CHADRON — Cheyenne, Wyoming-based Meteorologist Don Day gave a “State of The Union” of sorts for the weather in the Western High Plains and the Rockies at the Upper Niobrara White Natural Resources District’s field day at Chadron State College Tuesday. Looking at forecasts for Spring and Summer 2018 and on into early 2019, Day laid out his case for what past weather patterns indicate for the future.
The outlook is not great.
It’s been cold across the nation this winter, the western areas across the continental divide are going to stay warm, while the eastern part of the country is going to remain cold for the rest of the winter. The plains will continue getting hints of Arctic air, and this January will go down in history as one of the coldest on record. Snow pack in the Rockies is poorer the further south you go, with a dividing line of about Interstate 80.
“Some of the trends we’re starting to see already this winter are going to play a big part in what’s coming this spring and summer,” Day said. “The central and southern Rockies and the central and southern high plains are particularly dry right now, and the tendency in the pattern we’re in right now is for that to continue.”
The current drought monitor shows pockets of drought which developed last summer in both central Colorado and further north in eastern Montana into the Dakotas. There is a gap in eastern Wyoming, northeastern Colorado, and the Nebraska Panhandle.
“In late 2016 we were in actually a weak La Nina, or as I called it a ‘La Nada,’ but in the spring of last year we actually saw the Pacific warm up, and went into a weak El Nino and had a wet spring,” Day said. “Since then, in the fall of last year we’ve gone back into a La Nina pattern.”
La Nina is when the Pacific is cold, El Nino is when the Pacific is warm. In the simplest terms, La Nina can be thought of as a bathtub full of cold water, Day said.
“If you fill a bathtub full of cold water, there won’t be steam rising above it — there won’t be any water vapor rising into the air,” Day said. “The Pacific ocean is the biggest body of water, and the best supply of water for this part of the country. However, when that bathtub is cold, you don’t have a lot of water going into the air.”
This means there’s less potential for rain and snow. Conversely, an El Nino means a warm Pacific with more water vapor in the air and more rain.
“In this part of the country it is absolutely critical to understand those water temperature phases, because there is a strong correlation between how warm the Pacific is and how cold the Pacific is,” Day said. “If it’s warm, we’re wet, if it’s cold, we’re dry.”
The most recent El Nino/La Nina advisory predicts and 85 to 95 percent probability of La Nina continuing through the rest of the winter and into spring before returning to a neutral state in the summer, Day said.
“They say that every time — that La Nina or El Nino will go away,” he said. “It usually does in the summer, but right now we are full-fledged La Nina — we are going to be drier than normal.”
Day said that a lot of the time history does not repeat itself, but it does rhyme. Weather is not much different.
“We tend to see patterns, and for February to April in a La Nina year, we’re going to see it line up to what we’ve experienced in the last 90 days,” he said. “We’re going into a full-fledged La Nina, and there’s no turning back for the rest of the Spring.”
Another condition associated with La Nina, Day said, is that storms move fast due to a faster jet stream.
“The storms don’t linger,” he said. “It’s like guerrilla warfare — they come in, they hit, and then they’re gone.”
Day said when that happens, more than 50 percent of the precipitation occurs in the mountains, and storms often fail to develop on the plains.
“The same storms that brought the mudslides to California a week ago went from California to the Great Lakes in two days,” he said. “When that happens, we just don’t get anything heavy east of the mountains.”
Day believes that La Nina and El Nino like to cluster in groups of 3, 5 and 7 years.
“In 2011—2012, we had a really bad drought, and that was a very strong La Nina year,” he said. “After that, from about 2013 to 2017, we had generally speaking, good yields. That was about five years of an El Nino situation.”
The plains from Southern Canada down into the Oklahoma and Texas Panhandles are the most sensitive to temperature changes in the Pacific, Day said.
“We are in what I like to describe what I like to call a ‘wet desert’,” he said. “If we have two inches less rain in this part of the country in a year, it’s a big deal.”
The computer generated forecasts predict the water in the Pacific to warm up by the fall, but Day argues that the tendency is that this La Nina will be followed by another one.
“When you put back to back La Ninas together is when we get droughty around here,” he said. “I hate so say it, but if we look at the historical trends, the stars align and we’re looking at a dry signature.”
La Nina can occasionally bring good snow pack to the mountains, however, Day said there will not be a wet spring and summer east of the continental divide.
“What will happen during the course of the summer, as the sun beats down on the equator, you’ll see this evaporate and go away,” Day said. “There’s a moment in time from June to August where we hold our breath, we kind of hold our breath and see whether or not this cold pool comes back up again.”
For the next month, Day said another arctic outbreak is likely for February, similar to what occurred over Christmas and New Years, however, it is going to continue to stay dry.
Day predicts that the southern plains are going to have a very dry summer, and that he doesn’t like to see the droughts in the high plains and in the southern plains not connecting.
“A lot of times we’ll see those areas of drought grow together, and I would say our greatest conditions of dryness are 2019 and 2020,” he said. “If those two areas grow together and our soil moisture deficit is down, these things really feed back on themselves. If your soil moisture profile is poor during the summer, you’re not going to regenerate your afternoon thunderstorms as much.
“It’s a vicious cycle — dry spring, dry winter, dry summer — and only a warm Pacific can break that cycle.”
Day said that the sun is the “red-headed step-child” of climate prediction that many meteorologists ignore at their own peril.
“The international panel on climate change does not consider solar activity important,” Day said. “But they are doing it at their own risk, because low solar activity has a strong correlation with climate fluctuations — warm and cold.”
Peaks in solar activity (sun spots), correspond to warm fluctuations, Day said, whereas dips in activity correspond to colder periods.
“This is important, because if we have a solar minimum that coincides with a La Nina, we have a recipe for drought,” Day said. “We are hitting our solar minimum in 2020, so we have to watch this very carefully.”
Day said that if the earth is just a half-a-degree cooler because of solar activity, the oceans will cool, and when the Pacific is cool we get drought.
“We can go back and look at other solar minimums and droughts and find some very strong correlations,” Day said. “Not everywhere is the same, but for this part of the country it can have a big impact.”
Using historical trends, sea surface temperatures and solar activity, Day said the conditions are right for a dry pattern.
“I hope I’m wrong — I hope that a year from now we’re in a full-fledged El Nino, and that we’re nice and wet,” Day said. “I just don’t see that happening, unfortunately.”
Source: www.starherald.com