Tornado Composite Charts for the Canadian Prairies

Abstract

Composite charts of tornado situations are presented for the surface, 850-, 700-, 500-, and 200-mb levels for Manitoba and Saskatchewan. These charts do not cover all possible situations but are only for the most common type and for the regions of highest frequency. Tornado situations were typed according to surface-level synoptic patterns. The most common occurrence (76 per cent) was along an instability line which preceded, and was parallel to, a cold front. This instability line may have intersected a diffuse warm front near the tornado location. Three other categories were noted. The average airmass characteristics and composite charts are very similar to those found for the Great Plains area of the United States.