AMS April science highlights

Flood Fatalities in the United States

A study in the March issue of the AMS’ Journal of Applied Meteorology and Climatology compiles a nationwide database of flood fatalities for the contiguous United States from 1959 to 2005. Assembled data include the location of fatalities, age and gender of victims, activity and/or setting of fatalities, and the type of flood events responsible for each fatality report. Analysis of these data reveals that a majority of fatalities are caused by flash floods; that people between the ages of 10 and 29 and over 60 years of age are found to be more vulnerable to floods; and that human behavior contributes to flood fatality occurrences. These results also suggest that future structural modifications of flood control designs (e.g., culverts and bridges) may not reduce the number of fatalities nationwide. For a copy of the paper contact Stephanie Kenitzer.

Tornado Warnings, Lead Times, and Tornado Casualties

A paper in the April issue of the AMS’ Weather and Forecasting explores the conventional wisdom that holds that improved tornado warnings will reduce tornado casualties, because longer lead times on warnings provide extra opportunities to alert residents who can then take precautions. The researchers from Austin College and University of Texas – Pan American examined the relationship between warnings and casualties by using a dataset of tornadoes in the contiguous United States between 1986 and 2002. They asked two questions: Does a warning issued on a tornado reduce the resulting number of fatalities and injuries" Do longer lead times reduce casualties" They found that warnings have had a significant and consistent effect on tornado injuries, with a reduction of over 40% at some lead time intervals. The results for fatalities are mixed. An increase in lead time up to about 15 minutes reduces fatalities, while lead times longer than 15 minutes increase fatalities compared with no warning. The results for fatalities and injuries both indicate that the effectiveness of warnings declines when lead times exceed 15 minutes. This may occur because residents discount warnings with long lead times. That is, if a tornado does not begin shortly after a warning is issued, people might dismiss the warning as a false alarm. For a copy of the paper contact Stephanie Kenitzer.