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FOX LAKE - Wisconsin's warmer months can be volatile, full of weather changes that can impact a dairy instantly.

Severe weather is possible nearly every day in May, Eric Snodgrass said during the second installment of "Weather: More Than A Guess", a three-part World Class webinar being presented by Professional Dairy Producers of Wisconsin. The pattern continues through June and July.

Understanding weather trends and implications is critical for farmers making decisions on their dairy operations, said Snodgrass, director of Undergraduate Studies for the Department of Atmospheric Sciences at University of Illinois.

He showed the quick and easy tools available to monitor, predict and alert farmers to severe weather risks from hail, lightning strikes, straight-line winds and tornadoes.

Hailstorms

Hail can be incredibly destructive, falling with punishing force on animals and crops.

The world record hailstone measures 19 inches in circumference, weighed two pounds and came crashing to earth at 225 mph in 2010.

It was plucked out of the yard by the South Dakota homeowner, washed off and stored in the freezer. "He intended to use it to make a daiquiri for his wife when she got home and saw all the destruction, but he called the National Weather Service instead," Snodgrass said.

Hail can be tracked by radar, which everyone has free access to via apps like weatherunderground, myradar and Snodgrass's favorite, radarscope.

Another site, spc.noaa.gov, shows hail reports every day, while his site, Agrible Inc., detects hail down to the minute as it moves across the landscape and fields and generates reports.

On May 15, Dane County was rattled by hail the size of golf balls, while hailstones hitting De Forest measured over two inches in diameter. Looking at the colored radar maps for the day, Snodgrass pointed out the pinks and purples. "That's hailstones," he said.

To date, 2017 has registered 118 percent of normal on hail reports.

Wind stress

Wind can also cause substantial damage. Every year, there are 15,000 separate reports of wind damage, Snodgrass said, with the agriculture industry taking a huge hit. So far in 2017, reports are running 175 percent of average. "That means there's a lot of preseason, early season events causing a lot of damage," Snodgrass said.

Winds over 58 mph are classified as severe. On radar maps, watch for squall lines that take the shape of an arm in a bicep curl. Watch the forearm and elbow, which are shaped by a very strong back-to-front flow in the storm, and can produce severe winds of 58 mph and more. "We call this a bow echo because it looks like a hunter's bow, drawn back and flexing," Snodgrass explained.

Another "really cool feature" is the line that forms on the gust front of storms, causing a very particular, dramatic, shelf-like cloud. "A shelf cloud is purely a warning cloud. It is all bark and no bite, telling you that in about three minutes after it passes over the top of you, severe storms are on their way," Snodgrass said. "It is an indicator of strong, straight-line winds."

Lightning

Clouds become electrified through the production of snow, ice crystals and hail within them that tumble around within the updraft of the storm. The continuous action produces a static buildup of electricity that produces lightning.

Be aware that a lightning strike carries between 5-10 billion jewels of energy, over a billion volts and between 20,000-30,000 amps, with some carrying charges as high as 300,000 amps.

On average, 600 people are struck each year in the U.S., but only 10 percent of them die. "That's because, for most of us, the lightning stays in our skin, rather than going through the center of our body," Snodgrass explained.

People killed by lightning are often hit in the head, which causes electrocution, or by a heart attack when lightning disrupts the electrical signal between the brain and the heart.

On average, there are nine million lightning strikes a day on Earth. "Unfortunately for those of us in dairy, this can have a major impact on herd health," Snodgrass said.

Cattle are particularly vulnerable because they tend to take shelter under trees. If a tree is struck by lightning and the bark is dry, the sap and interior water will superheat and the tree can explode.

If the lightning stays in the moist bark, it can travel into the ground and become a horizontal "ground flash" that electrocutes the cattle or gives them heart attacks. Snodgrass illustrated with a disturbing photograph of a tree with a ring of dead cattle around its base.

"Either way, trees are deadly for cattle, which means if you get a sense that storms are coming, having your cattle out in the field away from trees is actually better for them," he noted.

Another photo showed a line of dead cattle, lying with their heads between the strands of an electric fence that was hit by lightning.

Cattle are particularly vulnerable because of their stance. Their front legs intercept between 800,000 and 1 million volts, while their back legs may only intercept 500,000 volts. "The voltage difference drives the current through their body and that kills them," Snodgrass explained.

He advises farmers with cattle to keep an eye on blitzortung.org or lightningmaps.org, which show the lightning action live, so they have the warning and time to move their animals inside or away from trees and danger.

Tornadoes

From 1989 to 2013, the average number of tornadoes in Wisconsin during May was three. This year, two have already been chalked up, roaring through on May 16.

A tornadic thunderstorm, or a super cell, is one of the smallest of storm types, but pound for pound, it is the most powerful expression of weather on earth. They are unique because they visibly rotate, almost always in a counter-clockwise direction.

Generally, tornadoes form on the southwest sides of supercell storms that are moving from the southwest to the northeast. Meteorologists watch for the "hook echo" on the backs side of storms, knowing the insides of the hooks can have tornadic circulation.

Mobile homes rank highest on the tornado fatality list, blamed for 43 percent of deaths.

Do not stay in a mobile home if a tornado is on the way, Snodgrass stressed. "It is a death trap. Drive away at a 90 degree angle from the tornado or run," he urged. "The typical width of a tornado is 200 yards. You can run pretty fast when one is coming."

Meteorologists know the ingredients necessary for severe weather are high humidity, a trigger mechanism like a front, an unstable atmosphere, and windshear (winds get faster with height and cross). When these four gradients come together, the world-class meteorologists at the Storm Prediction Center begin a "watch" of the area.

Their site, www.spc.noaa.gov, produces maps every day for the upcoming eight days. "Rely on them. Look at where they are forecasting severe weather and plan accordingly," Snodgrass advised.

Farmers can also get, for free, a bevy of pertinent information at www.atmos.illinois.edu/~snodgrss/Ag_Wx.html, where Snodgrass has gathered the best models and weather maps available, including NOAA.

Twice a week, the energetic meteorologist posts a information-packed video about the upcoming weather and its impact on agriculture. "It's free and a very useful resource. Use it," he advised.

Snodgrass will wrap the series up on June 14 with "Weather Outlook for Summer and Fall". For more information or to register, visit www.pdpw.org or call PDPW at 800-947-7379.

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