OREGON STATE UNIVERSITY

Abrupt shift to summer masks record-setting dampness of early June

06/29/2010

CORVALLIS, Ore. – For the second consecutive year, the weather in Oregon has made an abrupt shift to summer-like conditions, turning off the rainfall spigot almost overnight and putting the record-setting sogginess of early June firmly in the rearview mirror.

Or at least, we can hope.

“What happens in spring doesn’t necessarily correlate to what will happen in the summer, so it’s difficult to say whether we’re in for a long dry spell, or whether the rains will return,” said Philip Mote, director of the Oregon Climate Service office at Oregon State University. “But it has been interesting to watch how abruptly we’ve gone from spring-like to summer-like weather the past couple of years.”

Mote says weather-watchers shouldn’t look for deep meaning in such conditions. Rainy springs and abrupt shifts to summer are certainly not unprecedented, he pointed out.

“One unusual thing about this year is how quickly we’ve transitioned out of the El Niño event,” Mote said. “It gave us pretty dry conditions in January and February, and then we slammed into this pattern of wet weather. Right now, according to NOAA, we are on a La Nina watch. It would be somewhat unusual to go from El Niño conditions to a La Niña event so quickly.”

If La Niña does indeed settle in, it may not affect summer weather, Mote said, but likely would make for a cooler and wetter winter.

All of the El Niño/La Niña observation doesn’t change the fact that 2010 was one of the wettest late springs on record – and, in fact, it WAS the wettest spring on record at the Portland Airport. Portland set an all-time record for rainfall in the month, with 4.27 inches, topping the previous record of 4.06 inches set in 1984, according to Tyree Wilde, a meteorologist with NOAA’s National Weather Service in Portland.

The May-June combined rainfall record also fell this year, as Portland logged 8.95 inches, breaking the old mark of 7.47 inches, also set in 1984.

“All records for the Portland Airport go back to 1940,” Wilde said, “so these are historic records with 70 years of data.”

Not only was this spring wet, it wasn’t particularly warm – even by Oregon standards. The thermometer at the Portland Airport didn’t reach 80 degrees for the first time in 2010 until June 12 – the latest such reading ever. The previous record of June 9 was set in 1991.

Portland wasn’t alone in its cool, wet weather, according to Kathie Dello, a research assistant with the Oregon Climate Service office, which is in OSU’s College of Oceanic and Atmospheric Sciences. Corvallis, Eugene, Salem and Pendleton all reached their monthly average for rainfall by June 4, and though these cities didn’t set records for the month, they were among the highest rainfall totals recorded.

“It was the third wettest June for Pendleton, seventh for Eugene and eighth for Corvallis,” Dello said. “But several places set records for one-day rainfall in June – on either June 2 or June 3 – which shows how wet it was during the early part of the month.”

Among the one-day records:

  • Corvallis had .75 inches of rain on June 2, breaking the previous record that day of .44 inches, set in 2006;
  • Pendleton had .84 inches on June 2, breaking the record of .65 inches (1971);
  • Eugene had .78 inches on June 2, breaking the record of .48 inches (1958); Eugene also set a record for June 3 with .63 inches, topping the old mark of .45 inches set in 1977;
  • Salem had 1.03 inches on June 2, breaking the record of .44 inches (1988); it also set a record for June 3 with .55 inches, surpassing that day’s previous record of .52 inches set in 2008;
  • Hood River had .67 inches on June 2, breaking the record of .35 inches (2006);
  • McMinnville had .57 inches on June 2, breaking the record of .47 inches (1988);
  • Burns logged .50 inches on June 2, breaking its old record of .32 that day (1947).

There was an upside to the wet, cool spring, according to Mote, who is a professor in OSU’s College of Oceanic and Atmospheric Sciences.

“In February, we had some perilously low snowpack levels and it didn’t appear that we had time to recover,” Mote said. “It was of particular concern because we were in an El Niño year, so late snow didn’t seem likely. Low snowpack levels late in winter can create very low flows in many streams and rivers during the summer.

“But much like in 2005, we got some late, heavy snowfall and the situation improved dramatically.”