Approach of Winter Doesn’t Necessarily End 2022 Atlantic Hurricane Threat

Posted: October 21, 2022 3:16 am

An unconventional Atlantic hurricane season could still have a few surprises in store even as October winds to a close. After a rapid start in June and the first days of July, the basin went uncharacteristically quiet until a flurry of storms in early September, including the destructive and deadly Hurricane Ian that brutalized much of Florida.

The Atlantic season officially continues until November 30, but the calm in the wake of Ian has many people declaring an early end to tropical activity. This assumption could prove surprisingly errant.

Expert: As Shear Fades, Tropical Development Could Restart

Atmospheric wind shear is one of the most important factors in preventing the formation of hurricanes, according to AccuWeather Senior Meteorologist Paul Pastelok, and he says that’s the reason for the current lull.

“There is just way too much shear in the basin,” he explains, adding that tropical development is unlikely through the remainder of the week. A calming of the atmosphere that reduces shear could allow new systems to sustain development as the calendar flips into November.

Forecasts from AccuWeather highlight the potential for as many as two or three storms during the coming weeks. Specifically, Pastelok highlights the potential for development in the Lesser Antilles, a hurricane development area that often launches storms toward the southeastern U.S.

La Niña Hasn’t Been Enough to Meet Yearly Averages

The potential for post-Halloween hurricanes is not the only unusual thing about this season’s Atlantic activity. La Niña, which usually favors busy hurricane seasons, has not been enough to push this year’s count of named storms to even an average level from June 1 onwards.

According to the National Hurricane Center, this count typically hovers around a dozen, with half reaching hurricane status and three becoming major hurricanes in Category 3 or higher. This year saw just eleven, five, and two, respectively, with the name Lisa waiting in the wings for a potential number twelve. The past two seasons, both of which were La Niña years as well, saw much more tropical activity, with 30 named storms in 2020 and 21 in 2021.

Atmospheric Metrics Suggest More Storms Are Overdue

Meteorologists also look at another factor in tropical patterns. Accumulated Cyclone Energy (ACE) measures the severity and lifespan of tropical systems. Long-duration storms like Hurricane Fiona log more ACE. Milder storms like Tropical Storm Karl generate far less. By October 16, the Atlantic typically registers 107.2 units of ACE.

This year’s measure over those dates was just 84.1, according to researchers at Colorado State University. This deficit suggests that the atmosphere just might have enough left in the tank to disrupt the fall foliage season with tropical winds.

Eruption May Have Slowed Normal Summer Storm Pace

Pastelok believes that volcanic activity could be one reason that La Niña’s effect on tropical development has been atypical. “One potential factor in holding back tropical storm and hurricane numbers, compared to the last two extremely active La Niña years, may have had to do with the eruption of the underwater Tonga Volcano in January,” he said, adding that the burst of heat from the eruption forced “massive amounts of water vapor high into the atmosphere, and because this occurred in the tropics, it may have simply cut down on thunderstorm development,” cutting off the development of tropical storms before it ever started.

The Tonga eruption may have even had a worldwide impact. Volcanic activity has long been recognized as a source of global reductions in temperatures, as evidenced by the short-term impacts of Krakatoa’s 1883 eruption. That event lowered temperatures in the Northern Hemisphere by almost one full degree Fahrenheit over the ensuing year. A similar outcome from Tonga would mean that it may have played a part in the suppression of both the Pacific and Indian tropical seasons as well, Pastelok says, and the cooling may also have an impact on winter weather in North America this year.

History Has Something to Say About Hurricane Season, Too

With fewer than 10% of an average season’s storms becoming active in November, should Gulf and Atlantic coast residents relax? History would say no. Despite the arrival of the official end of hurricane season in a few weeks, the last three Novembers have seen at least one named storm.

In 2020, November brought both Hurricane Eta and Hurricane Iota, both of which reached Category 4 status by the time they made landfall in Nicaragua. Eta also hit the continental U.S. as it meandered through the northern Caribbean to Cuba, then turned hard to the left into the Gulf of Mexico and set its sights on Florida, coming ashore as a tropical storm north of Tampa at Cedar Key on November 12.

Skip the Old Sayings and Stick to Science

A familiar proverb says of the hurricane season that in “October, it’s over.” While the rhyme makes it easy to remember that the tropics do begin to calm this time of year, history and this year’s observations suggest that a better verse might be “November, still remember”.

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