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The Atlantic is now more likely than not to see an above-average number of hurricanes this year thanks to the unusually high temperatures in the ocean, according to a forecast from the US National Oceanic and Atmospheric Administration (NOAA). This is despite the strengthening El Ni帽o climate pattern which usually reduces hurricane activity over this region.

The agency now forecasts a 60 per cent chance that there will be more named tropical storms and hurricanes in the Atlantic this year than on average. A storm gets a name when its sustained wind speeds hit 63 kilometres per hour (39 miles per hour) and becomes a hurricane when the speed reaches 119 kilometres per hour (74 miles per hour). NOAA projects between six and 11 hurricanes, including two to five major hurricanes, will develop from a total of 14 to 21 named tropical storms.

An average season, which runs from June to December, would see seven hurricanes 鈥� three of them major 鈥� develop from a total of 14 named storms, according to the agency. The forecast, which includes the five named storms already seen this year, is a substantial shift from NOAA鈥檚 May that the Atlantic hurricane season would most likely be normal.

at NOAA says the El Ni帽o climate pattern developing in the Pacific Ocean and the record-warm Atlantic sea surface temperatures are the primary factors behind the new forecast, though for opposite reasons. Indeed, the competing effects of the Atlantic heat and El Ni帽o winds to a 鈥渃lash of the titans鈥�.

In general, El Ni帽o is associated with fewer and weaker storms in the Atlantic because of its influence on wind patterns there, creating wind shear that 鈥渞ips apart鈥� storms as they form, says at Colorado State University.

The raised water temperatures in the north Atlantic work against that dampening effect, fuelling storms with warm, moist air, says Barbero. 鈥淸The heat in the ocean] is shutting down the signal from El Ni帽o that usually knocks down hurricanes,鈥� he says, adding that strong wind shear associated with El Ni帽o hasn鈥檛 yet been seen in the Atlantic.

That is to be expected given the El Ni帽o pattern only recently formed and began strengthening towards its usual peak at the end of the year, says at Pacific Northwest National Laboratory in Washington state. 鈥淓l Ni帽o affects late-season hurricane activity more because that鈥檚 when the signal manifests more strongly,鈥� he says.

According to the from NOAA, also out today, the temperature anomaly in the eastern Pacific has continued to strengthen and there is now a 2 in 3 chance of a 鈥渟trong鈥� El Ni帽o by the end of 2023. Barbero says not knowing precisely when it will strengthen is the main source of uncertainty in the Atlantic hurricane forecasts.

This may also explain why NOAA鈥檚 forecast remains more conservative than some from other groups, including the UK Met Office, which has most recently 19 named tropical storms this year, nine of which would be hurricanes. Researchers at Colorado State University 18 named storms, half of them hurricanes.

Balaguru says numbers that high suggest a major hurricane season could be ahead, comparable with 2017, which saw 17 named storms and 10 hurricanes, six of them major, that caused nearly $300 billion of damage, a record. However, he points out the number of storms doesn鈥檛 translate directly to destruction. 鈥淛ust because you have more storms doesn鈥檛 necessarily mean you鈥檒l have more land-falling storms.鈥�