October 26, 2013

How unusual has been this month's fog event?

A  lot of folks have told me that they never experienced a fog event like this before in Seattle.  Others suggested it is unique for October.   Personally, I can not remember anything like this in October for many years.

But we need better, more quantitative, answers and there is no one better to ask than the individual I call Dr. Fog, a.k.a. James Johnstone, a local scientist that was worked for years on the West Coast fog and low ceiling problems.  This guys specializes in low clouds.

Examining Seattle-Tacoma Airport data, Dr. Fog found all the hours since 1951 for October 1-23 with the cloud ceiling (the height of the bottom portion of the cloud deck)  below 400 m (1300 ft) , thus representing situations with either fog or low stratus.  Depressing stuff.

By this measure, 2013 was the third worst October period on record in terms of average number of hours per day with such low ceilings:

1988:  10.0 hrs/day
1986     7.8
2013     7.4

Here is a plot of the situation in time:
So, this October was only the worst in 25 years!   I feel better already.  But for those less than 25 years old or folks living here for shorter periods, this IS the worst they have experienced.

Let's compare 2013 against 1988 using other graphics provided by Dr. Fog/Johnstone.  1988 had considerably more hours of low ceiling than 2013, but we had more low ceiling hours during the middle of the summer.

 The Victoria Times-Columnist also noted that the past period is the worst since the foggy times of 1988 and 1986.

A company called Weatherspark has some nice summary graphics. Here are their hour summaries of weather conditions for 2013 and 1988.  Grey is fog, green is rain.

First, 2013.  Big dose of fog the last few weeks. But no rain.

1988.  More fog.  Plus rain mixed in. (note this figure goes to the end of October).  The implies they could not escape as easily by ascending into the mountains.  MUCH worse.  During the past few weeks, you all knew you could escape the dismal low clouds with a short drive or climb.

Anyway, I hope everyone is feeling better....1988 was worse.   But we did experience the most foggy two weeks in October since 1988.  And keep in mind that October is fog season in the Northwest.

Tomorrow it is will all change as a strong trough moves through form the northwest.

 Dr. Johnstone's Home


  1. Cliff

    The summary fog/rain graphic from Weatherspark is excellent. The density and sharp display of information is something Edward R. Tufte would love.

  2. So at last we arrive at the end of Act 1 Scene 1 of Macbeth: "Fair is foul, and foul is fair: Hover through the fog and filthy air"

  3. My house has a weird micro climate and last year we got over a week of fog all day long, while it was super sunny just a few miles away. It was really unfair.

  4. I haven't been too freaked out by the fog. I do remember those two years in the late 80's quite well. Now that was depressing. I wondered at the time if that was becoming a new normal for us. Thankfully it did not continue.

  5. Well with the change in synoptic pattern we can all take comfort that Cliff will be able to return to his normal self. The gateway to the Gulf of Alaska Low's is opening. I am sure his family will be relieved!

  6. This fall has also been one of the most "red" in recent memory in terms of foliage.

    Is there a possible connection between the "foggy" weather pattern and the "redness" of the leaves?

  7. Does anyone recall a fog event that seemed to last the whole month of December in the early 1990's ?


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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