When they gain sight of it again to the mesonets’ northwest, the funnel is as wide as any Lee and Finley have ever seen. Conservatively, the tornado may be at least three-quarters of a mile across. At M1’s ten o’clock, Lee suspects the thing is tracking a hair north of east and will cross the road ahead. Strung along the highway, TWISTEX closes the distance.
“This thing is absolutely gigantic,” Lee says. “We’re gonna be careful on this one. This is a high-end deal.”
The M1 camera is centered on the skinny strip of bright western horizon, where the sun’s light ends and miles of frothing, sea-foam clouds carousel cyclonically, from north to south. But below the mesocyclone’s low rim, rain and wrapping condensation hide something even darker. Often enough, the rain briefly clears and they see it, hundreds of yards across, tapered like a spearhead whose tip is driven into the earth. Here, the catastrophic EF4 winds sweep away the feathering edges of the meso and file the vortex smooth. Lee pulls M1 to the side of the highway and instructs M2 and M3 to do likewise.
“It’s almost stationary,” he observes. He assumes the tornado will cross the road ahead at some point, and Lee has no intention of being anywhere near the thing when it does. The mesonets are now in an ideal position to collect data. He resolves to press no farther. With the sun now entirely occluded by the wedge, it’s as if they’re witnessing a solar eclipse, the funnel nearly black and its gilt edges flaring gold.
At about this moment, the probe truck passes Lee. They’ve retrieved TOWER and are angling for a second intercept. Inside the truck, Tim is clearly unnerved. The wedge menaces the highway, as though daring them to cross its path, to step into the threshold of a door that is about to slam shut. Manchester may have been all white knuckles, but to attempt to deploy now would be suicide. “I dunno, guys, this is getting too fucking close,” he says. Then, to Carl, who is driving: “There are people everywhere, man. This is too damn dangerous. Stop! This thing may translate to the east now. We’re just going to have to wait this one out.”
Carl pulls off onto the breakdown lane a quarter mile or so ahead of the mesonets—and about 400 yards from the tornado. Without warning, a massive RFD surge rocks the probe truck and each of the mesonets. Rain curtains sweep over the fields and obscure the tornado.
“M2 is picking up a good RFD from the west.”
“M1 is, too. Hopefully it doesn’t get so strong that it knocks these power lines down.”
“The tornado is becoming rain wrapped from M2’s standpoint.”
“Roger. We’ve got large debris coming up on the east side of it.”
After only a minute, the view clears out again. In M1, Lee and Finley spot the tornado’s trailing edge. A single subvortex emerges against the backlighting sun and separates from the mother circulation for an instant. Then it rotates back around the south face, out of sight. Even the hardened researchers are reduced to monosyllabic expressions of awe.
“Wow,” Finley says, her voice hushed.
They can see now that a second RFD surge has touched off a transformation. What first appeared as a ragged wedge now more closely resembles an enormous stovepipe, as though a pair of great hands has molded and squeezed the funnel into something sleeker, narrower, and infinitely more violent. Its vortical profile rises a precipitous ninety degrees from the earth below like a superstructure’s mammoth colonnade, a true destroyer of cities.
Tim, Carl, and Grzych kneel in the sheltering lee of the GMC. From this distance, they can just make out a row of 160-foot power transmission towers. They must weigh many tons apiece, but next to this thing, taller than any mountain, the towers seem brittle and tiny. As the edge of the vortex moves to overtake the first, the metal spire emits a brilliant blue pulse of light and folds down onto itself. The shrieking tangle of steel beams shears from its concrete footings. One after the next, the towers fall. From its point of anchorage, one of them plows the prairie for some four hundred yards before the wind finally releases it.
The wall moves onto the highway, as Tim had predicted. Then the rain curtain swings back around and shields the tornado from TWISTEX’s view. Laubach suggests finding another road to pick up the chase, but Lee urges him to hang on just a little longer. He wants the mesonet sensors to savor the entire evolution of this transformative RFD. There seems to have been a direct correlation between the surge and the tornado’s most exceptional intensity. But because Tim had been unable to deploy on the tornado in its maturity, they lack the data to prove that the surge amplified wind velocity within the vortex. Lee has only the feeling in his gut.
Even more striking is the final RFD surge, currently ongoing, which the mesonets are picking up even as the storm moves away. In contrast to the warmth of the preceding pulse, this one is markedly chillier. The change in temperature must mean it originates from some other place in the storm, where a common downdraft’s evaporative cooling plays a more prominent role. The divergence both in temperature and strength between this and the previous surge could not be any starker. Yet both originated from within the rear-flank downdraft. How could the same downdraft behave so differently within the same storm? This is what Lee and Finley seek to figure out.
In fact, TWISTEX may now be in possession of something priceless. In the long history of atmospheric research, only two coordinated mesonet data sets have ever been collected from top-percentile tornadoes, and one of them is theirs from Manchester. This is now the third in existence, and it documents
