NORMAN, Okla. — The atmosphere was in turmoil before sunrise one day last week, and more than 58 million people were at risk.
A tornado threat was stalking the Texas and Oklahoma panhandles, and the Dallas-Fort Worth metroplex. Damaging winds were a danger along the entire length of Interstate 70 in Missouri. A possibility of quarter-size hail lurked as far north as Minnesota and Wisconsin.
The following day would bring even more menaces in more places. By the weekend, at least five people would be dead as storms raged, trees splintered and homes and businesses were destroyed.
But before the funnel clouds and cracks of thunder struck, a handful of government meteorologists huddled at the Storm Prediction Center, just south of Oklahoma City, to divine the future. Inside a quiet second-floor room, they studied dozens of computer monitors, drew maps with lime-green Sharpies and colored pencils and looked for the atmospheric ingredients that could turn clouds into killers.
Their forecasts are getting more precise, and more vital. Every tornado or severe thunderstorm watch in the continental United States — 450 last year alone — starts at the center in Norman, Okla. So far this year, forecasters have issued more than 90 watches. And the severe weather season is only intensifying.
The center, part of the National Weather Service, allowed a reporter and a photographer to observe meteorologists over a single day as they built forecasts with a blend of science, history and a measured dose of human instinct.
“A lot of people would like to make it black and white,” Russell S. Schneider, the center’s director, said in his office, where he keeps aged newspapers with accounts of tornadoes past. “It’s not. The key to this is embracing the grayness.”
Wednesday, 11:21 a.m. Central Daylight Time
Past a maroon-and-white sign reading “Critical Severe Weather Day. Enter For Official Business Only,” six forecasters were studying the 48 continental states from Room 2370.
It was an intense, if quiet and orderly, scene, with the forecasters swiveling in their chairs from one monitor to another, peering at high-resolution satellite pictures, forecasting models, radar data and surface observations. They were in chat rooms with Weather Service offices across the country to gather real-time accounts and to field questions about pending forecasts that are rooted in probabilities.
“You can’t look at everything,” said Bill Bunting, the chief of forecast operations. “If you did, your forecast would be after the event, so the challenge is knowing what to look at, what weight to place on a given piece of data.”
The meteorologists’ eight-hour shifts were governed by Coordinated Universal Time, a rhythm of regular forecasts and the twitches of weather emergencies. But they were looking for consistency, especially when conditions were imminent.
The center’s so-called Day One outlooks are published five times a day. By late morning, the number of people in danger had climbed past 62 million.
A few raindrops were falling. The winds were steady. Clouds had shrouded the Oklahoma sky in a shade of granite.
“You see how fast they’re moving? That’s never a good sign,” Mr. Bunting said as he reached for his cellphone and a commercial radar app.
Forecasters had emerged from their technology-packed, fortified building to watch their “gold standard” of meteorology take flight.
It was a latex balloon.
For the Storm Prediction Center and other weather offices that are part of the National Oceanic and Atmospheric Administration, the balloons — about 6 feet wide and affixed with devices that help experts detect pressure, relative humidity, temperature and winds — remain fixtures of forecasting. On this day in Norman, meteorologists filled four, marched them out of a garage and let them go.
The enormous balloon that Mr. Bunting had come to watch lifted off as quickly as a child’s at a birthday party. The forecasters trained their eyes on it, watching its instrument dangle and dance as it gained altitude and raced into the atmosphere. About two minutes after release, the balloon was out of sight.
It was already gathering data, sending it to Weather Service computers on the earth’s surface every one to two seconds. Mr. Bunting walked back into the building, whose windows can withstand winds of 166 miles per hour, and stopped at the restaurant for a muffin.
The Flying Cow Cafe’s television was switched to the Weather Channel.
“Hey Norman,” Jeremy Grams, a lead forecaster, said into the phone. “We’re just waiting on Amarillo.”
Conditions were poised to worsen in Oklahoma and Texas, and Mr. Grams was drawing up plans for a severe thunderstorm watch — a formal advisory that an organized storm, with winds of at least 58 miles per hour or hail that is an inch in diameter, is possible.
On a conference call with three Weather Service offices monitoring the affected counties, Mr. Grams offered his colleagues a meteorological overview. The main threats, he said, seemed to be large hail and damaging winds. He asked for feedback about the center’s watch plan. There were no objections.
“URGENT,” the bulletin read. “IMMEDIATE BROADCAST REQUESTED.”
Tornado forecasts were born in Oklahoma in 1948, when meteorologists at an Air Force base used observations, instincts and five-day-old weather records to suggest that a twister might be coming. Their prediction turned out to be accurate.
Today’s forecasts depend far more on technology, and they have become far more precise and better able to assess a storm’s strength and consequences, all helpful for emergency workers.
But human instinct is still critical. The Storm Prediction Center is the rare workplace where everyone has pencil sharpeners because, even now, forecasters will draw some maps by hand.
In what counts for a lull, Mr. Grams reached toward a pencil box and set to work, carefully charting the conditions of the nation’s midsection. Constant dew points were linked. Isobars — lines of constant pressure — were illustrated with a black Sharpie marker. A red marker designated a low pressure area. He scribbled notations and shaded parts of the map.
Sketching maps might seem old-fashioned, but the forecasters said it helped them think through their data.
As Mr. Grams’s shift neared its 4 p.m. end, his replacement, John Hart, appeared. They had a brief conversation about what the atmosphere was doing. Mr. Hart mostly listened before he slid into Mr. Grams’s seat.
He quickly decided a severe thunderstorm watch was appropriate for parts of Kansas and Oklahoma. But he was cautious about the timing and scope.
“You issue a watch too early, people become complacent,” he said.
After consulting with five Weather Service offices, he deleted three Oklahoma counties from the watch.
Most forecasters have wanted to work in weather since they were children. Decades before he joined the center, Rich Thompson’s third word was “wain.” Mr. Grams remembers a tornado that struck Minnesota when he was 3. Thanks to Hurricane Camille, Mr. Bunting became interested in weather when he was 9.
The scope — and consequences — of the storms they have charted are similarly sharp in their memories. They know the triple-digit death tolls that sometimes come, even when their forecasts are tragically accurate. Just last month, 23 people died in Alabama after a well-warned tornado outbreak.
“You just see the injuries, the damages, the fatalities just piling up, and you’re thinking, ‘What’s the point?’” Mr. Thompson said as he considered some of the larger outbreaks on his watch. “It’s like, I did the best I could, and we just had the most people killed in one of these kinds of forecasts on record. I kind of wondered and thought, ‘Is it just the limit of what we can do?’”
Indeed, the forecasters know that all they can do from Oklahoma is to come up with predictions and alert the public — and to be as credible as possible, he said, “so that when we jump up and down and yell and wave our arms, people take it seriously.”
Down a hall, another arm of the country’s weather bureaucracy was busy: The Weather Service’s Norman forecast office, which tracks conditions in 56 Oklahoma and Texas counties, was confronting the nastiness that the Storm Prediction Center had feared.
The room resembled Mission Control. Forecasters and researchers crowded around banks of computer monitors. Four local television stations, their coverage filled with fresh footage of funnel clouds, flashed on a large screen. Fourteen minutes after the office issued a tornado warning, the phone rang. It was an emergency manager in Ellis County, Okla.
“Tornado still on the ground,” a forecaster reported after taking the call.
Minutes passed. Scanning their screens, the meteorologists decided the threat was nowhere near finished. They soon issued a new tornado warning.
It showed up on television screens in seconds.
In the Storm Prediction Center, a one-second music clip from the Robert Redford movie “The Natural” alerted forecasters to a tornado warning somewhere in the country.
As sunset approached, the center’s meteorologists turned their attention to the next day. They worried about what they saw.
Thursday, 8:11 a.m.
Much of the nation was fixated on the maelstrom in Washington: Attorney General William P. Barr’s news conference about the special counsel’s inquiry was about 20 minutes away. But the forecasters in Oklahoma had actual storms to obsess over.
As Mr. Barr prepared to step to a lectern, the center issued an outlook for the day. Trouble still seemed likely, especially around New Orleans and Jackson, Miss.
About 29 million people were at risk.
Alan Blinder is a national correspondent based in the Atlanta bureau. With a primary focus on his native South, he has reported from more than two dozen states since joining The Times in 2013. @alanblinder