Date of this Version
Great Plains Quarterly Vol. 3, No. 4, Fall 1983, pp. 195-205.
Hail, lightning, flash floods, erosion, severe gusty winds, and tornadoes produce multimillion- dollar losses to the economy of the northern plains each summer. Research into these meteorological phenomena has been fragmented by the presence of political boundaries in the Great Plains, especially the 49th parallel, which separates the United States and Canada. Perceptions of and responses to the thunderstorm hazard still differ north and south of the border. Tornadoes, for example, have only recently appeared in the weather forecasts for the Canadian prairies, and such responses to summer storms as weather modification experiments and hail insurance coverage have been made in different ways in the two countries.
Because the most spectacular manifestation of thunderstorm weather, the tornado, occurs most often in the southern and central plains, and because storms have traditionally been considered more severe in these areas than in the relatively sparsely populated north, most of the detailed research into the thunderstorms of the plains has been done in a few limited regions, particularly in Oklahoma, Kansas, southern Illinois, and eastern Colorado. This article treats the thunderstorm hazard in the more northerly portion of the Great Plains, as shown in Figure 1. As it is clear from my data that the thunderstorm problem is common to both the American and Canadian sections of the northern plains, I examine the sometimes different responses to storm problems on either side of the 49th parallel. Finally, I show that a more unified approach to the thunderstorm problem in the northern plains is emerging, as researchers on both sides of the international boundary marshall their resources to produce a more effective system for monitoring and understanding the characteristics of storms and their impact on the land and people of the plains.
THE SCALE OF THUNDERSTORM HAZARD
Tornadoes and devastating hail and lightning storms vie with drought as the chief components of the "climatic image" of the southern and central Great Plains. Farther north, blizzards and drought receive the most attention; thunderstorm weather has seemed less important. Only recently has a more accurate assessment of the damage done by northern plains thunderstorms begun to emerge. In Iowa, Steve Eshelman and John Stanford investigated the 1974 thunderstorm season and found a vast and largely unsuspected amount of damage. Recent work on the Canadian prairies has produced similar results. This research suggests that the decline in thunderstorm severity from Kansas and Colorado northward may be less than is usually perceived. One reason for this perception is that population density, an important factor in accumulated storm damages, is relatively low in the northern plains.
Crop losses caused by hail in the northern plains states and on the Canadian prairies are very high. This region is the spring wheat belt, where the hail season and the growing season closely coincide. Stanley Changnon's study of hail losses in the United States showed that loss costs for crop-hail insurance (the ratio of losses paid to the amount of risk underwritten) in the northern plains states are high, with some of the largest values being found in eastern Montana and Wyoming. Changnon found that over the decade from 1960 to 1969, North Dakota led all other states in dollar losses to hail. Hail-insurance loss costs on the Canadian prairies are similar to those immediately south of the 49th parallel. In view of the large area of cropland, it is not surprising that dollar losses are high. In Saskatchewan alone, crophail damage in the 1960s has been estimated at about one-seventh of the loss in the entire United States for the same period. Thus hail remains an important hazard throughout the northern plains and into the Canadian prairies.