Perigean spring tide


A proxigean spring tide is a tide that occurs three or four times per year when a perigee coincides with a spring tide. This tide usually adds only a couple of inches to normal spring tides.

Astronomical causes

The Moon's orbit around Earth is elliptical, which causes the Moon to be closer to Earth and farther away at different times. The Moon and the Sun are aligned every two weeks, which results in spring tides, which are 20% higher than normal. During the period of the new moon, the Moon and Sun are on the same side of Earth, so the high tides or bulges produced independently by each reinforce each other. Tides of maximum height and depression produced during this period are known as spring tide. Spring tides that coincide with the moon's closest approach to Earth have been called perigean spring tides and generally increase the normal tidal range by a couple of inches.
The Ash Wednesday Storm of 1962 which inundated the entire Atlantic coastline of the United States from the Carolinas to Cape Cod, resulting in a loss of 40 lives and over 500 million dollars of property damage, coincided with a perigean spring tide.