Unusually Strong East Wind Ahead

March 16, 2016

6pm Wednesday…

March & April are the months where we see the seasonal shift of wind in the Columbia River Gorge.

Easterly wind dominates in the cool season (November-early March) because the land is colder than the ocean.  Colder land, longer nights, and weak sun angle mean colder air can more easily pool over the land.  That means high pressure.  Air moves from high pressure to low pressure, so we get easterly wind far more often in that cool season.

Westerly wind dominates in the warm season (April through early October) because the land turns warmer than the ocean.  High pressure develops more often over the eastern Pacific and intense heating of the lower elevations east of the Cascades often causes an area of surface low pressure to form (mainly in the hottest 3 months) out there in the Columbia Basin.

The transition time is mid-March to mid-April.  At this time we can get strong wind from either direction, but we don’t get long periods with the wind stuck in one direction or the other.

But tomorrow and Friday we’ll see an unusually strong east wind develop at the west end of the Gorge due to strong high pressure dropping down over the Rockies.

MarkEastWind_DownslopeToo

This “event” is somewhat similar to the Veteran’s Day windstorm we saw 16 months ago.  Pressure gradients are not as strong though so it shouldn’t get quite that wild.  Still, the WRF-GFS has 50-60 kt wind just a couple thousand feet over our heads tomorrow night and Friday morning

cross_section

Note the similarities to that event in November 2014 except 10+ degrees warmer:

veteransdaywindstorm

That same model also shows 15-18 millibars gradient from Spokane to North Bend early Friday.  In the storm last year it was up around 21 mb.  But, we also saw 10s of thousands of power outages, some trees down, and a few gusts over 50 mph!  I don’t think it’ll get quite that crazy, but the WRF-GFS is painting gusts of 40-50 mph across the metro area during the overnight and morning hours Friday.  Very strong for March!  Our RPM is also showing spots of 50-60 mph gusts along the favored east wind spots east of Hockinson and Battle Ground.  I think that is way overdone.  The screaming message here is that along with our sunshine we’re going to see a very strong east wind event for about 24 hours starting Thursday afternoon.

Chief Meteorologist Mark Nelsen