"Supermoon" at its largest tonight

PORTLAND — We lucked out and got to see little bit of the “Supermoon” last evening.  The peak viewing will be tonight when the full moon rises at 9:16 p.m.  But, as you likely know, solid cloud cover is expected to cover the show.  Here is all you would ever want to know about what appears to be the largest moon of the year, courtesty of Jim Todd, OMSI Director of Space Science Education:

June’s full moon takes place at 4:32 a.m. PDT on Sunday, June 23.  It is called the Strawberry Moon, but it can also be called the Rose Moon or Honey Moon. When we look at the full moon on Sunday, it will be just 221,824 miles away making it the Moon’s closest approach to Earth in 2013.

Photos: Stunning weekend ‘Supermoon’
Full moons vary in size because of the elliptical (oval) shape of the Moon’s orbit. Perigee, or the Moon’s closest approach to Earth is about 31,068 miles closer than at its apogee or farthest distance. The Moon’s distance at perigee changes by 3 percent over a period of 18.6 years, but in general while at perigee, a full moon would appear about 14 percent bigger and 30 percent brighter than a corresponding full moon at apogee, but it’s not really all that much more dramatic than a regular full moon.
In March 2011, the full moon was less than one hour away from perigee, a near-perfect coincidence that happens about every 18.6 years.  On May 2012, the full moon was a within a minute of reaching actual perigee position.  The point of the moon’s full phase at 4:32 a.m. PDT in June 2013, and perigee at 4:09 a.m. PDT, fall within an hour of each other.  On August 2014, the full moon and perigee will be just 3 miles closer to Earth.
Before 2011, the comparable biggest/closest full Moon was March of 1993, and presumably the next comparably large full Moon will be 18.6 years from then sometime in late 2029.
Many are calling this full moon the “Supermoon,” blaming it for dramatic land and ocean tides which trigger earthquakes. The tides are greatest during full and new moons, when the sun and moon are aligned either on the same or opposite sides of the Earth.  A very small correlation exists between full or new moons and seismic activity, because the stronger tidal forces caused by the alignment of the sun and moon puts added stress on tectonic plates. However, seismologists have found no evidence connecting lunar perigees to heightened seismic activity. Instead, the Earth constantly stores up energy and releases it any time the built-up energy becomes too great.

KGW Meteorologist Rod Hill, follow me @




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