Kate Jaimet
The Ottawa Citizen
In Canada, griping about the weather forecast is almost as popular as griping about the weather.
While the weather isn't getting any better, forecaster Richard Verret has news for those meteorological malcontents: The weather forecast is.
"We see that it is improving over the past 10 years," said Mr. Verret, chief of the weather elements division at Environment Canada's Canadian Meteorological Centre. "We have a better understanding of the processes in the atmosphere now than we did 10 or 15 years ago."
Mr. Verret's not just blowing hot air. He studied the "today" and "tomorrow" weather forecasts for temperature and precipitation from 1994 to 2003, and presented the results at the Canadian Meteorological and Oceanographic Society congress last week.
In 1994, he said, morning forecasts could predict the day's maximum temperature to within three degrees, about 80 per cent of the time. Now, 90 per cent of the temperature forecasts are correct within three degrees.
But beware of the night-time minimum forecasts: that's when most mistakes slip in. "It seems to be easier to forecast the maximum temperature than the minimum," Mr. Verret warned. "It is very surprising. I cannot find any good reason for that."
As well, Mr. Verret said, the weather forecast is wrong more often in the winter than in the summer. That's because in the summer, the air is warm from Florida to Canada, creating a stable air mass that lies over the continent like a lazy sunbather on a beach.
In the winter, the difference in temperature between the pole and the equator is much greater, creating rapidly shifting hot and cold air masses. Those moving masses make forecasting the weather in winter like trying to shoot at a moving target.
"The faster it moves, the lower your success will be," Mr. Verret said. "In the summer, the target is more stable."
Unfortunately, meteorologists cannot predict rain or snow as accurately as they can foresee the temperature. If forecasters had to predict whether there would be precipitation the following day, they would get the answer right only about 55 per cent of the time. That's why they prefer to use the probability of precipitation measure, telling people the likelihood of their wedding being rained out, while leaving some room for hope.
Radars, satellites and better computer models have all helped to improve the forecasting of both precipitation and temperature over the past decade, Mr. Verret said. But the knowledge and experience of human forecasters is also crucial, especially in hazardous weather. "You can fly on an airplane on autopilot from Paris to London, but you need a pilot when things go bad."Source: Ottawa Citizen, www.canada.com/ottawa, 9 June 2003.