Today 07:00 Last updated, today 07:00A number of states in the US experienced very severe weather last weekend. Dozens of large tornadoes have been sighted, causing much destruction. Many buildings are in ruins, but early warning systems prevented fatalities in Nebraska.
On Friday evening it started to storm in the Midwestern US. At that time, there were at least 80 tornado reports in five states. The city of Omaha, Nebraska, was particularly hard hit by the tornadoes. More than a hundred homes have been damaged or destroyed.
On Saturday and Sunday there was another warning of severe storms with strong tornadoes. From Michigan to Texas, more than 50 million people were threatened by severe weather on Saturday. On Saturday night, a tornado outbreak claimed several lives in Oklahoma, where reports of large and extremely dangerous tornadoes occurring simultaneously have been reported. According to the National Weather Service, category EF-3 tornadoes reached winds of more than 140 mph (220 km/h) in areas including Oklahoma. The ‘Enhanced Fujita’ scale (EF) describes the strength of a tornado based on damage reports. It ranges from EF-0 to EF-5, where EF-0 represents small tornadoes with wind speeds between 105 and 135 km/h and EF-5 for very severe tornadoes with wind speeds above 320 km/h.
The storms also brought heavy precipitation, posing additional hazards. The heavy rainfall may locally lead to a moderate to high risk of flash flooding. In Trinity County, Texas, 10 inches of rain fell on Sunday and water rescues were conducted.
A low pressure area over the Plains caused this severe weather. Moist and warm air was brought in from the south, a favorable situation for large storms. In addition, there was a lot of wind shear in the region due to a ‘low level jet’. That is a fast-moving band of air in the lower layers of the atmosphere. It can transport warm and moist air northwards at high speed, contributing to the formation of thunderstorms and tornadoes.
