June 28, 2010

The Unending Trough

The weather west of the Cascade crest has gone downhill again and the we will stay in this June funk for the next several days.

The reason: the amazingly persistent trough over the eastern Pacific. But before I get into that, above is an interesting graph, which shows the water usage in Seattle for this year, 2009, and for averages over 1985-1991 and 1999-2008 (courtesy of the nice web pages of Seattle Public Utilities).

The water usage this year is really down compared to either 2009 (a warm, dry year) or normal. It looks like few of us are irrigating our gardens, with usage just above winter levels. Another interesting fact is how much less water we use now compared to the 80s, even though population is up. Clearly, water-conserving toilets and shower heads are making a major difference, and perhaps some individuals are making better landscaping decisions (drought-tolerant plants, drip irrigation, etc). With low water usage and a cool wet late spring, Seattle reservoir levels are above normal!

Now about that trough. Below are the upper level (500 mb) weather maps for last night and for the next few days. A low or trough dominates the eastern Pacific off our coast, and that brings clouds and some light rain showers this time of the year. Highs in the mid to perhaps upper 60s for a while.

The current forecast for July 4th? You don't want to know and I don't want to tell you. And there is plenty of time for the forecast to change. Just have indoor options for your big holiday barbecue!


  1. Just wanted to post as a water department employee (former) that although I am sure low flow devices must have some effect, in general the decreases in water usage we've experienced don't come from the residential side of things at all, but from water conservation and reuse practices within commercial (small) and industrial (large) settings.

  2. "The current forecast for July 4th? You don't want to know and I don't want to tell you. "

    But KIRO TV in their noon broadcast today predicted cloudy skies but no rain for the 4th, and no problem seeing the fireworks.

    So, who's going to turn out being right -- Rick Van Cise or Cliff Mass.

  3. Hey Cliff, I was in a funk on Sunday, which is unusual for me, and I asked everyone I've run into since, at least fifteen people, and EVERY ONE of them said they were either in a funk too, or downright depressed. Was it the weather???

  4. Cliff, can you give a more precise source for that graph? I'm curious about it. In particular, I'm intrigued by how much less noisy the 99-08 summer line is compared with the 85-91 summer line. And why does the WY2009 year fluctuation seem to track so closely (albeit lower) with the 85-91 line? (I also wonder why this graph isn't 0-based.)

  5. Cliff - I know you didn't do this on purpose, but your water consumption graph is a bit deceiving. By having the minimum value on the Y axis set to 100 instead of zero, the chart gives the visual impression that the reduction in water consumption is far higher than it really is when you read the numbers and really study the chart.

    The book "The Visual Display of Quantitative Information" is an excellent resource on this and related topics.


    In my professional work, I make a specific effort to display quantitative data so that the graphics match my words.

    Given the largely degree of math illiteracy in our society, I think technical professionals have an obligation to be careful how we display quantitative data so as not to mislead.

  6. The point of the graph is the relative value. Showing this year as the lower boundary is statistically and editorially relevant to the point.

  7. I'm hesitant to say almost anything about potential for summer-like weather, but http://www.cpc.noaa.gov/ is making it look more and more certain with each passing day that there will be a significant warm-up over the region next week. A bit late for July 4, but at least it's something.

  8. It was 38 degrees this morning here in Sequim.

  9. Thankfully, this unending trough will be ending soon.


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

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