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Tornadoes, thunderstorms wreak havoc in the Midwest and South

The storms hit a number of states, and damage dozens of homes in one Missouri town alone

Anticipating further storms Friday, officials in parts of the Midwest and the South were assessing damage from strong thunderstorms and tornadoes that struck Thursday. From Texas to Southern Illinois, blinding downpours — up to five inches of rain in some places — diminished visibility on roadways, and, according to the Storm Prediction Center, large baseball-sized hail fell in places such as Franklin County, Mo., creating large holes in siding and damaging window sills and gutters.

Reports of tornadoes came from Missouri, Illinois and Texas. One of the more powerful ones — with winds of up to 110 mph — hit University City in St. Louis County, Mo., damaging 94 homes. Power lines and trees were downed across several states.

While the storms, which arrived in waves throughout the day, created brief chaos, they paled in comparison to ones that hit on April 27, 2011, when more than 162 tornadoes touched down between Missouri and New York, and 328 people were killed.

Thursday’s thunderstorms formed as clusters and squall lines of severe weather formed early in the morning. While severe storms and tornadoes can materialize anytime of the year, the spring and fall typically see an increase in such events.

During these seasons, strong winds in the upper levels of the atmosphere, vertical and horizontal wind shear and instability between contrasting air masses create the perfect conditions for severe storms.

When warm, moist southern gulf air interacts with cool northern air moving south, there is friction, instability between the two air masses. In an atmosphere that's unstable, vertical air movements, become larger, resulting in turbulent airflow and sometimes thunderstorms.

From supercells to tornadoes

Strong winds in the highest levels of the atmosphere and at the surface heighten the threat for storms to grow in size and potentially turn severe.

When winds aloft become strong and change direction with height, lasting longer than hour, they become supercells. A supercell thunderstorm is characterized by the presence of a mesocyclone: a deep, persistently rotating updraft. The longer these storms remain supercells and begin to rotate, the greater the likelihood the system may produce a tornado.

More severe weather is expected Friday as the storm moves across the Mississippi Valley towards the east coast. Damaging winds greater than 65 miles per hour are likely and more flooding due to heavy rain will be prevalent across the Great Lakes. Severe weather watches are already in effect from Louisiana through the Appalachian Mountains. 

With The Associated Press

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