Mild and Murky. Also latest on La-Nina and our Winter Weather.
Tonight
A very mild night with a little light rain or drizzle at times. Low cloud will cover most hills and possibly even some coastal fog in the west and south of the island. Min temperature 8-10'c
Wind W 12-18mph increasing to 14-20mph later in the night. around 5mph lighter in the centre and the east.
Tomorrow
A cloudy mild start with the risk of some light rain and drizzle in places, especially over the hills. The risk of hill fog is rather high and perhaps even some coastal fog at times in the west and south. As the day goes on a few brighter spells may develop, especially in more eastern parts of the island. Temperature 11-12'c generally
Wind W 15-20mph, less in central and eastern parts.
La-Nina?
We have been asked a few times over the last couple of days about the risk of snow due to La-Nina, so lets explain a little more. La-Nina/El-Nino is the state of the pacific ocean, more specifically the temperature of the equatorial mid/eastern Pacific.
During a La-Nina event the pacific cools, sometimes rather dramatically and this is due to an increase in strength of the trade winds. The strong winds blow surface water away from the coast which allow for strong upwelling of much colder water from below. During an El-Nino event the trade winds weaken or even change direction which prevents any cold water upwelling to occur which in turn warms the sea surface dramatically. These changes in water temperature can then have an effect downstream in the atmosphere which can then influence our weather here in the UK. This winter season we have a weak La-Nina that is forecast to hold on for a little longer before turning to neutral conditions by late winter.
How will this affect us in the UK? Strong La-Nina winters often start very cold but turn milder as winter goes on. This year however we had a weak to moderate La-Nina to start which is likely to be part of the reason for our recent cold snaps, but now we are getting deeper in to winter we have other factors that are overriding what is now a rather weak La-Nina which in turn is likely to lead to a few weeks of very unsettled weather which may also be unseasonably mild at times. There are a few signs that by the second week of January we may see a few colder snaps once again and also some evidence to suggest that late January may be rather settled with high pressure. Beyond this is extremely difficult to forecast as there are a few different conflicting signals but it seems probable that high pressure will remain fairly close to the UK for a fair amount of this winter which means less in the way of wet stormy weather over all, although we are expecting some fairly stormy weather from Christmas day onwards for a week or two.
