For an event as unusual as a total solar eclipse, enthusiasts hope more elements than just the moon and sun align.
In space, unusual solar activity might make the viewing experience extra dazzling. But on Earth, clouds and rain could mar the experience.
“Clouds are obviously what everybody cares about, in terms of viewing the total solar eclipse,” said Deirdre Dolan, a meteorologist with the National Weather Service’s Weather Prediction Center. “For those who are going to southern Illinois, it looks like luck is on their side.”
During the 2017 total solar eclipse, thick clouds settled over Carbondale and other parts of Illinois dampening the experience for many disappointed viewers.
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After Monday’s event, the contiguous United States won’t see another total solar eclipse for 20 years adding to the pressure of picking an optimum viewing spot.
Early predictions indicate southern Missouri, southern Illinois and central Indiana will have clear skies and offer some of the country’s prime observing locations.
But many meteorological factors — such as water vapor and air temperature — that combine to produce cloud cover can complicate and change forecasts as eclipse day approaches.
“The sun is one of (the) main drivers of weather here on Earth,” Dolan said. “(It) is also responsible for convective-type clouds, meaning the sun heats the surface, the air rises, and then a cloud forms. So when you lose the sunlight, you can get a decrease in shallow convective clouds, which could increase chances of viewing the solar eclipse.”
With a sudden loss of sunlight, like what will happen during totality, humidity increases briefly, temperatures drop and winds die down, which could dissipate any puffy, cotton-like convective clouds that are low to the ground.
During El Niño years like this one — when warming surface waters in the eastern Pacific Ocean lead to drier and warmer conditions in the northern United States and Canada — there’s typically more cloud cover over the southern Illinois region in April, according to the National Weather Service. While this winter’s milder temperatures could lead to more evaporation in the Great Lakes that adds to the cloud cover, Dolan said winds are forecast to be blowing from the southeast so vapor likely won’t be a factor.
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Dolan recommends viewers check live satellite data to stay updated on cloud cover over the Great Lakes. The National Oceanic and Atmospheric Administration’s website at star.nesdis.noaa.gov/goes offers publicly available images, updated every 5 minutes.
At 1 p.m. Central every day leading up to the eclipse, NOAA will be sharing updates on cloud cover on social media platforms for the Weather Prediction Center and the National Weather Service, as well as on the center’s website homepage at wpc.ncep.noaa.gov.
Early precipitation forecasts for the day of the eclipse are “also good news,” Dolan said. There is a less than 15% chance of rain for certain parts of southern and eastern Illinois.
A storm system is forecast to move from the southern Rockies to the central Plains and the Midwest this weekend, which could affect travel for visitors and those planning to pitch tents.
“It could be a little bit soggy,” Dolan said.
“Anybody who is traveling anywhere along the path of totality … Check the weather on your travel days as well as eclipse day to make sure that you can remain safe and that you are weather-aware the entire time,” she said.
Will the sun put on a show?
The partial solar eclipse behind the Spirit of Progress statue depicting the goddess Diana on top of the Montgomery Ward Building in River North on Aug. 21, 2017. (Brian Cassella/Chicago Tribune)
While many may be concerned about the chances of bad weather on the ground, scientists say there are exciting viewing possibilities for space weather, or the activity happening on the solar surface which often influences conditions on Earth.
“Unfortunately, we can’t really tell what’s going to happen on the day of,” said Carina Alden, a space weather analyst with the NASA Goddard Space Flight Center. “Solar activity is much harder to predict compared to terrestrial weather.”
This year, the sun is entering the middle of its 11-year cycle and its most active stage. Sunspots, the dark blemishes on the solar surface responsible for its magnetic action, will be at their largest and most intense. Though they are mostly indiscernible from Earth because of the sun’s brilliance, once the moon starts to dim the intensity of the star, viewers might be able to spot them.
Solar flares, too, will be dramatic and more noticeable as the sun is covered. And during this period of heightened activity, there is always the possibility for an explosion of plasma from its atmosphere.
“Just like we have hurricane season, tornado season, we have periods of high solar activity and periods of low solar activity,” said Bryan Brasher, project manager and media liaison at the NOAA Space Weather Prediction Center.
Some “major players” — large sunspots that have led to a lot of recent activity on the sun’s surface — have recently rotated away from Earth, Alden said.
“Which doesn’t mean, necessarily, you won’t be able to see anything when totality hits,” she said. “There may possibly be something else that pops up, but right now it’s pretty quiet.”
Brasher said new sunspots might develop. And if they’re big enough, they would be visible through eclipse viewing glasses. But “no promises there,” he added.
What you need to know about next week’s total solar eclipse
The corona, the sun’s outermost atmosphere, usually resembles a pearly white halo around the moon during a total eclipse. But with this much solar activity, plasma streamers might make the halo spikier. The corona will look bigger and more intense than it did during the 2017 total eclipse.
During a total eclipse in 1860, an observer drew an active corona with streamers, but it also featured an interesting circular burst of plasma. He didn’t know it then, but he had seen a coronal mass ejection happen just as the moon hid the sun. Experts believe it might be the only photographic or hand-drawn rendition of such a phenomenon occurring during totality.
Several factors would have to align for an explosion to happen at just the right time. There’s an even lower probability it would trigger a strong enough geomagnetic storm that coincides with the Earth’s magnetic field to make the northern lights visible farther south.
“(It’s) the most extreme example I can imagine — this would have to be like, a one in a million chance,” Brasher said. “It would require a lot of things to happen. But that’s not outside the realm of possibilities.”
In addition, other planets will be lining up next to the celestial protagonists: Jupiter will be visible to the upper left, and Venus to the lower right. Others might be visible but dimmer, including Saturn, Mars and Mercury.
Alden said she’s “just hoping that the sun gives us a little party while the moon is covering it.”
“It’s all up to the sun,” she said.
