AccuWeather issues 90-day forecasts and meteorologists are not amused

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ability to throw more computer processing power at forecast models has substantially improved the ability of meteorologists to predict the weather. A recent analysis found that a modern five-day forecast is as accurate as three-day forecast was in 1995. In the last three decades, thanks largely to numerical weather prediction, the useful window of forecasting has moved out from about 7 days to 10 days.

Yet beyond 10 days, most meteorologists will say, there is little predictive skill. This is largely due to the "butterfly effect," in which only a very small change in initial conditions will have huge changes after about 10 days. However, in August of 2013, this basic mathematical principle didn't prevent AccuWeather from beginning to issue 45-day weather forecasts.

According to an analysis by the Capital Weather Gang, a widely respected site that forecasts conditions for around Washington DC, these 45-day forecasts showed no "skill" after about 10 days. "AccuWeather is a for-profit company and they have every right to pass off less-than-accurate forecasts as they wish, but the public deserves to know that these 45-day forecasts are not rooted in any science currently available to meteorologists and have not demonstrated value," the site concluded. "Caveat emptor."

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