The tenor of the 2023 Northwest summer is now clear: modestly warmer and drier than normal but without "excitement".
By excitement, I mean record-breaking heatwaves or heat/wind combinations that might produce major wildfire events.
The atmosphere can get "stuck" into certain configurations due to persistent areas of sea surface temperatures and thunderstorm patterns in the tropics, among other reasons.
This year the atmosphere has been "stuck" in a situation that has brought excessive precipitation and cooler weather to California and warmer/drier weather to the Northwest.
A measure of the "stickiness" of the atmospheric flow can be seen in the sea surface temperatures along the West Coast, which has a lot of memory. As shown below, the waters off Californian and Oregon are substantially cooler than normal (the figure shows the difference from normal in degrees C, roughly double for F). Swimming on the Oregon coast will not be pleasant.
What exactly is this "stuck" atmospheric pattern we have been in?
I can illustrate with a plot of the difference from normal for the past 30 days of the heights of the 500 hPa pressure surface (or equivalently the pressure at around 18,000 ft) over the past 30 days (below).
A trough of low pressure has been stuck over the southwest US and extended into the eastern US (blue colors). In contrast, a ridge of higher pressure (yellow/orange colors) has been positioned west of BC and extends into southern Canada. High pressure over Canada during the past months has been associated with the boreal wildfires.
This pattern tends to make Washington State warmer and drier than normal but is not associated with major heatwaves for us. A cool/wet pattern for California.
Interestingly, the whole pattern is shifting now and this shift should dominate our summer.
Below is the European Center extended forecast through August 10th of the 500 hPa heights (again, think of pressure around 18,000 ft) and the difference from normal over that period (color shading). Averaged over this period, the forecast is for a ridge of high pressure centered over the Rockies and a trough over the eastern Pacific.
The forecast of the UW modeling system for next Sunday at the same level shows this pattern clearly: upper level tough offshore and ridge inland.
I can tell you what this means for us.
We will be dry during the next month, moving between periods in the 70s and lower 80s.
Here is the latest forecast for Seattle extending out 10 days. You see what I mean?
How about the Tri-Cities? This pattern is warmer for them, with highs getting above 100F for many days (see below)
For those thinking about wildfires, the grass and range fuels of the region are dry enough to burn, but we are not going to see big winds. So there will be grass fires, particularly if folks are not careful. But they won't be big ones.
The only place that will have some modest winds will be the eastern slopes of the Cascades. This is the normal climate of the region and why the wind turbines are there.
Bottom line: the lack of winds will work against major forest fires. But we have to be careful not to start grass fires.
While I appreciate all of your insight for the short term, I am a colder weather person. So much easier to stay warm and cozy than cool and comfortable. Also, my wife is all about Hallmark Christmas in July and I am seeing all this snow on TV, so I am really looking forward to snow and cold again. Living in Okanogan, last winter was awesome with now on the ground from first part of November clear until spring thaw. Now I know we won't have that again, but one could dream. Any of your models looking out to when we could expect fall like temps or even what winter may bring?
ReplyDeleteNothing is certain of course, but El Nino tends to be warmer and dryer for Washington State.
DeleteEastern Washington experienced a warm, dry May and June which continues into July. The snowpack came off early exposing surface fuels to drying earlier than normal. We are looking at a warm, dry weekend coming up with a predicted dry front bringing strong winds by Monday, and the extended outlook calls for continued warm, dry weather into August. Maybe you will be right about no big fires this summer, maybe we will luck out with no dry lightning outbreaks, but the potential for big fires for Eastern Washington exists and is considerably greater than normal. For west of the Cascades, we will have to wait and see if it continues dry and if a significant east wind situation develops later this summer.
ReplyDeletefive pm in Everett...mostly cloudy today...and a few raindrops on my windshield!..Sun is trying to break through...Temp is 71....A slow warmup, I guess.
ReplyDeleteSome honest-to-god liquid droplets of precipitation actually reached the surface of the Earth in parts of the lowlands of western Whatcom County today. A fact of which I am aware only because I experienced it first hand. The "rainfall" was so scant and so sparse that to call it even a trace would be an act of generosity which would inspire Saint Nicholas himself.
ReplyDeleteI would not call this past week ‘hotter’ than usual. It has been quite cold actually. It feels like fall!
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