Weather patterns tend to “get stuck” for long periods of time, and we’ve certainly seen persistent conditions like that this summer. Weather patterns can reinforce themselves and therefore stay in place for days or weeks. And oceanic influences, such as those associated with El Nino and La Nina, can cause weather patterns to “lock in.”
Take a look at the temperature situation at SeaTac Airport from May 1st through yesterday (below). The blue bars show observed highs and lows, the brown shading shows the typical or climate range, the red shows the record high, and the blue shows the record low.
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Mid-May to late June is associated with below average temperaturewhile early July was warmer than normal. A cool (and wet) June is one reason why wildfire acreage in our region has been lower than normal so far.
Looking at the latest 10-day forecast for Seattle, we see that the forecasts are stuck in a very boring pattern, with temperatures still in the low to mid 80s. The average high temperature for this time of year is around 77-79 degrees F.
No major heat waves are forecast and nighttime temperatures are cool in the early 60s to early 50s, so you can sleep well without cranking up the air conditioning.
Why are we stuck in the low to mid 80s? To explain, here is the average high pattern (at 500 hPa or about 18,000 ft) for the coming week. The shading shows the difference from normal.
A (higher) mountain range is clearly visible, but focused inland. The pattern that has kept western Oregon and Washington warmer than normal is not related to the 90-degree heat wave we had last week (where the mountain range was focused on the coast).
We are now entering the warmest and driest time of the year. Enjoy.
