Atlantic set to close peak hurricane season on ‘generally anaemic’ note

The Atlantic hurricane season will quiet down in line with historical averages for the final two weeks of the 2022 season, analysts at Colorado State University’s Tropical Weather & Climate Research department have said in their final two-week forecast of the season.

“We believe that the next two weeks have the highest probability of being in the normal category,” researchers said, offering a 90% chance of accumulated cyclone energy (ACE) readings in a range from 1 to 9, the middle tercile of the historical record for the period.

CSU noted that the National Hurricane Center (NHC) sees only a 20% chance that a current disturbance in the eastern Atlantic will develop and that upper-level westerly wind shear should keep a cap on the system.

Global models offer a “generally anaemic” picture as “anomalously strong vertical wind shear” across the entire Tropical Atlantic and Caribbean tear at any potential disturbances. But researchers warn that a specific La Niña pattern shifts convection conditions east which could alter wind shear impact into late October.

The Madden-Julian Oscillation (MJO), a moving pattern of atmospheric variability over the east Atlantic said to create supportive conditions for storm systems, has stagnated and should hold a phase “typically associated with quieter periods” for the next two weeks.

The forecast has a no-brainer element to it as mid-to-late October is frequently quiet and the neighbourhood two units of ACE still likely from ongoing tropical storm Karl is sufficient to push the two-week tally into the middle tercile.

Little can be done to rescue CSU’s full-year forecast, last confirmed in early August, for an above-normal season with Fiona and Ian leading the way to what remains a “slightly below normal” season to-date.

When CSU last offered a full-season forecast, the Atlantic was said likely to deliver 18 named storms and a total of eight hurricanes, of which four could hit category 3 or higher.

For all the talk of an above-normal season, CSU only issued two two-week forecasts for above-normal activity, of which only the late-September forecast came true. The full-season forecast for above normal activity matched that from most key research centres who had cited strong La Niña conditions and warm Atlantic surface temperatures.

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