Warm air is transported northward, surging up the Mississippi and Ohio valleys and spawning severe weather. Behind, cold air wraps into the system, converting precipitation to snow and leading to hefty accumulations in the higher elevations of Colorado and Wyoming.

The storm’s “comma head” wraps around its center on the west side in northeast Colorado, coinciding with the zone of fierce blizzard conditions. This is where the worst of the snow and wind overlap, a narrow corridor of 80 mph winds and three-inch-per-hour snowfall rates. The storm’s center is like a sink drain, air masses of varying temperatures, moisture and densities spiraling inward and upward, dropping the air pressure even lower.

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East of the center, a “dry slot” marks low-humidity air entrained into the system (shown by the tongue of yellow and orange shades above), the leading edge of an arctic chill that clears skies and allows some breaks of sunshine. If you were in Kansas or parts of Nebraska, you probably would have found yourself in a period of furious wind and rain, followed by a sudden calming (still with gusty winds) and gorgeous sunshine, with an abrupt return to mixed precipitation or snow.

In these kinds of systems, if you don’t like the weather, just wait 15 minutes.

Here’s a close-up of the storm in this intensification phase:

Lightning and thundersnow from space

As the storm rapidly intensified, it unleashed a string of vicious thunderstorms over eastern New Mexico and the Concho Valley and Panhandle of Texas. Initial supercells with several tornadoes merged into a violent squall line that produced damaging winds close to 80 mph as far east as Dallas.

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From space, NOAA’s GOES-16 weather satellite was peering down, detecting lightning flashes with its near-infrared optical detector. The sensor can “see” lightning day or night — even if no light is visible from the cloud top because of sunlight from above.

Watch as the storms churn out intense flash rates over New Mexico and Texas (shown as the colorful blotches from blue to red), collapsing around sunrise Wednesday and becoming more isolated. Farther northwest, a few sporadic lightning strikes pop up within and just northwest of the cyclone’s core, embedded in a zone of conditional symmetric instability — in other words, it was none other than thundersnow.

The forcing — or support for vertical rising motion — that yields thundersnow is often meager at best. That’s why the lightning flashes are much rarer. But amid the heavy snowfall, a number of sporadic lightning bolts punctuated the winter storm.

Most ground-based lightning detection systems only “see” ground bolts, but by looking instead at their light spectrum, satellites in the air can see bolts within the clouds, too.

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Here’s one more loop of the storm’s lightning eruption:

Radar shows tornado signature in Alabama

The bomb cyclone generated large amounts of spin in the atmosphere.

After sunset Thursday, a pair of classic supercell thunderstorms developed over east-central Alabama. Multiple reports of tornadoes and damage prompted the National Weather Service in Birmingham to identify “at least 9 areas of interest” spanning 10 counties.

The National Weather Service said it would dispatch three teams to survey the damage, the third visiting Chilton County, through which passes Interstate 65 between Montgomery and Birmingham.

This particular storm — the northern of the two — developed striking supercell structure, taking on the pronounced “hook echo” on radar, as shown in the image below.

“A confirmed tornado was located over Gap Of The Mountain,” warned the Weather Service at 7:44 p.m., a minute after this radar frame came in.

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Meteorologists were able to confirm a “damaging tornado” that was “radar indicated.” That inference was due in part to the doughnut hole on radar — also known as a bounded weak echo region, or BWER. That’s where the storm’s updraft is strong enough that rain can’t physically fall, and is indicative of rapid vertical motion often corresponding to a tornado.

A storm of multiple dimensions

The supercell thunderstorm, shown below, produced a “possible tornado” near Heltonville, Ind., on Thursday afternoon, and exhibited textbook storm structure. What would it have been like to be in line for this storm?

First, you’d get light rain, quickly becoming moderate to heavy. Then some small hail would mix in — pea size at first, a few dimes pelting the ground. The rain would let up as a two-minute spattering of half-dollar-size ice chunks pummeled the ground. And then abruptly — calm.

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But that calm marks the worst part of the storm — the brief moments in the “inflow notch” of the storm are immediately ahead of the tornado. If the hail comes to a quick end during a severe thunderstorm, that doesn’t mean the storm is over. You may very well be beneath the core of the storm’s updraft, where a tornado is most likely. After the twister passes, additional rain and hail fall on the backside beneath the rear flank downdraft. Seventy mph winds can accompany this downdraft as well.

Given how quickly storms were moving Thursday, all of this may have occurred in barely 10 to 15 minutes — from calm, partly cloudy skies through the hail and to a tornado.

Doing the wave

When a big disturbance ripples through the atmosphere, it can do just that — ripple. As the storm was getting organized Monday night into Tuesday, it left a trail of gravity waves oscillating in its wake.

Imagine filling an aquarium with olive oil and water. The oil will sit atop the water, as it is less dense. If a pocket of water races upward and punctures the oily layer, a wavelet will propagate along the interface between the two.

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These gravity waves can result when rapidly rising air has enough vertical momentum to puncture a layer its density would ordinarily not allow it to. It rises above that level and then cools and sinks, eventually warming and rising again and repeating the process. It’s similar to how a bobber behaves when landing on the surface of a pond. Those outward ripples can occur visibly or invisibly in the atmosphere. In this case, we can see it where the fluctuations in air pressure locally enhance or eat away at clouds/air saturation.