Winter bites!

A maximum of only 3.3C on Wednesday, which was 4.7C below average and a minimum overnight of -3.6C being 5.9C below average was due to the run of very cold air from the north to northwest air stream. Fortunately there was little wind strength during the past twenty-four hours, a maximum gust of just 10mph was logged, therefore there was minimal windchill.

The minimum was reached at 00.49 early on Thursday morning and recovered a degree or two during the following hours as cloud and fog formed, the latter limiting visibility to around 300m at 08.00 on Thursday. It was the coldest night since 28th November, just, when the thermometer fell to-3.7C.

Wednesday was dry, only the ninth this month, with the rainfall total standing at 109.1mm, which is 17.3mm above the 36-year average. We have now experienced four successive Decembers when the monthly rainfall exceed 100m (average is 91.8mm).

Snow in the morning and afternoon on Tuesday

Winter was fully established on Tuesday with snowfall just after 08.15 and again, a little heavier, at 15.40. In between there was a little sunshine, logged at 0.74 hours, that lifted the thermometer to a maximum of 3.9C, which was 4.1C below average. Although the thermometer dropped 2C in the afternoon snow, there was sufficient warmth in the atmosphere for any lying snow to melt.

The thermometer hovered around 1C for much of the evening but after midnight fell again to a minimum of -0.4C at 02.20 producing a frost, before rising again to reach 0.6C at 08.00 on Wednesday.

The barometric pressure has been slowly rising over the past two days, after the deep depression eased away, so that on Wednesday morning there was minimal cloud and the possibility of some sunshine with the wind very light, sometimes completely still.

The effect of the colder weather can be seen from the soil thermometer at a depth of 5cm with successive readings of 5.9C, 1.3C, 1.2C and 0.9C over the last four days at 08.00.

Northerly breeze brings very cold air

Under the influence of the cold air mass brought on a northerly breeze that gusted to 18mph, the thermometer struggled to reach 2.1C at 12.01 on Monday being almost 6C below average. After the very early morning light fall of snow no more fell during the daylight hours.

Overnight the wind fell out completely for long periods with the thermometer dropping to -1.2C at 04.54 before lifting to -0.3C at 08.00 on Tuesday.

A few light flakes of snow were observed at first light on Tuesday, not enough to cover the ground. However more light snowflakes began to fall just after 08.15 from a narrow band of precipitation travelling in on a very light northwesterly air movement.

The barometric pressure at 08.00 on Monday was the lowest since November 2010 with a minimum pressure of 969.9mb as the centre of the deep depression was overhead Southern England. By Tuesday a rise of almost 20mb, as the depression eased away and began to fill slowly, gave a current reading of 987.5mb, still very low.

Sunshine then early morning sleet and snow

Although the barometric pressure had been sliding for twenty-four hours and was quite low on Sunday we enjoyed 4.8 hours of sunshine, predominantly in the morning. The thermometer eased upwards to reach a maximum of 6.2C in the brisk westerly breeze that was 1.8C below the average.

The thermometer hovered around 1.5C late evening but just after midnight began to fall steadily to reach a low of -0.3C at 04.48 producing a short lived frost.

The first precipitation from a narrow weather front brought snow that started just before 06.00, with a modest layer in evidence, that soon turned to wet snow. Some pavements were icy after the cold night from the first rain and sleet to fall. It was mostly seen on gardens and lawns rather than hard surfaces. However, this quickly turned to rain and any evidence of snow melted as the thermometer rose to 0.7C at 08.00 although snow could be seen at 09.00 on the slightly higher fields rising to Savernake Forest.

Storm Bella brings wind and rain – lots of it!

Saturday was another gloomy, drizzly day with thick cloud ahead of Storm Bella. During the evening the wind began to pick up, but fortunately not as strong as the warnings given. A peak gust of 38mph was logged at 01.29 in the early hours of Sunday. The strong winds began t abate after 02.00.

The southerly air stream allowed the thermometer to recover from the cold northerlies of previous days and reach a maximum 9.4C being 1.4C above average. As the rain band eased away Sunday morning the temperature dropped away to read 5.0C at 08.00

The rain began in earnest just before midnight and brought us the wettest twenty-four hours since the 14th November with 17.7mm. This brought the monthly total to 106.2mm, which is 14mm above the 36-year average.

Sunday morning saw the showery back end of the main rain band with broken sky and occasional showers. The wind has now backed into the west and is much calmer.

The centre of Storm Bella will migrate down across the country in the next twenty-four hours with extremely low pressure centred over southern England on Monday. The barometric pressure has dropped 45mb since 08.00 on Saturday and is forecast to fall another 10mb by Monday morning. The wind direction with change considerably during this period but be much lighter in strength.