Earthquakes & Rainy Weather

July 19, 2007

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In the 10pm show tonight I’m talking about what might we see in the city of Portland with a great Cascadia Subduction Zone earthquake.  But did you realize that we know when the last huge earthquake occurred?  In the evening, January 26th, 1700.  Probably around a 9.0 magnitude quake just offshore.  How do geologists know?  If you have some time take a look at this info on the Orphan Tsunami of 1700 .  I think it’s fascinating reading, but of course I find almost anything scientific to be fascinating.  It’s a paper written by Brian Atwater  and others about the clues to a massive West Coast Earthquake.  And since I produced WAY too much content for a 2 minute story, here are two more graphics.  I could have spent a minute just on the Bonneville Landslide , pictured above.
Now, on to the weather…WET Need more info than that?  It was a nice break this afternoon and evening as showers quickly died down and the sun came out.  Most noticeable was the humidity, or more specifically the lack of high humidity this afternoon.  Dewpoints were way down in the lower 50’s this afternoon…all is back to normal in the Northwest.  That doesn’t include the bizarre late July rainy pattern of course.  A big slug of tropical moisture is approaching from the west this evening.  It’ll be here by daybreak and give us a very gray day tomorrow.  We actually have 2 of these systems on the way that include a significant low pressure center swinging northward along the coastline.  The first is tomorrow morning and the 2nd is Saturday night and Sunday morning.  Generally in the summer we have a large surface high pressure area offshore, so this IS unusual.  It messes up the windsurfers in the Gorge (no west wind), campers on the coast (too wet), and marine areas (no cold coastal upwelling without the northwest wind).
Because of these 2 systems, the weekend forecast does look off/on wet, but what about next week?  As I mentioned last night, I’m tired of pushing rain forward one day at a time.  So now that I see the 12z/18z GFS and to a lesser extent the 12z ECMWF show another upper-level trough nudging us the middle of next week, it looks safe to put a few showers in the forecast then.  Basically I don’t see anything in the next 7 days that shows the warm ridge to our east taking over again…Mark