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An investigation to ( 1) determine the 500-milli-bar level weather patterns associated with tornadoes moving from northwest toward southeast and from southwest toward northeast and, (2) show the significance of the contrasts between the 500-mb. level weather patterns of the two tornado types. A very high relationship between the direction of the 500-mb. level winds and the tornado direction was substantiated by a coefficient of correlation of +0.88. The typical 500-mb. level low center associated with the northwest to southeast type tornado was located over Hudson Bay about 1300 miles north-northeast of the tornado area. The low center associated with the southwest to northeast type tornado was positioned over northeast Montana about 900 miles northwest of the tornado area.

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