I will define a Super Inversion when temperature increases by more than 20F in the lower atmosphere (from the surface to roughly 3000 ft).
As noted many times in this blog, temperatures normally decrease with height, but in inversion situations that opposite occurs.
Inversions represent stable situations that suppress vertical mixing, and thus encourages low level fog and pollution.
The lower-atmosphere temperature structure near SeaTac Airport is shown below, based on observations taken by aircraft arriving or leaving the airport.
Around 43 F near the surface and 63F around 2200 ft. Wow.
The effects of the inversion were obvious in the surface temperatures around our region (see below). East of Seattle, an observation location on the slopes of Squak Mountain was 51 F, but 33 F was observed at lower elevations not more than a mile away.
Or consider the situation near Route 2. 57F near Gold Bar but near freezing a few miles away to the west at lower elevations.
The strong inversion was evident in the observations from the balloon-based radiosonde at Quillautye on the WA coast (below). The red line is temperature (in °C), and the height (y-axis) indicates pressure (700 in about 10,000 ft, 850 is about 5000 ft).
At this location, temperature increases by 13 °C (23F) in the lower few thousand feet. Wow again.
Mama Mia! That is an inversion.
Such strong low-level inversions result in an atmosphere lens that bends the radar signal down to the surface.
And it happened this morning, as the radar beam from the Langley Hill radar near Hoquium was bent to the ocean surface and was reflected back, creating a false echo that suggested offshore precipitation (see below). No precipitation was there.
Here are the latest air quality maps over the region. Generally good air quality except for an area in the South Sound.
But why? Inversions can suppress vertical mixing, allowing pollutants to concentrate.
According to an associate of mine in the Puget Sound Clean Air Agency, the relatively warm temperatures (high around 60F) today result in less burning of wood, a prime emitter of particulates. And, of course, there are no wildfires going on this time of the year.
The warm surface temperatures during the day also weaken the inversion at low levels, improving air quality.
The skiing is so good I went for a bike ride.
ReplyDeleteI think there must be something other than just an inversion happening along highway 2. Gold Bar is at elevation 207' and just to the west Startup is at elevation 148'. The temperature delta is 22 degree. That is 1 degree for every 2.7 vertical feet.
ReplyDeleteCurrently high winds in Mount Vernon/Skagit vicinity. Weather forecast says 13mph winds, but winds are gusting faster. Are winds caused by dispersal of this inversion?
ReplyDeleteMount Baker Ski Area has finally released its preliminary monthly snowfall totals for the season thru February 3. The total seasonal snowfall thru 2/3/26 is 274".
ReplyDeleteAt 38", the September-October total was 317% of the 15-year mean (2010-2011 to 2024-2025) for the period of 12" as well as the 2nd greatest snowfall for that period during the past 16 September-October periods after 2013, with 40".
At just 6", the November total was only 7% of the 15-year mean of 81". This is the least November snowfall for the 16 Novembers from 2010-2025 by a large margin, the next least snowy November for the period being that of 2019, with 22".
At 142", the December total was just about average, at 101% of the 15-year mean of 141".
At 81", the January total was 67% of the 15-year mean of 121".
The total thru February 3 was 7". Extrapolating from the 15-year February mean of 114" and the average number of February days for the 15 Februaries within the dataset (28.2666), the average daily snowfall during February is about 4", so the estimated average February snowfall thru February 3 would be 12". Therefore, the current February total is an estimated 58% of the 15-year mean.
Using the above criteria, the estimated average seasonal snowfall thru February 3 would be 481". Thus, the current total of 274" is about 57% of normal. This tracks pretty well with the current mean SWE to-date (thru February 7) for the 7 nearest SNOTEL sites of 51% of 1991-2020 median.
Comparing with the 2014-2015 season, during which the ski area had a total snowfall of just 303", and using the aforementioned criteria, the estimated seasonal snowfall thru February 3 was 194". So, the current season snowfall is an about 141% of the estimated 2014-2015 snowfall thru February 3. This tracks pretty well with the mean current SWE as percent of 2015 (thru February 7) for the 7 SNOTEL sites used in the above comparison of 128%.
Obviously, comparing snowfall to SWE isn't apples-to-apples, but it's the best we can do for the sake of this comparison and, based on the data, it appears that the comparison is reasonably valid and that Mount Baker Ski Area probably does not represent an outlier among the nearby SNOTEL sites which served as the basis for the comparison.
These dry, inversion patterns often lead to burn bans being imposed. But since this inversion has brought warmer temperatures with it, the burn bans haven't been necessary. Even Pierce County, where air quality hasn't been as good and burn bans are often the quickest to be imposed under these conditions, has managed to avoid burn bans this time around.
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