The probability of a consensus is not good!
Someone once said, "if it wasn't for the weather, most Canadians couldn't start a conversation." Timely weather topics include the record heat out west and the devastating flooding rains across parts of western Europe. Locally, for whatever reason, the overused and often misunderstood probability of precipitation has been trending on social media.
That prompted many of you to reach out.
Ruth writes:
“Seen this post made by someone the other day. I am surprised because I didn't realize this was how the percentages worked; I too thought when it says 40 per cent chance of rain in Cape Breton, it meant just that — not that 40 per cent of Cape Breton could get rain. This is an interesting topic. Thanks for reading.”
The POP was implemented by the Weather Bureau (now the National Weather Service) of the United States in 1966. Canada later came on board with the chance of precipitation.
You might find a forecast that looks like this: a mix of sun and cloud with a 30 per cent chance of precipitation.
What does it mean? Well, for starters, it does not mean:
• There's a 30 per cent chance it will rain and a 70 per cent chance it won't
• Three out of 10 times when the weather is similar, it will rain
• Precipitation will fall 30 per cent of the day (or night)
• Thirty per cent of the forecast area will experience rain, snow, or storms
In Canada, the correct interpretation is as follows: there is a 30 per cent chance that 0.2 mm of rain or 0.2 cm of snow will fall on any random point of the forecast region during the forecast period.
Really? If it's raining — then it's 100 per cent. That's how I see it, and that is why you will never find a “per cent chance
of rain” in my video forecasts. The seven-day boards cover an entire province or region; the chance of rain expressed in percentages is about the only visual way to indicate my confidence in the expectation of wet weather.
I prefer to qualify the likelihood of rain or snow with words that describe my confidence in the occurrence and specific location of forecast precipitation.
Be sure to watch my twicedaily weather video at www. saltwire.com/weather