Meteor Clouds

Some of the greatest treats of June are the relatively rare but stunningly beautiful noctilucent clouds that form very high in the Earth's atmosphere during this time of the year.

Thursday night, there was quite a show, as illustrated by the pictures below.

Picture courtesy of SkunkBay Weather (from central Puget Sound)

Eastern WA

Noctilucent clouds form high in the atmosphere, about 50 miles above the surface, when water vapor condenses on meteor dust, producing small ice crystals that make up the clouds.

Such clouds are only apparent from late May to early August within a relatively narrow band of latitudes (roughly 50 to 70 degrees)--leaving Washington State on the southern edge of the viewable domain.

Why such limitations, you ask?

First, the formation of such ice requires very, very cold temperatures and the upper atmosphere (called the mesosphere) is coldest during late spring and summer.

Second, the clouds are best illuminated by the sun located below the horizon, and summer provides the optimum sun angle.

Short Heatwave Followed by Normal Temperatures and Precipitation

It is now clear that our region will experience a short-period heatwave on Sunday and Monday, with the highs in Seattle reaching near 90F and eastern Washington climbing into the upper 90s.

This is after a relatively cool start to June and the expectation of normal temperatures the rest of the month.

A plot of the temperature at SeaTac, with observations (blue bars), and record highs (red) and lows (light blue) shown, indicates that we have generally been cooler than normal this month.  Record highs on any day are generally around 90F.

The crazy record high in 2021 is evident at the end of the month.  

To put this month in a better long-term perspective, I have plotted the average maximum temperatures at Seattle from 1-10 June for the past 50 years (a trend line is also plotted).

We have started this month, a bit below normal.  But you will notice a small upward trend (brown line) since the 1970s.   That could well be the influence of human-caused warming produced by increasing greenhouse gases.

Now turning to the forecasts, below is the latest National Weather Service forecast for Seattle. Friday and Saturday will be comfortable, but then temperatures increase, reaching 90F on Monday, before declining to normal next week.

Eastern WA will also warm, with the Tri-Cities climbing into the upper 90s before cooling into the mid-90s.   These are not exceptional temperatures in the central Columbia Basin.

 After this warming period, substation precipitation is predicted to return to the region, as shown by the total accumulation through thourgh June 25th (below).    Particularly heavy in British Columbia, which is very good for the Columbia River.  Very favorable for our power generation and irrigation needs.

Recent substantial rain has contributed to Yakima River storage, which is almost exactly at normal levels.   Very good for irrigation in the Yakima Valley this summer.