Forecast news: ‘In some ways looking at woolly bears is as good as anything’ — Dan Bean

From The Grand Junction Daily Sentinel (Dennis Webb):

The best tool for predicting Colorado winters is what’s called the El Niño Southern Oscillation, or ENSO, says National Weather Service meteorologist Joe Ramey of Grand Junction. That tool tracks water temperatures in the equatorial eastern Pacific Ocean. Warm phases are El Niños, and cool ones La Niñas, and the two appear to dictate how the winter jet stream sets up in the United States. El Niños generally mean dry and warm conditions in northern Colorado, and cool and wet ones in southern Colorado, with the opposite being the case for La Niñas. But this year those ocean temperatures are near normal, or what Ramey calls ENSO-neutral, or “No Niño.”

Ramey considers such seasons “wild cards” in terms of forecasting. He has tried to determine what might happen this winter based on past No Niño seasons, 19 of which have occurred since 1950. On average, western Colorado snowfall those years was below the latest 30-year average. Looking just over the past 15 years, there have been three No Niño years, including last winter, and those seasons were either dry or semi-dry.

Examining things other ways, it doesn’t get any better.

Ramey also considered the fact that another factor in our winter weather, the Pacific Decadal Oscillation, based on temperatures off Alaska, is in a cold phase. But in the case of nine No Niño seasons that had a cold PDO, snowfall was below average.

What about No Niño seasons that followed a previous No Niño season? Again, Ramey found nine out of the 19, and snowfall again was below normal.

Finally, Ramey took into account the encouraging sign of the wet fall we’ve been having. This time he found seven such instances out of the 19, all of which had below-average snowfall except, of course, in the fall.

“No matter how I tried to look at these 19 years, no matter how I sliced and diced it, it came in below normal,” he said.

Ramey is expecting a wet November and possibly December, a dry January and February and perhaps a wet March-April, especially if an El Niño arrives then.

A year ago, Ramey pointed to the fact that the last several previous No Niño years resulted in wet starts and finishes to the season, but with the midwinter being dry and the season usually ending up with below-average snow.

That led him to accurately predict that the same would happen last winter.

Now he said he’s making “basically the same forecast as last year because it worked.”

“I’m going to use that forecast until it doesn’t work again,” said Ramey, who is the first to acknowledge how hard it can be to get such winter forecasts right.

He notes that he didn’t even listen to himself, buying a ski pass to Powderhorn Mountain Resort and donating to the Grand Mesa Nordic Council for its trail grooming.

“I’ve literally put my money on a good snow season this year locally,” he said.

From The Grand Junction Daily Sentinel (Dennis Webb):

If you’re wondering what this winter’s weather might hold in store, you might as well consult with a woolly bear. The width of the caterpillar’s reddish-brown middle stripe is said to indicate what winter holds in store (wide supposedly means mild, narrow means severe). The belief doesn’t appear to be backed up by much science, but it’s perhaps as good as what forecasters have to go on as they take their best guesses about what’s coming this winter, particularly as it pertains to that all-important snowfall.

As with last winter, the challenge is exacerbated by the fact that neither an El Niño nor La Niña weather pattern is taking shape. Those patterns generally can give forecasters some idea of what to expect in terms of snowfall in Colorado.

“That’s a little bit of a problem. It does decrease the overall confidence in a winter forecast,” said Dave Samuhel, a meteorologist with AccuWeather.

That lack of confidence might help explain the differing projections about what the Centennial State might expect in the coming months.

AccuWeather predicts a little better than normal chance for precipitation this winter. The prospects are particularly good in the center and western parts of the state, Samuhel said. He said temperatures could average a degree or two below normal as well, thanks both to the expected storms and to cold temperatures from Canada.

Joe Ramey, a meteorologist with the National Weather Service in Grand Junction, sees a probability of below-normal precipitation for the season, but with some hope coming from signs that an El Niño may develop late in the season and boost March-April snowfall, at least in the southwest mountains. Much of his analysis stems from what the region has experienced in past No-Niño years (see related story).

But for anyone wondering, he also points out that the Farmer’s Almanac is predicting normal snowfall and “piercing cold” in Colorado and other nearby states including Wyoming, Kansas and Nebraska.

Samuhel said AccuWeather’s forecast is based partly on an expectation of a more active pattern of storms originating over the Pacific and heading east. It also looks at similar years that resulted in above-normal precipitation for Grand Junction.

Meteorologist Klaus Wolter, who works for the University of Colorado and the National Oceanic and Atmospheric Administration, has issued what he has termed a “fairly optimistic” forecast of above-average snowpack by Jan. 1 for all but the Yampa and Rio Grande river basins. His forecast presentation also says early season snowpack “appears to have more bearing on the final runoff yield than any other season.”

Jim Pokrandt, spokesman for the Colorado River District, can only hope Wolter’s optimism is borne out.

“We need a good snowpack and we need a couple years of good snowpack,” he said.

With winter approaching, a friend sent Ramey a picture of a woolly bear caterpillar with a center band of the same size as the outer ones.

“That’s supposed to mean something. I’ll tell you in May,” Ramey said.

Dan Bean, manager of the Palisade Insectary, hasn’t seen any woolly bear caterpillars this fall.

“Maybe that’s a bad sign,” he said.

He doesn’t get many signals from insects in terms of what specific weather might be coming. Every fall, they tend to dig into the soil.

“They don’t try to do any forecasting. … We know they all disappear and we know we’re not going to see them until next April or May regardless of what happens between now and then,” he said. “They’re playing it safe.”

He doesn’t claim any special insight regarding woolly bears’ reliability as winter prognosticators, but also points to the difficulty of such forecasting in general.

“In some ways looking at woolly bears is as good as anything,” he said.

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