Sunday in March & ends first Sunday in November.
These predictors have worldwide or very large area coverage.

Predictors of Local Interest to San Diego:

Actual sea level measurements -- tide predictions are calculated estimates of sea level whereas observations measure the actual sea level that occurred

not a complete list

© Peter Brueggeman. First published in July 1997.

Photo: Woman professional operating tide prediction machine. Washington, DC, 1944.
Credit: Association of Commissioned Officers. NOAA Historical Photo Collection