Spring Getting Warmer? Not Yet, Except This Year!

April 18, 2016

6pm Monday…

Today was a, dare I say, historic April day for warm/hot temperatures inland.  Take a look at the spots that hit 90:

MarkRecordHighTempsMetro

A bunch of official stations in the metro area were quite close:

PLOT_Highs_Metro

Easterly wind was a bit lighter today, but the atmosphere overhead was a little warmer too.  It all added up to an April scorcher.

As of this moment April 2016 is running warmer than the all-time warm April 2004 at PDX.  It remains to be seen if we keep that record for the next 11 days.  Very warm through Thursday, then cooler this weekend and early next week…we’ll see how that turns out.

Why so warm this month?  Today was the 4th day at/above 80 in Portland and we’ve never had more than 5 at PDX so it’s likely we’ll see more 80s than in every previous year.  We’ve had two episodes of strong upper-level ridging overhead.  Nothing too strange meteorologically, but each one has been at the upper end of what we can get this time of year.  Combine those two events and we get all the warm/hot days.

Has it happened in the past or is it all global warming/climate change?  (that 2nd term drives me nuts even though I get the reasoning for its use).  It HAS occurred, but only once in the old Downtown records that go back into the late 1800s.

MarkJet_Warm_ColdSeparated

In April 1926, there were 5 days at 80+ (81,83,93,91) at the end of the month.  Plus, there was a separate 3 day stretch at mid-month (82,88,82).  I’ve mentioned this in the past, but downtown temperature records are a bit sketchier than PDX, mainly due to the fact that part of the time those temps were on the top of hot building roofs, in the case of 1926 it was 60 feet in the air on top of the Customs House building.

I just checked the entire NCDC Oregon Climate Zone #2 (western valleys) for April; this average ALL climate stations in the lower elevations westside.  Sure enough, you see April 1926 and April 1935 were both way warmer than the PDX record April in 2004:

multigraph

So, is this directly related to the climate warming?  In this case it could be, but you definitely can’t say our “springs are getting warmer”.  Notice from 1990 through about 2010 on average our springs were COOLING.  Note the warming from 1970 to 1990 too.  Definitely some cyclical action going on there.  It’s totally fair to say:

IN THE LOWER ELEVATIONS OF WESTERN OREGON THERE IS LITTLE OR NO WARMING SIGNAL YET FOR THE SPRING SEASON, BUT THE PAST 3 YEARS HAVE BEEN WARMER THAN NORMAL.  That’s the 3 month period from March-May.  Here’s the graph for those 3 months:

Oregon_tavg_Spring

That said, it is NOT the case for the other seasons.  We all know summers in our area are warming after the past few years don’t we?

Oregon_tavg_Summer

And the fall season too…warming:

Oregon_tavg_Fall

Winter…same thing, the last two have been near (or at) the top of the chart:

Oregon_tavg_Winter

So there you have it…

Looking ahead, it appears to stay relatively mild as we finish up April and early May.  The ECMWF monthly run showed normal to above normal temperatures continuing over the Pacific Northwest.  Here are the 4 500mb height anomaly maps for each of the next 4 weeks, not much different than the last run:

And the associated surface temperature anomaly maps:

So no sign of a long period of below normal temps; the warm spring of 2016 will continue…

Chief Meteorologist Mark Nelsen