Experts Question AccuWeather's New 90-Day Forecast

It might be best to think of this forecast as a weather fortune cookie, scientists warn.

Do you wake up in the morning and wonder if you'll need an umbrella today? How about what you'll need three months from now?

AccuWeather is aiming to answer both questions with its new 90-day forecast, launched this week. The calendar predicts the high and low temperatures, precipitation, sky conditions and other pieces of weather data with surprising specificity.

The company heralded the free forecast on Monday by claiming that it's "providing users with the most advanced notice and detailed information on local weather conditions."

Just don't confuse the report's specificity with accuracy, according to meteorologists. Many agree that it's impossible to predict the weather of any given day that far in advance.

"We're kind of gobsmacked by this," said Alison Bridger, chairwoman of San Jose State University's Department of Meteorology and Climate Science. "It's inconceivable that they could know it's going to be rainy in New York on May 9 ... unless they've got some deeper, new scientific understanding that they haven't told us about yet."

AccuWeather did not immediately respond to HuffPost's inquiries, but company President Joel Myers responded to questions about the forecast's reliability on NPR.

"All of our forecasts are based on the latest science," he said. "This forecast will give you information that will be better than you can have figured out in any other way."

John Nielsen-Gammon, Texas' state climatologist, said it is possible to talk about weather conditions far into the future -- such as whether El Nino will produce a wetter winter on the West Coast or if temperatures over a period will be above normal due to greenhouse gas levels.

"You can make guesses weeks or months or even years into the future," said Nielsen-Gammon, "but the thing you can't do is say that one day is going to have particularly different weather than a day before or after."

That didn't stop AccuWeather from doubling down on its long range forecasts. The site previously told users what to expect 45 days ahead of time.

AccuWeather is a private company based in Pennsylvania that offers some paid services to broadcasters and other clients, as well as free information on its website. It's carved out a niche with specialized forecasts. At the other end of the spectrum, the company provides MinuteCast, which spells out minute-by-minute when there will be precipitation over the next two hours.

If AccuWeather is shown to be on target with its 90-day forecasts, it would represent a remarkable breakthrough. The best weather models used by the National Weather Service and foreign governments have a much more limited lifespan.

At five days out, forecasts seen on news broadcasts are fairly solid, but many experts agree that their accuracy evaporates after 14 days.

In AccuWeather's defense, its announcement about the 90-day forecast avoided any guarantees on its precision. A separate post on the company's website warned that "people should not use long-range forecasts as a strict guide, but rather look at how the weather patterns evolve."

It's likely that users will grant AccuWeather a wide amount of leeway by making projections so far in advance. Colorado's climatologist and Colorado State University professor Nolan Doesken compared the 90-day forecast to the enduring popularity of the Farmer's Almanac, which produced long-range forecasts months before publishing the annual book.

"From a customer perspective, there is a demand for this service whether its accurate or not," he said.

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