By Paul Beckwith (with input from Matthew Ladd)
A few days ago in Ottawa, the temperature reached 21oC. The old record was 18oC and the average high for this time of year is 5oC. This is not a local Ottawa effect or a one-shot anomaly. Weather records that have stood the test of time for over 100 years are dropping like flies everywhere. What is causing this?
Canada’s main meteorological office generates its weather forecasts by running complex analogical weather prediction models (commonly referred to as the “analog method”). In the analog method the existing state of the atmosphere in a particular region is determined, and then compared against a massive database of atmospheric states for the same time and region in previous years. The closest matches of the atmospheric states are identified, and the forecast is basically obtained by examining how those prior systems evolved over time.