The Braer Storm of January 1993 was the deepest ever recorded mid-latitude depression. Not counting tropical storms, it was the lowest low ever.
However, it didn’t produce widespread damage, nor did it send gigantic surf to southern Europe. This is mainly because the explosive deepening didn’t occur until quite late in the storm’s evolution – in the far northeast of the North Atlantic, in a relatively small area between Iceland and Scotland.
Related Content: Remembering Hercules: The Gigantic Atlantic Storm That Rocked Europe
The evolution of the storm for the first three-quarters of its life was not particularly remarkable. In fact it was fairly typical of winter low pressures that form when the North Atlantic is in a ‘healthy’ fluid phase (see my article on the North Atlantic Oscillation here). It was only when it got to about 800 miles northwest of Ireland that things started to get interesting.
The system started off as a weak disturbance near Newfoundland around 8th January. It then moved out into the open ocean, deepening steadily as it tracked east-northeast. Late on 9th, half way across the North Atlantic, while continuing to strengthen and move steadily northeast, it began to develop a peripheral centre on its southern flank.
The two centres merged early on the 10th, and this is when the system deepened explosively. By midday on the 10th, just west of Shetland, the storm had come to an almost standstill and the central pressure had plummeted to a never-before-seen 914 mb. Winds were now averaging hurricane-force with higher gusts.
Typical factors that contributed to the storm’s intensity included an exceptionally strong upper airstream that pumped energy into the system from above, and a stark temperature gradient in the surface water that fuelled it from below. But the major factor that made the difference between the deepest low of all time and just another North Atlantic storm, was the merging of the two centres.
For about the next 36 hours, the storm remained almost stationary and continued to generate hellish conditions. It then moved off into the Norwegian Sea, weakened and finally died out about four days later.
The Braer Storm was not only the deepest, but also the fastest-deepening mid-latitude depression in history. In the 24 hrs between 9th and 10th January the central pressure dropped 78 mb. To put this into perspective, very few storms manage to drop as much as 24 mb in 24 hrs. If they do, they can be awarded the title of ‘explosive cyclogenesis’ and usually end up making big news (see my article on explosive cyclogenesis here).
An easy way to measure the explosiveness of storms is by using the Bergeron scale, where one Bergeron is defined as a pressure drop of 24 mb in 24 hrs. The Hercules storm had a rating of 2.0 Bergerons, but the Braer beats that hands-down with 3.25 Bergerons.
Forecast: UK + Ireland
The Braer Storm gets its name from the MV Braer, an oil tanker that was on its way from Norway to Canada. The Braer had already lost power and run aground in Shetland five days earlier, but it was the Braer Storm that finally put the nail in the coffin.
Around 85,000 tonnes of oil were spilled from the wreck of the Braer. This had some serious consequences including the deaths of thousands of seabirds and hundreds of seals, but it never turned out to be a major environmental catastrophe. The fact that the oil was thinner and more easily degradable than typical crude oil, combined with the constant heavy seas over the following few weeks, meant that the oil dispersed and very little ended up on the coast.
Compare this with the Prestige which broke up off Galicia in 2002. The amount of oil that leaked out of the Prestige spill was only half that of the Braer, but the oil was much heavier. It ended up contaminating the entire coasts of France, Spain, Portugal and beyond, with effects lasting months or even years.
And what about the surf from the Braer Storm? Well, the storm didn’t reach its full strength until it got relatively close to northwest Scotland. Along the north coast of Scotland and in the Scottish Isles, they would have got a gigantic, ragged swell with hurricane-force winds. We don’t know of anyone who surfed up there at that time, but let us know if you did.
Further south, almost everywhere else missed the main bulk of the swell from the core of the system. However, there was a broad westerly airstream that covered almost the entire North Atlantic south of the main system, which persisted for several days. This generated some large, long-period swell for most west and northwest exposures. I happened to be in Mundaka (hint: We've a live cam of Mundaka here) during that time and remember an epic swell that lasted days and days.
Will the record low pressure of the Braer Storm be broken sometime soon? Will we see a low pressure of less than 900 mb? As I’ve mentioned before, one of the effects of global heating is sudden, episodic events – ‘spikey’ weather, if you will. Therefore, the answer is yes. But of course we don’t know what it will look like.