John Hammond’s Month Ahead – Bloomin’ ‘eck! – Winter could drag into March

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

Where I live, crocuses and snowdrops are shooting skywards – adding a flash of early springtime vibrancy amidst the late winter drabness. They don’t know what’s about to hit them!

In all honesty of course, none of us do! But as I mentioned in my last blog, there are compelling reasons why I think February is going to take on a very different complexion, and computer forecast models are gradually latching onto these.

Oscillations of atmospheric energy crossing the Pacific are favouring a blocking of the jet stream closer to home. High pressure looks set to be the dominant factor through the next few weeks – something many of us have been craving for a while. A chance to dry out? Well, not completely. What falls out of the sky may often be white, rather than wet.

I see nothing too extreme initially. But there’s is an added X-factor, which may provide a sting in Winter’s tail…


Disruption looms

Cold continental air, (something we haven’t experienced so far this winter), will already have crossed the North Sea and established itself across much of the UK. It’ll be a frosty start to the week, with a few sleet and snow flurries drifting into some eastern counties.

However trouble will already be looming on the horizon. An Atlantic front will bring moisture into this cold mix, and by Tuesday a band of more persistent sleet and snow will be spreading across the UK. Its progress eastwards is uncertain. Indeed the snow may not even reach some southeastern parts. But a covering of snow is likely in many places and, for some places, rather more than that. Tuesday looks like being a disruptive day.

After a midweek severe frost, the sequence looks like it may repeat. A new frontal system will be approaching from the Atlantic and by Thursday another ‘event’ may be unfolding. Sleet and snow will make uncertain progress eastwards and also looks set to stall somewhere across the UK – blocked by the cold air to the east.

It may take a third attempt before milder air makes inroads across the UK. That looks most likely by the weekend, when more energetic frontal systems displace the cold block – at least for a short time. I expect temperatures to rise, with some some wet and windier weather to ‘enjoy’.

Those spring shoots will be grateful for their inbuilt anti-freeze…


The X-Factor

Any milder, wetter period looks temporary. This burst of energy from the jet stream will wane as high pressure builds across the UK once more. And with an increasing chance of continental winds returning, we may again tap into a feed of much colder air  – still lurking further east across Europe.

So I expect things to turn drier and chillier through this week. Scraping of windscreens may again become a regular routine for early morning commuters.

But what of the X-Factor I mentioned earlier? There are now compelling indictions that the Stratospheric Polar Vortex will weaken quite abruptly. This ring of strong westerly winds that circle the arctic at the top of the atmosphere can very occasionally even go into reverse as a result of what’s called a ‘Sudden Stratospheric Warming’ (SSW). The effect on our weather can be quite profound as this reversal of winds gradually works its way down through the atmosphere over several days.

Computer models are indicating that such an SSW may happen around mid-month. If so, there would be a much greater chance of more severely cold easterly winds surging our way. It may not happen but it’s definitely one to watch!



Winter lingers into March

Whether or not we experience the dramatic stratospheric impacts I’ve described, most longer range computer forecasts indicate that for the rest of February, attempts by the jet stream to bring consistently milder westerly winds will be relatively feeble. I expect the chilly theme to continue. With high pressure dominant, wet weather should be less frequent than earlier in the winter. But significant snowfall will be an ever-present possibility when fronts attempt to push moisture into that cold air.

Whether we experience a severe cold spell still hangs in the balance, but come what may, it looks like we may be well into March before reliably milder weather arrives.

Those spring shoots will be grateful for their inbuilt anti-freeze over the next few weeks.

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