August 20, 2020

Record Breaking Moisture over the Region

Tonight there is an amazing plume of moisture over fact, a record for the date and one of the highest on record.

Perhaps you can tell--it is very moist and sticky out there. The air seems thick and a bit oppressive.

You can see the plume of moisture on a weather satellite image that shows moisture content in the upper troposphere (roughly 18,000 to 35, 000 ft)--see below.   See the white, light gray plume passing over western Washington from the southwest?   That's the feature of interest.

Consider a plot of the climatology (daily max, min and average amounts) of water vapor in the atmosphere shown below.  This is a plot of precipitable moisture at Quillayute on the Washington Coast.  The idea is if you took ALL the water vapor in a vertical column of air above you and condensed it out, how much liquid water would be produced?  That is precipitable moisture.

The value today is represented by the gray dot:  1.57 inches.  That is what you would get if you squeezed out every bit of water vapor in the air above.  The record for the date is shown by the red line.  Wow!  We beat that record for the date!  And there are only a handful of dates in the complete record that have been greater.  You will tell your grandchildren about this one day.

So we start with a moisture-rich atmosphere and even some light rain tonight (see the radar image at 10 PM).  The rain evaporates and adds moisture to the air at low levels.

As a result of all this moisture, our dew points have been quite high tonight, reaching into the upper 60sF in the south Sound (see map).  Dew point is a good measure of the amount of moisture in a sample of air.  Mid to upper 60SF is quite unusual for the region...more like you would expect on the East Coast (click to expand image).  Several of these dew points tied or beat the daily record.

The humid air should stick around overnight, with drying by lunchtime.   But on the positive side, the humidity is perhaps good for your complexion.


Note:  My weekly online weather discussion will come out at 9 AM Friday.  And I am working on starting a weekly weather podcast.

My blog on the KNKX firing is found here.


  1. We live in the Lake Goodwin area, between Marysville and Stanwood. No rain, shower, or sprinkle. Out of all that moisture. Hoses back out for watering.

  2. Cliff, any thoughts about the solar minimum that we are in, and how hot it may get when it is over.

  3. very good video! I appreciate how you explain things in layman's terms for us commoners. Also, appreciate your position regarding the obvious persecution. Stay strong.

  4. Another thing about the dew point is the temperature can never get below the dew point temperature. When the two are the same you have 100 percent saturation, at that mostly occurs early in the morning.

  5. Good for forest fires too. Subduing them, that is.

  6. Interesting how alot of moisture doesn't always translate into alot of rain. I have seen many impressive moisture plumes with little rain under them. It goes to show that dynamics and lifting matter alot, a storm with a mediocre amount of moisture can produce alot of rain if it has good lift and dynamics.


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