John Hammond’s Month Ahead – Could hurricanes send us into an autumn spin?

Greetings from the Isle of Skye! It’s been a sparkling couple of days – vivid panoramas, the odd squally shower and, courtesy of some arctic air, an autumnal chill. Funny because, as you may be aware, long-range computer forecasts had confidently predicted that the weather would turn dry and increasingly warm by now. They’ve had a shocking month or two – repeatedly trying to bring the heatwave back. But the reality has been much more run-of-the-mill since early August.

Meanwhile out in the mid-Atlantic, the hurricane season has belatedly woken up. American forecasters are nervously monitoring the progress of ‘Florence’ as she approaches the coast. UK forecasters, meanwhile, will be looking for clues as to how Florence and her successors might jolt our jet stream – and our autumn – into a different phase.

 

Brief heat for the south next week

Wetter and cooler weather returns

Ex-hurricanes make their mark later

 

 

MONDAY 10TH SEPTEMBER – SUNDAY 16TH SEPTEMBER

Blowing hot and cold? More like warm then cool

A north-south divide emerges at the start of the new week. Northern areas, closest to the jet stream, will be plagued by rippling weather fronts, bringing rain and wind. Some western hills could see too much rain – one to watch. Meanwhile, to the south of this, a brief visitation of tropical air will deliver some warm and muggy conditions. Where the sun pops out, temperatures could easily reach the 20s Celsius. Not bad as we approach mid-September.

But let’s not dream of Indian Summers just yet. A cold front will sweep rain southwards by midweek. Cooler air and showery weather will probably characterise the rest of the week. Chilly nights will return, bringing the possibility of night frost to a few rural hollows. By the weekend though, light winds and some sunshine should ensure some comfortably feeling days, especially across the south of the UK, before more rain arrives from the west.

 

…my confidence in computer forecasts begins to fall off a cliff again

 

MONDAY 17TH SEPTEMBER – SUNDAY 23RD SEPTEMBER

Beware long-range forecasts

It’s at this range that my current confidence in computer forecasts begins to fall off a cliff again – like one of those shear drops I peered over at the top of a Skye mountain earlier today. The only way is down, and rapidly!

Rather than blindly ‘walking over the edge’ by following each fickle computer forecast, it’s best to take stock and look at a range of outcomes, while throwing in quite a dose of experience too.

We may well see a brief period of quite chilly arctic air dipping across us as the jet stream veers down from Greenland. Sunshine and blustery showers will blow in from the northwest. Cold enough for snow on the peaks that I’m currently surrounded by? I wouldn’t rule it out.

As the week progresses, though, more wet weather systems may start to head in from the west. And as a rule of thumb, the wettest and windiest weather will be across northern areas. Further south, we can expect  lengthier dry and warm spells.

 

…the chance of some disruption by early October

 

MONDAY 24TH SEPTEMBER – SUNDAY 7TH OCTOBER

Wild weather?

I expect storms in the western sub-tropical Atlantic to start to have an influence on our jet stream. With the ocean unusually warm off the eastern seaboard of the States, such storms are more likely to wander further north than normal. If so, these bundles of extra-tropical energy may jolt the jet stream into volatile modes of behaviour. A nightmare for computer models.

So we can expect rapid fluctuations in the forecast. My best bet is for an increased chance of one or more very wet and windy low pressure systems to be catapulted towards us. This brings the chance of some disruption by early October. In addition, tropical winds and air from the chilling arctic will be  vying for supremacy along this zone of jet stream energy. Pulsing north then south in rapid succession, I expect big fluctuations in temperatures as the new month arrives.

Yes, it’s that time of year of wardrobe challenges. T-shirts one day and overcoats the next. Too early for a winter-warming dram? It’s never too early in this part of the world…

 

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