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Show Summertime usually dry By MARK EDDINGTON Staff Writer ' BOUNTIFUL It does not necessarily follow that a wetter than normal spring will result in a wet summer, according to National Weather Service meteorologist William Alder. Nevertheless, Alder said the Wasatch Front hasn't enjoyed a wet summer since the early '80s and is overdue over-due to have another one. Long-range forecasts issued by the National Weather Service call for near-normal temperatures and slightly above average rainfall. Whether that will happen this summer or next remains to be seen, he said. "Summertime patterns are very subtle and weather experienced in one season does not presage what weather will occur in the next," Alder said. Just how much precipitation falls along the Wasatch Front over the summer depends on where the subtropical sub-tropical high pressures form. A subtropical high is sort of the steering mechanism of the atmosphere, sitting somewhere across the southern half of North America. If the high rests around Texas, monsoonal moisture will often go up into Colorado rather than Utah. If the high rests over the four corners area, than areas along the Wasatch Front usually receive abundant amounts of rainfall; a high situated a little further west will steer rains into Nevada and California. Meteorologists know how it works, but the hard part i is predicting just where the subtropical highs will set up. Highs during the fall and spring are often fairly static, forming patterns which make it easier for meteorologists to make long-range predictions on precipitation levels. But highs are not as cooperative over the summer and are constantly on the move, often causing dramatic changes in precipitation outlooks. "It's a tough call because it's such a fine line. Sometimes even charts just a few days old will not account ac-count for subtle changes," Alder said. These subtle changes often cause not so subtle differences dif-ferences in the amount of rainfall. A subtle shift in the location of subtropical highs is often the difference between be-tween drought and a monsoon. Meteorologists study sea temperatures, conditional climatology-where troughs and ridges set up. and analyze past weather patterns when making a long-range long-range forecast. With an accuracy of between 55 and 60 percent, long-range forecasting is still very much of an inexact science. For example, meteorologists failed to predict the higher-than-normal rainfalls during the spring. There is also little consensus over how volcanic eruptions erup-tions and other natural and manmade cataclysmic disasters affect weather patterns. "Just what effect these things have depends on what expert you talk to," Adler said. "And a lot of the experts ex-perts won't say what the effect will be until after the fact," he added. |