Matthew Cappucci at the Washington Post: “Imagine someone telling you the weather forecast for New Year’s Day today, two months in advance, with exact temperature bounds and rainfall to a hundredth of an inch. Sounds too good to be true, yes?
A new study in Science says it’s simply not possible. But just how far can we take a day-by-day forecast?
The practical limit to daily forecasting
“A skillful forecast lead time of midlatitude instantaneous weather is around 10 days, which serves as the practical predictability limit,” according to a study published in April in the Journal of the Atmospheric Sciences.
Those limits aren’t likely to change much anytime soon. Even if scientists had the data they needed and a more perfect understanding of all forecasting’s complexities, skillful forecasts could extend out to about 14 or 15 days only, the 2019 study found, because of the chaotic nature of the atmosphere.
“Two weeks is about right. It’s as close to be the ultimate limit as we can demonstrate,” the study’s lead author told Science Magazine.
The American Meteorological Society agrees. Their statement on the limits of prediction, in place since 2015, states that “presently, forecasts of daily or specific weather conditions do not exhibit useful skill beyond eight days, meaning that their accuracy is low.”
Although the American Meteorological Society strongly advises against issuing specific forecasts beyond eight days, popular weather vendor AccuWeather has, for years, churned out detailed predictions many days further into the future. It initiated 45-day forecasts in 2013, which it extended to 90 days in 2016 — and has been heavily criticized for it….(More)”.