Anatomy of a Super Storm


On the weekend of April 29th and 30th this
year, a series of thunderstorms slammed the southern and midwestern US, spawning flooding
and tornadoes that killed at least 20 people. The Monday afterward, I saw this satellite
animation on Twitter. It showed the thunderstorms’ formation and
movement across the US, and I was like, wow … that is very cool and a little bit unlike
any satellite image I’ve ever seen of a storm. I wrote a note to the National Weather Service
saying that I wanted to know everything about this storm’s formation, and they wrote me
back and then I gave them my phone number and then they called me because I have a very
cool life. So here’s why that satellite animation looks
so impressive, and how it shows the perfect combination of factors that led to those devastating
storms. The first thing to note is that this video
looks different from other satellite videos of storms not just because the storm was pretty
epic, but because this is one of the first visualizations created from a new weather
satellite that launched last November. It’s called GOES-16, where GOES stands for
Geostationary Operational Environmental Satellite, and it’s the latest in a series of weather
satellites that first started launching in 1975. GOES-16 is still in its testing phase, and
this is some of the first imagery from the satellite that’s been made public. It provides significantly higher resolution
than older satellites, both in terms of image quality and number of frames taken. We’re talking four times the resolution
gathered five times faster than older satellites. The satellite collects real-time data as frequently
as every 30 seconds, allowing a better understanding of exactly what happens with storms like this
one. But enough about this satellite; let’s talk
about the storm. In the first few seconds of the video, you
can see a stationary front stretching across the midwestern United States. A stationary front forms when cool airmass
and a warm airmass meet, but neither side is able to overtake the other. That can lead to cloudy weather and a lot
of rain. This particular stationary front was set up
by a cool airmass across the northern and western part of the country and unseasonably
warm weather in the south and east. Since both of these masses of air were similar
sizes, neither could move the other. So that’s our stationary front. There was a lot of warm, wet air along the
front, trapped under a cap of warm, dry air. The warm, moist air wanted to rise, but it
couldn’t get through the hotter air above it. Until, finally, it broke through. There were similar conditions across much
of the midwest, which allowed thunderstorms to develop really quickly along the entire
front. There were also winds running mostly parallel
to the front, so these thunderstorms moved in the same direction, one after another. That’s what meteorologists call training,
because you end up with a bunch of thunderstorms moving along the same path, like train cars
moving along a track. The cap of warmer, drier air was broken in
succession all down the front. The warm, moist air at the surface shot up
and cooled, and water vapor condensed, releasing tons of energy, and also all that rain. Some of the storms that developed were supercell
thunderstorms — the really severe kind that can have super strong winds, cause flash flooding
… and sometimes produce tornadoes. Thanks to the amazing resolution of the GOES-16
satellite, you can see one of the telltale signs of a severe thunderstorm: those little
dark splotches. In intense thunderstorms like supercell thunderstorms,
warm, moist air shoots up into the atmosphere, cooling as it rises. Eventually, its temperature becomes the same
as the ambient air. When that happens, the storm flattens out
at the top, forming what’s known as the thunderstorm’s anvil, because the clouds
look kinda like an anvil, all flat at the top. But in the center, where the air was rising
the fastest, the air shoots up past the top of the thunderstorm anvil, in what’s called
— appropriately — an overshooting top. That’s what those little black splotches
are. And this is what they look like from above. Meanwhile, this stationary front, unfortunately,
remained stationary as more warm, wet air was sucked up into the atmosphere. And so not only did the rain keep falling,
it kept falling in the exact same place, in some cases more than 25 centimeters in one
day. The next day, the same system spawned tornadoes
in east Texas. You can see the parent thunderstorms here. By the end of this video, the thunderstorms
had been going on for almost 48 hours, stretching across much of the south and east. In a normal situation, by this time the jet
stream, a high-level wind pattern that usually runs west-to-east across North America, would
have blown the whole thing substantially to the east, possibly even out into the Atlantic. But it just so happens that the jet stream
dips and waves occasionally, and on the weekend of April 29th and 30th those dips were highly
amplified, making the jet stream move more north to south rather than west to east. So instead of quickly moving east, the storm
moved very slowly, and there were multiple days of thunderstorms across the same areas. That led to a devastating flood and loss of
life. But with the new, high-resolution data that
scientific instruments like NOAA’s GOES-16 are collecting and sending down to Earth in
real-time, we’ll only get better at identifying and reacting to these events. This episode of SciShow, and also lots of
other great things, was brought to you by the federal government spending money on the
National Oceanic and Atmospheric Association so that everybody has access to this remarkable
data like this. And also by our supporters on Patreon. Thanks y’all. If you want to watch more SciShow, here’s
a video about why tornadoes really, really hate the United States… so much.