Colorado State researchers predict above-average Atlantic hurricane season

WEATHER NEWS: Colorado State researchers predict above-average Atlantic hurricane season

Researchers at Colorado State University are calling for the seventh consecutive above-average Atlantic hurricane season. The scientists, who study large-scale features of the atmosphere and the ocean, are already spotting signs that point to season even busier than 2021. It’s their 39th year issuing preseason forecasts.

Atlantic hurricane season 2021 caused $70 billion in damage

Their outlook, published Thursday morning, calls for 19 named storms compared to a recent average of 14.4.

The 2021 Atlantic hurricane season produced 21 named storm, third most on record, exhausting all of the names of the National Hurricane Center’s conventional naming list. While Colorado State is predicting two fewer storms this year, it is calling for a more active season in terms of metrics that take into account storm intensity and duration.

“The team predicts that 2022 hurricane activity will be about 130% of the average season from 1991-2020,” the outlook states. “By comparison, 2021’s hurricane activity was about 120% of the average season.”

The outlook also calls for a 71 percent chance that a major hurricane will make landfall somewhere on U.S. soil. Major hurricanes are those that reach Category 3 strength or greater, containing maximum sustained winds of 111 mph or more.

The risk of a major hurricane along the East and Gulf coasts and in the Caribbean is substantially elevated compared to the 1990 to 2020 average, the outlook said.

Unusually warm sea surface temperatures and the lack of an El Niño pattern are among the factors influencing the university’s outlook. The team uses a statistical model based on 25 to 40 years’ worth of data.

The past five years have featured a slew of landfalling major hurricanes — eight to be exact. Harvey, Irma and Maria terrorized the United States in 2017, Florence and Category 5 Michael lashed the nation in 2018, Laura and Zeta in 2020 and Ida in 2021. Since 2016, half a dozen Category 5 hurricanes have roamed the Atlantic.

Every year since 2016 has fallen into the anomalously active or hyperactive categories from a standpoint of ACE, or Accumulated Cyclone Energy — a measure of how much energy storms expend on their winds. By the books, hurricane season starts on June 1, but NOAA has mulled shifting up the advertised start date to May 15 in the face of recent trends and early season tempests.

The Colorado State outlook, headed by researcher Philip Klotzbach, calls for the following:

  • 19 named storms, including tropical storms and hurricanes. The average for a season is 14.4. It’s worth noting that named storms can occur anywhere in the Atlantic basin, and the number has no bearing on how many actually make landfall — or where.
  • 9 hurricanes, more than the seasonal average of 7.2. Hurricanes have winds of 74 mph or greater.
  • 4 major hurricanes, or those whose winds reach Category 3 strength or greater. That’s more than the average of 3.2 major Atlantic hurricanes per season.
  • A 47 percent chance that the East Coast gets hit by a major hurricane, with a roughly equal 46 percent chance for the Gulf of Mexico from the Florida Panhandle to Brownsville, Tex.. That’s more than one and a half times the average likelihood.

The average ACE for a season is also 132, but this year Klotzbach and his team are predicting hurricanes will rack up 160 units of ACE. That’s 21 percent more than a typical season.

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No matter how you slice it, Atlantic hurricane season 2022 is looking to be extra busy. Why though? The Colorado State researchers cite a lack of El Niño.

Currently, a La Niña is dominating weather patterns across the western hemisphere. Characterized by a cooling of water temperatures in the east tropical Pacific, La Niña weakens high altitude winds from the east in the tropical Atlantic. That reduces wind shear, or a change of wind speed and/or direction with height. Wind shear has a tendency to tear apart fledgling tropical systems, so a lack of wind shear can encourage nascent storms to blossom. A dearth of wind shear is integral in supporting the rapid intensification of tropical systems.

Hurricane researcher Kim Wood, an assistant professor in the Department of Geosciences at Mississippi State University, was not surprised by the forecast. In a recent paper, she, Klotzbach and colleagues analyzed hurricane activity over the past 32 years and found conditions have leaned more toward a La Niña state, which has aided active hurricane seasons in recent years in the North Atlantic.

La Nina conditions were present in 2020 and 2021, bolstering very active seasons with destructive Category 4 hurricanes such as Iota, which slammed Central America, and Ida that caused massive destruction along the Gulf Coast of the U.S.

However, the fact that La Nina could persist for a third year in a row is very rare. In fact, a La Nina three-peat has only occurred twice before in record-keeping back to 1950.

Projections call for La Niña to weaken and relax to “ENSO-neutral” conditions during the summertime — but, so long as El Niño doesn’t materialize to kick up wind shear, an average or above-average season should prevail.

Sea surface temperatures across the Gulf of Mexico and Caribbean are running a general 1 to 5 degrees above average too, which translates to considerably more “ocean heat content” to fuel tropical systems. Of course, it remains to be seen if waters remain that unusually warm in the months ahead.

Low wind shear and unusually warm waters could later prove a recipe ripe for rapidly-intensifying storms. Wood and her colleagues found high-end rapid intensification events, during which tropical cyclones increased by at least 57 mph (50 knots) in 24 hours, have increased significantly in frequency over the past three decades – likely due in large part to human-induced climate change.

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Researchers also previously found climate change has caused hurricanes to move slower and drop more rain in a concentrated area, such as the case with Hurricane Florence in North Carolina in 2018 or Harvey in Texas in 2017.

Rising sea levels also worsen storm surges, which can cause more flooding and infrastructure damage.

“More and more people are living close to the coast, and thus we’re just increasing our vulnerability to these storms,” said Wood. “Even if there’s just one [storm] that makes landfall this year, that’s going to be a big one for whoever lives there.”

AccuWeather, the State College, Pa.-based private forecasting company, has also issued an Atlantic hurricane season outlook and is calling for 16 to 20 named storms and 6 to 8 hurricanes, very much in line with Colorado State.

2022′s first storm, once it’s named, will be called Alex. Should all of the 21 names on the National Hurricane Center’s list be used, forecasters will turn to a supplemental list set of names. The supplemental list was developed after the record-setting 2020 hurricane season, in which 30 named storms formed, forcing forecasters to use Greek letters after 21 storms had earned names.

Colorado State has evaluated the accuracy of its seasonal hurricane forecasts, made in April, since it began issuing them in 1984. Through 2013, the forecasts did not offer much predictive skill. However, it says its forecasts “have shown considerable improvement in recent years.”

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