The intensity of the Atlantic hurricane season hinges on the outcome of a rare confrontation between the forces of nature.

Two colliding climate giants, one natural and one with human-signatures, will disappear this summer to determine how calm or chaotic the Atlantic hurricane season will be.

An El Niño is brewing and the natural weather event significantly dampens hurricane activity. But at the same time, record ocean heat is bubbling up in the Atlantic, in part because of human-caused climate change as a result of the burning of coal, oil, and gas, and fuels storm surges.

Many forecasters aren’t sure which weather giant will prevail because the scenario has never happened before on this scale. Most expect a close draw – something about average. This includes the National Oceanic and Atmospheric Administration, saying there is a 40% chance of a near-normal season, a 30% chance of an above-average season (more storms than normal) and a 30% chance of a below-normal season.

On Thursday, the federal agency announced forecasts for 12 to 17 named storms, five to nine that will become hurricanes, and one to four that will become major hurricanes with winds over 110 mph. Normal is 14 named storms, seven of which become hurricanes and three of which are major hurricanes.

“It’s definitely a rare kind of setup for this year. That’s why our odds aren’t 60% or 70%,” NOAA seasonal hurricane forecasting lead Matthew Rosenkrans said at a news conference Thursday. “There is a lot of uncertainty this year.”

No matter how many storms are brewing, forecasters and FEMA Administrator Dean Creswell reminded coastal residents from Texas to New England and people in the Caribbean and Central America that it only takes one hurricane to be a disaster if it hits you.

“That’s really what it boils down to: Which one will win or will they cancel each other out and you end up with a semi-regular season?” said Colorado State University hurricane researcher Phil Klotzbach. “I respect both of them.”

The two forces could not be more opposite.

El Niño is a temporary natural phenomenon in the warming of the Pacific Ocean that occurs every few years and changes weather around the world. Climate models predict that as the world warms, El Ninos will get stronger.

Decades of observations show that the Atlantic Ocean is generally calmer with fewer storms during El Niño years. Warmer El Niño waters cause warmer air over the Pacific Ocean to reach higher in the atmosphere, affecting winds and creating strong upper-level winds that can decapitate and kill storm surges, Klotzbach said. It’s called wind shear.

El Nino’s effects are not direct and “not in your face like a very warm ocean,” said Brian McNoldy, a hurricane researcher at the University of Miami. Rosencrans said El Nino and its variations are the single largest annual factor in NOAA’s forecast, accounting for up to 38% of its forecast.

The Atlantic, especially the African coast hugging farther east where storms form, is about 1.8 to 3.6 degrees Fahrenheit (1 to 2 degrees Celsius) warmer than the average for the past 30 years and is warmer for this time of year, Klotzbach said. Not only do warm Atlantic waters make storms stronger and better able to withstand El Niño shear, but they create an opposite direction of upper level winds that can counterbalance El Niño.

“It’s starting to outpace 2010 by a decent margin, which is worrying because 2010 smells so bad,” Klotzbach said.

“Undoubtedly, abnormally warm ocean temperatures have a human imprint on them,” said former NOAA hurricane scientist Jim Kossin, who is now with risk management firm The Climate Service.

Scientists don’t even have previous years that look the same, Klotzbach and McNoldy said, to help figure out what’s going to happen.

So what will win between El Niño and the hot oceans?

“I know it’s not a satisfactory answer to say ‘we just don’t know’ but we don’t know,” said Christine Corpocero, a professor of atmospheric sciences at the University of Albany.

The lead in the field, Colorado, predicts just under 13 named natural storms, six hurricanes with two of them becoming major. All but a few private, university, and government forecasting teams and models call for a near-normal Atlantic hurricane season with between six and eight hurricanes.

But they also hedge their bets.

“AccuWeather expects close to normal to slightly below normal season due to the appearance of El Nino,” said AccuWeather senior hurricane forecaster Dan Kotlowski, who then added that the warm Atlantic Ocean is complicating everything. “Because of the widespread warm waters, there remains a higher than normal chance of a high-impact hurricane affecting the United States this season.”

The University of Arizona is looking at the same two colliding forces and seeing a different outcome, forecasting nine higher-than-normal hurricanes, 19 named storms and five major hurricanes because it expects “the Atlantic side will be dominant, resulting in very vigorous activity,” said the University of Arizona professor of atmospheric sciences. Zubin Zeng.

Forecasters have run out of names for and with 30 Atlantic storms in 2020 21 storms in 2021. Last year it was normal. Earth has had a La Nina for the past three years, which has generally resulted in increased hurricane activity in the Atlantic. Hurricane season runs from June 1 to November 30.

McNoldy said this summer could be quieter in the Caribbean where El Niño shear could have a bigger impact, but it’s busier in Bermuda and the U.S. East Coast north of the Caribbean, where El Niño isn’t as strong.

Random chance plays a big role, Kossin said, “It’s a bit like rolling the dice but with (the warm ocean) adding and (El Nino) subtracting the weights to the dice.”

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