Natural Hazards and Disasters

Class 10: Tornadoes, Ice Storms and Meteotsunamis

Class Slides

Tornadoes

Tornadoes are relatively narrow, violently rotating air columns that cause intense, although local, destruction. They extend between a thunderstorm's cloud base and the ground surface. Because the outer wall of the rotating air column is rather sharply defined, even though tornadoes inflict extreme destruction on everything within their path, the areas immediately adjacent to a tornado's touchdown may be completely unaffected.

Ice Stroms

Winter storms that bring heavy freezing rain can lead to many hazards including glazes on roads and other exposed outdoor surfaces and overload infrastructure and trees with ice loads. Freezing rain occurs when relatively warm humid layers of air are above cold layers and rain falls from the warm layer into the cold one. While it falls through the cold layer, the rain is still liquid but cools down rapidly and can be supercooled, but still liquid, when it hits a surface. At that moment, the rain drops freeze on contact, and the ice layer can rapidly increase in thickness.

Meteotsunamis

Meteorologically generated tsunami-type waves are known as meteotsunamis. Meteotsunamis can be created by three main mechanisms:

1. A meteorologic disturbance
2. Resonance between the speed of the meteorological disturbance and deep-water wave speed
3. Amplifying qualities of a harbor, bay or inlet

Meteotsunamis can occur in the oceans or large lakes. Like other tsunamis, they reach the largest amplitudes in shallower areas or where the coastal geometry leads to amplifications.

Class Reading List

Tornadoes

Wikipedia, 2017. Tornadoes. https://en.wikipedia.org/wiki/Tornado.

Snow, J., 2017. Tornadoes. Encyclopeadia Britannica, https://www.britannica.com/science/tornado.

Tippett, M. K., Cohen, J. E., 2016. Tornado outbreak variability follows Taylor’s power law of fluctuation scaling and increases dramatically with severity, Nature Communications, 7, 10668, DOI: 10.1038/ncomms10668, pdf, html.

Ice storms

MRCC, n.d., Ice Stroms. Living with Weather, Midwestern Regional Climate Center. http://mrcc.isws.illinois.edu/living_wx/icestorms/.

Houston, T. G., Changnon, S. A. 2007. Freezing rain events: a major hazard in the conterminous US. Natural Hazards, 40, 485-494.

Meteotsunamis

Monserrat, S., Vilibíc, I., Rabinovich, A. B., 2006. Meteotsunamis: atmospherically induced destructive ocean waves in the tsunami frequency band. Natural Hazards and Earth System Sciences, 6(6), 1035-1051. doi: 10.5194/nhess-6-1035-2006. pdf.

Thomas, E., Ryan, G. (eds.), 2010. Meteotsunamis. https://meteotsunami.weebly.com/index.html.

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