Stormy weather could bring disruption

Quiet weather is expected to give way to unsettled and potentially stormy conditions during the final full week of January. While details remain uncertain, there is a potential for high impact weather to cause disruption. Snow could also pose a hazard in parts of the north.

Two storms in quick succession?

An area of low pressure is forecast to rapidly deepen over the Atlantic on Thursday, 23rd January, before approaching the UK on Friday, 24th January. At this stage computer models have yet to pin down its exact track, with some suggesting it will move closer to Iceland, while others indicate it could cross the north of the UK. Additionally, its intensity remains uncertain, with some models predicting it may already be weakening as it reaches the UK. 

The chart above shows the area of low pressure tracking northeastwards on Friday, moving to the north of Northern Ireland and across Scotland. The strongest winds are expected on its southern flank, with gusts of 70 to 80 mph shown affecting Northern Ireland, northern England, and southern Scotland.

However, as noted, there are differences between various computer model runs, particularly in terms of positioning and intensity. The ensemble plot below shows forecast wind gusts at midday on Friday, with each 'stamp' representing the forecast from one of the runs that make up the model. Multiple runs with slightly different starting conditions are used to account for uncertainty, making it possible to assess the probability of different scenarios.

Based on this data (and input from other models), the greatest risk of disruptive winds from Friday's area of low pressure is in the northwest of the UK. However, there remains a chance it could track farther south, which would shift the area at risk from strong winds southwards, although it would still likely affect central and northern regions rather than the south.

Another scenario is that the low pressure remains far enough from the UK for strong winds to only affect the far northwest. Forecast details may take some time to firm up.

Second disruptive storm?

If the first low pressure system doesn’t cause significant problems, a second one might! Since it is not yet possible to be confident about how the first system will develop, making predictions about the second is even more uncertain. Nonetheless, it also warrants close monitoring.

The chart above illustrates one possible outcome, showing the second deep area of low pressure moving across Northern Ireland and northern Britain early on Monday. In many ways, it is similar to the first system and could also cause disruption. Gusts of 50 to 70 mph could affect large parts of the UK.

Heavy rain and in the north the chance of snow

In addition to it being very windy, there will be heavy outbreaks of rain associated with the low pressure systems and their weather fronts. With rather cold air over the northern half of the UK initially, there could be a period of sleet or snow on the leading edge of the precipitation. Significant accumulations are possible over the Pennines and Scottish mountains, potentially causing disruption on high level routes for a time. However, milder air is expected to return, meaning snow will likely turn back to rain fairly quickly. 

The potential for deep areas of low pressure to arrive in quick succession increases the risk of flooding. The highest rainfall totals are forecast to be in the north and west of the UK, where over 100mm of rain is possible in some areas during this period.

The roller coaster winter continues

This winter has brought a very mixed bag of weather to date, and that trend looks set to continue through the rest of January. A mild December has been followed by a cold January so far. A stormy period appears likely to be the final twist this month, although there are tentative signs that high pressure could start to exert more influence by early February. If that happens, quieter conditions with more frequent dry periods could be expected.