Geographical and Seasonal Distribution of North American Cyclogenesis, 1958–1977

Abstract The geographical and seasonal distributions of cyclogenesis are studied for the North American sector for the period 1958–77. The primary zone of cyclogenesis is located between 35 and 40°N with this zone providing a maximum in all seasons except summer when a broad maximum exists between 45 and 55°N. Of the individual months, March provides a maximum and September a minimum. The most active areas are: 1) the East Coast, including the Gulf of Mexico coast in winter, 2) Colorado and Great Basin, 3) Alberta and Northwest Territories. A pronounced maximum exists in the Colorado–Great Basin area in March, while at the same time a minimum is present in Alberta–Northwest Territories. As summer approaches the Colorado activity declines markedly while activity in the Alberta–Northwest Territories region increases somewhat. Of the various regions, the greatest concentration of cyclogenesis occurs in the Colorado region. This is attributed to the sharp eastward decline in the terrain in this region and to ...