The following is a transcription of the April 2023 climate conversation between Denver7 chief meteorologist Mike Nelson and Colorado Public Radio’s Ryan Warner for CPR’s “Colorado Matters” show.
Listen to “Colorado Matters” Monday-Friday: 9 a.m.-10 a.m. & 7 p.m.-8 p.m.; Sundays: 10 a.m.-11 a.m.
In this month's discussion:
- Why is it so windy in Colorado?
- The different types of wind and how wind is measured
- Snow, fire, floods: Wacky spring weather in Colorado
- Mike's previous work on the Trans-Alaskan Pipeline and evolving thought on climate change
RYAN WARNER, CPR: We saw red flag warnings this week up and down the Front Range, onto the plains – in essence, critical fire weather conditions. What all goes into determining a red flag warning?
MIKE NELSON, DENVER7: We have a couple of factors: temperature, humidity, and wind along with the dryness across eastern Colorado right now. Even though we've made great progress getting out of the drought in the western half of the state, we still have moderate to extreme drought in some parts of southeastern Colorado, especially down around Pueblo. And so when you get a warm, windy day, with all of the dry conditions there, that leads to fire danger.
RW: Would you say Colorado is windier than many other states because of the effects you're talking about?
MN: Absolutely. Colorado is a very windy statebecause we're in the high plains. We have the mountains that squeeze the winds around quite a bit. But just central of the continent. The air masses that come down from Canada versus the air masses that come up from the south, we get a lot of weather fronts that go through [Colorado] that drive our winds. It's why when people say, you know, “The wind doesn't always blow,” well, honestly, if you've been out in the eastern plains of Colorado, or certainly if you've gone through Wyoming, it tends to blow most of the time.
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RW: I also think of some of the more specific kinds of wind. I learned just several years ago about derechos. I know there are other specific terms for wind. Can you speak to the different kinds of wind?
MN: Well, a derecho – which is Spanish for “straight ahead” – is a strong, straight-line wind. So that's just blasting out of the bottom of a thunderstorm, hitting the ground and going out straight in front of that thunderstorm. Sometimes we call it a “gust front,” if you will, but a derecho downburst, a microburst, [are] all kind of the same thing, except the derecho tends to be on a larger scale, where it may kind of plow through an area and leave a lot of damage. There were a couple of them in the Midwest [in 2020] that would leave – for 70 or 80 miles – just a big, long line of trees down.
We can get those in Colorado, [but] we don't tend to get the really strong winds like that. We tend to get more microbursts that come out of small thunderstorms. Two other things: A Bora wind is a strong, downsloping wind, but it's cold air that comes down behind the cold front, in the wintertime especially. A Chinook, of course, is a downslope where the wind comes down the mountains. That tends to be a warmer wind because when air travels downhill, it warms up about 5.5 degrees Fahrenheit for every 1,000 feet of descent. So if you have 30-degree air that's up on the Continental Divide, by the time it warms up when it reaches the Denver area, you'll have temperatures in the 50s, even low 60s.
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RW: What do you say we hold off on tornado talk until next month when the season gets underway?
MN: I think tornado talk starting in May is a good idea because we're right on the cusp of the severe weather season here in Colorado.
RW: Spring in Colorado is a study in contrasts. And speaking of contrasts, we've got red flag warnings that we've seen this week on the Front Range, on the plains, as I said. Meanwhile, on the western slope [we have] flood warnings – what gives with this contrast?
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MN: Well, it's starting to warm up, of course, so we're gonna get days where you get very windy conditions because the wind feeds off of the contrast in temperature from north to south across North America. So, as it's getting warmer from the south and winter is kind of gradually giving it up as far as its extent to the north, you get a lot more wind in there because you have a greater temperature contrast north to south. As it's warming up as well, that deep snowpack that we've had – that we've been blessed with this winter – is starting to melt out, so we're getting a lot of snowmelt flooding. And in the weeks to come, if we get some really warm weather in the last part of April and the first couple of weeks of May, that is going to be a serious problem across western Colorado because that water will come down in a hurry.
RW: You know, I realized I lost a thread on something, which is: How is wind speed measured? Is it those funny little things that look like measuring spoons?
MN: Well, that's an anemometer. And yes, I built one out of little cups, Dixie Cups, when I was a kid and had a little thing that would click on a roller skate wheel. And that's how I measured the wind when I built my home weather station as a 10-year-old, but now they can actually use ultrasound. So at the new weather station [...] out at Central Park, we'll have just these little prongs that stick up and using ultrasound, they can measure how the wind is going by these and measure the speed so there's not actually the little spinning thing at all anymore.
RW: By way of background, you have helped erect this weather station in Central Park, formerly the Stapleton airport. When DIA opened, the weather station was moved there. But you lost the continuity of Central Park data. And so you have advocated for this kind of secondary weather station in Central Park, which will marry all of that old Stapleton data with what happens on that very site closer to the city of Denver henceforth.
I was thinking the other day of the expression, “April showers bring May flowers.” Is that generally true in the arid west, Mike Nelson.
MN: Actually, much of the West, if you've been watching on the news feeds, parts of Texas and California are having these amazing “super blooms” of flowers, like the poppies out in the Antelope Valley in California because they've had such a wet winter. So yes, in general, across the West, the wet winter gives way to great flowers in April and May. Here, yeah, [...] things are leafing out and things are starting to really get going. A lot of the pansies and stuff are already blooming, the daffodils [too]. So it's a great time, after a long winter. But remember the old adage is, no matter how warm it gets in April or early May, don't plant that vegetable garden until after Mother's Day.
RW: Yeah, that whole idea of “fool's spring.” Of course, I think of the wildflowers and the festival around them in Crested Butte, in more of an alpine environment.
I caught something in your Denver7 bio that stood out to me. I'll just quote it. Mike helped to provide forecasts crucial to the construction of the Trans-Alaska Pipeline. That's an oil pipeline built in the 70s. And today, Mike Nelson, you are a vocal booster of renewables. And I was just curious how you feel about that pipeline work today?
MN: Well, that was over 40 years ago. And for the weather consulting company that I worked for in Madison, Wisconsin, we had to try and forecast what the conditions would be in northern Alaska up around Prudhoe Bay, so that they could get the big trucks out there to lay down a road – an ice road – in order to haul in all the equipment. So it was a long time ago, it was fascinating forecasting. And certainly the oil that has come from the Alaska pipeline has been good for national security. I will tell you this, when I talk about climate change, I give this about fossil fuel: Fossil fuel has been a miracle. Life without fossil fuel was cold, dark and short. And nobody wants to live in a hut with a candle. However, the reality is that when you light fossil carbon on fire, the carbon dioxide produced in the atmosphere traps heat and warms up the planet. It's not politics, it's just physics. So we have to stop doing that as quickly as we can, because the CO2 from the very first Model-T car is still in the atmosphere, trapping heat and warming up the planet. It's called the residence time of the carbon dioxide, which is centuries.
And so a lot of the warming that we see is baked in. But it's never too late to stop making things worse. Then, as we transition to renewable energy, we don't have to make that decision [whether] we're going to live in a hut with a candle. That's a false choice. We can have our modern society and we can do it without continuing to put as much carbon dioxide into the atmosphere as we do. [...] Every single day worldwide right now we are adding about 100 million tons of carbon dioxide into the atmosphere. [That’s] heat-trapping gas that is making the world warmer. It doesn't mean you won't have a cold day, it doesn't mean it won't snow in April because that's weather, but the long term temperature of the planet is warming up.
RW: You know, I respect that that part of your biography remains online, because I think it speaks to an evolution. It speaks to the notion that when we get new information, we can change our minds, we can change our perspective. And I think that message Mike feels really important right now, when [...] there's a lot of digging-in of heels around any number of issues.
MN: Well, we've seen an awful lot of that, a lot of tribalism, if you will. And the thing that I like to point out to people is that two of the greatest transformative bits of legislation in the United States were the Transcontinental Railroad and the interstate highway system. Both transformed our nation, both were signed legislation by Republican presidents. And so from the political side, I'd like to say that we just need to all come together to find solutions, and we can power our economy with much more renewable energy. I'm not closing the door on nuclear. I've talked to a lot of people and I try to keep a very open mind on that. But the fact of the matter is, we have to stop lighting fossil carbon on fire as quickly as we can, because the planet's heating up.
RW: Mike, thanks so much.
MN: Always a pleasure.