Volkswagen using hail cannons in Mexico, farmers say it causes draught

A
metering rule is placed beside hailstones after a hail storm hit
the city of Zurich July 1, 2012.
REUTERS/Arnd Wiegmann

• A VW plant in Mexico has caused controversy by blasting
  hail cannons at the sky in an attempt to stop hail from
  smashing their valuable car inventory.
• Farmers say the cannons are causing a drought that’s
  wrecking crops.
• There’s a surprisingly long history of hail cannons —
  humans have tried to stop ice from falling from the sky for at
  least hundreds of years.
• No one has any idea whether hail cannons work.

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Hailstorms can be terrifying and expensive. Suddenly, balls of
ice start falling out of the sky with enough
force to smash cars and vineyards, causing
serious injury or death to anyone unlucky enough to be caught
outside.

An attempt to control these storms is causing controversy,
despite questions about whether it’s possible to prevent hail in
the first place.

A Volkswagen plant in Puebla, Mexico, has incurred the wrath of
nearby farmers who say that by firing “hail cannons,” which blast
shockwaves into the sky to theoretically prevent hail from
forming, the automaker is causing a drought.

The
AFP reports that farmers believe the cannons have prevented
any precipitation from falling since May, during the rainy
season. The farmers are now seeking almost $3.7 million in
compensation for at least 5,000 acres of affected crops.

When the cannons are fired, “the sky literally clears and it
simply doesn’t rain,” Gerardo Perez, a farmer leading
protests, told AFP.

In response, Volkswagen reportedly has said it will install mesh
netting to protect the cars, and turn off the mechanism that
causes the cannons to auto-fire under certain weather conditions.

“Once the anti-hail nets are installed in the yards, they will be
used as the main measure for the protection of vehicles, while
the devices will serve as a secondary tool and will only be used
in manual mode,” a VW spokesperson
told the Financial Times.

But even manual use is unacceptable, local environmental
official Rafael Ramirez told AFP.

“The company can take other measures to protect its cars, but
people here can’t live off anything but their land,” he said.

A
1901 image of a hail cannon meeting.

Plumandon/Wikimedia
Commons/Public Domain

Shooting hail out of the sky

According to the FT, the German automaker installed the cannons
earlier this year.

Even though these particular hail cannons are new, the idea of
preventing hail by preemptively shooting it out of the sky first
is not.

According to a
1965 paper by the Royal Meteorological Society, Herodotus and
Caesar made note of the fact that barbarian tribes tried to shoot
arrows at oncoming storms. In parts of Europe, guns were used to
shoot at storms, until Holy Roman Empress Maria Theresa
prohibited the practice in 1750 — apparently, it was a source of
complaints by neighbors of the storm shooters, who were upset
about the way the weather changed as a result. (History repeats
itself.)

By 1896, new types of hail-cannons had been designed, according
to a paper published in the
Bulletin of the American Meteorological Society (and
spotted in a history of hail cannons published
in Atlas Obscura).

These cannons were like mortars, firing large and loud smoke
rings — the idea being that smoke particles might stop hail from
forming. When these first cannons, designed by a winemaker, were
tested during storms, it didn’t hail. The idea caught on, with
winemakers throughout Europe trying to get a hold of the devices
to protect valuable crops. There were 2,000 cannons operating in
Italy by 1899.

Storms would approach, cannons would be fired. Sometimes, it
wouldn’t hail and cannons were praised. Other times, hail would
fall, with the failure chalked up to operator error. Within a few
years, these smoke cannons fell out of favor. No one could tell
if they did anything.

Shutterstock/Paolo Gallo

Blasting ice with soundwaves

Instead of using smoke or projectiles, modern hail cannons — like
those used at the Puebla Volkswagen plant — rely on loud
shockwaves, fired repeatedly every few seconds as a storm
approaches.

As one New Zealand hail cannon manufacturer explains it, they
fire a burst of explosive gas inside the cannon to generate the
shockwave.

“This shockwave, clearly audible as a large whistling sound, then
travels at the speed of sound into & through the cloud
formations above, disrupting the growth phase of the hailstones,”
the manufacturer
wrote.

Winemakers and auto manufacturers make use of the cannons to try
to protect their valuable goods. In 2007, a California NPR
station reported that winemakers were using the cannons to
try to prevent hail formation. In 2005, CNN
reported that a Nissan plant in Mississippi upset neighbors
by repeatedly blasting the loud cannons to break up hail.

But still, no one knows if the cannons actually work.

“Scientists say there is no way to prove if these cannons really
work, but farmers say it is cheaper to try the cannons than to
buy hail insurance,” reported NPR, in that story.

“There’s no evidence that they actually do anything,”
meteorologist Harold Brooks of the National Oceanic &
Atmospheric Administration’s Severe Storms Laboratory
told Automotive News in 2005. “It may be possible. But if
they really do something, they’re doing it through some unknown
science that we don’t know about.”

Skeptics have also pointed out that like hail cannons, thunder
produces loud shockwaves — but hail shows up anyway. 

Modifying weather isn’t theoretically impossible, but it has
proven to be unpredictable and difficult to control.

It’s unclear whether the VW cannons in Mexico can prevent hail or
cause drought. Either way, it sounds like mesh netting to protect
the cars might be a safer option.