Peak Gusts Last Night: A “Non-Event” In Valleys

March 10, 2016

4pm Thursday…

Well, I should have stuck with 30-40 mph gust forecast from Tuesday night.  We ended up forecasting gusts 35-45 mph in the metro area.  Instead it was more like 25-35 mph.  Just a breezy night as the cold front went through around midnight to 1am.  PDX and Troutdale were two of the higher windspeeds recorded in the lowest elevations:

PLOT_Wind_Metro_PeakGusts_MANUAL

Of course on the North Coast the wind was huge; strongest of the winter at Astoria!

MarkCoast_PeakWindGusts

Unfortunately one person was killed in that part of Hwy 26  where we see trees fall during the big storms; those first 10 miles east of Hwy 101.  So again, the biggest storm of the season out there.

Why was the wind weaker than expected in the valleys?  For one, as mentioned in a previous posting, you want isobars (lines of equal pressure on a surface pressure map) lined up east/west.  Then the southerly wind is forced to ride straight “down the gradient” through the north/south aligned Willamette/Puget lowlands.  Yesterday’s event was a terrible one for that; only 8-9 millbars pressure gradient from Eugene to Olympia.  With a typical (average) wind field higher up in the atmosphere, one would expect about these speeds.  But yesterday there was a much stronger than normal south/southeast wind overhead.  A good 70-80 mph at 5,000′!  The assumption (by all of the human forecasters including me) was that more of that would surface around the cold frontal passage time.  Not much of that did and as a result models did better than humans this time.  They generally had not shown a significant event.  On the other hand, around 9:30pm I did notice the 00z WRF-GFS forecast a spot of 45+ kt wind gusts over the north Willamette Valley around 1am…one of the reasons I didn’t call off the whole thing just before the 10pm newscast.

wgsfc.09.0000

But, with almost nothing happening at 10/11pm here in the valleys, my “forecast-mood” went downhill quickly in both those newscasts.  Anyone watching got the impression that I wasn’t very excited about any strong wind on the way…especially at 11pm.  Ahh, the good times doing TV!  Note I had tweaked the wording to POSSIBLE in this graphic I used both hours…

LIANA_HEADLINES

On to the next weather event…a cool and rainy weekend…great.

Actually it does look like tons of snow on the way to the Cascades Sunday through Tuesday…good news for spring break skiers!

Chief Meteorologist Mark Nelsen