TWO Buzz

Weather news and views from Brian Gaze.

Could winter pay the UK an early visit

Signs of high pressure blocking?

Published 11th November, 11:35

The first third of November has been characterised by unsettled and mild conditions. Can we expect an early taste of winter later this month?

In general, most computer model runs are pointing towards a continuation of the changeable or unsettled theme. Therefore, all regions can expect further wet and windy periods. Nonetheless, there are indications of high pressure building at times, and perhaps in places which could increase the chance of cold weather in the UK.

Higher pressure building?

The chart below shows forecast mean surface level pressure from all of the individual runs within the GEFS model. It is for London and goes out to 16 days ahead. During the next seven days, there is a clear upward trend in pressure. The thick purple line, representing the ensemble mean, rises from a low point of about 995mB up to 1025mB.

However, after 17th November a downwards trend returns, but by that point there is a very wide spread of solutions. In other words, the individual runs within the computer model have diverged significantly, with pressure forecasts ranging from as low as 960mB to as high as 1040mB, by 24th November.

Temperatures climbing?

Although it has felt chilly at times recently, the Central England Temperature (CET) for the first third of the month is actually well above the long term average. Provisionally, as of the 9th November, it is 8.9C which is 2.4C above the 1961 to 1990 average.

The chart below shows forecast temperatures for the next 16 days in London. In the short term forecast maximums rise to about 15C which is mild for the time of the year. They then dip until around the 17th November before trending upwards again. Generally, temperatures look quite close to the average in the days which follow, but probably a little bit above it at least in the south. Nonetheless, there are a few cold runs in the mix.

No clear signal for cold…yet

As I've explained, there is no clear signal for an early cold period in the medium range computer model data. Taken at face value, things look quite average.

However, there are other considerations. In particular, a number of computer model runs are showing high pressure blocking to the northeast of United Kingdom as an important feature. In turn, there seems to be less support for high pressure to become entrenched to the south of the UK, a pattern which is often leads to very mild winters.

In conclusion, if you’re hoping for cold weather there isn’t really anything on the menu just yet. Nonetheless, some of the ingredients for that particular dish appear to be falling into place.

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