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What's that weather forecast mean? Hard to say (clearly)

A typical online weather forecast from the National Weather Service (for Seattle, as of noon on Jan. 24th).
National Weather Service/NOAA website
A typical online weather forecast from the National Weather Service (for Seattle, as of noon on Jan. 24th).

You might not have realized it, but weather forecasts have been getting more accurate for the past ten to twenty years. Forecasters have a lot more precision about when and where different weather systems will hit.  But, this isn’t always communicated very clearly.

So, thousands of America’s leading meteorologists are discussing "better communication" at their their annual conference in Seattle. They especially are talking about how to communicate better about dangers during severe weather events, when they're coordinating with emergency agencies, power companies and road crews. 

But, the president of American Meteorological Society says it's a challenge even getting the word out on daily weather forecasts.

Part of the problem is how much time it takes to explain something technical.

"It is really hard, particularly for a scientific idea that's very technical, to explain it to someone who doesn’t have a scientific background," says Peggy LeMone, AMS president and an atmospheric scientist at the National Center for Atmospheric Research.

These days, there’s pretty good weather data that can tell you precisely around Puget Sound, for example, that it’s more likely to rain in Everett, be dry in Federal Way, but slightly cloudier in Bellevue. TV news can spend five minutes showing you how the clouds are moving across the area, where the rain-shadow is, and which towns are getting the high winds.

But, in many cases, it's too much detail. The public often needs a simple graphic or icon that says whether it'll be sunny, cloudy or rainy. On the radio, at KPLU, we have to give a forecast in under 30 seconds, and it has to cover all of western Washington. That doesn't leave room for many subtleties.

And, there’s also the issue of math, and the fact that most of us are math-challenged.

"If you surveyed a number of people about what it means to say, 'There's a 40 percent chance of rainfall today,' you'd get a lot of answers," says LeMone. It's not clear, even after after the meteorologists' society has been meeting for 91 consecutive years, how to simplify this for the general public.

The rest of the week, the AMS is also discussing how climate change will affect weather forecasts, and even how to keep tabs on ‘space weather,’ which affects satellites orbiting Earth.

Tip: To get a more precise forecast for your home or office, go to the National Weather Service Seattle homepage, and type in your zipcode in the box in the upper left corner of the screen. (You still have to make sense of percentages and probabilities.) If you like details, you'll also enjoy reading the "area forecast discussion," wherein the meteorlogist explains what's really happening.

Keith Seinfeld is a former KNKX/KPLU reporter who covered health, science and the environment over his 17 years with the station. He also served as assistant news director. Prior to KLPU, he was a staff reporter at The Seattle Times and The News Tribune in Tacoma and a freelance writer-producer. His work has been honored by the American Association for the Advancement of Science (AAAS) and the Knight Science Journalism Fellowships at Massachusetts Institute of Technology.