Babet 'Beast From The East': A Meteorological Perspective

Three people have sadly died and countless others are facing severe disruption because of the unusual but certainly not ‘unprecedented’ (as some media outlets are suggesting) weather conditions associated with Storm Babet, which has mainly affected eastern Scotland and north east England, although flooding has been quite widespread across eastern and central England too (now Wales). I think those victims and their families deserve a sound, evidence-based explanation for their suffering beyond the inevitable ‘extreme weather caused by climate change’ speculation in the press. They deserve to know why the elements have conspired to bring about the exceptional weather we have experienced over these past few days and which is still affecting parts of Scotland. Because in these British Isles, extreme weather from the north, east, south or west, be it wind, rain, snow, cold, heat or drought, has always affected us from time immemorial and has claimed countless lives over the centuries. The only thing ‘unprecedented’ now is our ability to forecast such events and to rationally explain them using our enhanced powers of observation (the unprecedented collection of weather data) and our progressed scientific understanding.

So let’s start with a look at the surface pressure weather map from two days ago:

What is immediately apparent is the complex mass of occluded fronts (where warm fronts merge with cold fronts) over central Scotland and eastern England, bringing exceptional persistent rainfall deriving from the easterly airflow track across the North Sea (which is still relatively warm at this time of year). The isobars are also very tightly packed which means that the winds coming from the east and north east are not only laden with moisture but also very strong. High pressure is centred over Scandinavia, drawing air from continental Eurasia across the UK. This is why one man was killed by a falling tree and two other people have died in floods. The set up is unusual - Britain is most often affected in autumn and winter by strong, moisture-laden winds coming off the Atlantic, where western parts of the British Isles are most severely affected. That’s a direct consequence of the general global circulation and the direction of the earth’s rotation. But sometimes, atmospheric conditions occur which disrupt that general pattern and we in the British Isles get weather which comes from the East (i.e. the European continent and Siberia).

It often happens in winter when we get the so called ‘Beast from the East’ carrying extremely cold, dry air from Siberia which, if it tracks across a wide enough area of the North Sea, picks up enough moisture to deposit as snow in bitterly cold blizzard conditions. High pressure over Scandinavia results in a very cold continental airflow across the UK. Babet is just the ‘Beast from the East’ happening in October, which has been unseasonably warm so far in Britain; hence a lot of rain and very strong easterly winds. The unseasonably warm temperatures form the sole basis for otherwise unsubstantiated media claims that Babet has been fuelled by man-made climate change. But really, it’s the unusual but not unprecedented dynamic meteorological set up which is responsible for Babet and the damage it has caused, not a global rise in mean surface temperature which may or may not have contributed slightly to heavier rainfall overall.

Circulation patterns. The northern hemisphere jet stream configuration, the persistence of a high pressure cell over Scandinavia; these are the things which contribute most significantly to weather coming not from the west, as usually occurs around this time, when the jet stream sinks south across the UK and starts directing Atlantic storm tracks this way, but from the east. In actual fact, the jet stream is at present very far south over Spain and North Africa.

Tomorrow, the configuration looks even more extreme, with the jet stream plunging as far south as southern north Africa and then doing a very sharp turn and heading northwards into southern Europe, missing the UK completely. This is quite unusual for the time of year.

We can speculate that it may just be the result of the random vagaries of the weather or it may be as a result of changes in general circulation patterns initiated by the eruption of Hunga Tonga, as I pointed out in this post a while ago:

But autumn in the UK is looking like it may be dominated by high pressure, not Atlantic low pressure, which normally brings rain and high winds. This is the forecast for five days time, with high pressure centred over the UK and the jet stream being directed south over Iberia. In winter, such a set up will bring cold, still nights and bright frosty days, with little wind - so all those turbines generating ‘clean’ energy won’t be working and we’ll have to source whatever energy we can - during times of high demand - from dwindling ‘dirty’ fossil fuel generation. But the government assures us that the lights won’t go out.