The perigee (closest) full moon, which happens once every 14 months, is happening this weekend. To be exact, the full moon peaks on early Sunday morning (7:32am), June 23rd, and this full moon will be the closest and largest full moon of the year. In fact, this will be the moon’s closest encounter with Earth until August 2014. On Sunday, the moon will appear bigger and brighter and be about 221,824 miles away from Earth - which is roughly 30,000 miles closer than when it is at is farthest location way from Earth.
The term supermoon has been used to describe this upcoming full moon and it seems the going definition for supermoon, coined by an astrologer in the late 1970’s, is as follows: a new or full moon which occurs with the moon at or near (within 90% of) its closest approach to Earth in a given orbit (perigee). During a supermoon, the sun, Earth and moon are aligned with the Earth in the middle. Using this definition, there are 4-6 supermoons per year on average, but this year has only three (May, June and July) and the other two in 2013 did not (or will not) occur during a full moon. This month’s supermoon can be considered the supermoon among supermoons for 2013 or, if you want to sound more technical, a super-duper moon.
How about the effect on tides? Gravitational forces exerted on the Earth by the moon and sun cause our planet’s ocean tides to rise and fall and the high tide during this supermoon will be a couple of inches more than what it is during a normal moon. All full moons bring higher-than-normal tides and perigee full moons bring the highest (and lowest) tides of all. However, the boost in high tides is not likely to cause any flooding problems at the shore unless there happens to be a strong weather system to accentuate the effects – and this appears unlikely for the Mid-Atlantic region this weekend.