New moon happens when the moon (in its monthly orbit of Earth) goes more or less between the sun and Earth.
Full moon happens when the moon (in its monthly orbit) is on the opposite side of Earth from the sun.
Perigee – from the root words peri meaning near and geo meaning Earth – is the moon’s closest point to Earth in a month.
So the new or full moon closely coincides with perigee several times each year. When that happens, in the language of popular culture, we have a supermoon.
And the full supermoon of September 18, 2024, will be a Super Harvest Moon plus have a partial lunar eclipse.
Then the full supermoon of October 17, 2024, will be a Super Hunter’s Moon and the closest full supermoon for 2024.
supermoons have the potential to cause higher-than-usual tides. High tides during the full or new moon are called spring tides. High tides during a full or new moon at perigee are called perigean spring tides, or, sometimes, king tides. And nowadays you sometimes hear them called supermoon tides.
These perigean or king or supermoon spring tides tend to follow the date of new or full moon by a day or so. These especially high tides are highly dependent on the shapes of local coastlines and on local weather conditions.
Flooding typically occurs when a strong weather system accompanies an especially high spring tide.
About 3 or 4 times a year, or more often, a new or full moon coincides with the moon’s closest point to Earth, or perigee. There’s usually only a small difference – typically a couple of inches (or centimeters) – between these “perigean spring tides” and normal tidal ranges. But, at these times, if a storm strikes along a coastline, flooding can occur.
The closest full moon supermoon in 2024 will recur after 14 lunar months (14 returns to full moon) after the closest full supermoon of 2023. That’s because 14 returns to full moon almost exactly equal 15 returns to perigee, a period of about one year, one month, and 18 days.
In 2024, there will be 5 new supermoons in a row from January to May. And there will be 4 full supermoons in a row from August to November. The closest full supermoon will be October 17.
