NWS’s Narrow Line

The National Weather Service has decided to stick with a narrow black line to project the path of hurricanes, despite concerns that such a graphic does not express the uncertainity of their forecasts and could give the public a false sense of security.

The decision was made not on the basis of science, but “was made after the weather service sought opinions from the public, the news media and emergency service workers, receiving 971 e-mailed responses.” Respondents apparently thought they were smart enough to figure the details of the forecast out for themselves.

Roger Pielke Jr., who directs the University of Colorado’s Center for Science and Technology Policy Research, wrote a paper a few years ago that contradict the simplicity of such forecasts. Pielke considered the renowned flooding of the Red River, and found that characterizing the flooding in terms of a single number, i.e. flood stage, led to “misjudged risk assessment, overconfidence in forecasts, and ultimately poor decisions about how to fight the flood.”

His results seem to apply directly to the case of hurricane forecasting, where common uncertainties of 50 to 100 miles can make a real difference in forecasts. He says that local authorities often do not want the messiness of a probabilistic forecast, and that the NWS is (over)reacting to such a failure to accept responsibility.