Wet, cool spring — the worst ever?


Wow, what a spring! Yes, it HAS been wet! And cold!

But I keep hearing people say, “this has to be the wettest spring ever!” Or, “I can’t remember a wetter spring!” Unfortunately, the facts don’t bear out either statement.
Locally (at Hyslop Experiment Station between Corvallis and Albany, on Highway 20), our average or “normal” precipitation for March through May is about 10 inches (9.86 to be exact). This year we had 13.76. The all-time record is 16.19 inches, set in 1996. Okay, so we’re a couple inches below that. But we must be in the top three, right?

Nope. This was only the 10th wettest. Mind you, we have 121 years of record, back to 1890. But several recent years have been wetter than this year, including 2003 (15.33 inches) and 1998 (14.32”). Other years with nearly as much as this year include 1991 (13.23”) and 1996 (12.45”). By the way, the driest March-May was in 1952, with only 3.02 inches. But then June that year had 3.84 inches! Things do have a way of evening out around here, don’t they?

Speaking of June, after 4 days we already have more than an entire month’s average total. We have received 1.99 inches (average for the entire month is 1.46). This week we had one new record set (.75 inches on the 2nd, beating the old record of .44 set in 2006), and another approached (.85 inches on the 4th, whose record is 1.00” in 1984).
And what about temperatures? Well, it certainly seems cold! Let’s take a look.

The average high temperature for March-May this year was 59.3 degrees. The long-term average (1971-2000) is 60.8, so this year was 1.5 degrees below the average. The coolest month relative to average was May, 3.6 degrees below. The highest temperature for the month of May was only 76, on the afternoon of the 14th; nearly every year we hit 80 in May at least once. Historically, this year ranked 26th coldest out of 121 years of record. The lowest ever was 55.5 degrees in 1955. 2008, at 58.5, was colder than this year.

The average low temperature for March-May, this year, was 39.4 degrees, compared with a long-term average of 40.5, so we were 1.1 degrees below the average low, and the 42nd coldest out of 121 years. Again, 1955 was the coldest at 36.1 degrees. 2009 (38.2) was colder than 2010.

Summary: this spring was unusually cool and wet, but by no means extreme. It just seems that way! Several recent years have seen comparable conditions.

Meanwhile, last winter’s El Niño event, which can be blamed for the dry winter and wet spring, is fading fast. From the Australian Bureau of Meteorology BOM): “Climate indicators across the equatorial Pacific are currently neutral. Equatorial Pacific Ocean temperatures, trade winds, the Southern Oscillation Index and cloudiness over the Pacific are all at levels considered typical of neutral conditions (i.e. neither El Niño nor La Niña).”

BOM goes on to say: “Climate models predict continued cooling of the Pacific Ocean sea surface, with the majority of models surveyed by the Bureau predicting that this cooling will be sufficient to see the development of La Niña conditions later in the year. No climate models suggest a return to El Niño conditions.”

La Niña winters tend to arrive late, be very stormy in mid-winter, be associated with deep snowpacks, and give us increased chances of flooding. They also tend to be colder than average. In fact, our wettest and coolest winters in Oregon tend to come during La Niña winters.

Forecast: we often use the past to predict the future. That’s how we can predict future conditions during El Niño and La Niña years. In this case, I wanted to see if wet, cool springs told us anything about summer weather. Here’s what I found:

For precipitation, I chose the years with the wettest springs: 12 inches or more from March through April (recall that average is about 10); there were 22 such years. Then I looked at total rainfall for June and July. 11 of the 22 had wetter-than-average Junes, and 9 had wetter-than-average Julys. In other words, flip a coin!

Then I looked at temperatures. And the news wasn’t good (that is, if you were hoping summer was “just around the corner”). For the historically cool years (March-May equal to or cooler than this year), more than two-thirds had cooler than average June-July months. Yes, there were exceptions, but the odds would seem to favor continued cool. Bummer.

Until August, anyway. I’m predicting warm, dry August-October, followed by a wet and wild La Niña winter. With lots of snow in the mountains, some big wind storms, and plenty of rain.

Be forewarned.

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