The 2019 US tornado season included an ‘extraordinary’ occurrence by John Roach•
|The tornado that struck Jefferson City, Missouri, was one of 556 nationally that occurred in May, an unofficial record for the month. (Twitter photo/Jefferson City Mayor Carrie Tergin)|
A pair of unforgettable tornadoes bookended the 2019 U.S. tornado season, which is effectively over; the National Oceanic and Atmospheric Administration (NOAA) has no reports of tornadoes so far in December. The U.S. tornado season typically runs from March through November or sometimes into early December, although tornadoes can occur at any time.The year’s deadliest event was an EF4 tornado that killed 23 people in Lee County, Alabama, in early March. Tornadoes and their destruction killed a total of 38 people in the U.S. this year.Last year, the U.S. set a record low for the number of fatalities with just 10 people killed, the lowest number since tornado fatality record-keeping began in 1875. The previous record low total was 12 in 1910. Tornadoes cause an average of 80 U.S. fatalities annually.However, one of the costliest tornado outbreaks in Texas history, amazingly, resulted in no deaths when it struck north Dallas on October 20 and 21. AccuWeather estimates the total damage and economic loss from that severe outbreak of 10 tornadoes – including an EF3 – will approach $4 billion.”The tornado outbreak this past October was extraordinary in the sense that, thankfully, nobody was killed,” said AccuWeather Founder and CEO Dr. Joel N. Myers. „Nobody – not one person! That’s the story – the amazing progress that has been made in weather forecasting accuracy over the last 50 or more years and our ability to get life-saving warnings to people in advance so they can take action and get out of harm’s way certainly paid off in this case.”In between the events in Alabama and Texas, 556 tornadoes occurred nationally in May, unofficially breaking the record for the month of 542 set in 2003, though the monthly total has yet to be confirmed. The 25-year average for May is 269 tornadoes.
|Aerial image shot by a drone shows a Home Depot store in Dallas, Texas, that was obliterated after a destructive nocturnal tornado ripped through the area on Sunday, October 20, 2019. (SevereStudios / John Humphress)|
AccuWeather’s 2019 forecast released in February accurately pinpointed the areas to be hit hardest this year, with a higher frequency of severe weather risks in the traditional Tornado Alley — notably Oklahoma, Kansas and parts of Texas – which is more than they had experienced on average the previous three years.”People were starting to question whether Tornado Alley should be shifted farther east, but our forecast accurately called for more events in the traditional area this year,” said AccuWeather Lead Long-Range Meteorologist Paul Pastelok.Texas, with 188 tornadoes, has experienced the most of any state in the U.S., according to preliminary, unconfirmed data from NOAA. Kansas is second with 127, while Oklahoma and Mississippi are tied for third with 98.”We are trying to prepare people in advance where disruptive weather can occur more frequently throughout the season and impact their safety, work or everyday plans,” Pastelok said. „We work to save as many lives as possible and to give people, companies, those in emergency services and others as much advance notice as possible to prepare and to take action.”NOAA’s preliminary reports show there have been 1,603 tornadoes in 2019, but that total is not a confirmed final number. The inflation-adjusted annual tornado running total – which attempts to remove overcount by multiplying the preliminary total by 0.85 – is 1,363, according to NOAA.
|Students from Beauregard High School in Beauregard, Ala., post a sign on the school’s fence in support of the victims of the deadly tornadoes Monday, March 4, 2019. (AP Photo/Julie Bennett)|
There were 1,169 tornadoes in 2018, and the 25-year average is 1,199 tornadoes a year, according to NOAA’s Storm Prediction Center. AccuWeather’s forecast in February for 2019 estimated an increase of roughly 20 percent over the 25-year average.Tornado-related fatalities have been trending downward despite more people living in tornado-prone areas. The reasons for this trend include advances in weather science and technology, the increasing accuracy and speed of processing warnings and the effectiveness of warning methods such as through mobile apps, as well as better cooperation between government weather services and the American weather industry that includes AccuWeather.AccuWeather is a proud and early partner of NOAA’s WeatherReady Nation resiliency program, which helps to continue this trend, and the company is proud to get these lifesaving warnings out to the public rapidly and accurately through its apps and website.
- The Old Farmer’s Almanac released its Christmas weather predictions.
- The forecast for December 25 calls for snow in much of the country.
- Other regions will experience rain over the holidays.
Winter weather may be a disaster for holiday travel, but there’s still something magical about waking up on December 25 and seeing a fresh blanket of powder covering the ground.If you’re dreaming of a white Christmas, you might be in luck: The Old Farmer’s Almanac predicts that several parts of the United States will get snow this year.According to the publication’s famous long-range predictions, people living in the Northeast can expect „a snowy, picturesque Christmas Day.” It’s also likely that states in the Lower Lakes, Upper Midwest, Heartland, High Plains, and Intermountain region will have a white Christmas.These fresh flakes are forecasted to fall in the days just before the holiday, in alignment with the Almanac‘s prediction that the U.S. will experience a „snow-verload” this winter.”The 2020 Old Farmer’s Almanac is calling for frequent snow events—from flurries to no fewer than seven big snowstorms from coast to coast,” explains a press release for the annual extended forecast.However, those snowstorms aren’t all going to arrive on Christmas. Some parts of the country, like the Appalachians and Ohio Valley, will experience weather that’s more wet than white. It’s also predicted to rain in parts of Florida, the Southeast, and along the Pacific coast.The Old Farmer’s Almanac was 80.5% accurate in predicting last year’s crazy winter weather, so you might want to pair some snow boots with your family’s matching Christmas pajamas this year.
As cold weather settles in across North America, some communities have already started up their snowplows, while others keep watchful eyes on the forecast. Snow and ice can wreck travel plans, but they also play important ecological roles. And frozen water can take amazing forms. For days when all talk turns to winter weather, we spotlight these five stories from our archives.
1. The strange forms water can take
Beyond snowflakes and icicles, frozen water can behave in surprising ways. For example, during very cold snaps, lakes can appear to steam like a sauna bath.
As Colorado State University atmospheric scientist Scott Denning explains, this happens because the liquid water in the lake can’t be colder than the freezing point – about 32 degrees Fahrenheit. As water evaporates from the relatively warm lake into the cold dry air, it condenses from vapor (gaseous water) to tiny droplets of water in the air, which look like steam.
When it gets extremely cold, ice can form on the ocean’s surface. Waves break it up, so the water starts to look like an undulating slurpee. “For anyone willing to brave the cold, it’s wild to stand by the shore and watch the smoking slushy sea with its slow-motion surf,” Denning writes.
2. How road salt tames ice
When a big storm is forecast, utility trucks often will head out to pre-treat streets and highways, typically spraying rock salt or saltwater solutions. But contrary to popular belief, salt doesn’t melt ice.
Water freezes at 32 degrees Fahrenheit, but mixing it with salt lowers its freezing point. “The salt impedes the ability of the water molecules to form solid ice crystals,” explains Julie Pollock, assistant professor of chemistry at the University of Richmond. “The degree of freezing point depression depends on how salty the solution is.” When dry salt is spread on ice, it relies on the sun or the friction of car tires to melt the ice, then keeps it from re-freezing.
Pulses of salt can harm plants, water bodies and aquatic organisms when it washes off of roads – especially during spring runoff, which can carry huge doses. Researchers are working to find more benign options, and are currently studying additives including molasses and beet juice.
3. Why trees need snow
Snow may seem like nothing but trouble, especially if you have to shovel it. But it’s also a valuable resource. In the Northeast, environmental scientists Andrew Reinmann and Pamela Templer have found that winter snow cover acts like a blanket, protecting tree roots and soil organisms from the cold.
In experimental forest plots where Reinmann and Templer removed snow from the ground, they have observed that
“…frost penetrates a foot or more down into the soil, while it rarely extends more than two inches deep in nearby reference plots with unaltered snowpack. And just as freeze-thaw cycles create potholes in city streets, soil freezing abrades and kills tree roots and damages those that survive.”
Climate change is shortening northeast winters and decreasing snowfall, with serious effects on forests. “Losing snowpack can reduce forest growth, carbon sequestration and nutrient retention, which will have important implications for climate change and air and water quality all year-round,” Reinmann and Templer predict.
4. Frozen reservoirs
Snow is even more valuable in western states, where many communities get large shares of their drinking water from snowpack that lingers at high altitudes well into the warm months. Here, too, warming winters mean less snow, and scientists are already observing “snow droughts.”
Adrienne Marshall a research fellow studying hydrology and climate change at the University of Idaho, defines a snow drought as a year with snowpack so low that historically it would only happen once every four years or less.
“Today, back-to-back snow droughts in the western U.S. occur around 7% of the time,” she writes. “By mid-century, if greenhouse gas emissions continue to increase, our results predict that multiyear snow droughts will occur in 42% of years on average.”
Snowpack is also melting earlier in the spring, which means less water is available in summer. These changes are affecting cities, farms, forests, wildlife and the outdoor recreation industry across the West year-round.
5. Can we make it snow?
If nature doesn’t deliver as much snow as we need, what about helping it along? Many western states and agencies have tried to do just that for years by cloud-seeding – adding particles to the atmosphere that are thought to serve as artificial ice crystals, promoting the formation of snow.
There’s just one hitch: No one has proved it actually works. Nonetheless, “Western states need water, and many decision-makers believe that cloud seeding can be a cost-effective way to produce it,” write atmospheric scientists Jeffrey French and Sarah Tessendorf.
In a 2018 study, French, Tessendorf and colleagues used new computer modeling tools and advanced radar to see whether they could detect ice crystals forming on silver iodide particles injected into clouds. They hung imaging probes from the wings of research planes, which flew in and out of the seeded areas of clouds. Sure enough, in those zones ice crystal formation increased by hundreds, leading to the formation of snow. No such results occurred in non-seeded regions.
More research is needed to see whether cloud seeding can change water balances over large areas. And ultimately, even if that proves to be true, another question will remain: Whether it’s worth the cost.
This story is a roundup of articles from The Conversation’s archives.
[ Get the best of The Conversation, every weekend. Sign up for our weekly newsletter. ]
Jennifer Weeks, Environment + Energy Editor, The Conversation
This article is republished from The Conversation under a Creative Commons license. Read the original article.
At first glance, these newly released images by NASA may look like lava churning in the heart of a volcano, but they reveal otherworldly storm systems whirling in a way that surprised scientists.
The swirls in the photos are cyclones around Jupiter’s south pole, captured by NASA’s Juno spacecraft on Nov. 3, 2019. Juno has been orbiting the solar system’s largest planet since 2016 and has seen these polar cyclones before, but its latest flight over this region of the planet revealed a startling discovery – a new cyclone had formed unexpectedly.
|Six cyclones can be seen at Jupiter’s south pole in this infrared image taken on Feb. 2, 2017, during the 3rd science pass of NASA’s Juno spacecraft. (NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM)|
Prior to its early November pass, Juno had photographed five windstorms arranged in a uniform, pentagonal pattern around one storm sitting stationary over the south pole.
„It almost appeared like the polar cyclones were part of a private club that seemed to resist new members,” said Scott Bolton, Juno principal investigator from the Southwest Research Institute in San Antonio.
It is unclear when exactly the new cyclone formed, but it changed the arrangement of the storms from a pentagon to a hexagon.
Winds in these cyclones average around 225 mph, according to NASA, wind speeds higher than any tropical cyclone ever recorded on Earth.
|An outline of the continental United States superimposed over the central cyclone and an outline of Texas is superimposed over the newest cyclone at Jupiter’s south pole give a sense of their immense scale. The hexagonal arrangement of the cyclones is large enough to dwarf the Earth. (Credits: NASA/JPL-Caltech/SwRI/ASI/INAF/JIRAM)|
The discovery of this evolving meteorological phenomenon almost didn’t happen as Jupiter itself almost caused the mission to end abruptly.
Juno is a solar-powered spacecraft that relies on constant light from the sun to keep the craft alive. Flying through Jupiter’s enormous shadow would take about 12 hours to complete, which would cut off the power source, drain the spacecraft’s battery and potentially spell the end of the mission.
„Our navigators and engineers told us a day of reckoning was coming, when we would go into Jupiter’s shadow for about 12 hours,” said Steve Levin, Juno project scientist at NASA’s Jet Propulsion Laboratory.