Climatology

2022 Hurricane outlook: La Niña sets stage for an active Atlantic season | Weather

Hurricane Season starts on June 1, and like the last two seasons, it is expected to be busier than normal.

Water temperatures in the Atlantic have spiked, and are now warmer than normal, which can provide fuel for the storms.

Jhordanne Jones researches tropical meteorology at Purdue University and took notice of the increase, as did many of her colleagues. Earlier in the year, temperatures were actually below normal. But it changed quickly.

“We did a complete 180 between March and April.”

Tropical cyclones are the more generic term for tropical storms and hurricanes. Atlantic storms are called hurricanes, western Pacific ones are called typhoons, but they are structurally the same type of storm.

Before tropical cyclones can develop, the atmosphere needs to be prepared as well. This season, a large-scale La Niña phenomenon is in place. La Niña is a paired connection between the atmosphere and the Pacific Ocean which leads to colder than normal water in the central and eastern Pacific near the equator.

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The atmospheric component leads to more uniformity in the direction of the winds across the tropics, including in the Atlantic. A uniformity in direction allows tropical systems to organize and remain intact more easily.

The opposite case, El Niño, leads to more wind shear, or less uniformity, making it more difficult for tropical systems to develop and thrive.

So in general, La Niña years are more active than El Niño years. For the curious, these are two ends of an even broader circulation known as ENSO – the El Niño-Southern Oscillation.

Several organizations produce outlooks for the Atlantic hurricane season, but some of the pioneering work began at Colorado State University from William Gray in 1984. One of his graduate students, Philip Klotzbach continues to lead the research and outlooks today.

In an average year, there are about 14 storms that reach tropical storm or hurricane status in the Atlantic basin (Atlantic Ocean, Caribbean Sea and Gulf of Mexico) with an active storm on 70 days during the season. This year, the CSU team expects another year above average, with 19 storms and 90 days during the season with an active storm somewhere in the Atlantic basin.

NOAA, the parent agency of the National Weather Service, will announce their hurricane season outlook on May 24, and the CSU team will update their outlook on June 2.

Figuring out where a tropical system will hit before the season even starts remains a game involving statistics, history and climatology. The Gulf Coast, Florida, and the Southeast have historically been at greatest risk. But there is emerging evidence that areas farther north will be at greater risk as the climate continues to warm up.

Even so, there are reliable locations to look for the storms to form at different times in the season. For example, the Gulf of Mexico is shallower than the open Atlantic, which plays a role.

Jones notes, “Earlier in the season, there will be more forming in the Gulf of Mexico because it warms up faster than the rest of the basin.”

There have already been studies to indicate hurricanes are stronger farther north than they were about a half-century ago, and this is largely because the average temperature of the Atlantic Ocean has warmed.

Even in seasons that are not particularly active throughout the Atlantic, it only takes one system to make a huge impact. Hurricane Andrew is the classic example from 1992. Only seven storms formed that season, with four becoming hurricanes. Andrew was the costliest hurricane on record at the time, although six storms have since exceeded its level of damage.

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For areas away from Virginia’s coastline, flooding from tropical rainfall has historically been the largest threat. The three highest crests of the James River in Richmond have all come from tropical systems in the latter half of the 20th century, and the epic flash flooding in Richmond at the end of August 2004 also had tropical roots.



Cars remain in a parking area in Shockoe Bottom Tues., Aug. 31, 2004 after remnants of tropical storm Gaston caused flooding in Richmond, VA.


MARK GORMUS


Tropical systems are easier to detect now than before routine satellite imagery of the entire Atlantic was available, but even after reconstructing the activity of those older seasons from ships logs and additional forensic practices, the recent surge of activity during the last couple of seasons is dramatic .

Thirty storms formed in 2020, and 21 formed in 2021, far above the 14 in an average year. New research continues to be brought to light about how active one season is compared to others, including a study earlier this month suggesting that a decrease in air pollution from 1980-2020 is playing a role in the number of storms in a season.

But at the same time, warming water is tending to make the storms stronger when they do form. Not every hurricane is stronger, but the proportion of strong hurricanes, compared to the total number of hurricanes, is going up.



Warming Atlantic Waters

Average water temperatures in the tropical Atlantic Ocean. Data: NOAA. Graphic: Climate Central.




Hurricane Intensity Uptick

The percentage of hurricanes reaching major hurricane status is increasing, when compared to the total number of hurricanes. Data: NOAA. Graphic: Climate Central


In central Virginia, the wind might get our attention initially with a hurricane, but we have to be especially mindful of the rain and flooding. As Jones has observed, “At the end of the day, it’s really the water that is the scariest part of it.”

Warmer air and water means more evaporation into hurricanes, which leads to heavier rain. There is also emerging evidence that the forward speed of tropical cyclones may be slowing down. Combining those two factors leads to larger rain totals over any one particular area.

Plus, as cities continue to grow outward to suburban and exurban areas, there is an increase in pavement and concrete, both impermeable surfaces which send water rushing toward streams and creeks far more rapidly than well-vegetated areas. More flooding results.

There are no signs that Virginia is at a dramatically higher risk in 2022 versus previous years. The CSU team puts the chance of a named tropical system impacting Virginia at 65 percent this season, a little bit higher than the longer term average of 46 percent.

In August 2004, remnants of Hurricane Gaston hit the Richmond area

PHOTOS: Richmond’s last major James River flood in 1985

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