How accurate are long range forecasts? The science behind predicting the weather

CBC Alberta and Saskatchewan have teamed up for a new pilot series on weather and climate change on the prairies. Meteorologist Christy Climenhaga will bring her expert voice to the conversation to help explain weather phenomena and climate change and how it impacts everyday life.

Let's face it. Long-range forecasts can be hit or miss and the further into the future you go, the more you're left guessing what weather you're going to get. 

In general, forecast reliability is often met with a high level of scepticism. Meteorologists are likened to baseball players, where batting .300 can get you to the major leagues. 

But how accurate are forecasts really? What wizardry is behind professionally predicting the future?

Although forecasting can be an art, it does begin with hard data.

Stephen Kerr, manager of training and development at Environment and Climate Change Canada, says in order to see what's coming in the weather, you first have to examine what is happening now. 

"A meteorologist essentially follows a process called an analysis, diagnosis and prognosis," Kerr says. 

They first look at radar, airport reports of weather conditions like temperature, wind and pressure, even data captured by weather balloons to get a grasp on how the atmosphere is behaving. 

During the diagnosis phase they turn all those reports into a weather story of the day.

"They look at this data and then they really make a clear picture as to what's occurring," Kerr says. 

"What's driving it? Then at that point, the meteorologists can start looking into the prognosis, thinking about the evolution of how the weather will unfold by using their scientific knowledge."

The prognosis stage is where mathematics comes into play. 

Meteorologists analyze numerical weather models. These use equations to predict what will happen using the current conditions. 

These computer models will show an evolution of pressure, wind, temperature and other atmospheric phenomena over a set period of time. Some models will intricately show the next day or two, others will extend further in time, sometimes up to 10 days or more.