Thursday, April 2, 2020

It's Bizarre: March was Colder than January In Seattle

Everything seems topsy turvy and unnatural these days, and there is a meteorological oddity that must be added to the list:

March was cold than January in Seattle this year.

I knew March was a cool one, but it was not until Dr. Joseph Zagrodnik, a talented atmospheric scientist working at WSU's AgWeatherNet organization, pointed in out to me, did I realize how unusual the past month had been.

According to Dr. Zagrodnik, the average temp in March at Sea-Tac Airport was 44.8 degrees F compared to 45.1 F in January.

How unusual is this?  Rare, but not unprecedented.  March has been cooler than January 8 times in the 126 years we have temperature records in Seattle, with the last time it occurred in 2006.

To appreciate this oddity visually, the graph below shows the numbers of year the March minus January temperatures fell in various bins.  On average, March is about 5F warmer than January, but in some extreme years March has been as much as 17F warmer.  That would get folks attention. Ten years were close to zero (within .5F of zero) and only a handful (3) were .5 to 1.5F cooler in March.
Another way to appreciate our cool March would be to look at a map of the difference of this year's March temperature from normal  (see below).  Western Washington was much cooler than normal, with some areas 4-5F cooler than typical values.    More normal temperatures east of the Cascade crest.

I know your next question: Why?

A good question. It has to do with an unusual weather pattern that has persisted over the North Pacific during the past month, one that includes a ridge of high pressure offshore with persistent cool, northerly flow over the Northwest. 

The figure below  shows the  height (like pressure) anomalies (difference from normal) around 18,000 ft above the surface (500 h Pa pressure).  Unusually high heights offshore (red) and lower than normal heights (blue/purple).  This is a cold pattern for us, with unusually strong/cold northerly flow over the Northwest coast.
Finally, I wanted to show you an extraordinary picture taken yesterday (Wednesday) around 5:20 PM from the Seattle SpaceNeedle PanoCam.   With cold air aloft and great instability, there was a magnificent line of cumulus clouds along the western slopes of the Cascades.  Just stunning.





6 comments:

  1. Indeed. April is unusually cold so far, as well. Looks like it will warm up in a week or so, but despite that, according to IHME, we peaked w/Covid-19 deaths on 3/27. That's preliminary info which just came out last night, but I think it speaks to the spirit of those in our state, even if that stat changes. I weep daily at the strength, courage and cooperation I see daily; not just here, but throughout the world.

    As always, TYSM for all you do.

    Be well.

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    1. Re: covid data. when i look at IHME data, the predicted peak (for deaths per day) is April 17th. 1 week better(?) than last weeks prediction, but still more than 2 weeks out.

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  3. While the evidence is far from conclusive, it does seem there are signs that coronavirus may be sensitive to heat (though that makes me wonder why we're seeing outbreaks in Florida). So, to that end, let's hope that at some point we break out of this persistent, unseasonably cool pattern and start to get some early season hot days! Even if such warm weather does not spell doom for coronavirus, it would at least enable us to enjoy our confinement a little more, enjoying (still legal) outdoor exercise and sitting out on the deck or patio.

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    1. There are outbreaks in the hot areas near the equator and throughout the southern hemisphere where it is late summer/fall. Outbreaks seem to correlate with areas with lots of travel rather than with climate.

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  4. Cliff,

    I like the Space Needle photo! It's a reminder of the beauty in the world.

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