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The tornado hit exactly when they said it would

TECHNOLOGY

Morgan Jackson, a cashier at a general store in Mayfield, Kentucky, checked the weather all day on Friday December 10, 2021. Her phone was bleeping with loud alerts and customers were chatting incessantly about the tornadoes that were likely to head their way that day. Friends and family were also calling in to compare notes.


“We all knew the storm was going to hit,” she says. “There’s no way a single person here didn’t know the storm was coming.”


For residents of Mayfield (pop. 10,017) subjected to the flurry of alerts and text messages, the urgent pleadings of TV meteorologists and the barrage of warnings on social media, one thing was clear: This was not a tornado that came without warning.


Jackson says she was surprised how accurately forecasters had pegged the timing of the tornado, one of several that swept through Kentucky that night. “They said it would hit at 9.30 and it hit at 9.30,” she says.


Weather prediction technology has become so precise in recent years that tornadoes are almost always foreseen — a vast, if somewhat unheralded, improvement in forecasting.

In the late 1980s, before the use of Doppler radar and other technologies, meteorologists were able to issue warnings for 46 of 88 violent tornadoes in the United States, federal data shows. In recent years, powerful tornadoes have been preceded by warnings 97% of the time.


Unlike hurricanes, tornado warnings come with a much shorter lead time: around 15–18 minutes on average. December 10’s tornadoes had better-than-usual warning times, in some cases three times as long. But when tornadoes strike at night, as they did this time, residents are more likely to miss the warnings. At night, they’re 2.5 times as likely to result in fatalities, research shows.


This tornado was a monster, an EF-3 storm with winds of 217–264kph. Its footprint was up to 1.2km wide, and it shredded warehouses and houses along a path of more than 350km.


The drumbeat of warnings began days before, with reports from the national Storm Prediction Centre that tornadoes were quite likely. “It was kind of a no-brainer as far as issuing a warning goes,” says Michael York, a meteorologist at the National Weather Service in Paducah, Kentucky. “It was one of those that is impossible to miss if you have any training at all.”


Experts say the United States has reached a point where the technology to predict tornadoes is no longer the main obstacle to saving lives. The huge strides in tornado prediction rates have been made possible by a cascade of scientific advances. The introduction of Doppler radar in the 1990s and subsequent upgrades have allowed forecasters to measure the wind inside a storm, to distinguish between rain, snow or hail and to see and predict the formation of tornadoes. The proliferation of weather satellites allows scientists even more visibility into the formation of storms — and, crucially, the conditions that might create a tornado. The National Oceanic and Atmospheric Administration (NOAA) operates 16 satellites.


The deluge of data from these technologies is crunched and modelled in real time by some of the world’s most powerful supercomputers. “In many ways the tornado warning system — and everything that leads up to it — is one of the most incredible success stories in applied science,” says Harold Brooks, a senior research scientist at NOAA’s National Severe Storms Laboratory. “We don’t miss violent tornadoes essentially ever now.”


Before Doppler was deployed to predict tornadoes, the best authorities could do was rely on a more primitive form of radar and a small army of weather spotters communicating by ham radio.


The consequences of the leaps in technology have been clear, researchers report. “Tornado fatality rates have dropped off the map,” says Stephen Strader, a geography professor at Villanova University who studies disasters. His research shows the number of people killed by tornadoes in the US dropped steadily from 1920 — when there were 2.3 fatalities per 1 million people — to 1990, when there were 0.25 fatalities per million. Experts say lives were saved not only by the technology that helps predict tornadoes but by better education and building codes.


In the wake of December’s tornadoes, a number of scientists have made comparisons to a similar event nearly a century ago to illustrate how awareness of a coming danger saves lives. In 1925, when the best authorities could do was send warnings by telegraph, a tornado travelled across parts of Missouri, Illinois and Indiana for about 350 kms — similar to the distance travelled by the biggest of the recent tornadoes. The 1925 tornado killed nearly 700 people, about 10 times the death toll of December’s worst tornado.


TOP PHOTO Raychel Sanner


In many ways the tornado warning system — and everything that leads up to it — is one of the most incredible success stories in applied science. We don’t miss violent tornadoes essentially ever now.

Harold Brooks


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