Major hurricanes expected to increase in 2023, researchers

Researchers at the University of Arizona, who have successfully forecast hurricane activity since 2014, the 2023 hurricane season is expected to be very active after two relatively quiet years.

The forecast calls for a total of nine hurricanes between June and November, five of them classified as "major" hurricanes. These major hurricanes have wind speeds of up to 150 miles per hour and fall under Category 3 or higher.

While the number of hurricanes making landfall is expected to be fewer than in previous years, the number of major hurricanes is likely to be similar to the 2017 hurricane season, which saw devastating hurricanes such as Maria, Harvey, and Irma. In general, the average number of major hurricanes per year is two.

Xubin Zeng, who leads hurricane season forecasting at the University of Arizona, attributes the expected increase in hurricane activity to higher ocean temperatures and rising sea levels, both caused by global warming.

Since water vapour is fuel for hurricanes, the increase in water vapour over the oceans due to global warming is expected to cause more major hurricanes, even if the total number of hurricanes does not necessarily increase. Additionally, higher ocean surface temperatures are creating the ideal conditions for hurricanes to form.

Rising sea levels are also affecting storm surges, which can cause flooding, and a 2020 study projected that by 2100, tidal surges and storm surges will cause 68 percent of coastal flooding.

Zeng stressed the importance of emergency management agencies in providing critical services to people in affected areas during the potentially active hurricane season.

People living on the coast and in hurricane-prone areas should be aware of the increasing threats to their homes and property due to climate change and prepare accordingly, Zeng added.

El Niño, La Niña, Hurricanes explained

El Niño and La Niña are two opposing weather patterns that occur in the equatorial Pacific Ocean, characterized by differences in sea surface temperatures, precipitation, surface pressure, and atmospheric circulation.

El Niño results in above-average sea surface temperatures in the eastern Pacific, while La Niña is characterized by a periodic cooling of sea surface temperatures. This year, the presence of El Niño is expected to decrease hurricane activity in the North Atlantic, but warm ocean surface temperatures over the Atlantic may increase it.

The UArizona Hurricane Forecast Team will update their predictions in June after determining which ocean basin will prevail. Hurricanes are severe storms that form over warm tropical oceans, beginning as areas of low pressure that intensify thunderstorm activity as they move through the moisture-rich tropics.

Warm ocean air rises, cools, and condenses into droplets that further fuel the storm by releasing heat. According to the National Oceanic and Atmospheric Administration, hurricanes are storms with winds of at least 74 mph.

While atmospheric winds are useful for predicting individual hurricanes, they are not useful for predicting hurricane seasons due to their short memory. By contrast, ocean temperature remains constant over a longer period, making it a better metric for predicting hurricane seasons ahead of time.

UArizona's hurricane forecasting process

UArizona researchers release their annual hurricane predictions twice, first in April and then again in June. In April, they use the seasonal forecast from the European Center for Medium-Range Weather Forecasts to process the forecast through machine learning.

In June, forecasters incorporate both the model output and observational data for March through May. This marks the ninth consecutive year of UArizona's hurricane forecast, and their model has been successful due to the team's active tuning and model revision each year.

The researchers published two scientific papers on the predictive capabilities of their hurricane forecast model in the journal Weather and Forecasting, in 2019 and 2015.

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