Cliff Mass Weather Blog: The Current Heat Wave in the Northwest: Facts vs. Hype

We are currently in the midst of a hot spell where some locations have broken daily temperature records (records for a particular day).

Let me describe what is happening and why.

Here are the highs from yesterday (Sunday, July 7). 70 degrees along the coast and in the waters of Northwest Washington. Low 90s in Puget Sound, around 100 degrees in Portland and low 100 degrees in the Columbia Basin.

Why is it so warm?

We start by being near the time of maximum solar intensity and longest daylight hours. Temperatures can warm up until 5-6pm at this time of year.

But the real secret is the location of the high pressure aloft, which today and yesterday was positioned in the “sweet spot” for warmth in the NW – over SW BC. The map below shows today’s upper level (500 hPa) map, with shading showing where the values ​​differ from normal (orange and red are higher than normal). Perfect for local warnings.

And it is true that global warming is happening. You can assume that a temperature increase of about 2F is due to increased greenhouse gases. For example, a place that was 93F yesterday would be 91F today.

We would still have heat waves without global warming.

So what about the future?

The Seattle Times is up to the same old trick, claiming that a “100-degree heat wave” is looming over Puget Sound (see today’s front page clip) and that “it’s one of the warmest nights on record.” Scary.

And that is not true.

Let’s look at the surface air temperature prediction from the very high resolution UW forecast model near the time of maximum temperature (5 p.m.)

At 5 p.m., temperatures in most of the Puget Sound area were in the 80s and 90s, but warmer in the area around Portland and MUCH WARMER (over 100 degrees F) in the lower elevations of the Columbia Basin.

Tomorrow will be similar west of the Cascade crest, except south and southeast Puget Sound will be a few degrees warmer.

Sorry, Seattle Times....no century temperatures predicted near Puget Sound. But much warmer around the Columbia basin…over 104F in many places.

But what about Wednesday? It’s much cooler in the west, and even eastern Washington is starting to retreat.

Why the cooling? Because the upper ridge weakens and moves east and the upper trough moves in (see upper level map on Wednesday). Marine air starts to flow into western WA.

But there is To be a danger in this change.

As cool air and high pressure move into western Washington, it will create strong winds on the eastern slopes of the Cascades (see wind forecast for late Wednesday). Red, gray and green indicate stronger winds.

Winds can blow strong and cause forest fires.

Finally, what about the Seattle Times’ claim that we’re experiencing one of the warmest nights on record?

Completely wrong.

Even at the insanely warm SeaTac airport, last night’s low temperature wasn’t even close to the record (see below). The chart shows the highest minimum temperature each year, and the red line is last night at SeaTac. Many years have warmer minimum temperatures.

And using a much better weather station (Olympia), last night’s minimum was nothing unusual. Most years have warmer minimums.