May 16, 2019

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1 big thing: We still don't know how tornadoes form

A supercell thunderstorm in Henrietta, Texas, in May 2015. Photo: Jason Weingart/Barcroft Images/Barcroft Media via Getty Images

With a multiday severe weather outbreak poised to strike the central U.S., an armada of weather researchers is heading into the Plains. Their mission: to solve some of the elusive mysteries of tornado formation.

Why it matters: Scientists know what to look for on Doppler radar imagery to detect tornadoes, and the National Weather Service warns people with an average lead time of about 15 minutes. However, meteorologists have not overcome the hurdle of determining why one storm produces a tornado while another identical-looking storm does not, which is needed to improve the false alarm rate.

Background: Using data from past storm experiments, researchers suspect that the low-level environment near and inside particular quadrants of a supercell is critical to generating and maintaining a tornado.

  • In particular, researchers want to know more about the forward flank of a storm.
  • However, until recently, gathering in situ data just above the surface in this part of a supercell has been nearly impossible.

Details: For the new project — "Targeted Observation by Radars and UAS (Unmanned Aircraft Systems) of Supercells," or TORUS — scientists will send up 4 drones simultaneously, each designed to fly at or below 2,500 feet in the forward flank, where air is ingested into the thirsty thunderhead.

  • TORUS also includes mobile Doppler radar units, ground-based observing platforms and weather balloons.
  • Notably, a NOAA P-3 hurricane hunter aircraft is also part of the project. It will fly ahead of supercells to scan them with its powerful radar and other sensors.

How it works: Previous tornado research projects have focused on an area of the storm just to the north and behind the thunderstorm's updraft, where a surge of relatively cool, moist air can swiftly wrap around the rotating updraft. This is known as the rear flank downdraft.

  • Now, though, some scientists think they may have been looking for clues in the wrong spot, so TORUS is targeting a different slice of the storm.
  • Adam Houston, TORUS lead investigator, tells Axios the project is designed to look into how a storm's rotation triggers a tornado.

Leigh Orf's modeling work at the University of Wisconsin-Madison points to the importance of interactions between the air in the forward flank of a storm and the main updraft in the center.

“Our theory is that the air that feeds the storm can have properties that cause the storm to strengthen. It’s sort of like eating high energy air,” Orf tells Axios.

  • This inflow originates near the ground in what is known as the "cold pool." As air gets sucked deeper into the storm, it spins and stretches horizontally, a property known as vorticity.
  • “As the updraft is slurping up all this vorticity-rich air, it causes the [air] pressure to drop" within the supercell, he says. "Eventually, there’s a threshold that’s crossed where a tornado will form."
  • Orf is eager to see if TORUS finds that the modeling is onto something.

The bottom line: “We do not have a complete picture of tornado formation, period,” Houston says.

2. Climate change may subtly shift Tornado Alley

Adapted from Gensini and Brooks, npj Climate and Atmospheric Science 2018. DOI: 10.1038/s41612-018-0048-2. Data: NOAA; Map: Harry Stevens/Axios

While scientists prowl the Plains in search of monster storms, others are looking at broader-scale trends that show tantalizing clues about how Tornado Alley may be shifting both geographically and temporally as the climate changes.

Why it matters: The U.S. has the greatest number of tornadoes of any nation on Earth, and where they occur affects emergency management preparations, insurance markets, and individual decisions on whether to build a storm shelter. If, as global warming continues, Tornado Alley migrates, or outbreaks become more massive, this would shift the risk distribution.

Details: According to Harold Brooks, a senior researcher at the National Severe Storms Laboratory in Oklahoma, the overall number of tornadoes of EF-1 intensity or greater touching down in the U.S. each year has not changed in a statistically significant way, averaging around 500.

  • However, his research and that of others has shown an increase in tornado risk in parts of the mid-South and a slight decrease in what is more traditionally considered Tornado Alley in the Plains.
  • A 2018 study showed regional shifts in tornado frequency, with an uptick in tornadoes east of the Mississippi River and a slight decline to the west.

Between the lines: Some of the emerging trends are seemingly contradictory. Tornadoes are occurring on fewer days per year, but major tornado outbreaks are spawning more EF-1 or greater twisters than used to occur in a typical large event.

A warming climate does opposing things to supercell thunderstorms.

  • It provides more energy in the form of higher air temperatures and greater amounts of water vapor in the atmosphere, a combo meteorologists refer to as convective available potential energy.
  • But it also may reduce the availability of wind shear, which is another crucial ingredient for tornadoes.
  • In a warming world, there may be fewer days with both ingredients present to produce tornadoes, but when these ingredients do combine ... watch out.

What they're saying: Brooks says it's not yet known what physical mechanism is causing the big tornado days to get bigger, while fewer days with a small number of tornadoes occur. Nor is there a clear cause for the spike in activity in the mid-South.

  • "That’s a big question that I would love to know the answer to," he said, noting that research is underway to find out.

3. Ultima Thule comes into view

Ultima Thule viewed on Jan. 1, 2019. Image: NASA/JHU-APL/SwRI/NOAO

Newly analyzed results from NASA’s New Horizons flyby of Ultima Thule reveal clues about the evolution of our solar system, according to a new study published in the journal Science.

Why it matters: New Horizons found that Ultima Thule appears to be leftover debris from the early days of the solar system and has remained largely untouched by the heat of the sun since it formed 4.5 billion years ago, reports Axios' Miriam Kramer.

  • This means that any data gathered could help researchers piece together the ancient history of our solar system.

What they found: Ultima Thule — which is located 1 billion miles from Pluto in a part of space called the Kuiper Belt — likely formed when two objects gently smushed together during the early days of the solar system.

  • This type of formation runs counter to one of the leading theories that these deep space objects formed in chaos, violently crashing into one another at the speed of a bullet.
  • But if the two lobes of 2014 MU96 — unofficially called Ultima and Thule — smacked into each other at those speeds, “they would blow each other to smithereens,” study co-author Alan Stern told Axios.
  • Instead, New Horizons found the two lobes touching one another, forming what’s known as a “contact binary.”

Background: New Horizons made its flyby of Ultima Thule on Jan. 1. The spacecraft launched from Earth in 2006 on a mission to Pluto. New Horizons made its planned encounter with Pluto in 2015.

What’s next? The new study was reportedly written with only about 10% of data collected during the flyby, so future studies should reveal even more about the nature of MU69 and other objects.

  • New Horizons is still in good health. Scientists working on the mission are now looking to the future, thinking about another possible extended mission.

4. Ebola is more likely to spread in and around the DRC

Data: DRC Ministry of Health; Chart: Andrew Witherspoon, Harry Stevens/Axios
Data: DRC Ministry of Health; Chart: Andrew Witherspoon, Harry Stevens/Axios

The Ebola outbreak in the Democratic Republic of the Congo now has 7 hotspots and is considered to have an increased risk of spread within DRC and to neighboring countries, the World Health Organization said in an update today, Axios' Eileen Drage O'Reilly reports.

What's new: The WHO expects case numbers to continue to grow due to the inability to reach all the hotspot areas and persistent pockets of community resistance that are causing people to stay away from Ebola treatment facilities or to go after the infection is too advanced. An unusually high 68% of deaths were among people not in treatment centers this week, the WHO said.

Health care workers continue to face peril, as well. Not only are some getting infected — 102 people, or 6% of total cases, per WHO — but violence continues to target them as well.

What they're saying: DRC Ministry of Health spokesperson Jessica Ilunga tells Axios:

"The security situation has always been complex. However, over the last few months, it is getting worse, and Ebola responders and operations are more often targeted by acts of violence mainly perpetrated by community-based militias. While these local militias have close links with the community, one should avoid using these acts of violence to gauge the level of community engagement in the region."
— Jessica Ilunga, DRC Ministry of Health

But, but, but: The news is slightly tempered by a welcomed but "unpredictable calm" in recent violent episodes in the DRC, accompanied by an increase in security around treatment centers, the WHO stated earlier this week.

Go deeper: Read the rest of Eileen's story

6: What we're reading elsewhere

Left: Beresheet impact site. Right: An image processed to highlight changes near the landing site among photos before and after the landing, revealing a white impact halo. Image: NASA/GSFC/Arizona State University

Chinese investments fuel growth in African science (Antoaneta Roussi, Nature News)

Documenting Climate Change by Air, Land and Sea (Josh Haner and James Estrin, New York Times)

Beresheet Impact Site Spotted (NASA Planetary Science)

Despite Measles Warnings, Anti-Vaccine Rally Draws Hundreds of Ultra-Orthodox Jews (Kimiko de Freytas-Tamura, New York Times)

Experimental brain-controlled hearing aid can pick out voices in a crowd (Sharon Begley, STAT News)

7. Something wondrous: Venus' mysteries

Venus seen in 2007. Image: ESA/MPS/DLR-PF/IDA

Some refer to Venus as Earth's "evil twin." Although the two planets are close in size, Venus is far from temperate. The planet's atmosphere is chock-full of carbon dioxide, and the surface temperature is a sizzling 470ºC, or 878ºF.

Why it matters: Studying Venus can provide lessons for the roles that greenhouse gases are playing here on Earth, and it offers a foreboding, cautionary tale.

Details: The thick clouds in Venus' atmosphere produce rain of sulphuric acid, and the surface is "baked and barren" and "lava-strewn," according to the European Space Agency.

  • Venus is an intriguing planet but difficult to study with landers as is done on Mars, since its dense atmosphere maintains a temperature that's hot enough to melt lead, the ESA notes.
  • The image, taken by the ESA's Venus Express, was taken using ultraviolet light on July 23, 2007. The view consists of the southern hemisphere from the planet's equator to the pole (right to left).

Venus offers a cautionary tale for Earth, since the planet is thought to have undergone an extreme climate shift that is referred to as a "runaway greenhouse effect," the ESA writes.

Thanks so much for reading, see you back here next week!