Atlantic hurricane season 2021 is coming to an end
A season of above-average activity has provided scientists at the Rosenstiel School with numerous research opportunities that could improve predictions and help save lives.
With deadly and destructive Hurricane Ida just minutes from making landfall in Louisiana, University of Miami researchers David Nolan and Kurt Hansen raced against the clock to deploy weather devices that would measure speed and direction. of the cyclone wind.
âWe were far enough inland to only get rain and gusts of wind,â said Hansen. But still, he admitted, the experience was a bit heartbreaking.
Like firefighters running towards danger, he and Nolan, professor and chairman of the department of atmospheric sciences at the Rosenstiel School of Marine and Atmospheric Science, had traveled to Louisiana to place various instruments directly in Ida’s path in order to collect critical data on winds and storm surges. that could one day help save lives. From Galliano to Raceland, they positioned anemometers and other sensors on the ground and near dikes in these communities, sheltering in place at a hotel in New Orleans when the storm struck.
“Our hotel lost electricity and water, the roof was leaking quite a bit and fallen trees almost blocked our exit,” recalls Hansen, a doctoral student. student in Nolan’s lab. “We had planned to leave from New Orleans, but had to go to Tallahassee to catch a flight.”
For Hansen and Nolan, their research trip to Louisiana to collect data on Ida was the highlight of the Atlantic hurricane season 2021, which ended on November 30. The final tally: 21 named storms, seven of which were hurricanes, with eight storms landing in the United States.
The 21 named storms marked the third largest hurricane season, behind the record 30 storms of 2020 and the 28 that formed in 2005. And for the second year in a row, the season exhausted the entire list of storm names on the National Hurricane Center’s list of names.
âThe 2021 Atlantic hurricane season has been important no matter how you plan it,â said Brian McNoldy, senior associate researcher and tropical cyclone expert at Rosenstiel School. âThere were a lot of storms, a lot of cyclonic energy built up and it was very expensive. This is the sixth consecutive season with well above average activity, something that has never happened before in the historical record, which dates back to 1851. ”
But it is Ida who will be remembered this season. The ninth named storm of the season, Ida made landfall as a Category 4 hazardous storm on the anniversary of Hurricane Katrina. Ida cut power to millions of customers and caused devastating flooding that killed 95 people across the United States, from Louisiana to New York.
The storm caught some forecasters off guard, going from a Category 2 hurricane to a monstrous hurricane with 145 mph winds in just a few hours.
The rapid intensification of the storm, however, did not surprise Lynn “Nick” Shay. A professor of ocean sciences and associate dean of research at Rosenstiel School, Shay had witnessed storms reaching monstrous levels before. Through his pioneering research, he knew that huge circular pools of hot water called whirlpools can overload storms. And in Ida’s case, that is precisely what happened, said Shay, who, using satellite imagery, had observed a particular vortex very closely in the days leading up to the Ida’s landing in the United States.
In total, Shay has deployed around 100 storm watchers to measure different scientific aspects of Ida, and the data will be used to assess the thermal structure along Ida’s path and in the large hot vortex that the storm brought. meet.
“It is important to note that the vortex that Ida encountered had deeper isotherms and a higher ocean heat content than what we observed previously,” said Shay, who writes a scientific paper on the phenomenon.
He and his team are well prepared for the upcoming hurricane season, having already repaired and upgraded profiling floats that measure temperature, salinity, current and pressure at depths up to 6,000 feet.
The busy 2021 Atlantic hurricane season has provided ample research opportunities for other scientists at the Rosenstiel School, including Quinton Lawton, a PhD. atmospheric science student, who studies how atmospheric waves interact with each other to influence the formation of hurricanes.
He is particularly interested in a type of wave called the Kelvin Wave. “Current research has indicated that these waves may make hurricane formation more likely after they pass through the Atlantic,” said Lawton, noting that studying these waves could help improve hurricane forecasts.
âThere have been several hurricanes that have formed this year after the passage of large Kelvin waves,â he said. “Scientists were able to collect data on the formation of these hurricanes using satellites and other observation platforms, and this provided me with more cases to study why these large-scale atmospheric waves make hurricanes more likely to form. ”
If anything, Miamiians and all Floridians will remember 2021 as another year when the Sunshine State was largely untouched by the catastrophic storm that struck other U.S. states. And luck, McNoldy said, was one of the reasons for that.
âIn any given year, whether relatively calm or overactive, it is possible that one or more storms will affect our region. But there’s no way of knowing ahead of time what the season will bring us, âsaid McNoldy. âLooking back, 56 hurricanes have passed within 100 miles of Miami over the past 171 years, which is an average return period of one every three years. This does not mean, however, that we should expect one every three years. There are multi-decadal oscillations in activity and inter-annual changes in large-scale piloting patterns. So some years we get more than one, and sometimes we go five to 10 years without one. If we focus the distance at 50 miles, the return period increases to one every 5.7 years. ”
But there’s no concept of being late for a storm, McNoldy said. âHurricanes don’t know or remember what previous hurricanes did a month ago, let alone five years ago,â he said.
Experts from the Rosenstiel School have answered additional questions about the 2021 season.
Asked how many storms have intensified rapidly this season and whether that rapid intensification was due to hot water eddies, and whether climate change played a role, Shay responded.
âIt is not clear whether the deeper isothermal depths and increasing thermal content of the oceans are due to climate change or ocean thermodynamics. Caution should also be exercised regarding the interactions between the atmosphere and the mesoscale ocean during rapid changes in intensity. Warming could be contributing to it – we just don’t know how much in the two fluids, âhe said.
“This is why we monitor the changes daily throughout the year from space,” he added. “What is clear is that the hot core vortex surface signature of the loop current that fed Ida was about 70-75 cm compared to more typical values ââof 55-65 cm in the Gulf of Mexico. With a 22-year time / space series estimated from satellite missions, we are examining this carefully with the different merged in-situ data sets, including sea surface temperatures, âhe said. He continued. “With the exception of the continental shelf waters of the northern Gulf of Mexico that Ida passed through before reaching land, sea surface temperatures remained fairly warm in the Gulf for most of the time. of the month of October. “
Emphasizing that the season saw a shortage of activity in October, but ended quietly, at McNoldy, he admitted that âthe season essentially came to a halt in the first week of October, which makes the overall activity levels even more impressive. . It is not clear why it closed so early, as many typical environmental settings have continued to appear favorable for development, âhe noted.
âSubjectively, it appears that there has in fact been a lack of incipient disturbances from which storms could form,â he added. âIn other words, we didn’t have nascent systems that weren’t developing – we barely had nascent systems. But I don’t yet have a precise answer as to why this was the case.