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El Niño's wind shear kept the Atlantic hurricane-free through September for the first time on record
El Niño kept the Atlantic free of hurricanes through September for the first time in reliable records by holding wind shear high over warm water. The mark could still fall if the National Hurricane Center upgrades Tropical Storm Fay in its post-season review.
The Scientist · Science desk
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What happened
- The same El Niño has supercharged storm activity in the eastern Pacific and given Hawaii one of its busiest seasons on record.
- Fay began as a tropical depression far out in the Atlantic on Sept. 19, and one satellite estimate put its winds at 84 mph on Sept. 20.
- Meteorologist Michael Lowry says that satellite method tends to produce falsely high wind readings.
- Even if Fay is upgraded, it would still be the latest first hurricane to form in the Atlantic's reliable record.
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Why it matters
- precedent If Fay stays a tropical storm, Scientific American rates this among the likeliest seasons to reach Nov. 30 with no Atlantic hurricane, an outcome the record has never shown.
- constraint Outlooks built on El Niño expected a quiet Atlantic and still underestimated it, so they are a better guide to a season's direction than to its depth.
- exposure For the United States, an Atlantic-only tally understates this year's tropical cyclone exposure, because Hawaii's season ranks among its busiest.
This season separates two ingredients that usually arrive together. By late summer the Atlantic is normally warm, and wind shear, the cross-cutting winds that hinder developing storms, tends to relax. September is usually the peak for that reason [5]. This year the water is amply warm and the shear has stayed [6]. With the ocean heat in place, the suppression has to come from the atmosphere, and Scientific American attributes it to El Niño [6]. "No hurricanes through September is unprecedented in the modern record and it's a little surreal to look at the maps every day this month and see the deep tropics basically shut off," meteorologist Michael Lowry said [4].
The chain runs across two oceans. Warm water shifts east in the Pacific. That changes where heat enters the atmosphere and alters atmospheric currents. Over the Atlantic, the result is more shear and more air pushing downward, and both stifle cyclone development [7]. The magazine describes this El Niño as exceptionally strong and likely to become the biggest in living memory [2].
A single season is one case, and the attribution rests on that physical chain [7]. Lowry's reaction is the closest the article comes to measuring the season against expectation. "We expected a notably down year activity-wise across the Atlantic due primarily to the record-setting El Niño, but none of us in the hurricane space could've confidently predicted it'd be this dead through September," he said [12]. The thing one season doesn't tell you is how often an El Niño this strong produces a lull this deep. The article does not say how many seasons the reliable record covers [1].
About two-thirds of the season is gone. June 1 through Sept. 30 is 122 days of a 183-day season that closes Nov. 30 [1][2][3]. Past the September peak, hurricanes become harder to spin up, the magazine notes [13].
Communities hit hard in recent years get a reprieve, according to Scientific American [16]. "After a decade of active to hyperactive hurricane seasons with some of our costliest and deadliest U.S. hurricanes," Lowry said, "this is one record I'm relieved to see!" [15]
What to watch
- The National Hurricane Center's post-season review of Fay's satellite wind data, which decides whether the no-hurricane-through-September record stands.
- Whether any Atlantic storm reaches hurricane strength before the season closes on Nov. 30.
- Final eastern Pacific and Hawaii storm tallies, which would put numbers on activity described so far only as supercharged and among the busiest on record.