visualization

A warm and dry summer

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Just a few graphics to revisit and see where we stand with temperatures and precipitation totals for Seattle Washington in 2016-17.

Temperatures

Seattle's 2017 summer began very pleasantly. It began early, around mid-May. June and July were extremely pleasant, with sunny skies nearly every day and temperatures in the mid-70s. But when the calendar flipped over to August, a smoky heat wave rolled into the region. Combined with a very dry past three months, the region feels hot and tinder dry currently.

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Precipitation

Like last year, the year began very wet. In fact, using the water year calendar which begins on October 1, Seattle had nearly 13 inches more rain than a typical water year by early May. This exceeded 2016's huge totals on that date. 

But, around May 16, the spigot was shut off. And aside from one drenching, winter-like day in mid-June, the region has been very dry.

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The cold return...

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In mid-February there was some small hope that we’d break out of this coldish streak we’ve encountered in Seattle since early December. It turns out this was wishful thinking. There were maybe a week’s worth of slightly warmer-than-normal days to enjoy, but these were accompanied with some heavy rains as well. For a week now, we’ve flipped back to a cooler-than-normal situation. The long-term forecast is much of the same continuing through March. It’s not really that cold; it’s above freezing. But I think a lot of us are looking forward to some more springlike temperatures. I’m pretty sure the plants are.

Daily departures from 30-year normals.
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As I mentioned, we had some heavy rains the first half of February. These nearly matched the heavy rains of last October, before we hit a relatively normal-to-dry period from November through January. For a brief period, it appeared we might catch up with last year’s very wet winter. But the rains seem to have taken a pause now that the cold weather has returned.

Onto March…

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A warm, wet storm arrives. Is this a turn towards spring?

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Early this morning, about 3:30 A.M. a pounding, wet rainstorm woke me up. I sleep beneath a skylight, and though it has yet to leak on me in 17 years, I suspect one day it will. It is in a skylight’s nature to do so. This squall came after an all day rainy Wednesday.

The seasonal water year begins on October 1 in Seattle and runs through the next September 30 for any given period. This year’s water year began exceptionally wet starting about mid-October. Storm after wet storm blew in. But in December — a normally wet month — we seemed to get a reprieve. January was similar except for perhaps a few rainy, individual days.

February seems to have picked up where October left off. We started with snow, but it’s been the strong storms the past few weeks which have really added to the precipitation totals. 

They say more is on the way later this weekend. If true, we may catch up with last year’s very wet winter. But, even with these heavy rains, that would be a tall order.

 

Cumulative Precipitation for Several Seattle Water Years. Seattle is known for rain. But mostly our rains come in the winter half of the year. Therefore, a local meteorological measure of time is the water year, which runs in our region from Oct 1 through Sep 30. The chart above tracks the cumulative amount of this year's water precipitation (blue, dashed line).

The most recent five water year tracks are illustrated in black, with last year's water year track in shown as the heavy black line. The remaining gray tracks are water years for the 2002-03 through 2011-12 seasons.

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The recent rains have been warm. This is shown on the far right end of the chart below. Spring often hits Seattle in late February, with our relatively mild Pacific climate. Maybe the cold snap we recently experienced (highlighted on the chart) is over for good and we’re moving into spring. The daylight sure is stronger and richer.

I hope this is true, but it's too early to tell.

 

Daily Temperature Departures from 30-year (1981-2010) Averages. A significant change occurred in the early part of December where a lengthy, relative warm year switched to a cold period for about two months.

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