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The monthly storm induced rises are presented for the return periods, or recurrence intervals, indicated in the tables. Storm rises occur as a result of high winds and changes in barometric pressure. The monthly rises are based on an analysis of the maximum annual rise for each year which is the difference between the maximum and mean water level for a given month at a given gage location. The monthly rises are intended to be used in combination with the monthly mean lake levels provided in the Monthly Bulletin of Lake Levels for the Great Lakes. For example, at Milwaukee the probability that a 0.9 foot "storm induced rise" will be exceeded is 0.20 or 20 percent. This represents a return period, or recurrence interval of once in 5 years for the month of May. If the May level for Lakes Michigan-Huron is forecasted to be 580.0 feet, then there is a 20 percent (or 1 in 5) chance that a level of 580.9 feet will be equaled or exceeded at Milwaukee during the month of May. The monthly "storm-induced rise" values do not represent the actual events of any particular storm and the associated maximum water level that occurs during the storm. This is because the "rises" are derived from the differences between the monthly maximum hourly or instantaneous event and mean water levels for the month (average of the daily levels) and not the instantaneous pre- or post-water levels measured from specific, or individual storms that occurred in the past. Wave runup is the surge of water measured vertically from the still water level resulting from the wave acting on the shoreline structure, or beach. The runup is a function of wave height and structure type or shape and height. The wave height is a function of water depth, wind speed and direction, duration of the wind, and the offshore geometry. Large storm waves often break before reaching structures on the shoreline because the water depth is too shallow to support the wave.
To view the Storm Rise table for a particular lake region, please click on the region's name in the listing below:
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