EMAIL EXCLUSIVE: John Hammond’s Month Ahead – Signs of sparkle to lift the gloom?
It’s not turning into a good week for me. First the clocks go back, then dark November arrives; and to cap it all off, yesterday I forgot to bring a tie with me to the TV studios, and so had to hurriedly go shopping for a new one. However, the main reason for my chagrin is that the weather is showing signs of diverging from the my last forecast. Naughty weather!
I had thought that next week the Atlantic jet stream would begin to be stopped in its tracks as drier, chillier continental weather took over. The plot has changed – temporarily. The atmosphere has received a prod of energy that will inject waves of wet and windy weather further into the month than I’d expected. Yet here’s the dilemma. Computer forecasts are even more bullish about dry and chillier continental air eventually winning the battle by mid-month. Do we trust them this time around? Read on…
Mild and wet period
Drier and chillier after mid-month
No severe cold yet
MONDAY 5TH NOVEMBER – SUNDAY 11TH NOVEMBER
The dark and drippy side of November!
Though not entirely dry, the week looks like starting on a deceptively quiet and misty note, perhaps with a touch of frost for a few. Seeded by the weekend’s bonfires, fog may be an issue for some on Monday. Then it’s all change!
A huge vortex of low pressure will soon take up residence in the eastern Atlantic; and through the rest of the week, around its periphery, the jet stream will fling a succession of wet and windy spells towards UK. The timing of these can’t be nailed down at this range; but we can expect several spells of rain, and the potential for disruptive winds will need to be watched too. Western parts of the UK will be most prone.
Of course, there will be some drier and brighter spells, and for a time it will be relatively mild. So snow is very unlikely.
…we know what long-distance relationships can be like – fraught!
MONDAY 12TH NOVEMBER – SUNDAY 18TH NOVEMBER
Big changes in the atmosphere
One reason why the weather is briefly jumping into this frantic mode may be that up in the stratosphere, the westerly winds that circle the North Pole have suddenly accelerated to unusual strengths. Now we know what long-distance relationships can be like – fraught! Similarly the link between the top of the atmosphere and the bottom is not a straightforward one. But on this occasion those strong westerlies are linking down to help produce the surge of Atlantic weather systems towards us.
However, I still don’t believe that this will last long. There are indications that the stratospheric westerlies will begin to weaken. And computer forecast models are also indicating that further down through the atmosphere the waves of atmospheric energy that circle the northern hemisphere will also slow and perhaps even go into reverse by mid-month. The upshot of this reconfiguration is for the jet stream to stall its supply of mild, wet and windy weather from the west; and for a drier and chillier period to become established.
So a week or so later than previously thought (he said sheepishly), after a milder and wetter spell, I still expect drier, colder and frostier weather – certainly by mid-month, if not before.
Some festive weather will be welcome as pre-Christmas events begin to get into full swing…
MONDAY 19TH NOVEMBER – SUNDAY 2ND DECEMBER
A crunchy start to a mild winter?
Once ‘blocked’ weather patterns have become established, it can be difficult for the jet stream to remove them. The larger the block, the more stubborn it can prove to be. So I expect a fairly sustained dry spell to continue well into the second half of November, as a continental feed of air keeps most rain-bearing Atlantic systems at bay. Frosty days and crisp sunshine will make a pleasant change after a mild and wet spell. Some festive weather will be welcome as pre-Christmas events begin to get into full swing around the country. Here’s a selection.
But at this time of year, our very coldest weather tends to derive from the Arctic rather than the Continent. As we’ve already seen in the last week, when the north wind blows, some places can receive some notably early snowfalls. So it’s one we’ll keep an eye on, but there is no clear sign of any severely cold weather arriving just yet.
The question then is how soon the westerlies return. Just in the last week, I’ve read updates from two major centres, who remain bullish about a predominantly mild, wet and windy early Winter 2018/19. Our forecast is here.
In the meantime, do enjoy the fireworks this weekend, whatever the weather! A sparkle amidst the gloom is enough to lift the mood of even the most downtrodden of forecasters!