The Atlantic hurricane season has been surprisingly quiet. But forecasters say that won’t last.

Never, in the 20-plus years it had been issuing outlooks, had the National Oceanic and Atmospheric Administration predicted so many tropical storms to develop in the Atlantic hurricane basin, with conditions across thousands of miles of ocean aligned perfectly.

“That’s the highest forecast that we’ve had,” Ken Graham, National Hurricane Center director, announced at the annual preseason media briefing in May. NOAA seconded the motion in its Aug. 7 update with a warning that the 2024 season “could rank among the busiest on record.” Every other major forecasting service was on board.

Said Philip Klotzbach, hurricane specialist at Colorado State University, whose preseason outlook and August update were in line with NOAA’s, “It seemed about as slam dunk a seasonal forecast as we’ve ever had.”

Yet, after the dissipation of Ernesto, the Atlantic basin, which includes the Gulf of Mexico and the Caribbean Sea, went dead quiet. Some signs of awakening are evident, with the hurricane center giving two seedlings outside chances of becoming tropical systems later in the week, but Labor Day weekend proceeded without a tropical storm scare anywhere from the Texas to Florida to Maine coasts.

This would mark the first time in 27 years that not a single named storm, those with winds of at least 39 mph, has developed in the Atlantic between Aug. 21 and Sept. 2, said Klotzbach.

What explains the lull? “That’s still an open question,” said Matt Rosencrans, the Climate Prediction Center scientist who is NOAA’s chief long-range forecaster.

While the meteorological head-scratching proceeds and the atmosphere shows off its complexity, hurricane specialists do believe a prime suspect is the unusual behavior of the atmosphere over West Africa.

They also caution the season isn’t over. On average, about 70% of all Atlantic hurricanes have formed after Sept. 6. Anyone remember Sandy, in October 2012?

The season, which began June 1 and ends Nov. 30, got off to a frightening start with Alberto developing on June 17, followed by Beryl, which on July 1 became the earliest-ever Category 5 hurricane, with peak winds that grew to 165 mph the next day.

That was followed by the short-lived Chris, and then prodigious rainmaker Hurricane Debby, whose career ended on Aug. 10. Some of the Debby-related moisture touched off some significant downpours in the Philly region.

Ernesto became the season’s third hurricane, storms with winds of 74 mph or more. On average two have formed by the end of August.

However, the overall tropical storm total, five, is one below the average.

In line with other major forecast services, NOAA called for seasonal totals of 18 to 24 named storms; 8 to 13 hurricanes; and 4 to 7 “major” hurricanes, those with winds of 111 mph or more. The averages are 14 named storms, seven hurricanes, and three major hurricanes.

The oceanic conditions couldn’t have been more favorable for tropical mayhem, said Klotzbach.

Near-record warmth has persisted in the Atlantic’s hurricane main development region, a climate-change indicator that researchers say is enhanced by generally cleaner air that has allowed more solar energy to reach the sea surface. Warm water is the fuel that drives the hurricane engine.

On the other side of the planet, the tropical Pacific has continued to cool off, ending the El Niño warming conditions that favored storm-shearing winds that ambush Atlantic storms.

Upper-air winds over western Africa that drive weather disturbances that can enter the Atlantic and eventually mature into hurricanes have been farther north than usual, said Rosencrans. That means the systems “can come off of Africa closer to dry Saharan air, and over waters not warm enough to sustain tropical storm development.”

Klotzbach said low pressure over west-central Africa has drawn drying winds from the north to the areas where hurricanes form. Winds circulate counterclockwise around low centers, and areas to the west of the center — in this case, the Atlantic — experience north winds.

In addition, he said that while the North Atlantic is warm, so is the upper atmosphere. Storms form when warmer air rises over cooler layers of air and condenses. If temperatures higher up are warmer, the air can’t rise.

Rosencrans said cloud-suppressing high pressure, or heavier air, over the North Atlantic has been putting a cap on thunderstorm activity.

Forecasters are confident that the season will rally, perhaps in the next week.

”I think it’s too early to bail on the season just yet,” said Klotzbach.

Rosencrans said those winds that were directing African systems over cooler waters have shifted to the south, where the waters are less hostile to tropical storm development.

He expects to see activity return in September, when on average four named storms develop, three of which become hurricanes, and two of those, major hurricanes.

“There is still a lot of the season left,” he said.