After looking at various forecast models and considering the climate of the region, it looks like we’re going to suffer There is only one more warm spell left for the rest of the year.
And by warm, I mean the event where temperatures in western Washington rise into the mid 80s or higher and eastern Washington near 100F.
I’ll start by showing you the forecast.
In Seattle, the NOAA/NWS National Composite Model (NBM) forecast system is predicting temperatures to warm into the mid-80s Thursday and Friday before cooling off over the weekend. Temperatures will drop below normal (upper 60s) next week. Today’s average high temperature in Seattle is 75F for reference.
To check, consider the European Center model which has a very clever forecast (the average of these forecasts is shown below). It’s quite similar to the NWS forecast….and this forecast extends into mid-month.
Moving on to the Tri-Cities next, the forecast for Pasco shows high temperatures above 100F Thursday through Sunday, with temperatures dropping to the low 80s next week.
The Central European Temperature Anomaly (relative to normal) forecast for mid-month (September 13-20) shows cooler than normal temperatures in western Oregon and near normal temperatures in the rest of the region.
Solar radiation and day length decrease rapidly in September, making it increasingly difficult to reach 80 by the end of the month. Take a look at Seattle’s monthly solar radiation last year to see what I mean. September’s values were MUCH DECREASE compared to July.
So why is the heat wave followed by a cool spell?
This is easily explained by looking at the upper level pressure/height model at 500 hPa (about 18,000 ft above sea level). The shading shows the deviation from normal, with red representing ridges or higher pressure aloft. Blue is ridges or lower pressure than normal.
But by Monday, the ridge will have moved inland and a cooling trough of lower pressure will move in. There could even be a few showers.
Same situation on the weekend (Thursday). So still cool.
Enjoy the heat, wear shorts and go swimming. The heat will pass soon and we will be moving into fall-like weather next week.
__________________________________
Reminder to UW Students: I will be teaching Atmospheric Science 101 this fall:
And if you’re over 60, you can take the class for $5 through UW Outreach Program…online or in person.
