BBC monthly outlook
Monday 1 May—Sunday 7 May
A wet start for some, but turning mainly dry again
The week will begin with a distinct north to south split on bank holiday Monday. With high pressure centred to the north of the UK, and a slow moving low pressure system drifting across the south, it's not surprising that many parts of Northern Ireland and western Scotland will enjoy a fine day with plenty of warm sunshine. Eastern Scotland will tend to be cooler as keen easterly wind keeps skies cloudier, and northern England will likely be similarly cloudy, with even the chance of patchy rain. Further south, expect a mixture of sunshine and heavy showers, which could be thundery at times.
By Tuesday, much of the country will be firmly influenced by the anticyclone to the north of the UK, with easterly winds bringing cooler and cloudier conditions to any districts adjacent to the North Sea coastline. Central and western areas will see the best of the sunshine, with temperatures edging into the high teens for western Scotland, Northern Ireland and northwest England. Southeastern areas of the UK will be under threat of cloudier skies and the odd shower at times. Overnight temperatures will be relatively mild for most, but northwest Scotland could see patches of frost in sheltered areas.
As the week progresses, the weather pattern is not expected to change a great deal from that of Tuesday. Heading into the weekend though, there is increased chance that rain will move into southern and southwestern parts of the UK again, as an Atlantic low pressure system crosses Biscay.
Monday 8 May—Sunday 14 May
Turning a little cooler and wetter for a time?
Our latest forecast suggests that as we move into the second week of May, the stubborn area of high pressure centred to the north of the UK will continue to dominate weather conditions across northern England, Scotland and Northern Ireland, with cloudier, cooler conditions to the east, and the best of the sunshine across western Scotland. Along with the likelihood of dry weather in the north, some forecast models are also suggesting that an influx of slightly cooler air will occur around the middle of the period, meaning that temperatures could become noticeably lower for a time across the northern half of the UK, and perhaps even further south at times. At the same time, the latest forecasting tools and computer models suggest that a low pressure system and its attendant weather fronts already affecting southern England and Wales will slowly track north and eastwards to bring a spell of more unsettled and cooler weather for much of the UK by the latter part of the week.
Monday 15 May—Sunday 28 May
An uncertain end to the month, but warmer perhaps?
An elevated level of uncertainty is an inherent feature of medium to long range weather forecasting, but even taking account for this fact, the level of uncertainty in the forecast of the end of May is relatively high at time of writing. The array of computer models that we utilise to make our forecasts are returning an unusually wide range of possible solutions for the end of the climatological spring. However, common themes of slightly warmer and drier than average conditions are at least two factors that the different models broadly agree on for the last weeks of May.
At this time of year, it is often the case that the jet stream takes on a broader, and wider meander in the vicinity of the skies above Europe, which often leads to the development of slow moving anticyclones, or 'blocking highs'. In such conditions, the impact on the UK weather can, at times, lead to very slow moving changes. It is therefore inferred that a blocking high will likely be the cause of the prolonged drier or warmer spell in our current forecast. Of course, we will continue to monitor forecasting model signals for the end of May, so stay in touch with the BBC Weather Centre to stay up to date with the latest thoughts on late May.
Next week
Check in next week as we have our first look at early June, which is of course the start of the climatological summer!
http://www.bbc.co.uk/weather/2635167#outlook