December 2015: record-breaking warmth and distinct absence of frost



December 2015 will, for many, be remembered by just how exceptionally, and consistently, mild it was - in fact, as the graph below highlights, every single day throughout the month saw daytime maxima above average at least somewhere in East Anglia. The same is also true for November, with the exception of one weekend around 21st-23rd where a brief northerly plunge of cold air saw some sharp frost and few wintry showers in parts of the region.

The mean temperature for East Anglia was 10.0C for December, which is 5.5C above average, making it not only the warmest December on record and smashing the previous record of 7.8C set way back in 1934, but also warmer than any November since records began. A far cry then from just 5 years ago when December 2010 set records for the coldest ever, with a mean temperature of just 0.0C - 4.5C below the average.

The persistent, humid southwesterly flow in December 2015 meant that it was often cloudy, with 83% of the average amount of sunshine hours, but rainfall was close to normal at 98% of the average.

Data: Met Office

Given how exceptionally mild the month was, the distinct lack of air frosts (0.2 days, compared with the average of 10.1 days) meant that the month produced the lowest number of December air frosts on record. In fact, the only time when air temperatures fell below freezing across East Anglia was actually during the early hours of 1st January (but still technically considered 31st December as each day's extremes/totals are measured between 09:00 - 09:00 UTC).

Dan Holley  5th January 2016


White Christmas

Christmas is fast approaching, and one question that's on many people's mind is - will it be a white one?

The definition of a White Christmas in the UK is one single snowflake falling in the 24 hours that make up Christmas Day, at any observation site across the country. Since 1960 this has actually happened 38 times, suggesting that on average a White Christmas is more likely to happen somewhere in the UK than not.

However, as you would probably expect there is a large variation across the country as to how likely you are to see a white Christmas - in fact, your chances in southern England are fairly slim with just a 6% chance in an average year in London, the probability typically increasing the further north you go with, on average, 3 in every 4 years producing a white Christmas in the Shetland Isles.

Click on image to enlarge

The 'snowiest' Christmas in the past 55 years, in other words the highest number of stations reporting sleet or snow falling (61%), was in 2004. However, many of us think of a white Christmas as one having a blanket of snow on the big day itself, and this is much rarer; the 'whitest' Christmas since 1960 was only 5 years back in 2010 where 83% of the weather stations across the country reported snow lying on the ground.

In actual fact, we are more likely to experience a White Easter than a White Christmas because in the early winter the seas around the UK are still relatively warm, and so any cold air approaching from the north or the east gets heavily modified by these warm seas, making it less likely to snow, especially to low levels in southern Britain. However, skip forward to early spring when Easter takes place, and the seas have lost a lot of their stored warmth through the winter season and are much colder - and so when cold airmasses arrive they are less likely to be modified, and more likely to produce snow.

Will it be a White Christmas this year? Keep checking the forecast as we get nearer to the big day...

Dan Holley  17th December 2015