The Proxigean Tide occurs when the Moon is at its closest point in its orbit to the Earth and in its New or Full Moon phase. At this time, its tidal effect on the Earth is maximum. Tidal gravitational forces vary as the third power of the distance between Earth and Moon, so even a small difference in distance can translate into a big effect. The orbit of the moon varies from a distance of 356,500 to 406,700 kilometers with an average distance near 380,000 kilometers. The variation between the maximum and minimum distances results in tidal force changes of a factor of 1.2 times the average tidal forces.

Visit the Lunar perigee and apogee calculator to calculate these distances yourself!

The times when this will happen often coincide with major coastal flooding events. Between 1997 and 2020 there will be 102 times when this will happen. You can see the list by looking at Fergus J. Wood's book Tidal Dynamics published in 1978 by D. Reidel Publishing company, Dordrecht Holland. There are tables computed by van Flandern at the U.S. Naval Observatory. Here is a short list of the most extreme events based on the time between perigee and syzygy being less than 5 hours:

Date            Phase


3/11/2003         New
1/10/2005         New
2/28/2006         New
12/12/2008        Full
1/30/2010         Full
3/19/2011         Full
5/6/2012          Full
6/23/2013         Full
8/10/2014         Full
9/28/2015         Full
11/14/2016        Full
5/25/2017         New
1/2/2018          Full
7/13/2018         New
8/30/2019         New
10/16/2020        New
12/4/2021         New
1/21/2023         New

New Moon is pretty bad because both the Sun and the Moon are on the same side of the Earth, and with the Moon near its closest point to the Earth, the tide- making potential is highest. I will probably not plan to be on the beach on the above dates!

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