The weather continues in a rather unsettled theme this week and over the next few days, with an upper low over the North Atlantic to the west of the British Isles driving a deeply cyclonic south-southwesterly flow across Britain today.
A rather active cold front swept east across Britain this afternoon and is clearing eastern England this evening. A band of squally rain is accompanying the passage of the cold front, the rain is quite intense with strong winds gusts on the rear of the frontal rain band, with some areas of line convection along the surface front as it clears. This has brought some difficult driving conditions for the evening commute, with some surface water flooding, as drains can’t cope with so much rain in a short space of time.
The line convection from the surface cold front towards the rear of the rain band is typical of a rearward sloping cold front or 'Ana' cold front. With the main zone of cloudiness and precipitation appearing in front of the surface front, with line convection along the surface front at the rear of the rain band, followed by a sharp clearance behind the front to colder, clearer and brighter skies.
This is in contrast to a front-sloping cold front, with cloudiness and precipitation appearing behind the surface cold front, as cold air overruns aloft. This means any line convection tends to be at the front of the frontal rain band where the surface front is, rather than at the rear, this tends to be more typical in summer.
Cold air overspreading aloft in the airmass following the cold front, associated with upper low to the west, is producing steep lapse rates over relatively warmer seas which is supporting a rash of heavy showers and thunderstorms pushing in from the west across Ireland and western mainland U.K this afternoon and evening.
Thunderstorm have been affecting parts of southern Ireland this afternoon and early evening, with hail up to a 1cm in diameter recorded near Wexford.
Heavy showers and a risk of thunderstorms will continue across more western areas this evening and overnight, forming clusters or bands as one or two troughs move in from the west, the showers getting inland across Wales, northern England and Scotland but staying near coasts further south.
Increasingly strong southwesterly winds associated with a deep low moving northeast to the north of Ireland will also be an additional hazard on top of the squally showers across the west this evening and overnight, particularly around Irish and Celtic sea coasts and in the northwest around northern coasts of N. Ireland and western Scotland. Gusts of 40-50mph are possible inland, but around exposed coasts and hills, gusts of 60-70mph are possible, perhaps higher than this, a gust of 78mph has been recorded at Aberdaron in northwest Wales recently.
The gales should ease overnight and become confined to the far northwest, but gales and squally showers will continue across northern and western Scotland through Friday – close to low pressure to the northwest of Scotland. While a ridge of high pressure builds in from the south, bringing a drier day for England and Wales, with just a few light showers in the west.