People of the East Kootenay, how do you like your Pacific air mass?
The recent cold snap and record snowfall earlier this month is just a memory, as a mass of moisture from beyond Hawaii has moved into southern British Columbia. And it’s going to be around for a little while yet.
But watch out — looming over our coming winter forecast is the spectre of La Niña.
Tim Ashman, an in-house meteorologist with B.C. Hydro, spoke to the Townsman on Wednesday about the coming winter, the current conditions, and the latest in forecasting.
If Kootenay residents were hoping not to have a repeat of last winter’s cold and heavy snow, those hopes may be dashed by the forecast.
“The season outlook for the Kootenays — winter and spring … is looking like a colder than average winter coming, and early spring as well, for the southern part of the province, including the Kootenays,” Ashman said. “The reason for this is that we have a La Nina in place.”
La Nina is an oscillating weather system in the southern Pacific.
“It fluctuates year to year,” Ashman said. “Some years the temperatures of the ocean are near normal, other years they become much warmer, or colder than normal. We know that currently they are cold. And ocean temperatures there are expected to remain cold through the winter.
“And there is actually a connection between what’s happening there, on the ocean, and what happens to our weather pattern over western North America. When that happens we get more cold weather outbreaks, and it also loads the dice for snowier conditions and higher precipitation as well.”
Ashman said forecasters can’t pin down exact details, which month will be the coldest or snowiest. “But overall, colder, snowier and wetter is looking likely.”
Even so in a cold winter, there can still be warm periods, and right now is an example of that, Ashman said.
“We actually have a weather system that is drawing moisture out of the tropics, which is pretty rare. So we’re getting moisture from southeast of Hawaii and off the Pacific Coast of Central America. It’s getting drawn north across the U.S. into southern B.C., and we’re getting rain.
“It will be warm enough for long enough that we’ll get rainfall rates that will melt snow. Not only the snow that’s at valley bottom, but some of the mountain snow will melt away as well. Not all of it, but we will definitely get water running off, and [BC Hydro] is looking at managing that run-off where we have reservoirs across southern B.C.”
Late autumn is the start of BC Hydro’s busiest time.
“There are weather impacts that we can deal with year round, but as far as frequency and province-wide impact, this is the busiest time of year.”
Colder than average conditions will likely lead to more snow events, Ashman said. especially at lower elevations, where BC Hydro has its transmission and distribution infrastructure. Snow and ice building up on power lines can lead to damage, and power outages as tree branches fall on power lines.
“We are expecting impacts that way. And we need to prepare to meet the demands of our customers. With more cold weather expected, more people will be heating, the electric heaters will be working harder, and we need to have that power available. So thats the generation side and resource management side.”
If you experience a power outage this winter, BC Hydro strongly recommends have an emergency kit at home, with flashlight, water, non-perishable foods, etc. Customers should know how to get ahold of B.C. Hydro is if the power goes out. They can find up to date information on the mobile friendly website, bchydro.com/outages, or call 1-800-BCHYDRO to report the outage. If a power line is down in your yard or on your street, stay back 10 meters, the length of a bus, and always assume a downed line is live.
More and more, weather forecasting is becoming an exact science.
“We can look pretty far ahead,” Ashman said. “There are different levels of predictability for different variables. There are things that are larger in scale, such as temperatures. If we’re talking about a very large Arctic air mass coming in from Northern Canada or Alaska, we can see that coming seven to 10 days in advance. As far as the exact details — the exact timing, and any snow associated with it, any ice — that’s a little closer on the time horizon.
“When we get into windstorms or ice storms, that’s more two to three days in advance. Rain storms and flooding events, three to four days in advance. And when it gets down to fine things like thunderstorm outbreaks, lightning, snow squalls that are affecting a fairly small area, that’s more like one to two days in advance.
The accuracy of weather forecasting has grown in leaps and bounds over the last three to four decades, Ashman said, with the new types of technology to monitor storms and weather systems.
“Satellite imagery coming in the 1970s, and numerical modeling and supercomputers helping with the modeling aspect — more and more technology and information coming in that can help us to predict things farther in advance with greater accuracy.”