Although Wednesday started warm with the daily maximum of 11.4C, unusually at 08.00, the thermometer began to slowly fall during daylight hours and especially after the cold front passed mid-afternoon. The active front brought several hours of rainfall, heavy at times, that amounted to 10.1mm. The minimum of -0.1C was logged at 08.00 on Thursday although the thermometer was continuing to fall under clear skies. The maximum was 4.3C above the long-term average and the minimum -1.4C.
It was a treat to discover after dawn the blue sky and promise of sunshine after the sun got up.
We are now fully under the flow of Arctic air originating between Greenland and Scandinavia being brought on a northerly then north-northwesterly breeze today being light but will produce a wind chill so that outside it will feel colder on the skin than that indicated on a thermometer.
The soil temperature at a depth of 5cm dropped from 9.4C yesterday to 2.2C today, both read at 08.00.
P.S.
The Daily Statistics sheet will not be available until my webmaster creates a new 2025 sheet. Being old I do not have advanced IT skills so I just fill in the spaces when they are available!
December 2024 Review
The month began with temperatures above average due to the warm, moist air brought on south-westerly breezes, moderate in strength.
A very disturbed spell arrived on the 7th thanks to Storm Darragh that brought very strong wind gusts to 45mph and sporadic bursts of heavy rain.
On the 9th we came under the influence of high pressure to the west and low pressure to the east. This resulted in winds arriving from the northeast as winds circulate clockwise around a high and anticlockwise around a low. The pressure variation was considerable, so the squeeze resulted in the extremely high winds and as they travelled across the North Sea collected much moisture. Fortunately, we did not experience the extreme wind gusts which were to the north and west of our area. We had five days of anticyclonic gloom with the thick, low cloud persisting all day and night. There were six continuous days when no UV light triggered the UV sensor. The very high barometric pressure of 1034.4mb on the 10th was the highest for a month.
This period was notable for the minimal diurnal range of temperatures, difference between maximum and minimum. On each of the three days, 10th to 12th, the variation was 1.6C, 1.0C and 1.1C respectively, as the persistent thick cloud obscured any sun to raise the temperature by day and at night provided a duvet to minimise any loss of warmth into the atmosphere.
After a few mild days mid-month, with a moist air stream from a southeasterly quarter and blustery winds gusting to 27mph, a significant change occurred during the night of the 18th. Two cold fronts passed over the UK around midnight that saw the wind promptly veer from the southwest to northwest. This change in wind direction brought a slightly drier air stream but a noticeably cooler air stream. The temperature had hovered around 12.5C for much of the 18th during daylight hours and early evening, but afer midnight fell steadily away to reach a low of 4.0C at 07.28 on the 19th.
The previous days had been dominated by a deep depression that eased away over Scandinavia and we then came under the influence of a very high pressure system in the Atlantic that brought brighter and drier air after the previous gloomy and damp days.
Two days of Arctic Maritime Air produced cold weather later on the 21st and 22nd but that was replaced by Tropical Maritime Air late in the day of the 23rd as a warm front crossed the UK. This meant it was warmer during the night than the earlier day as the thermometer rose from 5.5C at 17.45 to 9.8C by 08.00 the following morning. It also brought fog that limited visibility to 200m on the 23rd with 100% humidity thanks to the moist Atlantic air.
The maximum over the 24th to 27th fell slowly away with 11.2C, 9.7C, 6.4C and 5.9C respectively. The same pattern was seen in the minimum values over those four days with 8.4C, 6.2C, 4.9C and 4.2C respectively. I couldn’t see a pattern in the records over the past 40 years where the humidity at 08.00 was 100% for five consecutive days and persisted throughout each twenty-four period.
The other significant feature over that period was the lack of air movement due to the minimal gradient variation between a high-pressure system and a low-pressure system. The maximum air movement was just 13mph, 10mph, 7mph and 6mph for the days of 24th to 27th respectively as we were sitting almost under the centre of the anticyclone.
This extended period of limited air movement and minimal generation of solar energy due to the persistent low, thick cloud cover meant minimal green energy was generated over much of the country.
The rainfall total for December was 57.4mm being just 61% of my 40-year average or 36.6mm below. In fact, it was the driest December since 2016 with from the records extremes of 17.6mm in 1988 and 157.0mm in 2013.
The mean temperature was 1.7C above my long-term average. Analysing the maxima and minima data I found that the average maximum was 1C above average and the average minimum was a significant 2.3C above average. It was an exceptional month when no air frost occurred, this has happened only once before in 2015, my station started in 1984, however a low of 0.2C in the early morning of the 4th did produce a ground frost.
The warmest day saw the thermometer rise to 13.9C on the 1st with the coldest day on the 13th when the thermometer struggled to reach 5.5C, being 2.5C below the long-term average.
Annual Rain
The year 2024 was the third wettest since my station began in 1984. A total of 1126.8mm was recorded compared to the two previous wettest years of 1146mm in 2002 and the record set in 2023 with 1150.0mm. The trend for annual average rainfall has risen from around 800mm in the 1980’s to an average in the 2020’s of 925mm.
In those year bands above, the incidence of daily rainfall up to 20mm has risen from 4 to 6 and daily rainfall exceeding 25mm from 1 to 3.
