A waterspout formed over Lake Sakakawea, near New Town, around 10 AM CDT Friday morning, October 9, 2009. The National Weather Service received several reports of a waterspout and other funnel clouds over Lake Sakakawea Friday morning. L.M. Baker, a reporter with MHA Times of New Town, took pictures of the spout and forwarded them to local broadcast media and the National Weather Service. In the pictures it is evident that the spout is over the lake, is in contact with the water surface, and that water is being lifted into the air. The spout was visible for several minutes and dissipated before reaching land. Other funnel clouds were reported over the lake. It was reported that they did not touch the water surface.
A waterspout is, in simple terms, a tornado over the water. Waterspouts are not common in North Dakota, and this one 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 (rotating air) that translated onto the lake. This vortex may have been stretched vertically by the updraft (rising air) of the snow showers, leading to the waterspout forming. The spout dissipated quickly as it neared land as conditions from the land surface up through the atmosphere over it were more uniform than those over the lake.
This is a good example of the land – water – atmosphere interactions that drive our weather.
Photo credit: L.M. Baker with the MHA Times, New Town, North Dakota.