Tidal range
Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun, by Earth's rotation and by centrifugal force caused by Earth's progression around the Earth-Moon barycenter. Tidal range depends on time and location. Larger tidal range occur during spring tides, when the gravitational forces of both the Moon and Sun are aligned, reinforcing each other in the same direction or in opposite directions. The largest annual tidal range can be expected around the time of the equinox if it coincides with a spring tide. Spring tides occur at the second and fourth (last) quarters of the lunar phases. By contrast, during neap tides, when the Moon and Sun's gravitational force vectors act in quadrature, the difference between high and low tides is smallest. Neap tides occur at the first and third quarters of the lunar phases. Tidal data for coastal areas is published by national hydrographic offices. The data is based on astronomical phenomena and is predictable. Sustained storm-force winds blowing from one direction combined with low barometric pressure can increase the tidal range, particularly in narrow bays. Such weather-related effects on the tide can cause ranges in excess of predicted values and can cause localized flooding. These weather-related effects are not calculable in advance. Mean tidal range is calculated as the difference between mean high water and mean low water.
detectable_format:json_format, keywords:frequency