Extremes of weather normal for Utah

If it's roasting in the summer and freezing in the winter, on the average the weather is nice.

Actually, something like that is true. Utah seems to be going through a lot of weather extremes, particularly with the precipitation that allows residents to survive in a desert state.

But on the average the weather is, well, normal.

Some dry extremes, like the 1991-1992 water year, are followed by sopping wet times. For Salt Lake City, the normal precipitation for a water year (Oct. 1 through the next Sept. 30) is 16.5 Inches. But in 1991-92, only 12.18 inches fell in Utah's capital, while the following water year saw a drenching 19.26.

Sometimes the extreme years are close to each other, although not back-to-back.

This year, six years of drought seem to be ending with a fairly heavy snowpack. Although extremes following opposite extremes are rare, why do they happen at all?

Part of the answer is Utah's location and topography.

Mark Eubank, KSL's chief meteorologist, noted that high mountain ranges to the west tend to block storms moving in from the Pacific. That creates low humidity in the state. When Pacific storm fronts do break through, they may be big, soaking systems.

The East, unaffected by skyscraper mountain ranges, has extreme weather too, such as the hurricanes that regularly pound Florida. But they are expected seasonal storms, and the weather patterns tend to be more regular.

Factors influencing the weather include the sunspot cycle, which repeats every 11 years. Some experts think the decreased solar radiation reaching Earth may play a role in climatic variations.

El Nino and La Nina, changes in the Pacific Ocean's temperature, strongly influence U.S. weather. Utah is particularly at the whim of these because the state seems to be centrally located, a place where broad weather regimes shift easily to the north or south.

Then, other patterns have been glimpsed in the weather.

"There's a lot of things that we may not be tracking but that could influence this sort of thing," said Peter Wilensky, lead forecaster with the National Weather Service in Salt Lake City.

Much of the up-and-down nature of precipitation and temperature may be due to "just the natural variability of weather," he said. "The climate averages this stuff out."

This tends to support the maxim, "there really is no such thing as normal," Wilensky said.