Above: Simulation of a full Earth as viewed from the August 30 new moon. A new moon is between the sun and Earth. When the moon is new for us on Earth, Earth is full as seen from the moon. Image via Fourmilab.
Today – August 30, 2019 – presents the closest new moon supermoon of the year. In other words, it’s the year’s closest coincidence of new moon to lunar perigee, the moon’s nearest point to Earth in its monthly orbit:
Supermoons and high tides. Supermoons can cause higher-than-usual tides, especially along stormy coastlines. Luckily, we’re still a couple of days away from Hurricane Dorian’s landfall along the U.S. coastline. If a strong hurricane were to strike a coast on the day of, or day after, a supermoon, it might affect the mistaken idea that supermoons are “hype.” They aren’t hype. Whether they are full moons or new moons, they can cause real physical effects, including a stronger pull on the tides. Deborah: Thankfully, Dorian is expected to make landfall along the U.S. coast two days from now, on September 1 (Sunday). Bruce: I don’t really know how reassuring that is, for it’s my understanding that there’s a lag time of a few to several days between new moon and the ensuring spring tide. Moreover, the lag time might vary depending on topography. Information on this seems to be sparse but here’s a link at https://earthscience.stackexchange.com/questions/8956/why-dont-spring-tides-occur-at-full-new-moon-age-of-tide.
Get the latest on Dorian from the U.S. National Hurricane Center. Will this supermoon affect storm surge from Dorian, even though it happens two days from now? We don’t know, but it’s something worth thinking about.
The fact is that new and full moons always cause higher-than-usual tides – called spring tides. At or just after new and full moon – in other words, twice a month, the range between high and low tide is especially profound. Spring tides are not named for the season, but in the sense of jump, burst forth, or rise.
We’re smack-dab in the middle of a “season” of three straight new moon supermoons. The three new moons falling on August 1 and 30, plus September 28, 2019, all count as supermoons because of their relative nearness to Earth. The new moon on August 30, 2019, features the closest of the bunch:
New moon distance (August 1, 2019): 224,074 miles or 360,612 km
New moon distance (August 30, 2019): 221,971 miles or 357,227 km
New moon distance (September 28, 2019): 222,596 miles or 358,233 km
The year’s farthest and smallest full moon (micro-moon) will occur on September 14, 2019, which is one fortnight (approximately two weeks) after the new moon supermoon of August 30. Moreover, this micro-moon comes one fortnight before the new moon supermoon of September 28, 2019. The year’s farthest full moon on September 14 will be some 30,000 miles (49,000 km) farther away from Earth than the year’s closest new moon on August 30, 2019.
New supermoons tend to recur in cycles of 14 lunar months (14 returns to new moon), representing a period of about one year one month and 18 days. Next year, in 2020, the year’s closest new moon will fall on October 16, 2020, marking the midpoint in 2020’s “season” of three new moon supermoons:
New moon distance (September 17, 2020): 223,828 miles or 360,216 km
New moon distance (October 16, 2020): 221,797 miles or 356,948 km
New moon distance (November 15, 2020): 222,666 miles or 358,347 km
Source: The Moon Tonight
In 2020, the year’s farthest and smallest full moon (micro-moon) will occur on October 31, 2020. As in 2019, the 2020 full moon micro-moon will come one fortnight after the year’s closest new moon.
Bottom line: Today – August 30, 2019 – presents the closest new moon of the year, which occurs one fortnight before the year’s farthest and smallest full moon on September 14, 2019.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.