The last few days of February and the first few days of March 2018 came as a sharp reminder of what winter can really do to us. No part of the country was left untouched in the snow. Reports from both sides of the Bristol Channel showed deep snow while the warm and humid southwest of Somerset, Devon and Cornwall experienced its first ever Red Weather Warning. It’s been called “The Beast from the East”.
A Brief and Basic Explanation of Weather Systems
Eastern Europe through to Siberia is used to these weather conditions, but Western Europe is not. Three important factors drive the air’s global movements:
• Gravity. If you’ve not forgotten your GCSE/O-Level geography, you’ll know this is the magnetic pull of the surface of the Earth. It draws everything, including air, back down to Earth. The cooler it is, the denser it is at the ground level
• Our Sun: Slightly more complex, when the sun rises, the heating process increases air temperature which causes it to rise up through the atmosphere. This creates low pressure. But as it cools, it sinks back to the surface through gravity’s influence. This creates circulation and defines planetary wind systems
• The Coriolis Effect: This deflects global wind systems. The Earth is spherical. That means to complete a full circuit, a wind system in the north travels slower than wind systems to the south. This essentially “deflects” the wind systems based on that rotation
This system creates a Polar Jet Stream which usually leads to warm airs from the central Atlantic to hit us over the winter. We might moan about the weather, but our winters are relatively mild even without the effects of Climate Change.
Enter The Beast from the East
The Atlantic Jet Stream is not fluid; it is not always stable. When it gets out of synch, we can be suddenly hit with erratic weather dumping a lot of rain (or in this case, snow) in a short space of time. This is what happened with The Beast from the East. Weather systems like it occur when The Atlantic Jet Stream gets so erratic that it “twists” and folds into itself.
The wind’s direction is then reversed, causing for weather fronts to be drawn not from the west and southwest, but from the east – eastern and northern Europe, and, of course, the Russian Steppe all the way to Siberia. We understand precisely what caused The Beast from the East – it’s a process called Stratospheric Sudden Warming. There was a lot of water vapour in the air over the UK; combine this with the unusual cold front and you have mountains of snow that causes the country to grind almost to a halt.
Why It All Cleared So Quickly
Such sudden and intense storms rarely last and there is also a scientific explanation for that. Within a matter of days, most areas had lost all their snow with temperatures returning to normal or near normal for early March.
The cold wintery conditions of a weather front like “The Beast from the East” drives temperatures down. But it’s this severe cooling that creates conditions for milder weather to follow. Air will circulate slower than typical under these conditions. This creates calmer, smoother and more pleasant environments.
If The Beast from the East taught us anything, it’s how wildly different the urban and rural environment can be. Built-up areas may see longer-lasting effects because they are warmer (due to heat produced by buildings etc.) that maintains the rapid air circulation. This is one of those complicated areas, as often explained in climate science, where warming creates cooling.