Weather warnings have been issued by the Met Office for strong winds gusting to 60-70mph, isolated 80mph along south coasts. Also warnings for rain and flooding for the west and NE Scotland.
A high-pressure system drifting across northern Britain bringing mostly settled conditions this week has retreated to eastern Europe today. This allows Atlantic low pressure systems to move back in and control our weather as we start November, so a return to unsettled conditions, with spells of rain or showers and becoming increasingly windy too, with a risk of gales or even severe gales developing in places over the weekend.
The origins of this return to unsettled conditions can be attributed to strong jet stream coming out of NE Canada and powering across the North Atlantic today, before heading towards western Europe for the weekend. The strong jet stream winds of over 200mph fuelled by a big temperature contrast that developed across central and eastern USA during the week, as chunk of unusually cold arctic air for late October dropped down across the US Plains and formed a steep thermal boundary between it and tropical moisture across the far south and east of the US. This steepening gradient also spawned winter storm Bessie, which dumped several inches of snow across the Rockies, Plains and mid-west, before the storm deepened as it reached the northeast overnight, bringing a line of intense thunderstorms along a cold front eastwards, bringing wind damage with power outages.
The strong jet stream will arrive to the SW of Ireland later day, with the developmental left exit area of the jet (where air diverges aloft and converges at the surface causing lift) engaging a, up until now, fairly innocuous low pressure system to the west of Ireland today. The low subsequently deepens rapidly as it comes under the jet left exit, then tracks across Ireland tonight then northeast across Wales and northern England on Saturday, before becoming slow-moving across the northeast into Sunday as the low fills.
Watch the strong jet streak come out of NE Canda and across the Atlantic, engaging low west of Ireland and deepening it.
Very strong winds are forecast by models to develop on the southern side of this deep low as it tracks northeast across Wales then northern England, particularly across the far south of Wales and much of southern England. Gales or severe gales look to arrive across SW England and coastal fringes of south Wales between 4am – 7am, with gusts of 60-70mph over coasts and hills, perhaps up to 80mph or more with exposure. These very strong winds transferring further east across southern England, through the morning, with gusts of 50-60mph possible inland, 60-70 mph along southern coasts, Isle of Wight and the Channel Islands, perhaps up to 80mph in some exposed spots. Winds generally easing through the afternoon and into the evening, but gales or severe gales still possible along coasts and over hills in the south. As the result of the high winds, there is likely to be some disruption to travel across the south, with a risk of trees falling, damage to property and power cuts. The Met Office has yellow warnings out for strong winds across far south of Wales, southern England and E Anglia and for rain across Wales and parts of SW England along with NE Scotland.
Wind gusts on Saturday - 12z Friday UKV model run
As well as the strong winds, a swirl of slow-moving heavy and persistent rain moving in and spiralling around the low moving northeast will bring some large rainfall totals across parts of Devon, Wales and parts of NW England – particularly higher ground – which could receive 40-60mm in 24 hours. This amount of rain falling on already saturated ground and running into rivers that are still high from heavy rain last weekend with some still on flood alerts, means there is a risk of flooding returning.
Netweather short range model rainfall totals 6am Saturday - 6am Sunday
As the deep low moving northeast tomorrow starts to fill as we head through Sunday, winds will ease as isobars slacken, though there will still be bands of showers or longer spells of rain spiralling around the low which will be slow-moving across the north, so any prolonged rain adding to the flooding risk.