Hi, this is Julián from MinuteEarth. You’ve likely heard hurricanes referred to as category 1, 2,
3, 4, or 5; the higher a hurricane’s peak wind speeds, the higher the category, and supposedly
the higher the hurricane’s threat. The goal of this scale is to easily convey the danger
of an incoming hurricane to the public. Except it doesn’t work. In 2015, Hurricane Patricia
approached Mexico with the highest hurricane wind speeds ever recorded at 345 km/h a category 5 by
a lot, and based on the wind category scale should have made it the most destructive hurricane ever.
But – thankfully – it caused relatively minor damage and only a few people died.
On the other hand, Hurricane Stan – which hit Central America and Mexico in 2005 – was a mere
category 1 hurricane on the wind-speed-based scale, supposedly the lowest threat level,
yet it caused nearly 10 times more damage and killed over 100 times more people. Confusing,
right? The problem is that the category scale is based solely on wind speed, but there are two
other factors that are far more critical than wind in determining a hurricane’s true threat.
The most obvious factor is where the hurricane is likely to hit.
Hurricane Patricia happened to hit a rural, sparsely populated area with mountainous
terrain that quickly weakened the storm. Hurricane Stan tore through the populated Yucatan Peninsula
and got stronger in the Gulf of Mexico before slamming into heavily-populated central Mexico.
And once a hurricane does hit, water is a much greater threat than wind.
Ahead of landfall, a hurricane can push ocean water in front of it, piling it up into a
bulge called a storm surge that raises sea levels around the coast and produces massive
flooding. Storm surges are by far a hurricane’s most catastrophic product followed by rainfall
which can also cause dangerous flooding. So to accurately predict a hurricane’s threat,
we first need to predict the threat of storm surge and rainfall; which wind speed alone can’t do.
You also need to add a bunch of other things to the threat prediction model
including the hurricane’s size, how quickly it’s moving forward, a coastline’s terrain, and
average sea level. A larger storm slowly moving toward a flat, shallow coast, like Hurricane Stan
will cause the fiercest storm surge and most intense rainfall. Hurricane Patricia developed so
quickly and close to the shore that it didn’t have time to build up a storm surge at all, but the
damage it did cause was due to flooding from rain. So, if a hurricane’s potential route, storm surge,
and rainfall, and by extension, everything that factors into predicting a storm surge
and rainfall are better predictors of a hurricane’s threat than just wind speed,
why don’t we use all of that data to create a new category scale? In a perfect world,
we would, except we haven’t figured out how to reliably measure all of these things in real-time.
But that doesn't mean we're stuck with the unreliable wind speed scale. Because there
is a single measurement that beats wind speed alone at predicting destruction: air pressure
at the center of a storm. Low air pressure in a hurricane pulls in higher-pressure air,
making the hurricane larger, creating stronger winds, and making it likelier to produce a large
storm surge and lots of rainfall. We already measure air pressure in storms in real-time and
it’s easier to measure than wind speed; so if we replaced wind speed with air pressure to assign
categories to hurricanes, we’d be able to give people a much more reliable sense of the threat.
Ideally, we’d be able to use all the factors that best predict a hurricane’s
destructiveness to determine its category, but until then one thing’s for certain:
with the current scale, we’re simply throwing caution to the wind...and storm surge and rain.
Of course, we don’t just want to get better at measuring storms; we want to prevent worse extreme
weather from happening in the first place. And that’s where Wren, this video’s sponsor,
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