April broke heat records in Miami. It could bring a record-breaking hurricane season, too
Miami had an April so hot it had only a 1-in-666 chance of happening, and that record-breaking sizzle could mean Florida is in for an active hurricane season.
Brian McNoldy, a senior research associate at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, said this April was 6.1 degrees Fahrenheit hotter than normal.
“People who look at this all the time are in shock. You don’t break records by as much as we broke records,” he said.
And it wasn’t just scorching in Miami. This year tied for the warmest April on record across the globe, the European Union’s Copernicus Climate Change Service announced this week.
NOAA data shows that 2020 is so hot already it has a 99.9% chance of being one of the five hottest years on record.
That’s a problem, because heat is one of two main factors in determining how active a hurricane season will be. The warmer the ocean water, the more fuel to power a storm. The moisture from the water’s surface is absorbed into the hurricane, making it bigger and stronger.
“All other things being equal, if you’ve got a weak tropical wave cruising over an ocean that’s 2 degrees warmer and one over a normal ocean, the one that’s cruising over the warmer ocean is going to be the one that’s going to get stronger,” said McNoldy.
NOAA satellites show that the ocean is definitely warmer. The strip of ocean between the coast of Africa where hurricanes form and the Caribbean was 1.1 degrees Celsius warmer than normal in mid-April.
The other all-important factor for a hurricane season is whether or not certain weather patterns — known as El Niño or La Niña — emerge. When active, the patterns push global weather toward one end of an extreme. El Niño kicks up more wind shear in the patch of ocean Atlantic hurricanes often form in, which makes it harder for the hurricanes to strengthen. La Niña, on the other hand, cuts down on wind shear, making it easier for hurricanes to grow big and strong.
Without either system, the world’s weather remains more neutral.
A NOAA presentation released Tuesday predicts the globe will remain neutral throughout Summer 2020, “with chances favoring a La Niña thereafter.” The busiest part of hurricane season is usually September and October.
“What you’re hanging your hat on is what is El Niño up to this year and how warm does it look to be?” said Michael Mann, director of the Earth System Science Center at Pennsylvania State University.
His center’s forecast — released last week — calls for between 15 and 24 tropical storms, with a best guess of 20 named storms. It predicts La Niña will form later this year, which would combine with the hotter ocean waters to form one of the most active hurricane seasons on record.
“We have these bathtub-like conditions of extreme warmth combined with a La Niña-like state of the climate system,” he said. “In our statistical model, it’s the same sort of condition we saw in 2005.”
That was the infamous year the Atlantic Basin saw 27 named storms and 14 hurricanes, five of which made landfall on the U.S. There were so many storms scientists ran out of names and had to resort to naming them after letters in the Greek alphabet.
But even if no La Niña forms, the Penn State scientists still predict 14 to 23 storms with a best guess of 19 named storms.
A season prediction released in early April by Colorado State University also called for an above-average season but predicted only 16 named storms. 2019 saw 18 named storms.
Scientists warn that, as the planet continues to change under global warming, above-average seasons could become more common. While the impact of the changing climate on weather systems like El Niño or La Niña is harder to predict, the science clearly shows that warmer ocean waters increase the likelihood of stronger storms.
“The fact that we’re seeing record warmth in the tropical Atlantic far more frequently… That wouldn’t be happening without human-caused warming,” Mann said. “We wouldn’t be seeing that warmer season without humans burning fossil fuels.”
This story was originally published May 7, 2020 at 6:00 AM.
