Windrush Weather

Category: Commentary

  • Stormy and wet start to New Year

    Tuesday was the warmest day for a week with a high of 11.5C that occurred early on the 1st as the thermometer rose very slowly from a low of 7.7C. It was also dry with some brightness mid-morning, no sustained sunshine.

    New Year’s Day revealed more low cloud with the first rain drops and drizzle observed at 08.25 ahead of a very active weather front. The wind had been rising very slowly all day on Tuesday with the anemometer recording a gust of 40mph at 08.01 on Wednesday.

    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 2002 with 1146mm 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.

  • Another ‘blow’ on the way!

    Monday was the last of the gloomy, low cloud starts to a new day as the high pressure slowly departed and the breeze picked. The thermometer hovered around 7C all day but the maximum, most unusually, was logged overnight with a high of 8.0C at 01.49 early Tuesday. Thereafter, it eased downwards to reach a minimum of 7.7C at 08.00. Another twenty-four hours with a minimal diurnal range, difference between maximum and minimum of just 1.4C. There was no ran and no UV light triggered the sensor.

    Tuesday revealed a cloudy sky again after dawn but much higher than of late. The depression is getting closer with the barometric pressure having lost another 7Mb since Monday with a reading of 1022.2mb at 08.00. The wind is beginning to pick as the squeeze as the difference between high and low pressure begins to take effect.

    The low just off Scotland has been deepening with a current centre pressure of 987mb. As it gets closer to the UK the winds will increase dramatically over the next thirty or so hours. With Christmas in the past and strong winds ahead I have changed the three images that now show damage in the gales of 1984 in Savernake Forest, hopefully nothing like that over the next forty-eight hours.

  • Humidity drops below 100% today

    It was such a pleasure to have brief sunny intervals that were observed around midday on Sunday after the six dark, gloomy and damp days. As a result the thermometer crept up to 8.6C at 15.14 being the warmest day for four days and was 0.5C above average. The continuous cloud overnight meant little change in temperature overnight as the thermometer only dropped to 6.6C by 07.52 early Monday.

    There was a significant change in our weather just after 14.00 on Sunday as the humidity dropped below 100% as the weak cold front passed through. It was also the first day since the 22nd when no precipitation fell, which had been mainly in the form of drizzle.

    Monday revealed another cloudy start to a new day but the air was for the first time a little drier as the humidity at 08.00 read 96%, after six continuous days at 100% through day and night. The wind will be principally from the southwest quadrant and still relatively light.

    The recent high pressure, that acted as a dome trapping stale air beneath it is still very slowly easing away, down 2mb since Sunday but still very high. A weather front is approaching on Tuesday that will see a succession of depressions running along it that will bring wet and very windy weather, especially on Wednesday.

  • Weak cold front passing today will bring minor change

    Saturday was the last of the very calm, damp days and nights under the persistent cloud cover. The maximum of 6.3C that occurred at 13.32 was slightly up on the two previous days but still below average at -1.8C. The minimum was also below average at -0.1C, the first time for over a week, with a low of 2.3C logged at 23.58 just before midnight. Light drizzle occurred also as on previous days from the thick, low cloud amounting to 0.3mm.

    Sunday began as the previous six days still under the thick, low cloud that limited visibility to 300m after dawn. The humidity at 08.00 once again read 100%, the sixth successive day with 100%.

    The soil temperature, read at 08.00 at a depth of 5cm, has seen a slight decline over the past four days thanks to the lower maxima and minima with 8.4C, 6.5C, 6.1C and 5.1C today respectively.

    A weak cold front will pass over our area around midday that will bring a slightly drier and brighter air stream behind it, a very welcome minor change in our weather. The large area of high pressure is still influencing our weather and will do so for another two or three days before colder, brighter weather arrives midweek, but not before it gets very windy on Tuesday and Wednesday.

  • No change today in cloud cover although temperatures keep dropping

    Friday was a repeat of previous days with total, low cloud cover all day trapped under the high pressure. The misty conditions worsened as the morning progressed that saw visibility slowly descend to 200m by 11.00. The mist descended in the evening again but not as thick as previous days. Drizzle was often felt outside and amounted to just 0.6mm. The was once again very little variation between the maximum of 5.9C, being 2.2C below average, and the minimum of 4.2C, which was 1.7C above average, recorded at 06.56 early Saturday.

    The maximum over the last four days has slowly fallen away with 11.2C, 9.7C, 6.4C and 5.9C respectively. The same pattern is seen in the minimum values over the last four days with 8.4C, 6.2C, 4.9C and 4.2C respectively.

    I cannot 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 recent days has been the lack of air movement due to the minimal gradient variation with maximum air movement of just 13mph, 10mph, 7mph and 6mph respectively being almost under the centre of the anticyclone.

    Saturday began as previous days but it was mist masking the Marlborough Downs and Savernake Forest rather than fog.The temperature at 08.00 registered 4.4C, the coolest morning since the 23rd.

    The high pressure that has trapped the stagnant air below it is very slow declining and easing eayswtads over France. Three low pressure systems are Deve,oping in the eastern Atlantic that will slow begin to influence our weather from later on Sunday into next week. The barometric pressure at 08.00 was logged at 1029.8mb, down from the peak of 1036.1mb on Thursday.