Atlantic hurricane season has quietly started, and perhaps it’s time to start pointing to El Niño.
Quick review: El Niño is a natural climate pattern characterized by warmer-than-average 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.
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That potential footprint is in the form of storm-killing wind shear, which has ruined a hurricane season that has so far produced one short-lived tropical cyclone. It was the quietest start to the season since 2009.
Wind shear describes the change in wind direction or speed between different levels of the atmosphere. It can tear apart tropical systems or prevent them from forming in the first place, establishing a firm grip on the Caribbean Sea and the western Atlantic Ocean. June and July are usually the quietest months of the season, but this shear is causing a major disruption and could affect even the busiest season.
“El Niño’s biggest calling card is that wind shear,” said Michael Rowley, a hurricane expert for Miami-based CNN affiliate WPLG-TV.
Wind shear in the Caribbean was the second-highest July since satellite records began in 1979, according to National Oceanic and Atmospheric Administration data analyzed by Lowry.
And having so much wind shear in the Caribbean and western Atlantic, which are supposed to be areas of high tropical development, is “one of the stronger indicators we’re looking at for future seasonal hurricane activity,” Lowry said.
El Niño may not be entirely to blame for the severe wind shear that has been occurring since at least the season began on June 1, but it is the main suspect and the evidence is mounting.
NOAA meteorologist Matthew Rosencrans said the current behavior of wind shear closely matches what would be expected from El Niño, so the two are likely linked. He noted that the detailed studies needed to confirm this link will likely occur after hurricane season ends in November.
Uncertainty exists in a chaotic and complex atmosphere. Global weather patterns that unfold over weeks or months and daily weather are all connected in ways that are sometimes difficult to distinguish.
But Lowry said signs of El Niño are starting to appear in other global atmospheric wind and weather patterns, such as the Walker Circulation, lending credence to the idea that El Niño is being pinpointed.
The Walker circulation is part of the process that gradually increases wind shear over the Atlantic Ocean during El Niño periods. This is a loop made up of updrafts and sinking air, which promote and impede storm development, respectively. The air rises over the warmer Pacific Ocean and sinks over parts of the western Atlantic basin, helping to suppress the storm, which could grow into a tropical system.
Other experts have reached similar cautious conclusions.
“I don’t think we can say exactly 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 the Colorado State University hurricane season forecast.
“All the pieces come together in a way that makes sense and is consistent with the science we already understand.”
There is a strong statistical relationship between the strength of July wind shear in the Caribbean and the western tropical Atlantic and the peak hurricane season (mid-August to mid-October) when activity slows down. That’s because most opportunities for new tropical activity there are likely to disappear before they even begin.
This also means that storms that develop further east and cross the Atlantic Ocean (which is true for most tropical systems during the season) will face resistance when reaching these regions.
The majority of preseason forecasts predicted a quieter-than-usual hurricane season due to El Niño, which was predicted at the time. Now that confidence is growing that a Super El Niño is coming, several groups, including Colorado State University, have recently revised their storm numbers further downward.
However, the threat could still occur closer to the country, such as along the Gulf and Southeast coasts.
Tropical Storm Arthur, the only named tropical storm so far this season, was a very short-lived storm that formed along the Texas coast in June, but still caused life-threatening flooding in parts of the Gulf Coast. Arthur was still battling the storm’s strong winds, but the winds were weaker than they would have been further south.
Similar wind shear was in place over the Gulf Coast last week, but water temperatures are so high that it could be like rocket fuel for storms that manage to avoid wind shear.
Some computer forecast models are showing the possibility of rainforest developing from areas of showers and storms in the eastern Gulf Coast early next week. Either way, rain or not, heavy rain will be the main impact of this system along the west coast of Florida over the next few days.
The second named storm occurs on average around July 17th, so the entire season is technically not far behind. However, forecasters are increasingly confident that the storm will not develop overall by this month.
