Zooming around with Zoe: Perigean Spring Tide


GREENVILLE, N.C. (WNCT) — There’s a lunar event happening soon that could affect communities living along the Atlantic Coast.

According to NOAA’s high tide bulletin for 2021, higher than normal tides are expected along the mid-Atlantic coast and Alaska beginning this Sunday. The southeast Atlantic coast, including North Carolina, is expected a day later, on Monday and lasting through April 1.

In order to understand why this is happening, you have to know that the gravitational pull of the moon and the sun causes tides. When they are closer to Earth, they exert a stronger force on the oceans and therefore create higher tidal levels.

About once every 28 days, the moon reaches its closest approach to Earth, also known as a perigee. But, only a few times a year does it coincide with a full or new moon, called a Perigean Spring Tide, which is exactly what will be happening.

On Sunday, a full moon will be overhead and by Tuesday, the moon will be at its closest distance to Earth. The combination of the closeness of the moon and alignment of the moon, sun and Earth at full moon increases gravitational pull, causing higher than normal high ocean tides and lower than normal low tides.

In some locations, the difference between a perigean spring tide and a normal spring tide can be over a foot. Luckily for us, no major impacts are expected, but minor flooding in low-lying areas and coastal erosion is possible.

If you’re headed out to the coast next week and notice unusually high or low tides, now you know why!

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