Summer may heat Utah a little more than usual

It isn't the kind of global warming experienced at the end of the last Ice Age, but Utah should have slightly elevated temperatures this summer.

At the Climate Prediction Center, Camp Springs, Md., National Weather Service scientists run computer models twice daily on long-term forecasts.

"The last time, it was saying we should expect warmer-than-normal temperatures in the Southwest, including much of Utah," said Ed O'Lenic, senior meteorologist at the center. "We're calling for above-normal temperatures there in Salt Lake City."

Scientists at the center routinely use sophisticated forecast tools to peer into the future. These crystal balls aren't the usual type that gives forecasts for three to 10 days, but allow the experts to get an idea of meteorological trends months in advance.

The forecast tools are basically maps derived from both statistical as well as dynamic forecast models, O'Lenic said.

Modeling suggests a "fairly large trend toward warmer temperatures, in the southwestern United States primarily," he said. This seems to be a reliable trend, and is one of the factors that are calculated in the making the long-range forecast.

A new system, the Climate Forecast System, is used in the dynamic model, he said. "It really uses the physics of the atmosphere and the ocean to forecast forward in time over a period of about nine months."

The computer model runs twice daily. Each month, weather scientists gather a month's worth of these long-range forecasts and examine them.

One way to compare seasons is to come up with a single average temperature for that period. To do that, a forecaster adds up the highs and lows for the season, and divides that by the number of readings.

The typical summer temperature in Salt Lake City, averaged over 30 years, is 73.9 degrees, said Linda Cheng, meteorologist with the NWS Salt Lake Forecast Office, 2242 W. North Temple.

With that in mind, what average temperature does the Climate Prediction Center forecast for this summer?

From May through September, expect the average to be about 0.4 of a degree or half a degree above normal, O'Lenic said.

Temperature fluctuations are a normal part of weather cycles. So it's impossible to predict exactly how hot a particular day will get this coming summer.

About all that Utahns can do is remember previous summers and imagine this coming one as half a degree, on average, hotter than usual.

Consulting records that reach back 79 years, Mark Eubank, KSL chief meteorologist, said typically, Salt Lake City has five days when temperatures reach 100 degrees or higher.

During one recent year, 17 days were at the century mark or above, while the next year produced no days when the weather was that hot.

"About once every 10 years," Eubank added, "we won't have any 100s."

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E-mail: bau@desnews.com