Back inside, Dennis and Doug were becoming much more watchful. The 3 doppler radars close to Norman were beginning to see thunderstorm activity: there was as yet not much "vertical extension", forecasters' shorthand for the serious convection that can trigger hail and, under certain conditions still not fully understood, tornadoes.

   Dennis gave me a tour: over here sit the warning forecasters... short range forecaster over here... there is the person who handles staffing and scheduling... there are the interns (many from the nearby University of Oklahoma) who help us keep in contact with the public... and over here (and it's obvious Dennis considers this a favorite spot) the array of ham radios to keep in touch with several networks of weather spotters, folks working for emergency services or individuals who volunteer time to go out and gather ground truth about what the sky is doing. To the side, a large TV, tuned, for the moment, to the Weather Channel. Later that night, when local stations pre-empted sitcoms and game shows and sudsy dramas, this set would become an integral part of the Forecast Office operation.

   I hose-piped the room, capturing images most likely too shaky for broadcast, but giving us stills for the web. Then through the headphones I heard Doug call for the Office to go to generator power: something beyond the normal was obviously going on. Just routine, he said, when thunderstorms begin to build up. We want to be prepared so that we don't get surprised later on. And gradually, with a noisy generator humming out back, and increasingly watchful checking and double checking of what the radars were telling them, the forecasters went from relaxed to hyper-intense.

   You could track what happened that evening in the growing dimensions of the hail they began to talk about. At first there were reports of pea-sized chunks. Then dimes, and nickels, and quarters. Later there would be golf-ball and eventually at the height of the storm--baseballs. At first I didn't realize why there was all this concern for hailstones: then I realize they were proxies for the amount of energy in the thunderstorm cell. The more convection, the heavier the hail could be before its weight carried it down to earth. Hailstones were like a litmus paper, along with the far more precise radars, for the severity of the storm.

   The men and women were now criss-crossing the room, checking alternate computer displays to see if what they suspected was beginning to happen was really going on. From my involvement in the creation of the LFSTORM instructional materials and specifically the hands-on doppler simulation I had also developed a sensitivity to what I began to hear--quietly and first, and then more insistently "I'm not liking the behavior of this thing," says Doug, "it's got some circulation developing." Rotation, what makes a twister out of a super-cell thunderstorm was happening before our cameras, detected through the eyes of the doppler radars we hope students can build and explore in class. From what began as a quiet day at the Forecast Office by mid-evening we were in the heart of the storm.

Doppler Radar Image

  "It's got a little bell shape... that's what I was afraid of." "There's a detached echo which reminds me of the Choctaw tornado, May 3rd..." Then the key words from Chris, who was handling the detailed radar images: "We've got 40 inbound, 40 outbound, gate to gate"--doppler radar showing adjacent pixels with winds coming towards and going away from the radar--about the best signature of a tornado modern weather science has got: it said "tornado."

   By now Doug, who'd been hoping earlier to leave for choir practise, had long given up that dream, and knew he was stuck here for the duration. Earlier he'd generated bulletins announcing severe storms that might spawn twisters. Now he tapped out tornado watches and then warnings, consulting with colleagues, always aware and wondering out loud about alarming too many unnecessarily, or warning too few, too late. It reminded me of air traffic control--huge amounts of data changing instantly, with lives literally on the line.