Updated 5th September - 11th October 2nd November 2021
Mean temperatures are thus expected to be above the 1981-2010 long-term normal, typically by around 1.5C in most parts of the UK, but by nearer 1.0C in the south-east, due to relatively cool weather at times in Week 2.
Rainfall totals are forecast to be below normal in most regions, mainly because of the dry Week 2, but they may reach near average totals in some north-western and south-western parts of the country. Most eastern areas will be somewhat drier than normal.
Sunshine is expected to be not far from normal generally, but variable: many central and western regions will be much sunnier than average in Week 2, but then duller than average for the rest for the forecast period.
High pressure will dominate Britain's weather during this week, bringing dry and settled weather. There is some uncertainty around the positioning of the high pressure, which will affect cloud amounts, but in general it appears most likely that the north-west of Scotland (via moist south-westerlies) and East Anglia and the south-east (via northerlies and north-easterlies) will be most prone to cloudier weather coming in off the sea, around the periphery of the anticyclone. Sunshine is expected to be somewhat above normal during this week for much of Wales, western England and also south-west Scotland. Fog patches are also likely to form overnight in some parts of the country. It may turn wetter in north-west Scotland towards the end of the week with high pressure moving a little further south and a strengthening south-westerly flow.
Temperatures will tend to be a little above the seasonal average for most of the country during this week, but close to the long-term average in the south-east, where north-easterly winds will pull in cooler air masses at times. Scotland and Northern Ireland will generally be warmest relative to normal, with positive anomalies of 1 to 2C, due to warm air masses coming in from the south-west, on the northern flank of the high pressure area.
Rainfall will be well below normal, with some areas seeing no rain at all. East Anglia and north-west Scotland are likely to be wettest relative to normal, but even these areas will be somewhat drier than normal overall.
Sunshine is more uncertain, but is most likely to be generally above normal except in parts of eastern England, especially East Anglia, where a shortage of sunshine is likely in Norfolk.
Confidence in the outcome over the British Isles is relatively low for this week, but it looks probable that pressure will be relatively high over Greenland, and that the high over Britain will move slowly south-eastwards. This will result in pressure falling over the north of the UK, and a battleground between cold Arctic air moving south on the eastern flank of the Greenland high, and warm tropical maritime air from the Azores heading up from the south-west.
Thus, some wetter weather is expected especially in western Scotland, where there may be some significant orographic enhancement. However, pressure is still expected to stay quite high to the south-east, so there is a greater chance of it staying drier than average for central, southern and eastern England in particular. Temperatures will probably be above normal overall, as it looks probable that the warm tropical maritime air will dominate for most of the week, with the Arctic air mass kept away to the north, though there is some uncertainty over this.
As a result, much of the UK will probably be warmer and cloudier than average this week, though with above average sunshine for some sheltered eastern parts of England, with positive temperature anomalies of 1 to 2C. Rainfall will probably be above normal in central and western parts of Scotland and in Northern Ireland, but below average towards the south-east.
Confidence is again relatively low for this period, but the most likely outcome is a relatively warm and changeable end to October with mainly south-westerly winds, with the Greenland high easing and pressure staying quite high to the south-east of Britain. A general northwest-southeast split is likely with north-western Britain most exposed to frequent rain belts moving in off the North Atlantic, and south-eastern areas seeing longer spells of drier weather in between, and relatively light and infrequent rainfall. Temperatures will probably again be 1 to 2C above the long-term normal overall, with rainfall generally not far from normal. Sunshine will probably be below normal towards the south-west and near or rather above normal in the north-east.
Monthly weather forecast
The month ahead forecast is written by Ian Simpson and is updated every Monday.