THE FORMATION AND STRUCTURE OF A LARGE-SCALE DISTURBANCE IN THE WESTERLIES

Abstract

The period of 3?7 February 1947 was marked by a radical change in the circulation over North America from westerly flow with only small perturbations to a pattern dominated by large warm anticyclones over the northern part of the continent and an unusually large cold cyclone covering the eastern part of the United States and southeastern Canada. Analyses, particularly of the 5OO- and 200-mb surfaces, and vertical cross sections for this period are shown, with an especially complete three-dimensional analysis for 5 February. The wind and temperature distribution during the period are discussed, with emphasis on the principal polar front, the tropopause surfaces, the jet stream, vertical motions (especially in the lower stratosphere), and the large-scale meridional exchange of air masses connected with the breakdown of the zonal flow and the formation of warm highs in the north and a cold low in the south.