Perigean spring tide

A perigean spring tide is a tide that occurs three or four times per year when a perigee (the point nearest Earth reached by the Moon during its 27.3-day elliptic orbit) coincides with a spring tide (when the Sun, the Moon, and Earth are nearly aligned every two weeks).^[1] This has a slight but measurable impact on the spring tide, usually adding no more than a couple of inches.^[1]