2022 Season Summary

The 2022 Atlantic hurricane season was close to average in overall activity, with a total of

16 cyclones attaining tropical depression status,
14 cyclones attaining tropical storm status,
8 cyclones attaining hurricane status, and
2 cyclones attaining major hurricane status.

Before the beginning of the season, I predicted that there would be

20 cyclones attaining tropical depression status,
19 cyclones attaining tropical storm status,
9 cyclones attaining hurricane status, and
5 cyclones attaining major hurricane status.

The average numbers of tropical storms, hurricanes and major hurricanes (over the 30 year period 1991-2020) were 14.4, 7.2, and 3.2, respectively. The eventual numbers for 2022 were quite close to this average, though with realtively few major hurricanes. The (preliminary) Accumulated Cyclone Energy value for the 2022 season was 95, a little below average but well-within "near normal" range. This measure of activity accounts both for strength and duration of tropical cyclones. The exact value sometimes shifts when post-season analysis is complete. This year, my predictions were significantly above the outcome, except in the hurricanes category where it was fairly close. Other official forecasts, such as those by the NOAA and by Colorado State University, were similarly above the mark. So what happened?

As predicted before the season, La Niña conditions prevailed throughout the summer and fall. This meant that equatorial Pacific sea surface temperatures were below normal, as the above diagram indicates for different zones. Such a strong La Niña would usually correlate to increased Atlantic activity, and was a major factor in pre-season forecasts. Atlantic ocean temperatures in hurricane formation zones also ran above normal, so we'll have to look elsewhere for an explanation of the underperformance.

Of particular note is the fact that no tropical cyclones formed during the month of August. This was the first time this had occurred since 1997, and the first time ever that this was observed to happen during a La Niña, dating back to the mid-20th century when detailed observations of the El Niño cycle began. Further, the only storms which formed prior to August were three short-lived tropical storms. The first hurricane was Danielle, which reached hurricane status on September 3, becoming the latest first hurricane in the Atlantic since 2013. In contrast, September through November was an unusually busy period, more consistent with climatological patterns.

The main culprits for the August quiet period were elevated wind shear and dry air. The map above charts the cumulative anomalies in relative humidity in the mid-levels of the atmosphere over the period August 1-22, 2022, vs. 30-year averages. The main development region in the tropical Atlantic east of the Caribbean was the epicenter of a dry air spell which lasted most of the month. Saharan dust was a major contributor to the dry air event. It prevented tropical waves from developing convective activity, which in turn would allow them to build vorticity, gain latitude, and detach from the Intertropical Convergence Zone (ITCZ). When tropical waves reached the Caribbean, another obstacle awaited them.

The first three weeks of August also saw well above average wind shear in the Caribbean sea. Wind shear measures the difference in winds at different heights in the atmosphere; a greater difference in winds prevents atmospheric vortices from the low and mid-levels aligning vertically, or "stacking". This is a necessary ingredient for tropical cyclones to form and strengthen. In comparison to my pre-season prediction, this wind shear event was especially surprising, since I had cited models which indicated wind shear would be below average for the June-July-August period. It's not clear why the model forecast was poor, but the immediate sources of the shear were systems called tropical upper-trospheric troughs (TUTTs). These are large areas of low pressure in the higher levels of the atmosphere, in this case usually located over the central Atlantic northeast of the Caribbean. These features generate counterclockwise flow, which runs opposite to the low-level east-to-west trade winds in the tropics. This combination amounts to high wind shear.

In my region-by-region predictions, I put all sectors of the Atlantic basin at higher-than-normal risk, but had only the Gulf of Mexico at highest risk. Unfortunately, this part of the forecast verified. The strongest winds and largest impacts of 2022 came from Hurricane Ian, which made landfall along the Florida Gulf coast as a top-end category 4 hurricane. Elswhere, Hurricane Fiona was the most impactful; it primarily affected Purto Rico and neighoring islands, as well as Atlantic Canada.

Some other notable facts or records from 2022 include:

• The 2022 season ended a streak of six consecutive seasons in which a tropical cyclone had formed prior to June 1
• Tropical Storm Bonnie and Hurricane Julia both crossed from the Atlantic to the Pacific basins and retained their names; this was the first time this had happened twice on record
• When Fiona made landfall as an extratropical cyclone in Nova Scotia, it broke the record for lowest barometric pressure ever reported in Canada; the new record was 931.6 mb
• Martin and Nicole were hurricanes simultaneously, which was the third time this had occurred in November, after 1932 and 2001
• Nicole was the first Florida hurricane landfall in November since Hurricane Kate in 1985

The headline numbers for 2022 tell the story of an average season, but hide several surprising twists. This year is a good reminder that long-term hurricane season forecasts have a long way to go!

Sources: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf, https://yaleclimateconnections.org/2022/08/quiet-in-the-atlantic-will-we-go-0-for-august/