The fifth named storm of the winter proved to be the most potent so far as Eleanor brought hurricane force gusts across many parts of the British Isles. We review its multiple impacts on infrastructure and look to its root causes to consider how future storms could evolve.

What has been the damage so far?

Damage to critical infrastructure has been widespread, with many homes without power, roads and rail lines blocked by fallen trees, while several major road bridges were closed. Parts of Galway, Cork and Limerick were completely flooded as Irish first responders once again battled to protect vital infrastructure.

A 40 foot section of Portreath harbour wall collapsed as Eleanor battered Cornwall.  The Thames Barrier was closed for the 180^th time to protect London from flooding, in response to increasing surges forecast after high tide following the passage of the storm across the North Sea.

The Environment Agency issued 50 flood warnings and 110 flood alerts, with coastal areas under threat from a combination of a high tide and large waves. Storm surges were reported across North Devon and Cumbria. In Barnstaple, Pilton Park was completely submerged with water levels up to 3m higher than the normal range, while Cumbria Fire and Rescue Service were called out to incidents in the Silloth area where sea water is reported to have got into properties.

Inland, a vigorous frontal system with the storm brought locally severe rainfall totals, leading to surface flooding and inundation of sewers and drainage systems.

Where did Storm Eleanor come from?

While winter storms are nothing new, it’s important to understand their origin and whether this is a pattern that poses ever greater challenges for property owners and infrastructure managers.

Cyclonic low pressure systems are borne on the Jet Stream – It’s a well known phrase but what are they and how do they influence our weather in the UK?

The Jet Stream is a strong flowing ribbon of air that flows around our planet high up in the atmosphere, at around the level of the tropopause. Situated between the troposphere and the stratosphere, the Jet Stream flows at around 160kmph (100mph) in both hemispheres around the earth approximately 11km up in the atmosphere. They form and are strongest where air temperature gradients are steepest.

In winter, the temperature of the stratosphere can also have an effect on the strength and position of the Jet Stream. The cooler the polar stratosphere, the stronger the polar/ tropical differential becomes; encouraging the jet stream to gain in strength.

Common cyclonic depressions are caused by the difference in pressure and temperature over a region. This feeds strength to the jet stream, which is then invigorating the depression. The Coriolis Effect creates the rotation that is associated with depressions.

So why is Eleanor more notable?

It is not surprising then that, as a winter storm, Eleanor has packed a punch more than in other seasons. But it is the temperature gradient between warm and cold air masses that is the key with Eleanor.

The principal cause of the aggressive and direct jet stream that threw Eleanor at the UK is the extreme cold snap in the United States. As 2018 was ushered in, temperatures plummeted to -37C in some places. Indeed, on New Years’ Day, 90% of the country failed to make it above 0C.

The culprit? It’s the opposite of the more famous El Niño phenomenon, La Niña, which brings a natural cooling of the tropical Pacific Ocean and affects weather all over the planet.

Typically, during La Niña events, cold and stormy periods assault the north central and northwest United States repeatedly during the winter – and the UK is directly affected by a stronger temperature gradient on the north side of the Jet Stream. The US Weather Service says there is a 65 to 75 percent chance La Niña will persist through the winter, and probably through at least April, so we could be in for a very turbulent set of winter storms barrelling directly across the Atlantic.

The West could Face the Worst

The prevailing winds on these depressions mean that western parts of the British Isles are the most vulnerable to winds and flooding. Indeed, Hurricane Ophelia in October slammed right into the Republic of Ireland as the most easterly recorded hurricane in the Atlantic on record.

The devastation of Storm Eleanor and Hurricane Ophelia has highlighted the urgent need to better manage and assess flood risk in the Republic of Ireland.

Our enhanced FloodScore™ product for Ireland (to be launched later this month) aims to resolve this problem, offering the most up-to-date flood data set in Ireland. FloodScore Ireland is a property-level flood risk checking service that enables businesses to quickly evaluate and quantify flood risk to specific properties.

The product will be available as an online checking service, via API, as a full or partial database or as spatial GIS layers. It integrates the very latest Eircode property information as well as our proprietary, high-resolution Ireland FloodMap^TM.

We’ll soon be releasing more information on this innovative new product. Follow us on LinkedIn to stay up-to-date with Ambiental news. Alternatively contact us if you’d like to discuss FloodScore or any of our other products or services with one of the Ambiental team.