September 26, 2015

Perfect Sky Conditions Tomorrow for Supermoon Eclipse

Tomorrow (Sunday) night around sunset, Northwesterners will be able to enjoy a rare supermoon total eclipse with no clouds impeding the view.

We start with supermoon, a full moon that is unusually large and bright because of the moon's unusual proximity to the earth. Specifically, that moon will appear 14% larger and 33% brighter than normal. The moon's orbit around the earth is an ellipse, with the distance between the two varying between 222,000 and 252,000 miles.

Then. on top of that we will have an eclipse, with the earth lined up with the sun to eclipse the moon.  The combination of supermoon and a total eclipse is relative rare, with the last one occurring in 1982

 and the next one in 2033.  Even more impressive and unusual, this lunar eclipse is the last of a series of four, called a tetrad.

Supermoon events are often called blood moons, because the moon can have a reddish hue from light scattering off the Earth's atmosphere.  Here in the northwest, the eclipse will start at 6:07 PM and totality will last from 7:11 to 8:23 PM, when the sky will be quite dark.

The latest weather forecast model runs indicate clear skies over the region during the eclipse.  Here is the cloud prediction from the UW WRF model for 8 PM.   No clouds over Washington and Oregon.

So head to a nice view point tomorrow and enjoy a special celestial show.

But there is more.  Some folks believe that blood moon eclipses are particularly attractive to werewolves and vampires, so you might be a bit careful, particularly if you live in or near Forks. Other believe that a supermoon eclipse ending a tetrad might signal the end of the world.  So you might want to put your affairs in order on Sunday, just in case.

Viewing Tip
     A hill looking east would be good. In Seattle, the kite hill at Magnuson Park is nearly perfect, with a view across Lake Washington.  That is where I will be tonight.

Bicycle Weather Talk

I will be giving a talk: A cyclist's guide to weather information: how to increase your chance of a dry ride
Doors open at 6:30 p.m., presentation begins at 7 p.m.
Cascade Bicycling Center
7787 62nd Ave NE, Seattle


  1. Where do you suggest for viewing? We are newish to the area and live in Bothell. We are willing to drive up to 1/2 hour since it's a school night.

  2. Lyn, it looks like the partial eclipse will begin nearly an hour before sunset. Totality will begin only 12 minutes after the sun sets, so the sky will still be far from dark. Mid-eclipse, when the moon is darkest, is 48 minutes after sunset, and we'll still have twilight then. The Moon rises only 10 minutes after sunset. So, to see the show, you will want to have an eastern view as close to the horizon (the Cascades) as possible. Sky View Elementary School (in Bothell) might work if night lighting is off the ball field. Using Google maps sat view like I did could no doubt find you a spot with a clearer view. Good viewing luck to you all!

  3. I thank you for the reminder, Cliff.

  4. Note that the moon doesn't rise in Seattle until 6:53 PM on 9/27, while the penumbral portion of the eclipse is already in progress. Depending on where you're viewing from, you may not see moonrise until 7:00 to 7:05 as the moon rises over the Cascades.

    If I had time, I would drive to the other side of the Cascades to view the eclipse; say, Cle Elem or Ellensburg.

  5. Lyn,

    Park at Bothell High School, and walk over to the edge of the baseball field along 88th Ave. Across the street is a farm with very few trees. Enjoy!


  6. .. Big Moon, at Perigee synonymous with its main full point more phase-change wise. More specific alignment (the eclipse.) with the moon's also being on the "celestial" equator, says it all for me. / The first two points here looked at, of course resulting in a greater than normal pull from and where looking at main "external" gravity. ....

  7. Lyn,

    Like others, I suggest going somewhere with an expansive view of the eastern horizon. The Moon will rise over the Cascades already eclipsed. Magnuson Park in Seattle would be great, since you'd have Lake Washington to your east rather than land. Take binoculars or a telescope if you have them.


    Thanks for the forecast. Here's hoping this one works out. We tried to see the mini-totality lunar eclipse of April 4th, but were stymied by a last minute marine layer coming in before dawn. It was clear at 3 am, then cloudy at 5 am for the eclipse. Curses!

  8. Thanks, Cliff.

    Getting back to the forecast...

    I am bummed that there is little to no rain in the forecast.

    Is this deja vu all over again, or what???


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