The marine heatwave causing record Atlantic sea surface temperatures could increase the number of hurricanes forming this season.
Scientists at the National Oceanic and Atmospheric Administration in the US have been forced to increase their prediction for the 2023 Atlantic hurricane season to an above-normal level of activity, suggesting a 60% chance of 14-21 storms.
Of these, six to 11 could become hurricanes – with winds of 74mph or greater – and two to five could become major hurricanes, with winds of 111mph or more.
In May, the NOAA predicted just a 30% chance of an above-normal season, instead favouring a near-normal season. The latest outlook now suggests a 25% likelihood of this, down from 40%. There is a 15% chance of a below-normal season.
Hurricanes form in areas of low pressure over warm seas, usually around or above 27C. As the cooler air is heated over the water, it creates a flow of warm, moist, rapidly rising air, which can then transform into tropical storm cloud clusters.
The El Niño effect normally helps to lessen the number of storms by warming atmospheric air, but the strength of this year’s marine heatwave is counterbalancing this suppression.
In June, global ocean sea surface temperatures smashed the record for the month, according to the Copernicus Climate Change Service, with North Atlantic temperatures in particular ‘off the charts’.
Rising ocean temperatures pose a significant threat to marine life, but as seen in recent years, also have major impacts on land.
There were 14 named storms in 2022, and 21 in 2021, with eight and seven hurricanes respectively. Hurricane Ian, which struck in September last year, was one of the most powerful storms on record, with winds estimated at 161mph and leaving 161 people dead across the Caribbean and Florida.
‘The main climate factors expected to influence the 2023 Atlantic hurricane activity are the ongoing El Niño and the warm phase of the Atlantic Multi-Decadal Oscillation, including record-warm Atlantic sea surface temperatures,” said Matthew Rosencrans, lead hurricane season forecaster with NOAA’s Climate Prediction Center.
‘Considering those factors, the updated outlook calls for more activity, so we urge everyone to prepare now for the continuing season.’
Speaking to reporters, he added: ‘A lot of the predictions from May did not forecast the continuation of record warm sea surface temperatures. It’s very rare for most models to forecast continuations of records.
‘The forecast team has analysed these numbers and debated the result of that analysis for hours in making this outlook.’
However, the estimates are only for the total number of storms, not those that will make landfall – potentially causing major damage and posing a risk to life.
The hurricane season runs from June to November.
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