A series of ocean waves with extremely long wavelengths caused by large-scale disturbances of the ocean floor, typically from undersea earthquakes, volcanic eruptions, or submarine landslides. Tsunamis travel at high speeds in deep water and can cause catastrophic destruction when they reach shallow coastal areas.
Category: Weather & Sea Conditions
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Sea StateA description of the condition of the sea surface with respect to wave and swell characteristics, categorised using the Douglas Sea Scale from 0 (calm, glassy) to 9 (phenomenal, waves over 14 metres).Spring TideThe tide with the greatest range between high and low water, occurring approximately every two weeks when the sun, moon, and earth are aligned during new and full moon phases.SwellLong-period ocean waves generated by distant weather systems that travel far from their origin, distinct from wind waves generated by local conditions.Tidal RangeThe vertical difference between the highest high tide and the lowest low tide at a particular location.Trade WindsPersistent easterly winds that blow from the subtropical high-pressure belts toward the equatorial low-pressure belt, from the northeast in the Northern Hemisphere and the southeast in the Southern Hemisphere.TyphoonA mature tropical cyclone that develops in the western North Pacific Ocean, characterised by sustained wind speeds of 64 knots (119 km/h) or greater.
Back to DictionaryEntry updated May 2026