Storm Agnes formed on September 25, 2023, as the first named system of the 2023/24 North Atlantic storm season. Agnes is set to bring severe winds and waves to Ireland and the UK on Wednesday, September 27, 2023. Forecasters are particularly concerned due to unusually high sea surface temperatures in the Atlantic, which are contributing to the storm’s rapid intensification.
Agnes formed from the remnants of Tropical Storm “Ophelia” which recently impacted the U.S. East Coast. These types of weather systems often transition into intense extratropical cyclones as they move over the North Atlantic. The cyclone development process usually involves three key phases: a tropical phase, an extratropical transition, and a final re-intensification phase.
Agnes is forecast to experience a rapid deepening of its central pressure, falling around 20 hPa within a 24-hour timespan, just before making landfall in Ireland and the UK on September 27.
Higher-than-normal sea surface temperatures in the Atlantic are contributing to Agnes’s potential intensity. The Atlantic Ocean’s temperatures this September range from 29 to 31 °C (84 – 88 °F) across the tropical western Atlantic, and from 20 to 24 °C (68 – 75 °F) from the Northwest Atlantic towards the Bay of Biscay.
These elevated temperatures are expected to remain, increasing the likelihood of further intense tropical and extratropical development in the coming weeks and potentially also months as we head into the next Winter Season, Marko Korosec of the Severe Weather Europe noted.
Given its current track and intensification, Storm Agnes poses a significant threat to shipping across the Bay of Biscay from Tuesday night into Wednesday. Authorities are advised to take necessary precautions.
“Storm Agnes will move into western areas of the UK and Ireland on Wednesday, with the strongest winds most likely on Irish Sea coasts, though it will be a widely windy day across the UK,” meteorologists at the UK Met Office said.
“While the precise track and depth of Storm Agnes is still being determined, there’s a high likelihood of wind gusts around 80 – 95 km/h (50 – 60 mph) for some inland areas,” Met Office Chief Meteorologist Steve Ramsdale said.
“Exposed coastal areas could see gusts of 80 – 120 km/h (65 – 75 mph) with a small chance of a few places seeing around 130 km/h (80 mph). As well as some very strong winds for many, Storm Agnes will also bring some heavy rain, with the highest totals more likely in Scotland, northern England, Wales and Northern Ireland. Around 60 mm (2.4 inches) of rain is possible in a few places over high ground in Scotland.”
Residents of Ireland and the UK are advised to stay updated on local advisories and take necessary precautions. The storm’s rapid intensification, coupled with unusually high sea surface temperatures, raises concerns for potentially severe impacts.
Agnes is the first officially named system of the North Atlantic 2023/24 storm season, which started on September 1.
Storms are named when they could cause ‘medium’ or ‘high’ impacts in one of the three partner countries that make the list — Ireland, UK, and Netherlands. This enables consistent, authoritative messaging to support the public to prepare and stay safe during potentially severe weather events.
The full 2023/24 list is Agnes, Babet, Ciarán, Debi, Elin, Fergus, Gerrit, Henk, Isha, Jocelyn, Kathleen, Lilian, Minnie, Nicholas, Olga, Piet, Regina, Stuart, Tamiko, Vincent and Walid. The letters Q, U, X, Y, and Z are not included, which is in line with the US National Hurricane Centre naming convention.
1 A Violent Atlantic Storm Agnes will blast severe winds and waves into Ireland and the UK on Wednesday – Severe Weather Europe – September 25, 2023
2 Storm Agnes to bring winds and rain – UK Met Office – September 25, 2023
Featured image credit: ECMWF/TropicalTidbits
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