Although the summer turned dry by the fourth week of June, cooler temperatures and buckets of rain during the month's first three weeks left reservoirs full, putting water managers on early alert for spring flooding.

The National Weather Service has analyzed Utah's summer temperatures and precipitation in the context of the global climate and the temperatures of the equatorial Pacific Ocean and found that the mild La Niña of last year is morphing into a mild El Niño.

Typically, Weather Service hydrologist Brian McInerney said, that would mean "the desert southwest gets a little cooler and wetter, the Pacific Northwest gets warmer and drier."

But during the past 10 years, as the climate has shifted,

typical weather patterns haven't behaved as usual, said McInerney, who added the uncertainty prevented a meaningful forecast for this winter.

Tage Flint, general manager of the Weber County Water Conservancy District, says reservoir levels are high enough that when the irrigation season ends Oct. 1, he has to start thinking about flood management.

That's not unusual -- water managers watch the weather all winter to gauge what they should do with the reservoirs, Flint said. "We adjust those reservoirs all winter long," he said. "The only thing different this year is we have a higher level."

Drinking water would flow from the reservoirs first. After that, the water would run into the Great Salt Lake. But that doesn't mean next year's irrigation supply is absolutely secure. "It's not likely, but in the realm of possibility," Flint said, "to have a low-snow winter."

This summer's temp and precipitation statistics appear skewed, McInerney said, because of the heavy rainfall during the first three weeks of June, after which little to no rain fell.

And while the overall summer temperatures were cooler compared with the past two years, hot days of 95 or 100 degrees Fahrenheit were average or a bit above average, but the total number of days at least 90 degrees was below average.

Confusing? Only if you don't look at June, whose weather behaved more like a typical March. And by August, precipitation was down to less than 50 percent of normal.

Drought indicators started creeping up in Utah around Aug. 25. Before that, the agencies that track drought had not included Utah for four years, even as California and the Northwest dried up.

"Really, Utah has been drought-free for quite some time," McInerney said. "There has been no drought designation for Utah since 2005. ... We've had adequate reservoir supply, and the only year we had below average runoff was 2007."

 

ñEl Niño & La Niña

El Niño and La Niña are naturally occurring phenomena that result from changes in Pacific Ocean temperatures that affect the patterns of tropical rainfall from Indonesia to the west coast of South America -- a distance covering about halfway around the world.

During the winter, El Niño creates a strong jet stream and storm track across the southern part of the United States, and less storminess and milder-than-average conditions across the North. La Niña brings a wavelike jet stream flow over the United States and Canada, with colder and stormier than average conditions across the North, and warmer and less stormy conditions across the South.

Source: National Weather Service

What happened this summer?

To hear the answer from National Weather Service hydrologist Brian McInerney, go to www.wrh.noaa.gov/slc/river/presentations/