Although a wetter-than-normal water year has just wrapped up, meteorologists are anticipating below-average rainfall in the Seattle area for the next three months.
Seattle may have just wrapped up its driest summer on record, but you couldn’t tell that by looking at its so-called water year total.
Sunday marked the end of the water year, a 12-month period touted by weather enthusiasts as a better measure of the city’s precipitation total than the calendar year. Seattle posted 39.3 inches of precipitation during that stretch, almost 2 inches above its average according National Weather Service data.
Seattle’s water year starts Oct. 1 and ends on Sept. 30. (Bit of weather trivia: The “water year” isn’t necessarily the same for other cities. National Weather Service meteorologist Dustin Guy said it varies by location.)
“It just falls in line with the change of season,” Guy said. “We’re already well into our wet season.”
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Despite just wrapping up a wetter-than-normal water year, the weather service says there’s a 30-percent chance of below-average rainfall in the Seattle area for the next three months. The forecast doesn’t specify how much drier this fall might be than last.
Guy said the expectation of precipitation coming in below average over the next three months is in line with that of climatologists for the development of El Nino in the Pacific. The National Oceanic and Atmospheric Administration predicts a 50-percent chance that El Nino — the warm phase of climate pattern that changes every two to seven years — will form during the fall. The agency says there’s an almost 70-percent chance El Nino will take hold by the winter.
“That would correspond with our drier-than-normal outlook for our normal three months,” Guy said. “Typically in El Nino, the storm takes a more southern track,” which means Seattle will likely see a little less rain and warmer temperatures than usual.
Don’t get too excited, though. Seattle’s still going to be pretty wet.
“We are coming off a pretty dry summer,” Guy said. “Once we get past summer, we get into storm season and the monthly precipitation ramps up, even if it is below the average it will be wetter than recent months.”