University of Delaware Office of Public Relations The Messenger Vol. 5, No. 1/1995 Weather alert! Researcher's system in use in Philadelphia A hot weather alert system developed by a University of Delaware professor now warns Philadelphia residents when high temperatures may become life threatening, and it soon will be in use in other U.S. cities. Developed by Laurence Kalkstein, professor of geography in the UD Center for Climatic Research, the system is sponsored by the Environmental Protection Agency. Based on research that identifies the weather conditions that produce statistically significant increases in average daily mortality, the system was adopted last summer by Philadelphia's health department. Designed to provide the public with greater advance warning of dangerous heat, the new three-tiered, computerized system consists of a Hot Weather Health Watch, a Hot Weather Health Alert and a Hot Weather Health Warning. While all will be issued by Philadelphia's health commissioner, a Hot Weather Health Warning will be released in consultation with the National Weather Service. During the heat wave of June 1993, the Philadelphia Medical Examiner's Office recorded 118 heat-related deaths. Prior hot weather warnings were issued by the health department in conjunction with the National Weather Service forecast of two consecutive days of a heat and humidity index of 105 degrees or more for at least three hours each day. These warnings were based upon a subjective "comfort level," not medical evidence. According to Kalkstein, "There is no established scientific relationship between 105 degrees and human health. An advantage of the new health watch/warning system for Philadelphia is the identification of high-risk air masses that are actually associated with elevated mortality in the summer. In addition, by using National Weather Service forecast data for upcoming days, it will be possible to predict the arrival of a high-risk air mass up to two days before its arrival." The new system identifies a high-risk air mass through computerized analysis of National Weather Service prediction data. When such an air mass is detected, its impact on people is determined based upon a formula that includes the variables of temperature, time of year and length of a given hot spell. Derived from a study of 20 years of weather and mortality statistics, the formula predicts when potentially deadly heat will arrive in the Delaware Valley. Kalkstein's research has demonstrated that different regions of the country are affected differently by the weather. Heat is linked to an increase in deaths in cities such as Philadelphia, Boston and New York, but not in Dallas and New Orleans, where the climate produces less dramatic changes in weather. The system introduced in Philadelphia is the first of its kind, and researchers expect it will serve as a model for other cities. -Ed Okonowicz, Delaware '69, '84 M