Replace three on the predictions of warmth waves within the northwestern United States – watts with that?

Reposted from the Cliff Mass Weather Blog

June 26, 2021

A hundred year old heat wave event comes into focus

As we near the big heat event, powerful new prediction tools become available. Tools that provide higher resolution and a more nuanced view of the upcoming extreme heatwave event.

One such tool are ultra-high-resolution numerical weather forecast models. My group at the University of Washington runs the highest resolution operational weather forecast system in the region with a 1.3 km grid spacing. The resolution is high enough to accurately capture many of the local waters and the effects of our regional terrain features.

Let me show you the surface temperatures forecast today through Monday … all of them are displayed at 5:00 PM.

Today Portland and the lower Columbia Basin rise above 100F and Seattle rise into the upper 90s. The kind of conditions we typically experience once or twice each summer.

Sunday afternoon is a much warmer story. Portland is above 104-108 and central off-water Puget Sound is above 100F.

What about moisture? Will the air be so humid that evaporation will not be effective on your skin? The answer is no.
Here is the predicted relative humidity at the same time (Sunday 5:00 p.m.): Most of the region will have a relative humidity below 30%. Sweating or moisturizing the skin provides significant cooling. Very good.

And then there is Monday a day that will be the warmest day of the last century for parts of West Washington.
Just madness. If you’re right on Puget Sound the temperatures are tolerable (80s), but if you drive a few miles inland the temperatures will rise above 104 ° F. Go a little further inland, temperatures will be over 110 ° F. I’ve provided an enlarged view below for better viewing. I never expected to see temperatures like this in my life.
Eastside communities like Bellevue, Redmond, and Woodinville will be much harder hit than Seattle, Tacoma, and Everett.

Another powerful tool is high resolution ensembles of many predictions that allow us to see the uncertainty in the predictions.

Here is the University of Washington’s high resolution ensemble forecast for the temperature at Seattle Tacoma Airport, with the black line showing the mean of all the forecasts (a good forecast in general). Today (00/27) has the ensembles on the same page (the upper 90s). More variations on Sunday, but almost all over 100F (male around 104-105). And on Monday the mean is 110F with a range of 100-115. Yikes

Now I’m a bit fixated on high temperatures, but night-time lows are also important because they greatly affect the quality of our sleep and the ability to cool our homes and apartments.
The ensemble predictions above suggest a significant increase in daily minimum temperatures, with temperatures only dropping to around 75 ° F on Sunday evening / Monday morning.
Wow … that’s more than our typical highs this time of year (~ 72F). It will be very hard to cool off before the super warm day on Monday. We will break great low temperature records at many stations – the highest low temperature in history.
The good news in all of this? Tuesday will be significantly cooler, but still well above normal. More on that in my next blog.
When that is all over, I plan to investigate this global warming event in depth.

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