Wings Magazine

The weather makers

It was suppertime when the hail started to fall. Once the skies went dark over Calgary on Sept. 7, 1991, hailstones some 10 centimetres in diameter pounded suburban neighbourhoods for close to 30 minutes.

July 10, 2013  By James Marasa

It was suppertime when the hail started to fall. Once the skies went dark over Calgary on Sept. 7, 1991, hailstones some 10 centimetres in diameter pounded suburban neighbourhoods for close to 30 minutes.

Both the King Airs and the Twin Cessna aircraft are armed with flare racks on the belly and under the wings. (Photo: Weather Modification Inc.)

By the time the anvil clouds drifted off, they had left split trees,
broken windows and close to $400 million in property damage in their
wake. Roughly 160,000 separate insurance claims were filed in the most
destructive hailstorm in Canadian history.

“That single event brought the insurance companies to their knees,” says Dr. Terry Krauss, project director for the Alberta Severe Weather Management Society. “Our goal is to avoid the next $400-million storm.” Likely, no one knows better how to do that than Krauss. While working as a research scientist on the Alberta Hail Studies program from 1974 to 1984, Krauss earned a PhD in atmospheric science before leaving to quarterback hail suppression and rain enhancement projects around the world. In the past 15 years, Krauss has been the chief scientist and vice-president for Weather Modification Inc., and a project manager for the Alberta Hail Suppression Project, the Mendoza Argentina Hail Suppression Project, and the Saudi Arabia Rain Enhancement Program.


In response to the 1991 hail disaster, an operational hail suppression program was launched in Alberta, funded solely by private insurance companies. The project was introduced in 1996 as a five-year trial covering a 26,000-square-kilometre area around Red Deer and Calgary. Weather Modification Inc. of Fargo, N.D. was awarded the contract and Dr. Krauss was brought on to oversee the operation.

“The insurance companies were expecting $100 million per year in hail damage payouts,” Krauss says. “The actual payouts came out less than half.” The hail program was renewed indefinitely in 2001 and has continued every summer since then. “As long as it doesn’t get worse,” he says, “we get the benefit of the doubt.”

The dangers of flying near thunderstorms are well documented. Pilots are trained to avoid cumulonimbus clouds by a healthy margin for good reason. In that light, the practice of flying aircraft into developing storms to conduct “cloud-seeding,” has often been viewed as a dark art in aviation circles.

“Somebody always thinks it’s crazy,” says Weather Modification Inc. chief pilot Jody Fischer. “When you learn to fly, you are taught: ‘Here’s the thunderstorm. You go way around it.’ Now, we are going directly to the weather all the time,” he says.

Fischer began studying for an aviation career at the University of North Dakota in 1999. “I never really wanted to be an airline pilot,” he says. “I grew up in central North Dakota on a farm, so you are always outside looking at storms. I don’t know why but I always thought storms were cool.”

A hailstorm over Calgary in 1991 caused close to $400 million in property damage. Weather Modification Inc. is working hard to ensure this doesn’t happen again. (Photo: Weather Modification Inc.)

Weather Modification Inc. maintains a close relationship with the University of North Dakota to this day. According to Fischer, many of WMI’s pilots come up through UND’s Aviation Department as interns in a state-sponsored program that offers elective classes on cloud seeding. That is how Fischer got his start.

“My first flight was at night, at cloud base in North Dakota. There were no lights except for the lightning flashing all around. You are trying to figure out where the ground is, how high the cloud is. There are so many things going on that you forget that you were nervous. Then all of a sudden two hours goes by and it felt like it was 15 minutes,” he says.

Since then, Fischer has made a career as one of the select few pilots who purposefully fly through thunderstorms for a living. Though some might dismiss that notion as cavalier, it doesn’t take long to understand that Krauss and Fischer are not adrenalin junkies by any stretch. While flying in the vicinity of severe weather is certainly a calculated risk, they passionately convey a strong methodology to the science behind cloud seeding and flying through storms.

“The reason hail forms is because the rain process isn’t that efficient,” says Krauss. “Otherwise, a few particles couldn’t grow to giant size. Contrary to popular belief, we don’t break up the hail. We are treating the developing stages of a storm. All of our attempts are to prevent the large hail from forming.”

WMI maintains a fleet of four aircraft in Alberta: a King Air and a Cessna 340 are based at Springbank airport near Calgary, and another King Air and 340 are located in Red Deer. The project radar is mounted on a 12-metre tower at the Olds-Didsbury Airport halfway between Red Deer and Calgary. Three meteorologists watch the weather radar 24 hours per day during the project, which runs every year from June 1 to Sept. 15. “They will call us when they think weather is starting to get rolling they will send one or two crews to the airport on standby,” says Fischer.

The meteorologists brief the crews every day at 12 noon. “When the weather is prime, they tell us to get airborne,” Fischer says. “Once we get to the storm, then it is up to the pilot to find the right cloud to seed.”

The most dynamic storms arrive on the southern Alberta landscape on hot days, when southeasterly winds drag moisture to the foothills from as far as the Gulf of Mexico. When the risk of a hailstorm is apparent, the meteorologists launch patrol flights (call sign HAILSTOP) as a means to provide a quick response to the developing cells when the time for seeding is ripe.

“Once it’s time to seed, silver iodide (AgI) is the chemical of choice,” says Krauss. When dispersed, silver iodide acts as an ice-nucleating agent, allowing for the development of ice crystals within a cloud at a warmer than natural temperature. Though water freezes at 0 degrees Celsius, substantial ice is not found in cloud until temperatures reach -20 C. From 0 C to -20 C, supercooled water droplets can grow to large hailstones. The goal, according to Krauss, is to create millions of smaller ice crystals early in the process to prevent a few larger ones from forming.

Both the King Airs and the Twin Cessna aircraft are armed with flare racks on the belly and under the wings. The ejectable flares contain 20 grams of seeding material and will burn for approximately 37 seconds in the updraft of the cloud. The end-burning flares contain 150 grams of seeding material and burn for approximately six minutes.

“When we are top seeding, we are looking for clouds that are growing through our altitudes,” says Fischer. “Minus 10 seems to be where the most liquid water is and where the silver iodide does its best work.”

As the cloud seeders approach the storm, the seatbelts are tightened and loose articles are secured in the cabin. Even after 12 years in the business, Fischer admits there is always an element of uncertainty. “When you are approaching a storm and making a game plan, you have an idea how it’s going to go but it doesn’t always work the same way every time.”

Fischer explains that there are contingencies in place if the approach to the storm is not working out. “Every few flights it happens. You get too close, or you don’t read the storm right . . . It changes on you. We always have an out heading. We set our heading bug so that if things aren’t going right, you turn to that heading to get out of the weather.”

Still, Fischer explains that there are certain characteristics that by nature exist in every storm. Understanding the dynamics of what is actually going on inside the cell allows WMI crews to accurately fire the silver iodide where it will be most effective.

“At the outside edges of the cloud, the air is going down,” says Fischer. “So when you enter the cloud, you float off your seat a little bit. You are not ready yet to start seeding. Then when you get a little further in the cloud . . . BOOM! The updraft hits the airplane . . . you feel that positive G . . . (if you see) liquid water . . . it’s time to seed. So you fire a flare. Wait a couple seconds, if (the updraft) continues, you fire another one.

“As soon as you feel light in your seat, you stop and you are about to come out of the cloud. That’s what happens every time.” Two aircraft often seed the largest storms: one seeding at cloud base and the other aircraft at the -10 C level.

WMI has been operating in North Dakota since 1961. Now running hail suppression and rain enhancement programs in 19 countries, WMI has a remarkable safety record with zero crashes or fatalities over the past 50 years.

Last year in Alberta alone, WMI aircraft logged 383 flight hours, more than any of the previous 16 seasons and almost double their average activity for the season. And there is no indication that the program will be scaled back any time soon.

“How do you know when it’s too late to start seeding?” I asked. “When it’s hailing on the ground,” laughs Krauss. It’s a constant battle against nature, but in the 16 years that WMI has been on watch in Alberta, the $400-million dollar storm hasn’t reappeared on the horizon.


Stories continue below