So are we going to get snow and cold from the US? – No.
Much of our weather does originate on the western side of the Atlantic, many low pressures being brought across to the UK by the jet stream. However, the severe cold in North America is plunging down from the Arctic. It is extremely dry air, having travelled across a continent, from the Arctic, through Canada and much of the US to the Midwest, who are even today, under a Hard Freeze warning for temperatures of +15F (-10C) and a red flag warning (relating to not lighting fires outside due to the low humidity). In the northern states, it is still bitterly cold air -15F (-26C). There are wind chill warnings out, even though the winds are light, even the slightest breeze can cause a ‘feels like’ temperature of -25F (-32C).
The heavy snow fall, as seen in New York was from a deep low pressure, which brought the precipitation up the NE coast,and engaged with the very cold air drawn down from Canada. The remnants of this low have already come across the Atlantic and added to all our large waves, heavy rain and flooding woes.
The jet stream is enhanced by temperature contrast, so the severe cold in NE states has strengthened the jet stream and thrown more storms across the Atlantic at the UK, over recent weeks.
In the UK, we don’t have that cold drying land mass to our north. Any air coming straight down from the Arctic to us, feels cold, but has been modified on its travels, picking up moisture and interacting with the warmer sea temperatures at the surface (that, in itself, can produce snow showers). For the UK to get significant cold, we would look to air from Siberia, our feed of cold dry Artic air, which then only has a shorter sea track across the North Sea.
We can't give up on winter just yet, even though it has been quite mild and very wet for December. Remember March 2013, that was exceptionally cold and brought late snow, there is still plenty of time. Looking at the forecast models out to 10 days, there are hints of colder air coming towards the UK from the East, so from NE Europe. That would send our temperatures tumbling and interrupt this mild, wet and stormy Atlantic flow and introduce a more wintry setup. That is a fair way off in forecasting terms and just because it turns cold doesn’t mean you’ll be sledging. High pressure building over eastern Europe, can "block" the mild Atlantic flow, but it depends on the position of the High as to where our air flows in from.
The UK record low temperature was -27.2C recorded at Braemar in Grampian in 1982 and Altnaharra in the NW Highlands. Yesterday 7th Jan, the US low was -35F (-37C), and -47F on the 2nd Jan, which is -44C.
What’s all this about a Polar Vortex?Read all about the Polar Vortex Here
