Weather forecasting during the Olympics is always critical, but it will be even harder than usual this time around. Not only is Vancouver the warmest city to host the winter games yet but the Vancouver-Whistler region’s weather is incredibly complex because of the region’s varied terrain, which spans ocean, islands and fjords and rises to 6500-foot-high mountains.

Enter nowcasting, short-term weather forecasting that predicts the weather over the next 0 to 6 hours in fine temporal and spatial detail by combining in-depth current atmospheric conditions with high-resolution computer models. For Environment Canada, the official weather-service provider for the Vancouver 2010 Winter Games, nowcasting is the Olympics’ best bet at removing the element of surprise from the weather. It’s the first time that the Winter Games will have nowcasts. “We’re trying to be very precise as to when and where something is going to happen,” says Paul Joe, a scientist with the cloud physics and severe weather research group of Environment Canada.

“There’s a great need for on-the-spot, very short-period forecast for the Olympics,” says James Wilson, a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado. “You gotta know if you can run that event in the next hour.” Wild cards such as wind gusts, rain or visibility of less than 65 feet can force events such as the downhill slalom to be temporarily called off. Wilson wants to see nowcasts move beyond the games and into every weather person’s toolkit. “What happened before is the forecaster said ‘scattered showers.’ Well, that didn’t tell you anything,” Wilson says. “Now we’re trying to pinpoint the forecast more.”

At the Beijing Olympics, nowcast weather models successfully steered events clear of the heavy thunderstorms that roll through the city in the summer months. Other nowcasting applications include those for airports, road conditions and fire weather, according to George Isaac, a senior cloud scientist at Environment Canada.

To that end Environment Canada has deployed an extensive array of over 60 weather stations, including a Doppler weather-radar system and wind profiler. The end result is a detailed CT scan of all event venues and the Vancouver–Whistler corridor.

Typical weather forecasts predict an entire day’s weather using models that operate at a spatial resolution of 9 miles. Nowcasts for the Winter Games will detail hours of weather in 15-minute intervals at a spatial resolution down to six-tenths of a mile. To produce these detailed reports, scientists combine up-to-the-minute data from weather-monitoring instruments on the ground with computer weather models crunched by Environment Canada’s IBM supercomputer located in Dorval, Quebec.

The standard operational measurement for snowfall involves collecting snow in a bucket over 24 hours and melting it. Not so this time around. The winter games will have five new, different snowfall sensors in operation. The gadgetry used on the slopes to measure snowfall will include measuring light scatter from laser beams, a vertically pointing radar that’s derived from a police radar, and a miniature hotplate that measures the energy output required to melt snowfall. All of these instruments measure snowfall at 1-minute intervals, a thousandfold increase in temporal resolution.

For Isaac, nowcasting during the Olympics is the golden opportunity to showcase how science and technology can better predict the weather. “At the moment there’s a lot of art to the way the forecasters do it,” Isaac says. “We’re trying to make [weather forecasting] more of a science.”

Courtesy of Anne Casselman, Popular Mechanics