John Hammond’s Month Ahead – Wild, wet (and occasionally white)

John gives us his latest thoughts on likely weather trends over the next few weeks. To ensure you are reading the very latest weekly blog, check out Wow and Why

December hasn’t been short on variety, has it?! Sometimes mild and wet; occasionally cold and frosty; with some disruptive snow thrown in for good measure in some places too. As if to highlight the point, Christmas week will probably gift us all of these at some stage too! Our conveyor belt of weather systems, the jet stream, has wandered well away northwards, allowing us a benign few days. Well it’s set to swoop back down across the UK in the week ahead. In the process, expect quite a ride.

I don’t anticipate the rollercoaster easing up as we arrive at New Year either. Far from it…   



All change! 

Big Day? Certainly. Christmas Day is when the jet stream starts to head south, ushering in rain and then colder air from the north. Cold enough for snow? Not for many, but perhaps for a lucky few, especially on the hills of Scotland and Northern Ireland.

By Boxing Day morning, we’re all in the chilly air again. It may be bright and crisp for a time. But don’t expect things to quieten down for long. We’ll be looking to the west for the next ‘trouble-maker’ (or three).

The jet stream will catapult a series of low pressure systems in our direction which are set to bring bouts of wet and windy weather through the week. The timing and track of these is very unclear and will be for a few days. But the latter is crucial. Why? Because some significant snowfall is possible on the northern flank of these systems as they cross the UK.

By the weekend, the jet stream may be on manoeuvres slowly northwards again. In the process, more wind and rain can be expected. But, with milder air becoming established, there’s a lessening threat of snow.

New Year will be ushered in by some wild antics (by the weather at least)



Blowing in the New Year

In previous blogs I’ve mentioned the ‘Stratospheric Polar Vortex’ . This ring of strong winds at the top of the atmosphere has been, well, less than strong and rather ‘off-kilter’ in recent weeks. However, there are now signs that the Vortex will strengthen around the Arctic for a time, which may help to supercharge the jet stream further down through the atmosphere. This energised state increases the chances of wet and windy spells of weather for us too.

So the New Year will be ushered in by some wild antics (by the weather at least). At this range, detail of individual events is impossible. But we should expect some impactful periods of wind and rain to be delivered to our shores. With predominantly westerly winds, I don’t expect any prolonged cold or snowy periods.



Shhh… a quieter spell emerges?

This hyperactive period of weather may begin to pass. Much will again depend on the state of the stratosphere, but there are tentative indications that the Polar Vortex may weaken once more.

So while the New Year may arrive with a mixture of mild and wild, as the jet stream slows and meanders away from our shores, I expect longer drier spells, and perhaps lower temperatures.

How cold it gets will depend on the shape of these meanders as, crucially, this will determine wind direction. But, with a greater chance of winds from the north or east, then colder, frostier (and perhaps snowier) weather looks more likely as the month proceeds.