Of the known and unknown


The cruelty of this particular April, in the number of tornadoes recorded, is without equal in the United States. The record for the month has been shattered, and preliminary assessments say that of the four biggest clusters ever recorded, two have occurred in the past three weeks. What is happening here? With every passing day, it seems, more precise digital tools emerge to clarify the inner heart of a storm cell in rampage. And yet, for all that solid information, the natural world can still seem murky, unpredictable and downright scary when it roars into full-throated chaos. Tornadoes, in particular, researchers say, straddle the line between the known and the profoundly unknowable. “There’s a large crapshoot aspect,” said Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research in Colorado. “A little quirky thing can set one off at one time, and another time not.”
Tornadoes need warm, moist air interacting with faster, cooler air. That much scientists know for sure. “There’s a lot we understand about tornadoes,” Trenberth said. “They’re tied to thunderstorms and also require something that will cause the rotation to occur, a wind shear.” And all of these ingredients have been in abundant supply in the areas of the country that have been hit hardest this month than in any April since current counting methods began. Nevertheless, scientists can only guess when and where tornadoes will actually strike.
When technology can predict oncoming storm tracks and conditions with greater certainty than ever, and scientists assert with growing unanimity a human impact on climate, what is a natural act of God and what is more correctly the province of humans themselves? Where is the place of psychic shelter in an age when the lines between fate and human action are blurred?
The prevalence of hurricanes, droughts and floods has been linked in many climate models to the impact of a warming planet. Such a connection is more tentative when it comes to tornadoes. “Tornadoes are tougher,” said Jeff Masters, director of meteorology at Weather Underground, an internet-based weather service. Many climate models, for example, predict a weakening upper atmosphere jet stream over time on a warming planet, Masters said, which would presumably create less energy for tornado formation. But some of those same models also suggest wetter conditions in tornado country, which is the other key ingredient in storm formation.
At the same time, more people are also living in areas where tornadoes strike, across the broad swath called Tornado Alley in US’s midsection and south, so the number of observed and recorded tornadoes has steadily gone up. The population of the south grew 14.3 per cent over the past decade, according to the Census Bureau, compared with 9.7 per cent for the nation as a whole.
Much of the new construction took place on flat areas of flood plain, meteorologists say, where rains from storms in years past spread  cross the earth and either evaporated or were absorbed. The water now runs across pavement, seeking lower ground rendered more vulnerable to flood. And to top off that mix, the jet stream forces in April were among the strongest ever recorded, possibly because of La Nina conditions in the Pacific Ocean. A La Nina pattern, which leads to cooler water around the equator in the Pacific Ocean, is associated with wetter and stormier conditions through the middle of the country as cooler air from Canada surges into warm moisture heading north — made warmer, many climate scientists say, by climate change. And yet, since that crucial element of weather prediction is missing — when and where the next tornado hit might come — the question of trust and faith, if not fatalism, is easy to find.
If scientists cannot be sure — or trusted, as doubters of climate change might say — then where should an ordinary person on the ground turn for solace or strength in the raging maw of a storm? Perhaps, as the National Weather Service put it in an update recently about Alabama, there is only perseverance. “Many thoughts and prayers go out to those impacted,” the update said. “The weather never ends and we must continue.” The weather often has a political aspect, and a monetary one as well, as anyone who has lived through a major snowstorm only to see streets unplowed can attest.
Tornadoes, too, have political and monetary impacts, but more than many other natural phenomena they invite us, in their unpredictability and fierceness, to contemplate the possibility of a hidden hand directing them in their path. In March 1994, for example, a tornado hit the small town of Piedmont in Alabama, destroying the Goshen United Methodist Church in the middle of Palm Sunday services, killing 19 people inside. “Because it was a church, it brought up this issue: Is it an act of God?” said Ted Steinberg, professor of history and law at Case Western Reserve University in Cleveland.
It turned out to be more a result of human failing, said Steinberg, who was researching a book on natural disasters at the time. “It was a relatively poor community and there were no sirens there, so people in that leveled church had no warning,” he said. “Things can seem like acts of God or wrath of nature when in fact the reality, at least sometimes, is a failure of political will.”

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