The ominous warmth raises fears of an overactive hurricane season in the Atlantic. Seven of the past eight seasons have been above normal.
Last year, similarly unseasonable warmth fueled a storm season that was significantly more active than meteorologists had expected given the presence of an El Niño weather pattern, which emerged last spring and created conditions that tend to prevent Atlantic hurricanes from forming.
As meteorologists look ahead to this hurricane season, which begins June 1, they see an increasing possibility that El Niño will replace El Niño by late summer or early fall. This is another bad sign for the US coast, where La Niña is linked to active patterns in the tropical Atlantic.
It is still too early to say whether the warmth will last until hurricane season, or when La Niña might arrive. But Michael Lowery, a meteorologist at WPLG-TV in Miami and a former scientist at the National Hurricane Center, said the trends suggest, especially together, that an active season may be difficult to avoid.
“We have plenty of time before we get to the most important part of the hurricane season,” Lowry said. “But a lot will have to change…for forecasters to feel more comfortable going into hurricane season.”
Continuing trend of record warmth
Last spring, the strongest climate signal known to scientists — El Niño — gave every indication that hurricane activity in the Atlantic Ocean was slowing in the summer and fall.
The sign of El Niño is the rise of warm waters and towering clouds in the central and eastern Pacific Ocean. It leads to changes in atmospheric circulation that, on the other side of the planet, can make it difficult for tropical storms to form and strengthen: areas of high pressure with sinking air are more common over the Atlantic, and wind shear, when wind speed and direction differ over Different heights and increases.
The El Niño forecast has forecasters at the National Oceanic and Atmospheric Administration forecasting a typical Atlantic hurricane season, a downturn from years of increased storm activity.
But as El Niño develops, and unusual warmth emerges outside the Pacific regions where the weather pattern is known, forecasters have warned that a calmer season is far from certain.
By August, it became clearer: Ocean warmth would likely counteract the typical El Niño effect in the Atlantic, and the National Oceanic and Atmospheric Administration (NOAA) updated its forecast. The season ended with about 20% more activity than average, according to a statistical measure known as accumulated hurricane energy.
Now, with a new tropical climate season approaching, temperatures in the Atlantic may be more pronounced.
Why meteorologists have reason to worry
Sea surface temperatures are well above normal — 1.1 degrees Fahrenheit (0.6 degrees Celsius) higher than in any other year on record, said Philip Klotzbach, a tropical meteorologist in the Atlantic region known as the main development area for hurricanes. Colorado State University.
If this trend continues into this summer's hurricane season, it could mean an environment ripe for tropical waves flowing out of Africa to develop into hurricanes.
“Basically, it's the perfect recipe for hurricanes to form and strengthen,” Alejandro Jaramillo, a meteorologist at the National Autonomous University of Mexico, said in an email. “Warmer waters make additional fuel available for hurricanes, which can lead to the formation of stronger storms.”
One factor behind the Atlantic's warmth is weak winds over the ocean, Klotzbach said. This suppresses evaporation, allowing the water to cool by transferring heat to the air. Klotzbach said models indicate weaker-than-normal winds will continue through March.
Moreover, longer-term models predict that surface temperatures will remain high, and that by the heart of hurricane season, from August to October, precipitation will be above normal across the tropical Atlantic, suggesting a strong pattern of waves rolling off Africa. . Klotzbach said.
If those forecasts come true, “I anticipate a very busy season at the store,” he said in an email.
Meanwhile, climate scientists predict that La Niña will likely develop by August. While El Niño increases wind shear — which disrupts the rotating wind columns in hurricanes — El Niño tends to dampen it, clearing the way for storms to organize and strengthen.
The warm waters of the tropical Atlantic are part of a global pattern of record sea surface temperatures, fueled by El Niño and human-induced climate change. The planet's average sea surface temperature reached a record high of 70.2 degrees Fahrenheit (21.2 degrees Celsius) on February 9, according to the University of Maine's Climate Change Institute.
Why is it too early to panic?
Meteorologists stressed that it is too early to say how the hurricane season may end. Official seasonal forecasts from the National Oceanic and Atmospheric Administration (NOAA), the state of Colorado and other sources won't arrive for months, and even they carry a lot of uncertainty.
There are still many scientists who do not understand how the oceans behave and what leads to long-term changes in tropical weather.
For example, it wasn't immediately clear what caused the unusually dry Atlantic hurricanes of the 1970s and 1980s — until scientists realized that increased air pollution from Europe was cooling the tropical Atlantic by blocking sunlight, Kerry Emanuel said. Professor at Massachusetts Institute of Technology.
Likewise, it is not yet clear why the Atlantic Ocean is warming so much compared to other oceans, or how long this will continue.
Even if scientists could predict an active hurricane season with more certainty, “that's not what you want,” Emanuel said. “You want the number of damaging storms that make landfall.”
This is beyond the capabilities of meteorologists, and just last year the National Oceanic and Atmospheric Administration (NOAA) expanded its tropical forecast to seven days.
But the state of the Atlantic is such that even if ocean temperatures get closer to normal, there is still more heat in the water that could be available for storms in the summer and fall, Lowry said.
He added: “This is such an extreme case that it does not bode well.”
