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Weather updates from site founder Brian Gaze that keep you in the know.
December has been a mild month with the Central England Temperature (CET) 1.9C above the average to the 22nd. The next few days will bring spells of mild weather but there are signs of a change as we head towards the New Year.
The period between Christmas and the New Year looks likely to be characterised by drier and quieter conditions in the southern half of the UK as high pressure builds. North western areas may stay more changeable with an Atlantic influence continuing to bring the risk of wetter spells. Temperatures should not be far from the average and in the south the risk of frost will increase.
Things become less certain as we head towards the New Year. Several recent computer model runs have developed a cold northerly flow over the UK with high pressure centred to the west or northwest of the UK. This morning's GFS06z illustrates this pattern quite nicely.
The pressure chart below for 12:00GMT Sunday 1st January shows high pressure in the Atlantic stretching up towards Greenland and Iceland with northeasterly winds pulling down cold air across the UK. If this happened the risk of snow would increase and it would potentially lead to a more wintry spell of weather than we've experienced in the last few years.
In my experience the GFS model is very good at picking up these northerly outbreaks but it has a tendency to over amplify the upstream North Atlantic pattern. This leads it to show more potent and longer lasting cold spells than often transpire in our neck of the woods. Therefore, it's worth injecting a dose of caution into the discussion!
The GEFS ensemble model which is used to help determine the probability of different outcomes is worth a look. The postage stamp plot below shows the output from each each of the individual runs at the same time as the GFS chart above. The question is how many of the stamps show a cold outbreak as potent as the one the GFS06z operational run goes for? I would say only 2 out of the 20 but a number of others show a diluted version of it. This suggests the GFS06z operational run is at the more extreme end of possible outcomes and support for it is currently limited. However, the chance of somewhat colder weather is greater.
Some recent computer model runs have been indicating a change to much colder weather as we head into the New Year. At the moment the chances of a potent Arctic blast bringing a risk of snow look quite low but a more diluted northwesterly is more probable. I'll keep you posted on developments as we head through the Christmas period.
Finally let me wish you a very Happy Christmas and thank you for your support. This year has been another record breaker for TWO with the website setting a traffic record and the new amp and app offerings on IOS and Android doing well. On that note if you're an Android user check out the free TWO app v1.2 which was launched yesterday on Google Play.
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