June Gloom Comes Early

It is the transition that Northwest residents both expect and regret:   the intrusion of low-level stratus clouds into western Washington and Oregon. 

Usually occurring in late May, this year the transition came a bit early, with cloudy skies the rule today and yesterday over the western lowlands.

Below is the visible satellite image this morning.  The low clouds are stopped by the higher Cascades, and the Olympics are an island that extends above the clouds.

As an aside, the heavily irrigated eastern Washington is a sea of green.

The Seattle Panocam was well into the murk this morning (see below), and at my home in north Seattle, there was drizzle from the low clouds.

Yesterday was similar, and the high temperatures at many locations were below normal....the short heat wave is over!

As normal during our late spring June Gloom periods, the entire eastern Pacific is full of low clouds (the visible satellite image this morning is shown below)

The cool, moist marine air is only a few thousand feet deep, as shown by the temperature and dewpoint sounding at Forks, on the Washington Coast (red is temperature, green is dewpoint).  

When temperature and dewpoint are the same (in the lower portion of the sounding), the air is saturated...which means clouds!

Also note the strong inversion...temperature warming with height--above the cool air.  This inversion acts as a stable layer that prevents mixing of the low-level cool air into the atmosphere above.

Why do low clouds form in spring over the eastern Pacific?

Because of high pressure building aloft.  The weather map showing 500 hPa pressure (about 18,000 ft) for 11 AM this morning is shown below.

And at the surface:

Low-level high-pressure offshore pushes cool marine air into the westerm lowlands.  High pressure aloft creates upper-level sinking, which warms the air aloft.  This warm air creates the inversion that prevents the cool marine air from mixing with the dry air aloft.

We get stuck in this pattern for days or weeks this time of the year.   A good time for meteorologists to go on vacation.

Not All Temperature Records Are Equal

Some records are more significant than others.  

And some records are being used to hype normal temperature variability in unfortunate ways.

Consider yesterday (Sunday).   SeaTac Airport beat its daily record (77F0 for that specific date, reaching 81°F.   

The Seattle Times puts the 81°F day on the FRONT PAGE!  Must be a slow news day.

The Seattle Times story was heavy on hype, with several unfounded statements (see below).

Temperatures scorched past their record high.

Foreshadowing the inevitable summer of drought.  (This is total nonsense, by the way).

Should you worry about the RECORD high temperature yesterday?    Read on.

Why Monday's record did not mean much.

Monday's record high was a daily record.   

Daily records are frequently broken because there are so many opportunities to do so (365 chances each year!).    Breaking an annual record (the warmest day of the year) is much more significant.

Breaking the daily high-temperature record yesterday was particularly lame.  

Why?  Because the previous high temperature on that date (77F) was particularly low.  

You can see this by looking at the plot  (at SeaTac) of observed temperatures (blue lines) and record highs (red shading).   The previous record high temperature on that day (77F) was anomalously COLD.  The coldest daily high for ANY DAY IN MAY.    Even the end of April had warmer record highs. 

By the luck of the draw, May 3 never got above 77°F, and thus this was a record ready to be broken.  Low-hanging meteorological fruit.

The 81F record is still a low record high in May at SeaTac, cooler than ALL the other record highs for the month.

Breaking this wimply record has little meaning and does not foretell an inevitable summer drought as stated by the Seattle Times reporter (Conrad Swanson).

The latest forecasts are emphatic that there will be a cool down, with light precipitation returning.

The latest European Center Forecast has  SeaTac temperatures dropping to normal  (highs in the 60s).

Showers will return on Friday and Saturday (see below).

The kind of hype and exaggeration of heat and drought found in the Seattle Times and several amateur YouTube channels is unfortunate.

People are being misinformed and made to worry without cause.  Hyping climate change and exaggerating normal climate variability may get more clicks and revenue, but the costs of such misinformation are substantial.