Three named Atlantic storms in a week

By Ivan Smiljanic (CGI), Thomas August, Remko Scharroo, Mark Higgins (EUMETSAT), Vinca Rosmorduc (CLS)

This was the first time this had happened since the Met Office and Met Éireann storm-naming system was introduced in 2015.

On 16 February Storm Dudley (also named *Ylenia) hit parts of Ireland and northern England with winds up to 130km/h (81mph). Within a day the Met Office and Met Éireann had issued rare red alerts for another Atlantic storm — Eunice (Zeynep) — which was predicted to be one of the worst storms in at least a decade — maximum winds speeds reached 196km/h (122mph). Hot on the heels of Eunice, came Storm Franklin (Antonia) which hit similar areas of the UK. All three storms were associated with a very active jet stream in the North Atlantic.

As Storm Dudley arrived on Wednesday afternoon, Capel Curig in Wales experienced gusts of up to 130km/h (81mph). Emley Moor in Yorkshire saw 119km/h (74mph) winds, while Drumalbin in Scotland was hit by 114km/h (71mph) gusts. Thousands of people were left without power after Storm Dudley hit parts of the North East, Cumbria, North Yorkshire and Lancashire.

In Poland least eight tornadoes were spawned by Dudley, with three fatalities. As the result of the storm three people died in Germany, two in Lithuania and one in the UK.

The development and advection of Storm Dudley over the UK, Germany and Poland, associated to a strong west-to-east stretching jet stream, is captured by a loop of Airmass RGB imagery from 16/17 February (Figure 1).

On 17 February the Met Office issued a rare Red Alert warning (danger to life) for Storm Eunice, for western coasts of south west England and Wales. Later a similar warning was issued for parts of south east England, including London. In Ireland Met Éireann also issued a Red wind warning for southwestern areas. In continental Europe, where the storm was named Zeynep, Meteoalarm issued red warnings for parts of the Netherlands and Germany.

Wind gusts on 18 February reached 196km/h (122mph) off the Isle of Wight, and exceeded 136km/h (85mph) in a number of places in land. Sixteen deaths were reported in the Irish Republic, the UK, Belgium, the Netherlands, Germany and Poland; millions of properties and businesses were left without power and there were widespread travel disruptions.

The Meteosat-11 water vapour image loop (Figure 2) follows the explosive cyclogenesis process of Storm Eunice.

Two days later Storm Franklin travelled slightly further north, bringing strong winds and heavy rains to northern parts of the UK and Europe. Fourteen deaths were reported, a number of regions were severely flooded and, again, there was widespread damage.

The Meteosat-11 IR10.8 imagery (Figure 3) shows Storm Franklin's progress across the UK.

Meteorology of the storms

The strong jet stream which was responsible for the storms can be clearly seen in this Meteosat-11 Airmass RGB with wind at 300hPa overlaid (Figure 4).

On occasions (it was the case this time) a sting jet can be spotted by satellites when the end of the cold conveyor belt — a strong stream of cold air — forms a hook-shaped cloud that resembles the sting of a scorpion's tail. Sting jets are usually associated with the strongest wind episodes, and are part of the prevailing ‘mother’ jet stream. On the Airmass RGB from 18 February (Figure 5), captured during Storm Eunice, the warm conveyor belt is connected to warm and moist air protruding from the southwest along the cold front line (blue line in a warm sector). As it moves toward the warm front region (red line) this air raises up and condensates, participating in the formation of the warm front cloud shield.

This process can also be clearly seen in water vapour imagery, in the static image from the same time (Figure 6) and the animation from 17 February 00:00 UTC-18 February 10:00 UTC (Figure 2).

The cold conveyor belt moves beneath the warm conveyor belt bringing the relatively moist, but colder, air towards the occlusion point of this system. The associated cloudiness shows as less intense white shades in the Airmass RGB imagery, because lower-reaching clouds do not have very cold tops. The dry intrusion is coming from the west and swirling towards the centre of the occlusion. This is easily seen in the Airmass RGB as a red stripe, and in the water vapour imagery as a darker, and, thus, drier area.

Within Storm Eunice, the tephigram soundings from Metop-B showed the deep intrusion of dry and cold stratospheric air into the troposphere (Figure 7 and 8a, 8b, 8c). Ahead of the storm front (right), the structure of the troposphere is not yet affected by the intrusion.

As the storm front arrived, the sounding from the later overpass with Metop-C (Figures 9 and 10a, 10b, 10c) showed some intrusion of dry and cold stratospheric air into the troposphere.

Atlantic storms and oceans

Figures 11a, 11b, 11c and 12a, 12b, 12c show the significant wave height and wind speed in the north Atlantic observed by the Copernicus altimeter missions Sentinel-3A, Sentinel-3B, Sentinel-6A, and Jason-3, on 18, 19, and 20 February. During Storm Franklin on 20 February the highest wave heights (up to 17 meters) and wind speeds (up to 93km/h (58mph)) were measured by several of the instruments.

*Note: There are two main naming lists for winter storms: one created by the national meteorological agencies of the United Kingdom, Ireland, and the Netherlands, and another created by the equivalent agencies from Germany, France, Spain, Portugal, and Belgium.