After a busy start to September – especially after two months without any storm activity – the Atlantic is once again cooling off, with only one disturbance we’ll be following this week in the far eastern Atlantic.
The recent spate of activity that included Hurricanes Danielle and Earl has given a boost to overall tropical activity, but by no means has it erased the large deficit of activity observed through August. Accumulated Cyclone Energy or ACE – a scorecard of tropical activity that measures tropical activity by storm strength and duration – is still running about half of what it’s averaged from 1991 to 2020 and is at its lowest value to date since 2015, a year when the strongest El Niño on record in the eastern Pacific greatly reduced overall storm activity in the Atlantic.
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The quiet season so far during a strong La Niña when waters in the tropical Atlantic are running well above Atlantic is a headscratcher. Everyone has a theory – from the marine heatwave in the north Atlantic to the persistent intrusion of mid-latitude weather systems into the deep tropics to volcanic eruptions in the South Pacific – but it’s important to say when we don’t know, and the truth is we just don’t know yet. Higher than average shear and dry and stable air have certainly been problematic for storm development this season, but it takes time to unravel deviations from what even our most sophisticated, long-range numerical weather prediction models don’t accurately compute. Half the season is yet to be written, but assuming things don’t pick up markedly, researchers will have lots to comb through when it’s all said and done.
For now, we watch an unusually quiet mid-September Atlantic. The only disturbance our forecast models show any potential for in the coming days is a tropical wave set to roll off Africa tomorrow. Consistent with the theme of 2022, dry air and wind shear are going to be impediments for this one and development odds will stay low through the week.
Otherwise across the tropical Atlantic, skies look about a clear and calm as you’ll find them on Sept. 11, a strange but welcome sight at the height of what seasonal forecasts predicted to be a very busy hurricane season.
