Tornado in North Dakota, October 9, 2009

A waterspout formed over Lake Sakakawea near New Town. It did not form from a thunderstorm. Several factors contributed to the formation of this waterspout. Low pressure over the state was already producing upward motion and large scale circulation in the atmosphere. Cumulus clouds associated with a cold front passing through the area were producing snow showers. The combination of very cold air, in the upper 20s, and relatively mild water, near 60 degrees, caused significant instability in the lower several thousand feet of the atmosphere over the lake. This instability enhanced the instability associated with the low pressure and snow showers and changed atmospheric conditions over the lake. Strong surface winds interacting with the terrain around the lake may have formed a small vortex of rotating air that translated onto the lake. This vortex may have been stretched vertically by the updraft of the snow showers, leading to the waterspout forming. The water spout remained over the lake and there was no damage.

Several funnel clouds were reported late in the morning over Lake Sakakawea near New Town. See the tornado entry earlier the same day.