Hurricane Sandy: Does a full moon cause high tides? How?

Forecasters warn that storm surges from Hurricane Sandy could be particularly powerful, because the storm coincides with a full moon. How does that work, exactly?

NOAA
NOAA's GOES East satellite snapped this image of Hurricane Sandy at 10:45 a.m. EDT (1445 UTC) on Oct. 24, 2012, as it was headed for landfall on Jamaica.

Heaven and Earth may be aligning to turn Hurricane Sandy into a real monster, just in time for Halloween.

Forecasters expect Sandy to make landfall along the mid-Atlantic coast of the United States on Monday or Tuesday (Oct. 29 or 30). It may merge with a separate tempest hitting the region at about that time, creating an immensely powerful "Frankenstorm" whose effects could be magnified by the full moon.

When the moon waxes to its full phase Monday afternoon, high tides along the Eastern Seaboard will rise about 20 percent higher than normal, even without the help of Sandy's storm surge, said Joe Rao, a meteorologist for News 12 in Westchester, N.Y. (Storm surges occur when a hurricane's winds push the water surface above normal levels.)

"Add a big storm, and the full moon will only serve to exacerbate the situation by helping to accentuate the higher-than-normal water levels, possibly leading to moderate or major coastal flooding and beach erosion," Rao told OurAmazingPlanet via email.

A gravitational lag usually causes the highest tides to come a day or two after every full moon, he added.

"So the worst coastal flooding wrought by Sandy might actually come on Tuesday, all depending on exactly where and when the storm makes landfall," said Rao, who is also the Night Sky Columnist for OurAmazingPlanet sister site SPACE.com. [How to Prepare for Hurricane Sandy]

At full moon, the Earth, sun and moon are arranged in a line, with Earth in the middle. Tidal ranges are especially high at this time because the gravitational tugs of the sun and moon on our planet reinforce each other. The same effect is felt at new moon, when the three bodies all line up, with the moon between Earth and the sun.

Indeed, tides at the new and full moons are called "spring tides." The term has nothing to do with the season; it comes from the German verb "springen," which means "to spring up," Rao said.

Full and new moons have magnified storm impacts in the past, such as during the devastating "Ash Wednesday" tempest that rocked the U.S. East Coast in March 1962. The moon was full when this storm hit, but it was also at perigee — the point in its orbit when it comes closest to Earth — making things even worse.

A close lunar approach is one thing folks in Sandy's path don't have to worry about — small comfort, perhaps, but it's something.

"If there is any saving grace in this upcoming situation regarding Sandy, it is that Monday's full moon comes less than three days before it arrives at apogee (farthest from the Earth)," Rao said.

Mike Wall is a senior writer for SPACE.com, follow him on Twitter @michaeldwall. Follow OurAmazingPlanet on Twitter @OAPlanet. We're also on Facebook and Google+.

Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.