Replace on the predictions of warmth waves within the northwestern USA – watts with that?

Reposted from the Cliff Mass Weather Blog

June 24, 2021

Incredible temperatures are predicted and now there is high confidence that they will occur

There are two possibilities:

  • The northwest is about to experience one of the most incredible weather situations in many decades
  • There is a major flaw in virtually all of our weather forecasting systems

In all fairness, I am a bit shocked when I look at the raw predictions of the model or the statistically calibrated versions of its results. The predicted event is so extreme and beyond expectations that my natural inclination is to reject it.

But I can not. Multiple modeling systems do essentially the same thing. Large ensembles of many predictions show similar solutions from most runs.

Let me show you the latest.

Proximity to the water will be a major issue, and to get that right, high-resolution forecasting is important. So let me start by presenting the latest in high resolution UW simulations. The situation is so extreme that I had the colors changed to better define high temperatures.

Saturday is transition day. Temperatures at 5:00 p.m., near the time of the maxima, will exceed 100 ° C in large parts of the Columbia Basin and in the northern Willamette Valley (e.g. Portland). The 1990s will invade the interior of southwest Washington and southern Puget Sound. Warm but typical of the hottest days of a typical year.

Sunday is different. Temperatures in the Willamette Valley rise above 108F, as do the lower elevations of the Columbia Valley. Incredibly, some areas south of the Olympic Mountains reach over 104. Can you imagine the temperature gradients near the coast?… from the 60s to over 100F in a few kilometers? In central Puget Sound, temperatures near the water rise from the 80s to the upper 90s a few miles inland.

And now Monday at 2 p.m. The model resolution is a little lower, but the solution is absolutely amazing. Temperatures in excess of 108F are found in and near the western foothills of the Cascade, thanks to the warming easterly current that descends the barrier. 104F and above from the water around Puget Sound. It’s getting incredibly warm in the Fraser River Valley too.

If that prediction confirms that virtually every major observation site in western WA and inland Oregon will hit its all-time temperature record. And in several of these places there are observations that go back 70-120 years.
Later on Monday, the ocean air will move in along the coast, resulting in Tuesday being a little cooler west of the Cascade Ridge (see 5:00 p.m. Tuesday temperatures below). But it’ll be showtime for the Columbia Basin, where the model is aiming for temperatures above 112 F. It is not unthinkable that some places in east Washington will hit or exceed the all-time temperature record for the state (118 F).

The highly skilled model of the European Center – completely different in every respect (different data assimilation, different model, different developers) – follows the same story.
For Sunday 111F in Portland and 103 in Seattle.

And for Monday at 2 p.m. a world-shattering 108F in Seattle. You can see the cooling down (orange colors) on Monday afternoon.

Let me say it again: the ensembles of many forecasts show that there is a high probability that this solution is the preferred one. The National Weather Service’s most advanced statistical post-processing system (the National Blend of Models), which combines many forecasts in an optimal way, is now up for 101F on Sunday and 104F on Monday at SeaTac Airport:

And in Portland: 101F on Friday, 105F on Saturday, 112 on Sunday, and 108F on Monday.

Finally, some people have asked about the role of global warming in this event. Is global warming contributing to this heatwave? The answer is definitely yes. If it weren’t for global warming, we would have had a record heatwave. The answer is also yes.
Our region has warmed up to 1-2F in the past fifty years and that will add to the heat wave. The rise in CO2 is probably the largest contributor to warming
Keep in mind, however, that the temperature anomalies (differences from normal) will reach 30-35 ° F during this event. The immediate cause of this event is a huge / sustained high pressure ridge that is part of a highly anomalous amplification of the upper level wave pattern.
There is no evidence that such a wave pattern is anything other than natural variability (I have researched and published in the peer-reviewed literature on the exact same subject).
So without global warming, a place with 104F would have been 102F. Still a violent heat wave, just a little less intense.

Let me conclude with the golden rule of temperature extremes: the greater the temperature extreme, the SMALLER the contribution from global warming. Think about it.
PLEASE do not send me any emails or comments accusing me of helping “deniers” or calling me names of all kinds. I had enough of that from 350 Seattle activists and Charles Mudede from Seattle Stranger. I’ve spent my life working on weather forecasting and studying northwest weather, trying to get the best science across, whether or not it fits some people’s political agendas.


The new edition of My Book: The Weather of the Pacific Northwest will be released in August

The book contains new chapters on Northwest Forest Fire Meteorology and British Columbia Weather, and the rest of the book has been greatly expanded. It can be pre-ordered from Amazon.


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