June 14, 2017

Midwinter Moisture in June

Tomorrow is going to be an unusual June day over the Northwest.  An extraordinary plume of moisture that stretches across the the Pacific is now approaching our shores, and mid-winter amounts of rain will spread over the region.  A satellite image of the amount of water vapor in the upper atmosphere shows a "river "of moisture stretching from the southwest north Pacific to our coast.

Another satellite product of the amount of water vapor in a column of the atmosphere (for 3 AM this morning), shows large amounts of water vapor in the tropics as well as the extension of moisture heading northeastward towards the Northwest.

A forecast for this water vapor at 8 AM Thursday morning shows a very strong plume of moisture headed for the West Coast.  

This moisture plume and associated strong westerly flow will cause substantial precipitation over our region tomorrow as the moisture is forced up by our terrain.  Here are the 24h totals ending 5 AM Friday.   Really amazing amounts for mid-June, with 1-2 inches (pink colors) in many mountain areas and roughly a half-inch in Seattle.   Even eastern WA gets moistened.

To get an  idea of how unusual this moisture plume is for this time of the year, here is the standardized or normalized anomaly for the plume at 11 AM on Thursday from the European Center model (courtesy of Weatherbell, Inc.)   In this approach, the difference of the total water vapor in the column and the normal value for that date are found (the anomaly) and this is divided by a measure of the climatological variability (the standard deviation).  The plume approaching our coast has a normalized anomaly of about 4.5, which would have a return time of several years.

The implications of this event are substantial.  A major wet system in June, moistens the ground and pushes off the wildfire season.  It will also suppress water usage, which started to surge after our recent dry spell (see graphic).  Enjoy the rain....


  1. That last graph is really interesting! Any thoughts as to why water consumption dropped about 25% from the late 80's to the 2000's? The population has certainly gone up. Reductions in industrial use? Low flow faucets???

    1. Almost entirely high efficiency fixtures and Seattle Public Utilities investing in reducing leaks in their system.

  2. Can you share what the snow level with this storm will be? Low enough to see snow in some of the higher elevations like at Baker and Rainier?

  3. Just curious, the lines on the water usage graph are from 1985-1991 and from 1999-2014. Is there any significance to those years and why they show on this graph, or any significance in the years 1991-1998 that are not graphed?

  4. Sure rain delays fire season, but it also adds more fuel to the inevitable fires..

    Windy gusting well over 30mph at the Admiralty inlet.

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  6. Organic Farmer that is certainly true. In yesterday's warmth and wind there was a wind-driven brushfire in Renton that was significant and threatened homes despite fuels being very green still. Once they cure out it could get interesting, since vegetation appears to be very thick and heavy this year.

  7. Enjoy the rain? Come on, this weather year sucks!

  8. Cliff - why do you consistently make comments like this: "It will also suppress water usage, which started to surge after our recent dry spell (see graphic). "

    Why is water usage bad? Particularly, why is water usage bad in a year like this?

    You know about our reservoir system. You know that in 2015 - a year when everyone wanted to tell us we were in a drought of epic proportions (we were not) - we finished the year with 20 billion gallons of water left unused in our reservoirs. Then filled them back up in about 2 weeks of October rain.

    You know all of this, you wrote about it.

    Our water system here in Seattle is extremely healthy. One of the main reasons for that is the founding members of the region saw fit to build and maintain large reservoirs in the Cascades. We have naturally dry summers - again you have written about it many times - and reservoirs are critical in this climate.

    Tack onto that something else vitally important: the revenue from water use does not just go to the Utility. A significant amount of that revenue goes into the Seattle General Fund to pay for safety and services throughout the city.

    We want people to use water, particularly in years like this. We have plenty of water for the community, and for the environment (fish) this year. Please stop implying that water use is bad. It hurts our community in that not only is it divisive - and it is - but there is just no reason this year to impact the revenue into the city that the Utility supports.

  9. Water usage in and of itself isn't necessarily a problem, but water, treated specifically for drinking and sanitation, used for enhancement of the aesthetic qualities of grass, is.


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

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