Monday evening forecast 25/09/23
25 September - National weather forecast presented by Aidan McGivern.
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00:00start to the new week for many of us but that's all about to change. Storm Agnes
00:03has been named by the Met Office because of the potential for disruption from
00:06winds middle of this week. At the moment a relatively shallow system moving with
00:12the jet stream across the Atlantic but later Tuesday into Wednesday Agnes
00:16moves on to the cold side of the jet stream that allows it to spin up into a
00:19much deeper area of low pressure with a broad swathe of very strong winds on its
00:25southern flank and widespread gales over sea areas. But that's not the only
00:30weather happening this week. Before Agnes arrives there are some weather fronts to
00:34talk about, a couple of lows to the north and northwest of the UK and quite a
00:38breezy picture on Monday night ahead of the first weather front moving in for
00:42Tuesday. So with that breeze and with some patchy cloud around it's not going
00:47to be a particularly cold night. Nevertheless lighter winds towards the
00:50south and the east of the UK will allow some mist to form by dawn and there will
00:54continue to be some cloud patches even the odd shower towards western parts. The
01:00winds stay relatively high through the night in northwestern parts that will
01:04keep temperatures generally in the double figures but a fresh start I think
01:08where we've got those mist patches forming in the south and the east by
01:11dawn and early on on Tuesday just some showers making an appearance into the
01:16south moving up into the Midlands eventually East Anglia in the southeast
01:20odd rumble of thunder odd heavier downpour perhaps for a time. They clear away by
01:25lunchtime and then we've got this other feature the weather front that's sitting
01:29out to the west of the UK bringing some heavier more persistent rain early on
01:33for Northern Ireland and Scotland clearing to showers later and then
01:37really Tuesday afternoon looks like a mix of sunny spells and showers the
01:40heaviest downpours towards the west and the north odd rumble of thunder in
01:44Western Scotland and Northern Ireland. Quite a blustery day to come as well
01:48with the risk of coastal gales around some exposed northern and northwestern
01:52areas and that will make it feel on the cool side but actually towards the
01:55southeast with some sunny spells temperatures a little above average for
01:58the time of year 22-23 Celsius. Any showers do tend to ease away but then
02:04Agnes starts to move in this is showing the wind gusts values for Agnes as it
02:10approaches on Wednesday you can see these dark colors representing really
02:13quite extreme winds while Agnes is out to sea 80 to 90 odd mile-per-hour but
02:19this is while Agnes is out to sea and this is when it deepens at its lowest
02:24value as far as central pressure is concerned then begins to fill as it
02:30moves towards the UK but still some uncertainty on the precise track and
02:36depth of the low still a little of variation in the computer model output
02:41and so we have to be somewhat cautious in terms of identifying precise wind
02:47values by later Wednesday but it does look likely that it's later Wednesday
02:52through the afternoon and evening when those winds reach a peak across many of
02:56these western parts of the UK especially Irish Sea coast and that's why a wind
03:02warning has been issued quite widely across the UK but I'm sure details will
03:06be refined over the coming hours and days and within this area there's the
03:12risk of 50 to 60 mile-per-hour wind gusts and Irish Sea coasts are at risk of
03:16seeing 65 to 75 mile-per-hour wind gusts or even a touch more in some spots that
03:20could cause transport disruption and of course dangerous coastal conditions but
03:26before all that happens Wednesday starts off mostly fine for many especially
03:29towards the north and the east some early sunshine showers clearing the
03:32northwest of Scotland but then the rain ahead of Agnes moves into Northern
03:36Ireland western parts of Britain and the wind really picks up into the
03:40afternoon and early evening now that rain could also cause some issues with
03:45it falling on top of saturated ground across parts of Northern Ireland
03:48Northern England and Scotland and it's this part of Scotland higher parts of
03:53central and southwestern Scotland where there's the risk of 30 to 50 millimetres
03:57of rain perhaps 60 millimetres in one or two spots so that combined with the
04:01strength of the winds could cause some disruption but of course we'll refine
04:06the details over the coming days and we'll keep you updated right here at the
04:09Met Office