With the Atlantic hurricane season off to a quiet start, it may be time to point the finger at El Niño.
A quick reminder: El Niño is a natural climate pattern characterized by warmer than normal water temperatures in the equatorial Pacific Ocean and corresponding changes in weather patterns in the upper atmosphere. Together, these factors influence weather around the world over long periods of time.
This El Niño was officially declared in June and could become a record-breaking Super El Niño later this year.
⛈️ Get your forecast in the CNN Weather app
Its potential imprint takes the form of devastating wind shear, erasing a hurricane season that has produced two tropical storms to date, both very close to home. Tropical Storm Bertha formed in the Persian Gulf on Monday, but it’s still the quietest start to the season in a decade.
Wind shear describes changes in wind direction or speed between different levels of the atmosphere. It can destroy tropical systems or prevent them from forming at all. and he established firm control over the Caribbean Sea and the western Atlantic Ocean. June and July are typically the slowest months of the season, but the shift has been a major setback and could have implications for the peak months as well.
“The number one calling card of El Niño is wind shear,” said Michael Lowery, a Miami-based hurricane expert with CNN affiliate WPLG-TV.
Wind shear over the Caribbean was the second highest in early July since satellite observations began in 1979, according to the National Oceanic and Atmospheric Administration. data analyzed by Lowry.
And the presence of such significant wind shear over the Caribbean and western Atlantic, which should be active areas of tropical development, is “one of the strongest indicators we look to for future seasonal hurricane activity,” Lowry said.
El Niño may not take all the blame for the strong wind shear that has been present since at least the start of the season on June 1, but it is a prime suspect and evidence is mounting.
According to Matthew Rosencrans, a meteorologist with NOAA, current wind shear behavior matches closely enough what is expected from El Niño that the two are likely related. The in-depth studies needed to confirm the link won’t begin until hurricane season ends in November, he said.
Uncertainty lies in a chaotic and complex atmosphere: global weather patterns that develop over weeks or months and everyday weather are interconnected in ways that are sometimes difficult to distinguish.
But signs of El Niño are starting to show up in other global atmospheric winds and weather patterns, including the Walker circulation, Lowry said, lending more credence to the idea that El Niño has its hand in the balance.
The Walker circulation is part of a process that enhances wind shear over the Atlantic during El Niño years. This is a loop of rising and falling air that respectively promotes and impedes the development of a storm. Air rises over the now warmer Pacific Ocean and then falls over parts of the western Atlantic basin, helping to quell storms that could develop into a tropical system.
Other experts have reached similar cautious conclusions.
“I don’t think we can say for sure that the current wind shear is definitely caused by El Niño, but I think it’s very likely,” said Levi Silvers, a research scientist and co-author of hurricane season forecasts at Colorado State University.
“All the pieces fit together in a way that makes sense and is consistent with the science we already understand.”
There is a strong statistical relationship between stronger wind shear in the Caribbean and western tropical Atlantic in July and a less active peak hurricane season from mid-August to mid-October, as most opportunities for new tropical activity there are likely to be destroyed before they have a chance to begin.
This also means that any storms that develop further east and cross the Atlantic (as most tropical systems do during the season) will face resistance when arriving in these areas.
The vast majority of preseason forecasts were calling for a quieter than normal hurricane season due to the then-expected El Niño. Now, as confidence grows that a Super El Niño is approaching, some groups, including Colorado State University, have recently revised their storm numbers even further.
But threats could still emerge closer to home, in the Persian Gulf or along the southeast coast.
The first system to be named this season, Tropical Storm Arthur, was a very short-lived storm that formed just along the Texas coast in June but still brought life-threatening flooding to parts of the Gulf Coast. Arthur was still battling the storm’s destructive winds, but they were weaker than those he would have encountered further south.
Bertha faces the same wind shear situation as Arthur. But this time, the extremely warm water in the Gulf is expected to help counteract these destructive storm winds to some extent, giving Bertha the fuel to survive longer and become stronger than Arthur.
But wind shear will likely win out in the end and prevent Bertha from becoming a hurricane.
The second named storm forms around July 17 on average, so the season as a whole is technically not over yet. But forecasts are becoming more confident of no storms with each passing month.