Why the Weatherman Always Gets it Wrong

…or DOES he? – Does the local weatherman in your area always seem to get it wrong? Maybe it’s YOUR fault: new research indicates that only about half the population knows what a forecast means when it predicts a 20% chance of rain. The confusion comes because people don’t understand what the 20% chance of rain actually refers to. Many people think it means that it will rain over 20% of the area covered by the forecast or for 20% of the time period covered by the forecast.

Psychologist Susan Joslyn Joslyn and her colleagues tested more than 450 college students to see if they understood what weather forecasts meant. They didn’t. She says, “When a forecast says there is 20% chance of rain tomorrow it actually means it will rain on 20% of the days with exactly the same atmospheric conditions. With the exception of the probability of precipitation, most weather forecasts report a single value such as the high temperature will be 53 degrees. This implies that forecasters are sure the high temperature will be 53 degrees. But forecasting is not that exact and 53 degrees is in the middle of the range of possible temperatures, say 49 to 56 degrees.”

She believes that the errors are caused by the difficulty in making decisions when uncertainty is involved and says, “In dealing with a forecast about rain people must simultaneously consider several hypothetical outcomes, their corresponding levels of uncertainty and their consequences. For some people it may be easier to commit to a single outcome?and proceed as through the uncertainty has been resolved. In some cases they may not be aware of this simplification.”

Interestingly, we have found that this is the same thing that some people do when trying to explain UFOs and what we call The Visitors. Rain or shine (and in Nashville it’s usually shine), we’ll be holding our wonderful Dreamland Festival again this year in June. Will the Visitors join us? Come and find out!

Art credit: Dreamstime.com

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