At this time of year the weather should be turning much colder as winter approaches but more often that not here in the UK the weather never seems to follow suit, instead we’ve had a run of milder winters and generally disappointing summers. Milder winters are more common not only due to the globe warming significantly over the past 50 years but also the seas around the UK generally moderate the air.
However from time to time we do see certain set ups that allow much colder Arctic or Siberian air to flood the UK, bringing much colder temperatures than we would normally expect and this pattern is now showing real signs of developing and perhaps lasting for an extended period.
The pattern we are referring to is what we call a blocked pattern. This is where high pressure builds in the north Atlantic and over Greenland and effectively blocks the normal westerly Atlantic flow, which is what brings our nasty mild, wet and windy conditions. Instead this blocked pattern forces our weather to come from the north or even east, which in late Autumn and Winter is generally a cold to very cold direction. This pattern is shown very nicely with the latest 500mb height anomaly chart. Note how the red colours block or shield the UK from any weather off the Atlantic, instead lower heights are forced from the Arctic, which in turn brings much cooler air.
This cooler air again is shown nicely below. This chart is a temperature anomaly chart for the next 5 days and we see plenty of blue colours which indicate below average temperatures, a signal for colder weather.
So we have a signal for colder weather and a blocked westerly flow which may keep the cold weather over the UK for period of time, this not conclusive at the moment however. Colder weather will be dominant for the remainder of the week and of course there will be the usual questions of will it snow?
We can answer that. For the majority, the answer will be no. Our flow will generally come from the north which normally brings drier weather across much of the UK apart from north facing coasts and parts of Eastern Scotland/Eastern England. The chart below is a precipitation anomaly chart for the next 7 days, the yellow colours indicate drier than average conditions which as shown covers a vast amount of the UK. However some areas such as the ones mentioned above have green colours, this indicates wetter conditions, most likely in the form of heavy showers, and across northern areas these will be of snow.
So overall colder weather is expected along with drier conditions and some nights will be clear so sub zero temperatures will be attained across many areas, leading to frosts, perhaps hard frosts in rural areas. We are not expecting snowmaggedon like some media outlets have be suggesting, plenty of showers will affect northern and eastern coasts of the UK and some of these will be wintry so accumulations here are possible but for most, just expect dry and crisp days…………for now!!!