Environment
6:00 pm
Fri June 21, 2013

What To Expect During This Weekend's Supermoon, King Tide

SUPERMOON Photographer John Spade got this shot of the last supermoon on May 5, 2012. It shines on an Atlantic Ocean pier north of Fort Lauderdale.
SUPERMOON Photographer John Spade got this shot of the last supermoon on May 5, 2012. It shines on an Atlantic Ocean pier north of Fort Lauderdale.
Credit John Spade/Flickr

The sun, the Earth and the moon will align this weekend to leave a supermoon shining on a king tide.

But it’s all a little less spectacular than it sounds. At least, now it is. A few years down the road -- if the climate change people are right -- the king tide may be something to dread. But, right now, it’s just an incremental enhancement of an ordinary event.

"The king tide is just the highest tide of the season and it tends not to cause great problems, " said Jim Masterson, director of the Ocean Discovery Center at Florida Atlantic University's Harbor Branch Oceanographic Institute. "I wouldn't expect anything more than a few centimeters higher than usual."

The supermoon is what we see when the moon happens to be full at the time of its closest approach to the earth. Because it’ll be about 18,000 miles closer than its usual 240,000-mile distance, it will be brighter and measurably (if not visibly) larger than the full moon we usually see.

But, again, it's no big deal.

Mark Bennett, who manages the planetarium at the Miami Science Museum, said you could only tell the difference if you had been preparing to tell the difference.

"If every month you took a series of pictures of the moon compared to a building or a palm tree, you could measure that there was a slight difference,"  Bennett said. "Visually, it’s not a big difference."

But the king tide, arriving as South Floridians are reading Rolling Stone's speculative piece about how Miami will be reclaimed by the sea within decades, is worth another level of consideration.

It may be a higher tide by a matter of inches, but many experts believe the sea level is rising to a point where inches will be critical one day.

A tide that's not a problem now could be a real threat then.

"If sea level rises to a rises to the point that the mean sea level comes close to existing structures, then a king tide could cause problems, " said Steve Morey, who studies ocean tides at the Center for Ocean Atmosphere Prediction Studies at Florida State University.

At least the supermoon is no threat. It's not even related to the king tide, except that both require the moon to be at its perigee, the closest it gets to the earth. The best view of the supermoon will be at your local moonrise on Saturday.

It will appear to be gigantic as it clears the horizon, but that's just an optical illusion called the "moon effect."

After that, it will be a nice, bright full moon shining on cities and landscapes in, for all we know, their last years on dry land.