How Cold War-era weather modification dreams are coming true in Colorado’s ski country

Eric Hjermstad of Western Weather Consultants with cloud seeding equipment. Eric’s father, Larry, pioneered cloud seeding in the 1970s.
Hugh Carey / [email protected] |

Larry Hjermstad is a pioneer in cloud seeding, so naturally he has frontier stories.

In the 1970s, farmers in the San Luis Valley blocked his efforts to set up the region’s first seeding operation, which aimed to increase rainfall by spraying dust into the sky.

Suspicious of what he was doing, they blew up his radar antennae and fired at planes, Hjermstad recalled.



“They said, ‘We’re not sure you know what you’re doing,'” he said. “So I set up a committee and said to them, ‘Before each ranking, I’ll tell you exactly what I’m going to do.’ After the third, they said, ‘You don’t need to call us anymore.’ »

Hjermstad and his company, Western Weather Consultants, now run cloud seeding programs across the state, including Summit County.



For decades, local ski resorts have paid him to send plumes of silver iodide down their slopes as opportune thunderstorms approach, squeezing out a few extra inches of snow each time.

In recent years, however, water managers in the Front Range and even states lower on the Colorado River have begun to contribute a portion of the $250,000 to $300,000 it costs to run the program in the Summit County area, hoping the extra snow will flow into their water system when it melts.

Here in Colorado’s central mountain river basin, the company operates about 36 cloud seeding generators. These are small, almost homebrew devices that burn an inert silver iodide solution and blow it into the atmosphere.

Some of the generators are on private land, and when Western Weather Consultants detects an optimal storm coming, it sends instructions to landowners to turn them on. It varies, but Hjermstad claims the process can increase snowfall by up to 25%.

“If we could do this across the entire state with all the mountain ranges, we could add the (water) equivalent of an entire river,” he said.

So why aren’t they?

“Because there are still people who are skeptical.”

Snake oil or science?

The concept of cloud seeding has been around since the 1940s, when Bernard Vonnegut (brother of author Kurt) discovered that silver iodide could produce ice crystals when introduced into air chambers. fog.

In those exhilarating times, cloud seeding was touted as a way to produce rain where there was none, increase crop yields, and fill reservoirs to the brim.

This was a wild exaggeration, and cloud seeding’s reputation suffered.

“At first there were a lot of people claiming a 100% increase in snowfall, so I think the problem is that it’s been oversold for a long time,” said Frank McDonough, an atmospheric scientist at the Desert. Nevada Research Institute.

Studies in Australia and Israel have debunked the idea that planes spewing silver iodide willy-nilly will do a lot of anything. But a targeted approach that hits the right clouds at the right time in high mountains has gained scientific popularity in recent years.

“Most research programs have estimated that you can get about 10% (increases),” McDonough said. “Some storms you can get 25% and other storms you get zero.”

The increases may be modest — an extra inch in a ten-inch storm — but over the course of a season, that’s several extra feet.

A cloud seeding operation in the Tahoe area provides the annual water needs of about 10,000 homes, worth millions of dollars produced for pennies on the dollar, McDonough said.

Use of reservoirs

Not all clouds can be seeded, and the process is as much art as science. Ideal targets are hot clouds where there is plenty of liquid water floating around at freezing temperatures that has no particles to cling to.

On a cold day on the ski slopes, when a cloud hangs over the mountain, you can see the evidence of it in the ice that forms on objects.

“If you climb to the top of Pool A after a storm, you should see white ice that has grown on the lift towers and in the trees,” McDonough explained. “What happens there is that the water drops float through the cloud and as soon as they hit a structure, that structure serves as the location for a freezing event. With cloud seeding, this what you are doing is throwing dust in the cloud and creating frost in the cloud.

In other words, if you see ice forming on the towers while skiing this season, it means there may have been a missed opportunity to turn that into extra powder.

Vail Mountain, which has been under contract with Hjermstad for more than 40 years, hasn’t missed any of those extra snow opportunities, he said.

“Some storms they would be 18 inches and everyone else would be 12,” he said.

Breckenridge Ski Resort, Keystone Resort and Winter Park Resort are all sponsors of the Summit Region program. But snow that’s good for skiing is good for drinking later, and Front Range water managers have taken notice.

“Over time, there has been a lot more interest in weather modification programs in the state of Colorado,” said Maria Pastore of the Colorado River District. “We’re really excited to be entering the sixth season (of cloud seeding)…the main goal of the sponsors is to increase the water supply in the upper Colorado River basin.”

Western Weather Consultants claims that its two seeding operations in the High Country generate between 180,000 and 300,000 additional acre-feet of water per year, and this has been supported by independent studies.

An outside evaluation of Vail’s operation from 1977 to 2005 found statistically significant increases in snowfall ranging from 6.3 to nearly 29 percent.

“Over time, people have become more comfortable that the process actually does what it says it does,” Hjermstad said. “Why would Vail keep us around for 45 years straight unless they saw nothing?”