The Atlantic hurricane season has begun quietly, and many are starting to attribute this to El Niño.
For context, El Niño is a natural climate phenomenon characterized by above-average sea surface temperatures in the equatorial Pacific, which leads to alterations in upper atmospheric weather patterns. These elements together have a significant impact on global weather over prolonged periods.
This El Niño was officially recognized in June and has the potential to evolve into a record-setting Super El Niño later this year.
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The effects of El Niño are manifesting as storm-disrupting wind shear, hindering a hurricane season that has so far only seen two tropical storms, both forming very close to shore. Tropical Storm Bertha emerged in the Gulf on Monday, yet this remains the least active start to the season in over ten years.
Wind shear refers to the variation in wind speed or direction at different atmospheric levels. It can disintegrate tropical systems or inhibit their formation entirely — and it has firmly established itself over the Caribbean Sea and the western Atlantic. While June and July are generally the calmest months of the season, this wind shear is a significant hurdle that may also affect the peak months.
“El Niño’s most notable characteristic is wind shear,” stated Michael Lowry, a hurricane expert based in Miami with USdaily affiliate WPLG-TV.
The wind shear over the Caribbean has recorded its second-highest level at the start of July since satellite observations began in 1979, according to data from the National Oceanic and Atmospheric Administration, analyzed by Lowry.
The presence of significant wind shear in the Caribbean and the western Atlantic — regions typically conducive to tropical development — serves as “one of the strongest indicators we monitor for future hurricane activity during the season,” Lowry remarked.
While El Niño may not be solely responsible for the high wind shear observed since the season commenced on June 1, it is the primary suspect, and the evidence continues to accumulate.
Establishing the Connection
The current patterns of wind shear are closely aligning with expectations from El Niño, suggesting a correlation between the two, as noted by Matthew Rosencrans, a meteorologist at NOAA. However, comprehensive studies to validate this connection will not be conducted until after the hurricane season ends in November.
The unpredictability arises from the chaotic nature of the atmosphere: Global weather systems that unfold over weeks or months are interconnected with daily weather, creating complexities that are sometimes challenging to disentangle.
However, indications of El Niño are becoming evident in other large-scale atmospheric wind patterns and weather systems, including the Walker Circulation, according to Lowry, which further supports the notion that El Niño is influencing conditions.
The Walker Circulation contributes to increased wind shear over the Atlantic during El Niño years. It consists of a cycle of rising and descending air, which either promotes or suppresses storm formation, respectively. Air rises above the warmer Pacific before descending over parts of the western Atlantic basin, inhibiting the storms that could develop into tropical systems.
Other experts have drawn similar cautious conclusions.
“We can’t definitively state that (the current wind shear) is directly caused by El Niño, but it is highly probable,” mentioned Levi Silvers, a research scientist and co-author of hurricane season predictions at Colorado State University.
“All the elements are aligning in a way that is logical and consistent with the established scientific understanding.”
Implications for the Hurricane Season
There is a significant correlation between increased 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 many opportunities for new tropical activity are likely to be suppressed before they can develop.
This also indicates that storms developing further east and moving across the Atlantic — which is typical for most tropical systems — will encounter challenges upon reaching these regions.
Most pre-season predictions anticipated a quieter than usual hurricane season due to the expected presence of El Niño. As confidence builds around the emergence of a Super El Niño, several organizations, including Colorado State University, have recently lowered their storm forecasts further.
Nonetheless, threats can still arise closer to shore, particularly in the Gulf or along the southeastern coastline.
The first named storm this season, Tropical Storm Arthur, was a brief storm that developed right off the Texas coast in June, yet it still caused significant flooding hazards in parts of the Gulf Coast. Although Arthur faced destructive winds, they were less severe than what it would have encountered further south.
Bertha is encountering a similar wind shear scenario as Arthur. However, extremely warm waters in the Gulf are expected to slightly counteract those destructive winds, allowing Bertha to persist longer and potentially strengthen more than Arthur.
Ultimately, wind shear is likely to prevail, preventing Bertha from achieving hurricane status.
On average, the second named storm of the season typically forms around July 17, so the overall season is not yet behind schedule. However, forecasts are increasingly confident that there will be a general lack of storms this month.
