Will This Be The Coldest February in Sea-Tac History?

We have already broken one major record:  Seattle-Tacoma Airport had its snowiest February since record keeping began during the late 1940s:  20.2 inches.  Impressive.

Slush was also a problem in 1943

But I think there is an excellent chance we will break another record, this time for cold.  

Specifically, I think there is a very good change that Sea-Tac Airport will experience the coldest February on record as well....and that is really a very impressive record.

Hold your horses, some of you might exclaim!  We are only half way through the month!  Who knows what will happen? 

True.  But the first half of the month has been very cold, we have excellent forecast skill for the next week, our best guidance suggests a very cold pattern remaining in place, and this is a very short month.

The National Weather Services Climate Forecast System Model  (CFSv2) is predicting unusually cold temperatures for the rest of the month (see below).  The cold anomaly (difference from normal) is so large, it is off the scale! (dark blue is much colder than normal)

The NOAA/NWS Climate Prediction Center, which tries to bring in multiple types of guidance, is going an amazing cold anomaly for the last week of the month (see below).  I am getting chilled just looking at it.

So will we experience the coldest February in Seattle (Sea-Tac's) history?   

Checking official NOAA records, the coldest Februaries at Sea Tac were 35.6 F in 1956 and 35.9F in 1989 (these are daily mean temperatures, calculated by averaging the daily highs and lows).   To estimate this month, I start with knowing the actual highs and lows through today (almost halfway there!), and then complete the month using the forecasts from IBM/weather.com.  Their forecasts are excellent, using statistics to combine many sources of weather information. 

You will not believe what I got:  34.17F for the February average.   We not only beat the record, but shatter it.  

Whatever happens, we are almost guaranteed to be in one of the top five coldest Februaries for Sea-Tac. 

Why so cold?  Because the atmosphere is locked into an upper-level flow configuration of troughing (low pressure) over the western U.S. (see examples from last Saturday and this Friday morning--they look pretty similar!). 

 

And talking about cold, temperatures will drop below freezing tonight, particularly in a few hours when the skies clear further.   Slush will freeze into ice, but quite frankly wet slush is just as slippery as ice.  The only good thing about slush is that the weight of cars can push it out of the way, often allowing some traction.  And the slow warm up should greatly lessen the chances of flooding or landslides.






from Cliff Mass Weather and Climate Blog http://bit.ly/2DFo5Gp