Are we heading for a White Easter?
If you think we've escaped a proper winter so far in 2016, you could be in for a shock.
The Met Office is warning that we might be in for a White Easter.
It's all due to what is called a sudden stratospheric warming event bringing snow, ice and temperatures as low as -14C.
The plunge - the same phenomenon that triggered the 2010 Big Freeze - is expected to result in colder-than-average weather across the UK in late March.
The Met Office March to May forecast said: "The greatest risk of cold weather impacts is in late March and early April, due to the likelihood of a sudden stratospheric warming event.
"These events more often than not result in conditions associated with colder and drier-than-average conditions across the UK in early spring.
"There are renewed signals for a sudden stratospheric warming in early March, with the potential to increase the chances of cold weather later in March and early April."
Met Office definition of a sudden stratospheric warming event?
The term SSW refers to what we observe – rapid warming (up to about 50 °C in just a couple of days) in the stratosphere, between 10 km and 50 km up.
You may have heard of the jet stream which helps to steer Atlantic weather systems towards the UK. Well there are other jet streams high up in our atmosphere in both the northern and southern hemisphere which circumnavigate the Earth from west to east. One of these, the Polar Night Jet, circles the Arctic.
Sometimes the usual westerly flow can be disrupted by natural weather patterns or disturbances in the lower part of the atmosphere, such as a large area of high pressure in the northern hemisphere. This causes the Polar Jet to wobble and these wobbles, or waves, break just like waves on the beach. When they break they can be strong enough to weaken or even reverse the westerly winds and swing them to easterlies.
As this happens, air in the stratosphere starts to collapse in to the polar cap and compress. As it compresses it warms, hence the stratospheric warming.
