Storm Eowyn unleashed strong and damaging winds on the British Isles, and particularly on Ireland and Scotland.
The air pressure at the center of the storm dropped 50 millibars in the 24 hours to midnight on January 24. This more than doubles the definition of “explosive cyclogenesis”, in other words, a cyclonic (rotating anticlockwise) storm that is both rapid and severe – like a bomb going off. As a result, Eowyn may be called a “bomb cyclone”.
It is not unusual for winter storms to reach bomb cyclone status in this part of the world. However, only a very few in recent years have shown a rate of deepening that is comparable to Hurricane Ewin.
Storm Eowyn was predicted to be of exceptional intensity and has prompted the Met Office and Met Éireann to issue a red warning covering the entire island of Ireland and central and southern Scotland. It tells the public to expect widespread gusts of 80-90mph and up to 100mph in the most exposed locations. A record-breaking gust of 114mph has been provisionally reported this morning at Mace Head on the West Coast of Ireland.
Similar intense storms have caused widespread damage and tragically claimed lives. Some, such as the infamous Great Hurricane of 1987, have entered popular culture.
Éowyn’s place in history
The maximum gust during the Great Storm was measured as 115mph in Shoreham on the West Sussex coast. However, the anemometer stopped recording immediately, so the true peak may have been higher.
A scientific paper has cast doubt on the UK national low-level wind gust record (so, excluding mountain summits) of 142mph. It was recorded at Kinnaird Head Lighthouse in Fraserburgh, Aberdeenshire, Scotland on 13 February 1989. Researchers documented brief power supply interruptions to the recording anemograph, which could have given a faulty reading.
The record-highest wind gust measured in England sits at 122mph. It was recorded at The Needles, a very exposed site on the shore of the Isle of Wight, during Storm Eunice in February 2022. Less than similar strength was recorded in Brittany two years later (November 2023) during Hurricane Ciaran.
In Ireland, the strongest gust recorded by an inland low-altitude weather station was during pre-Hurricane Debbie in 1961, with 113mph measured at Malin Head, the northernmost point of mainland Ireland. A gust of 97mph was measured in October 2017 at Roche’s Point at the entrance to Cork Harbor during pre-Hurricane Ophelia.
The measurements we are seeing now during the storm’s passage are in line with those recorded during the most notorious storms of recent years and decades.
Do hurricanes ‘explode’
Like making a cake, there are several key ingredients to baking an explosively developed bomb cyclone like Hurricane Éowyn.
A strong jet stream – a ribbon of winds about six miles high in the atmosphere over the North Atlantic – is one. Winds here currently exceed 200 mph – their strength linked to the strong temperature contrast between the cold dip of air over the eastern US and the warm air away over the western North Atlantic.
This strong jet provides the energy for the storm’s development and also causes its race across the North Atlantic towards the UK. Storm Éowyn arrived off the US eastern seaboard during Wednesday January 22 and will have traveled more than 2,000 miles before arriving over western Scotland by Friday afternoon.
The low pressure center of Storm Éowyn crossed the jet stream from a south to north en route, which was an ideal track for explosive development.
Ewin’s heavy rainfall as it tracks towards the UK is the result of another key component to explosive storm development: deep clouds within the storm that generate energy when their water condenses. These clouds are fed by strong fluxes of heat and moisture from the warm ocean surface, and scientists have been detecting record-warm surface ocean temperatures in the North Atlantic in recent years.
role of climate change
When storms like Evin occur, people point to the role of climate change in boosting their strength. Our experiences of future storms will depend on what tracks these storms typically follow and how this affects their intensity. Stormy weather is, of course, not uncommon in autumn and winter on the British Isles and detailed research is needed to attribute the strength of any specific storm to climate change.
To date, observed trends in hurricanes have not provided a conclusive link with climate change. The latest assessment report from the Intergovernmental Panel on Climate Change, convened by the United Nations among experts concerned with all aspects of climate change, says there is “low confidence” in the direction of trends in the number and intensity of extratropical storms (( Which form outside the warm band around the Earth’s equator).
One reason this link is difficult to make is that the position and variability of the storm is very dependent on the jet stream, and its position varies greatly from day to day, week to week, and beyond. Large-scale climate patterns such as the El Niño Southern Oscillation and the North Atlantic Oscillation, and sea surface temperatures and sea ice extent are also likely to be important factors.
Despite this uncertainty, there are signs that in the future, winter storms may become more frequent and more clustered (such that multiple storms occur within a few days of each other), which could increase their overall impact. The frequency of storms may also increase with extreme winds. Precipitation is likely to increase, as a warmer atmosphere can hold more moisture.
Another thing that may change about intense storms in the future is their tendency to develop “sting jets.” Sting jets are descending into airstreams that can produce particularly destructive surface winds, such as in the Great October Storm, Hurricane Eunice, and Hurricane Ciaran. Sting jets are short-lived and occur over very small areas, making them difficult to predict and identify.
There is speculation as to whether a sting jet landed during Storm Éowyn. Post-event verification will be required. While the overall impact on wind speeds is uncertain, a small number of studies considering sting jets in future cyclones have predicted an increase in their likelihood.
Cyclones that are capable of producing sting jets also typically show more vigorous cloud development, consistent with the hypothesis that future intense storms will be influenced by our hotter and wetter climate.
,Author: Suzanne Gray, Professor of Meteorology, University of Reading and Ambrogio Volonte, Senior Research Fellow in Meteorology, University of Reading)
(This article is republished from The Conversation under a Creative Commons license. Read the original article.)
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
