John Hammond’s Month Ahead – Is the weather about to go into reverse…?

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

For much of this winter the weather has been leading long-range forecasters a ‘merry dance’. One reason is that the reliability of computer predictions has been (even) poorer than normal.

Why? Because conflicting drivers of our weather – be they from the atmosphere or from the ocean – have led the jet stream to behave in quite a fickle manner. It’s been hard to nail down its next move. I’ll admit it. Regular readers of my blog will know that I had expected high pressure to be fending the jet stream off and settling the weather down soon. Not so fast, John! Next week will probably turn out to to be very much more disturbed than previously expected.

However, as I suggested last time, an event in the stratosphere is about to unfold, which may well stop the jet stream in its tracks. High above our heads, a Sudden Stratospheric Warming (SSW) will occur in the next week. Sara and I discuss the SSW in this QuickChat. The chances are that it will have quite a profound effect on our weather in the month ahead.

 

MONDAY 12TH FEBRUARY – SUNDAY 18TH FEBRUARY

Rain, shine, gale, sleet, repeat…

It takes time for the effects of an SSW to work their way down to ground level. So for the time being, we continue to look to the west. Hurtling across the Atlantic, a very strong jet stream will deliver a series of deepening depressions to our doorstep.

Now, the timing and track of these will be hard to pinpoint too far in advance, but we can expect impacts from wind and rain. And in the wake of each depression, a fresh shot of cold Canadian air will be sucked into the mix. So for much of the time it will feel chilly with overnight frost when skies clear. Some transient snow is also expected, especially across some northern parts of the UK.

As the weekend approaches there are signs of the jet stream backing off somewhat, with some lengthier dry spells expected

Maybe not a UK Winter Olympics, but I wouldn’t pack the children’s sledges away just yet

 

MONDAY 19TH FEBRUARY – SUNDAY 25TH FEBRUARY

Stirrings from above

For a time it may be that a quieter and milder interlude is temporarily ushered in. But it’s during this week that we expect the weather to begin to change quite dramatically.

The ‘burrowing down’ of easterly winds to ground level as a result of a Sudden Stratospheric Warming can take many days; and the arrival of these winds to our shores is not a certainty. But with such a strong SSW, it is more likely than not.

Through the week, there is an increasing chance that easterlies will set in and we begin to feel the effects of a frigid block of air from the Continent.

I expect the weather to turn much colder with widespread frost. Given the inherent uncertainties with timing, it would be foolhardy to attempt any daily detail. But of course the prospect of disruptive snow will need to be monitored. Maybe not a UK Winter Olympics, but I wouldn’t pack the children’s sledges away just yet.

 

MONDAY 26TH FEBRUARY – SUNDAY 11TH MARCH

Winter lingers into March

The last major SSW event was in 2013 and was probably a major factor in the exceptionally cold March that year.

I’m not predicting a repeat performance – every event is different. But most long-range computer models robustly indicate that cold easterly winds are quite likely as ‘Spring’ approaches. Although the sun is becoming increasingly strong, it looks like the wintry prospects of frost and snow will endure well into March.

It’s worth injecting one caveat to this icy story. The ‘elephant in the room’ is that computer forecasts have had a poor winter – their ‘confidence’ is no guarantee of outcome.

However, given what’s happening in the stratosphere right now, I’d be surprised if at some stage we don’t feel quite an impactful sting in this winter’s tail.

That’s great news for kids of all ages; but for many others, the warmer days can’t arrive soon enough. In this game, you can’t please all of the people all of the time!