Midwestern Ice Storms: Frequency, Amounts, and Associated Weather

Midwestern ice storms can have significant impacts on ground transportation, communications, and power transmission, as well as the loss and damage of trees. Unfortunately, data on ice storms are limited and difficult to compile. This study will use data from three sources, each having their own strengths and weaknesses. The first source is the NOAA publication Storm Data. While the publication goes back to 1959, the first 20 years have a notable lack of ice storm reports. While more recent reports are more extensive, there is a wide disparity in the amount of detail provided including the actual amounts of ice accumulated. The second source of data are the cooperative weather observer forms that extend back to the beginning of the century. Diligent observers made notes of the occurrence of freezing precipitation or glaze and sometimes included accumulated amounts. The third source of data are the sites with hourly surface reports (NCDC TD-3280). These sites report the occurrence of freezing rain or drizzle as well as temperature, wind speed, and direction on an hourly basis. These sources are combined to provide information useful to designers and planners of transportation and utility systems as well as the insurance industry. Results include the spatial and temporal distribution of ice storms, the timing within the day and year, expected amounts of icing, and other weather associated with icing events.