Rare 'Black Moon' Coming: Its Effect on Oregon / Washington Coast Tides

Published 11/24/24 at 5:45 p.m.
By Oregon Coast Beach Connection Staff

(Manzanita, Oregon) – King tides are over for now. The Super Moon and Full Beaver Moon happened a week and a half ago. There's not even anything major in the wings for the Oregon coast or Washington coast in terms of storms. (Above: Bandon. Night skies should clear soon. Photo courtesy  Manuela Durson Fine Arts).

Yet there is the Black Moon coming up – and it too will be affecting tides along the beaches....in a way.

Think of it as like the anti-king tides, and certainly anticlimactic. Heck, it even means you can't see the moon. Yet this Black Moon thing is kind of rare.

According to Jim Todd, astronomy expert with Portland's OMSI, the second new moon happening within the lunar cycle is called the Black Moon. If you get two full moons within that cycle it's called a Blue Moon. This is the no-moon version of that.

“The next new moon will take place November 30 at 10:21 p.m. (245,793 miles) for the western time zones (Mountain Time, Pacific Time, Alaska Time and Hawaii Time),” Todd told Oregon Coast Beach Connection. “The rest of the world will see it on December 1 and December 30. The new moon is the start of a lunar cycle of 29.5 days, when the moon and sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the human eye, except during a solar eclipse.”

The Black Moon is rare because it only happens every few years – every 29 months to be exact.

Full moon above Manzanita - Oregon Coast Beach Connection

“Just as the Blue Moon is for second full moon, a Black Moon refers to the second new moon in a single calendar month,” Todd said. “The last Black Moon was on July 31, 2019. The Black moon is a name given in 2016 to various new moons or absences of them, within a year. It is not a term used in astronomy and there is no single accepted definition of it. “

So, it's not just a cool Emerson, Lake and Palmer song. How it affects tides is interesting as well: it will rein them in.

See Washington Coast Weather - Oregon Coast Weather (including tides) - Inland Oregon Weather

The moon gets to apogee on November 26 (Tuesday), which is the point where it is at its farthest from Earth. It reaches 251,850 miles away at 3:55 a.m. - not long after midnight on Monday.

“The moons vary in size because of the oval shape of the moon's orbit,” Todd said. “The moon follows an elliptical path around earth with one side ('perigee') about 31,069 miles closer than the other ('apogee'). When the moon is at apogee, the lunar tide-raising force is smaller, and the tidal ranges are less than average.”

Tidal ranges along the Washington coast and Oregon coast become smaller. High tides aren't so big, and low tides are not as low.

King tides are also known as spring tides or officially as Perigean tides – and they lag behind the full moon a bit.

“High spring tides typically follow the new or full moon by a day or so; as always, the variation in your local tide will depend on several factors, including the weather and the shape of your coast,” Todd said.

The moon above Depoe Bay - Oregon Coast Beach Connection.

Even though it's winter here, the sun is actually closing on its nearest to us for the year, and that helps activate king tides.

“When the earth is closest to the sun (perihelion), around January 2 of the calendar year, tidal ranges are enhanced,” Todd said. “At aphelion, when the earth is furthest from the sun, around July 2, tidal ranges are reduced.”

The tide graph below for Garibaldi on the north Oregon coast show some of those differences, with the most distinct examples of smaller tidal ranges a few days after the big tide events or the new moon.

That Black Moon – you could say lack-of-a-moon – comes with other good news for the Washington and Oregon coastlines. The week comes with some good tidings for weather: it's going to be clear and sunny around Thanksgiving. At night, that means good stargazing at times.

Also see What's the Difference Between King Tides and Oregon / Washington Coast Storm Wave Events

“Regardless, enjoy the moonless night sky,” Todd said. “Venus is low west after sunset, Saturn shines in the south most of the night, Jupiter rises in the early evening alongside Taurus and Orion, while Mars trails a couple of hours behind, visible high in the early morning sky.”

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