A man checks a damaged house in Mayfield, Kentucky, the United States, on Dec. 15, 2021. Rehabilitation is underway as assistance from neighboring counties and states has been pouring into Mayfield City, one of the areas worst hit by tornadoes, in the southwestern part of U.S. state of Kentucky.(Photo: Xinhua)

 The US state of Kentucky is awaiting President Joe Biden, who is scheduled to survey tornado damage, to meet with victims and deliver remarks there on Wednesday, showing that the federal government has attached great attention to the disaster that has claimed at least 90 lives across six states in the central parts of the country. 

The president's trip will include a stop in Fort Campbell for a storm briefing, and stops in Mayfield and Dawson Springs to survey storm damage. Compared with Arkansas, Illinois, Missouri, Mississippi and Tennessee, Kentucky was the hardest hit with more than 80 deaths aged from 2 months to 98 years, and over 100 unaccounted for.

Meanwhile, in Edwardsville, Illinois, the Occupational Safety and Health Administration is investigating the deadly collapse at an Amazon warehouse, which was caused by a tornado on Friday that devastated the area and killed six Amazon workers. 

Most workers who died there were not sheltering in the "designated location," the company said.

More alarmingly, CBS reported on Tuesday that the cluster of deadly storms occurring on December 10 to 11 is the latest sign that "tornado activity has waned in the Great Plains - historically known as 'Tornado Alley' - while picking up in the southeastern US, a manufacturing-rich region increasingly critical to the nation's supply chain." Amid the catastrophe, the early signaling systems placed throughout the middle of the country mostly worked as promised, reported The Wall Street Journal on Tuesday. People received text alerts and radio alerts from local officials and forecasters, which would have given them enough time to shelter in place, as they have done for years during tornadoes.

However, the power, speed and duration of the tornado caught residents, businesses and cities by surprise and overwhelmed many of their safety procedures. The tornado's estimated wind speeds of over 321 kilometers an hour would make it an EF5, the highest level on the Enhanced Fujita scale rating system, according to the report.

While meteorologists continued to analyze data on the tornado, its length was likely record-setting. "It sent debris 30,000 feet into the air, the cruising altitude of many passenger jets, and scattered prom photos, handmade quilts and wrapped Christmas gifts scores of miles away from the tornado's path," said the report.

The twister rivaled the 1925 Tri-State tornado that killed 695 people as it traveled 352 kilometers across Missouri, Illinois and Indiana. Bill Bunting, chief of forecast operations at the National Weather Service's (NWS) Storm Prediction Center, was quoted as saying that a rare confluence of weather conditions created the tornado.

No other major storms formed to disrupt the tornado's formation or block its path, according to Bunting.