August 14, 2021

The Bellingham Heat Surge and Improving Air Quality

On Thursday afternoon, the temperature at Bellingham, Washington, surged to 100F, breaking the all-time record for any day at that site.

Not surprising the previous all-time record (99F) was set during the extreme heatwave of late June this year, something illustrated by the plot of high and low temperatures at Bellingham this summer (below, purple shows daily high temperatures, cyan, daily low temperatures)

The interesting thing is that locations a few miles south of Bellingham were warm but nowhere near record-breaking levels that day (the high temperatures on Thursday are shown below, click on the image to expand).  Looking closer, there appears to be a swath of 100F temperatures extending from the Fraser River Valley and very warm highs over northern Victoria, BC.

Looking even closer, there were temperatures as high as 106 and 107F to the northeast of Bellingham!  Wow.

What in the world was going on?

I think there is an answer to this strange anomaly.  The effects of strong downslope flow, accentuated by the proximity to the Fraser River Valley.  As air sinks, it warms by compression.

Plotting the winds at 1 PM on Thursday, the northeasterly flow coming out the Fraser River Valley was obvious (red numbers are gust speeds, temperature to the upper left of the circles).

And looking at the surface observations at Bellingham Airport, the big temperature surges accompanied the strongest northeasterly winds.  You will notice that the temperatures surged from 72 to 91F in two hours as calm winds switched to strong northeasterly winds (direction of 40°--northeast, gusts to 26 knots).

It just so happens we received wind reports from aircraft arriving and leaving nearby Vancouver Airport that day (below).  Strong northeasterly winds aloft around 2 PM.

And strong, localized northeasterly surface winds pushing out the Fraser River Valley are found in the high-resolution UW WRF simulation for 2 PM Thursday (below).   Very warm temperatures were predicted to accompany the strong winds (pink colors).

Moving to a higher elevation (around 5000 ft, 850hPa pressure), the existence of high pressure/heights over BC and a trough (low) along the WA coast, led to a strong pressure/height gradient that produced strong northeasterly flow in the lower atmosphere.

Northeasterly flow that warmed as it descended the western slopes of the Cascades/BC Coast Mountains.  A current of such warm air descended into the Fraser River Valley and then jetted into Bellingham.

Importantly, high-resolution models accurately forecast this situation well ahead of time--and humans (admittedly including myself) did not spot it before it happened.  To show this, here is the previous day's high-resolution ensemble forecast for surface air temperature at Bellingham....upper 90sF were being predicted.

Closer in forecasts were even better.  

This event has gotten me thinking.  Our models and forecast guidance is getting so good now that we need a software system that will monitor the forecasts and bring unusual events to the attention of forecasters.  Sort of like the flight management systems on airlines.

Improving Air Quality

Finally, with the low-level influx of marine air last night,  air quality is vastly better in western Washington and temperatures are decidedly cooler.  Here is the latest EPA AirNOW graphic, with green circles showing good air quality.    There is still some smoke aloft, but that should slowly decline over the next day.

Still poor air quality in eastern WA, but it will improve there dramatically on Monday.


  1. Question, has weather forecasting when there is smoke improved over the last year? I recall last September the forecast, especially the daily high temperatures, seemed off, and looking airnow the predictions for air quality were not accurate

  2. Cliff: "Importantly, high-resolution models accurately forecast this situation well ahead of time--and humans (admittedly including myself) did not spot it before it happened."

    Sounds like HAL talking to Dave in 2001:

    "Well, I don't think there is any question about it. It can only be attributable to human error. This sort of thing has cropped up before, and it has always been due to human error."


  3. The Northeast flow from the Frasier River Valley is more common with winter Arctic air outbreaks but it occurs much less frequently and of shorter duration during the summer. I am curious what made this event warmer than any other warm outflow recorded at the Bellingham Airport. I believe Bellingham has now broken their all time high temperature record 3 times in the past 12 years. Before 2008 the previous record was 94 degrees.

  4. In winter, the Fraser River Valley is famous for channeling some of the coldest temperatures around. Here we see the apposite - providing some of the hottest. It's an interesting contributor to our weather.

  5. I found your report of Thursday's's record setting Bellingham temps surprising. I live in Bellingham and it didn't seem nearly as hot as the temps during the June heatwave. A quick Weather Underground search showed 98º in Bellingham, or for 102º in the Sumas area. Of course I have no idea how accurate that site is.

  6. In Lynden, the northeast wind blew strong most of the day and felt like a hot blow dryer. I have lived here all 50 years of my life and have felt nothing like it.

  7. Just to quibble, it has still never hit 100 degrees F within Bellingham city limits. The airport, where the reading was taken, is a bit north of town. The high of 89 over downtown as shown in the image makes sense. Immediately north of there, in the Columbia neighborhood, we maxed out at 92.

  8. More attention need to be paid to the "Kingdom of Whatcom" as a minorclimate, with the strong influence of the Fraser Canyon.

  9. Anomaly detection with machine learning could be deployed to monitor and report anomalies

  10. So glad, Cliff, that you remain adamant that global climate change never has any predictable consequences or even changes in probabilities on local weather (major eyeroll)

    1. why do you say something that is completely untrue? I have blogged repeatedly about the impacts of global warming. I have shown the model output.I have a number of papers in the peer-reviewed literature on the topic. Quite honestly, trolls like yourself get tiring. If I don't go apocalyptic you get upset and start the name calling.

    2. Cliff, I've been listening to and reading your stuff for what feels like 20+ years (and will continue to do so). I must say that although you do acknowledge the reality of anthropogenic climate change, the overall flavor of your blog is that it's not that big of a deal and there's never been a record hot day/month/year that can be attributable to climate change. So this "troll" makes a fair, though unartful, point.

      On another note, i have about 40 years worth of Washington weather memory. And these are not the summers of the 80s and 90s are they? I remember when 85 degrees just seemed kinda rare in the summer. Selection bias perhaps? Maybe we're too far into our feelings and you're too far into the data? What do you think?

  11. Cliff has been one of the few to discuss how allowing natural wildfires to burn sometimes prevents more catastrophic fires occurring later. More evidence here:

    It's interesting that the currently embattled CA governor is now defending his decisions to disallow forestry thinning efforts and giving PGE unlimited liability for their concurrent malfeasance. I wonder if CA residents will agree, given the traqic fires of Paradise and now the monstrous Dixie fire.


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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