Today is the last day of summer, so it is a good time to evaluate what has happened over the past three months.
Let's start with the average daily temperature. Below is the deviation of daily temperatures from normal for the western US.
Cooler than normal over much of California and southern Nevada, but warmer than normal over Washington and western Oregon--by around 2-4°F.
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For precipitation, much of California and eastern Oregon were wetter than normal, while most of Washington was drier than normal by a few inches.
Starting with the June 21- September 20 observations at Olympia, WA., from the late 1940s to this summer, we note a slot increase by around 3°F over the period, with this year being warmer than normal but not record-breaking.
Interestingly, the high temperatures this summer were very typical, with only a slight long-term trend in heatwave temperatures.
This is something the media has not been noting....the warmest temperatures are not rising much. The big warm-up is in the lowest temperatures each day.
For precipitation (below), we see a slow drying trend in a region-- a region that does not get much rain over the summer. This summer was drier than normal, but not nearly the driest.
Precipitation at Wenatchee? Modest drying over the years.
As shown above, general warmth and dryness this summer was not universal over the western US, and mainly over Washington State and western Oregon.
Why, you ask?
Because a persistent upper-level pattern developed, with higher pressure/heights over southwest Canada (red colors below) and lower heights/pressure over California. High pressure is associated with sinking air, producing warmer and drier than normal conditions.
Why was this pattern so persistent? I cannot tell you for sure.
Finally, how good was the seasonal forecast made by the National Weather Service before the summer started? As shown below, not that great....got the warmth over the NW but missed the cooling over the southwest.
Temperatures will warm up during the next few days, but nothing serious over western WA--mid to upper 70s at most.
Enjoy it while you can. In one month, we will be entering the murk of Northwest winter.
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Do you have the historical Nino anomaly values for the same time slices as the shown historical mean summer temps in Olympia, and is there a substantial correlation? And then would would a model of linear increase of temp combined with a Nino anomaly correction provide an even more accurate model/prediction of mean summer temp?
ReplyDeleteTo me, it felt more humid this summer than most other years, especially at night. What do the data say?
ReplyDeleteYes, I think it was. Relatively warm nights. Warm enough to go swimming in the rain on August 15th.
DeleteCliff, I wonder if you think there's any problem in the "lows" not returning to their historical value and what impact that might have on our region. I specifically think of the water - this is a fragile ecosystem, right? What if "rising temps" are not a problem in and of themselves, but when combined with warmer nights, the combination might become problomatic? I'm also thinking of snow pack - do we know what time of day the majority of snow falls in the cascades? I would guess that "at night" given the longer dark hours - does that cooling play a role?
ReplyDeleteThank you, Cliff Mass. I found your balanced perspective very insightful, especially noting that the biggest warming trend is in the daily low temperatures rather than heatwaves. Realistic and helpful analysis.
ReplyDeleteI didn't think it was much hotter than normal for much of the summer. Back when we had that short spurt early in the late spring/early summer where temps reached the mid 90's, my house got warm and a bit stuffy, it was the overall lows until recently where many nights we didn't drop much below 60F overnight. I think I did notice some increase in humidity, but nothing like 2019 when the blob was the culprit then. That made for an odd summer weather wise. I recall it being occasionally cloudy, but temps still well into the mid to upper 70's and humid. Not typical for this area.
ReplyDeleteThis summer, it still felt mostly normalish all summer, just not as warm at times as it could've been. Glad it's cooling down at night. My AC unit (window) is put away now. In about a month, I may have to switch to the flannel sheets going forward until sometimes this coming spring.
I am impressed by how much the average summer temperature has increased in the last 80 years or so- and even since I moved here in 1972. I fear it bodes for more fires unless we start getting more summer rain. Which I suppose will lag the temperature since the sea has a lot more thermal inertia- plus we have that upwelling.
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