The Washington Post

Super moon Saturday evening

New: Super moon photo gallery

Saturday evening, the biggest full moon since 1993 will rise from the eastern horizon. The moon will appear large because it’s reaching its “perigee”, the closest approach to earth in its orbit. According to NASA, perigree moons are 14% bigger and 30% brighter than moons on the “apogee” side of the moon’s orbit, when it is farthest away from earth. What’s special about Saturday’s perigee moon is that it’s almost coinciding with a full moon, a relatively rare occurrence. Some refer to this coincidence as a “supermoon.” writes “On Saturday afternoon at 3 p.m. Eastern Daylight Time, the moon will arrive at its closest point to the Earth in 2011: a distance of 221,565 miles (356,575 kilometers) away. And only 50 minutes earlier, the moon will officially be full.”

View the excellent video from NASA below for a nice overview of the super moon.

In Washington, D.C., moonrise Saturday evening is at 7:39 p.m. High pressure building in from the northwest should support excellent viewing conditions with clear skies.

As I wrote just a week ago, the astrological view that super moons are accompanied by natural disasters and severe weather is not substantiated.

The only known effect of a supermoon is slightly enhanced tides. NASA describes it like this:

A perigee full Moon brings with it extra-high “perigean tides,” but this is nothing to worry about, according to NOAA. In most places, lunar gravity at perigee pulls tide waters only a few centimeters (an inch or so) higher than usual. Local geography can amplify the effect to about 15 centimeters (six inches)

Here are some more useful articles on the super moon...

National Geographic: “Supermoon”: Biggest Full Moon in 18 Years Saturday

Starts with a Bang ( What the hell is a supermoon?

Jason is the Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science, and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association.


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