Central Coast Weather: Supermoon, Ocean Tide Change Forecast


Sean Lindsey poses in front of a supermoon along the Central Coast.

About every 2.7 years, we get two full moons or two new moons in a calendar month. A blue moon is the second moon of the month.

In January 2018, we experienced two supermoon occurrences. The first, called a wolf moon, occurred on New Year’s Eve and was followed by another supermoon on January 31 – a rare combination of red and blue moon, thanks to a partial lunar eclipse.

What is a Super Moon? This occurs when the Earth’s orbit around the sun is an oval, and the moon’s orbit around the Earth is also. The moon is about 30,000 miles closer to Earth at perigee than at apogee when farther away.

Thus, when the full moon or a new moon coincides with the perigee, it is called a supermoon. A full supermoon appears larger and brighter than usual.

All these different moon names piqued my curiosity: How many names are there?

Well, according to the Old Farmer’s Almanac, each full moon of the month has its own nickname.

“The June full moon — usually the last full moon of spring or the first of summer — is traditionally called the Strawberry Moon,” according to the Almanac.

This name was used by natives to mark the ripening of June strawberries ready to be picked.

In Europe, the wedding traditionally took place in June – hence the alternative term “honeymoon”.

This year’s Strawberry Moon will rise on Thursday evening. And the male moon will arrive on July 4th.

In August, the full moon is called a sturgeon moon, named after the large number of lake sturgeon where the Algonquins, the indigenous people of southern Quebec and eastern Ontario, fished.

The next full moon of the year that falls closest to the autumnal equinox – the first day of autumn – in late September is called the harvest moon.

October is the hunter’s moon.

The beaver moon occurs in November because these large hairy rodents are most actively preparing for winter. Coincidentally, it’s usually the last full moon before the winter solstice – the first day of winter.

December is the cold moon, the longest night of the year.

These full moons generally correspond to the highest and lowest tides of the month.

The maximum tidal range along the central coast can range from over 2 feet below the mean low water mark to over 7 feet above it, for a tidal range of over 9 feet.

California’s longest continuous tide record comes from the San Francisco tide gauge along the Golden Gate, which has recorded tide data since 1854.

The highest tide ever recorded at this location was 8.9 feet on January 27, 1983, and the lowest tide was minus 2.9 feet on December 17, 1933.

The greatest tidal range I know of is in the Bay of Fundy on the east coast of Canada, which can exceed 52 feet.

The highest and lowest tides, hence the greatest tidal range, usually occur in December and January when the Earth is closest to the sun, called perihelion.

After looking at the tide data for this year, I was a little surprised to see the predicted tide reach 6.9ft at 10:04 p.m. Thursday, followed by a low tide of minus 1.8ft at 5:31 a.m. Friday at Port San Luis tide. gauge.

In other words, sea level will move 8.7 feet in just over seven hours.

These rising and falling tides will create rip currents in bays and estuaries across California corresponding to the rise of the Strawberry Moon, the final supermoon of this year.

The central California coast has not seen tidal ranges close to this intensity since January 2018.

I decided to ask Dr. Ray Weymann, retired principal and chairman of the astronomy department at the University of Arizona, why we see such large tidal ranges in the middle of the year.

“The gravitational forces exerted by the moon and the sun create the timeless tides,” he told me. “Tidal forces are not the total gravitational forces exerted by the sun and moon on Earth, but the difference between these gravitational forces on the surface of the planet.”

The moon exerts more tidal force on the Earth than the sun due to its proximal proximity.

Thursday, the moon will be close to the earth. Being a full moon, the sun, earth, and moon are aligned, with both factors helping to create a large tidal range.

Marine biologist and Port San Luis Harbor Commissioner Jim Blecha made a fascinating observation.

In summer, negative low tides occur at night, while in winter, they occur during the day.

If the opposite were to happen, many intertidal (tidal pool) creatures and algae would not survive the intense sunlight directly overhead.

Remember, these are predicted tides. Sea water temperatures are warmer than usual for this time of year.

As water warms, it causes thermal expansion in the upper levels of the ocean. As a result, sea water levels can be several centimeters higher than predicted in tide tables.

Other factors such as atmospheric pressure and storm surges when winds blow over the ocean surface towards the coastline can increase the tides.

If the winds are strong enough, they can push and pool water on beaches and raise sea levels several feet – or several feet below if the winds are blowing seaward.

More worryingly, climate change will appear at an increasingly rapid rate.

“Global warming causes actual tides to be higher than predicted on tide charts, as warming waters and melting ice caps in Greenland and Antarctica cause sea levels to rise across the planet” , said NASA oceanographer and climatologist Josh Willis.

Central Coast Aquarium Fundraiser

Please join us on Saturday, June 26 for the Central Coast Capture. This is the annual fundraising event to benefit the Central Coast Aquarium’s mission to bring marine science education to everyone.

I’m going to talk about the strawberry moon. To learn more about this event and to purchase tickets, visit centralcoastaquarium.com.

San Luis Obispo Tribune related stories

Back To Top