This year’s La Niña a ‘head-scratching enigma’

Weird winter continues with spring storms in February

An interesting seasonal precipitation picture in Colorado.

By Bob Berwyn

SUMMIT COUNTY — With the latest outlook calling for La Niña to fade away during the next few months, some climatologists are scratching their heads over this winter’s somewhat unusual weather pattern in Colorado, which saw a reversal of historic snowfall trends.

“It’s an enigma,” said Klaus Wolter, with the CIRES Climate Diagnostics Center. In an email updating the SWCasts website, Wolter wrote: Record-snow around here in early February is not  something I would typically associate with La Niña, but will come in handy if the mountains west of us remain starved for moisture (despite some minor storms during the upcoming week).”

Temperature and precipitation anomaly maps show above normal temperature readings across most of the U.S. for the last 30 to 90 days.

Wolter was referring to record snow in northeastern corner of the Colorado mountains, west of Fort Collins and Boulder, where he recorded 162 inches for the season to-date at 8,500 feet, the most he’s seen in 22 years.

The bottom line is that the outlook for February – March period is on the dry side for the Southwest, including most of Colorado’s mountains, with the exception of the East San Juans and the Sangre de Cristo mountains.

But Wolter said the next few weeks should be a little more active, with a progressive weather pattern off the Pacific chipping away at this winter’s moisture deficit – call La Niña’s last gasp.

At the very least, he doesn’t foresee an immediate return to the long dry spells that marked the early part of winter, at least not in the near future. But Wolter cautioned that, if past patterns hold true, March could end up being rather dry.

All that adds up to a runoff in the Colorado River Basin that will be well below last winter’s — by as much as 8 million acre feet, Wolter said.

“My current estimate for Colorado River runoff in 2012 is similar to 2010 when it ended up between 12-13 million acre feet for naturalized Water Year flow (or about 8 MAF less than in 2011),” Wolter wrote in the executive summary of the SWCast.

Normally, La Niña (cooler than average ocean temps in the equatorial Pacific) brings a snow surplus to the northwestern part of the state, but this year, the snowpack west of the Continental Divide is lagging, only at about 70 percent of average in the Colorado River Basin.

“In a La Niña year, it’s supposed to be snowy in the mountains, and three out of four, or four out of five times, it is,” Wolter said.

The difference is notable, especially in comparison with last winter, which was “A La Niña on steroids, both on the low and high side,” Wolter said. “The other big question is where is it going to go from here?”

Snowfall picked up across parts of Colorado in late January.

While this winter may be atypical for Colorado, La Niña did behave as expected in other parts of the world — cold in Alaska, wet in Australia, pretty dry in South American and across parts of the southeastern U.S. And it has been extremely wet from southern Alaska down through British Columbia, where some towns, including Valdez, have seen near-record snowfall periods this winter.

Well above-average temps statewide for the past month.

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