Saturday under the cloud that had drifted in on a south-southeast breeze, that was occasionally brisk with a maximum gist of 16mph, limited any rise in temperature so that a maximum 6.1C at 11.59 was 2.2C below the long-term average. There was little UV light, registering a peak of 0.2 briefly just after midday, that followed 1.1 on the previous day. During the early evening the temperature had begun to slowly fall away, more so in the early hours under a clearer sky, that saw the minimum of 1.9C occur at 08.00 on Sunday, just as the sun was rising above the horizon.
Thanks to the cloud cover and relatively high humidity the equivalent loss of moisture through evaporation was minimal at 0.23mm less than half that recorded on Friday.
Sunday revealed a sky with just thin high cloud as the anticyclone is still influencing our weather and seems reluctant to give away to Atlantic weather fronts to the west of the UK. As a result, the day should be fine with variable sunshine. The barometric pressure at 08.00 was 1020.4mb. As the high pressure edges away it will cause the wind to veer a few degrees, and come from the south today.
January 2025 review
There was a mild start to the new month with a maximum of 11.4C on the 1st, some 4C above average, Arctic air arrived on the 2nd. For three days we endured the very cold air from the Arctic with a maximum of only 0.8C on the 4th followed by a hard overnight air frost that saw the thermometer drop to -4.8C. There was a wind chill that outside on bare skin it felt some 3C cooler.
There was a dramatic change later on the 4th as a deepening low-pressure system pushed ahead of it a warm front. Light sleet and snow fell in the early evening for almost four hours before it turned to light rain and drizzle.
First light at 08.00 on the 5th revealed misty conditions that limited visibility to 300m, and the temperature having risen slowly to 2.9C. However, there was a sudden significant sudden change as the warm air overcame the cold air that by 08.15 the thermometer read 7.8C, a jump of almost 5C in 15 minutes. By 08.30 the thermometer read 9.6C and at 10.00 10.4C. The wind direction had changed overnight from southeast to southwest. The rain and rapid thaw under the sudden warmth meant that the snow had all but disappeared by 10.00.
As the warm, moist air from the Atlantic reached the cold air it rose above it, being lighter, and in doing so the moisture in it condensed and cooled with sleet and snow falling as precipitation for four hours. Over the previous twenty-four hours the barometric pressure had dropped a very significant 30mb as the depression deepened rapidly with a pressure reading of 987.9mb, the lowest pressure since 26th September.
More snow fell on the 7th and 8th that was very reluctant to melt due to the very low temperatures by day and night. The coldest day of the month was the 8th when the thermometer struggled to reach 0.8C being a significant 6.3C below average. Due to the very cold nights combined with the snow lingering in the shade the coldest night was logged early on the 11th when the temperature dropped to -7.5C, the coldest night since 24th January 2023 when -8.0C was recorded.
During this period the extreme cold began to seep into the ground. The temperature at 08.00 on my soil thermometer, at a depth of 5cm, read from the 6th – 5.8C, 1.6C, 0.7C, 0.7C, -1.1C, and -1.8C on the 11th respectively.
A dominant high-pressure system centred over the UK became slow moving from the 12th. Trapped under the dome was a large pool of cool, moist air that produced many days with thick, low cloud and misty, murky conditions. There were two days, the 18th and 19th, when both the maximum and minimum were below average and a diurnal range of around 1C. However, it did bring over a week of dry weather although a few snow grains were observed on the 19th when the air temperature hovered around 1C by day. The other notable feature during many days were the calm conditions when the wind was not strong enough to stir up the stagnant air, in fact there were four days when the anemometer was stationary for many hours and a maximum air movement, couldn’t call it a gust, was in single figures.
There was a dramatic change from the 24th as the fifth named storm of the season arrived, called Storm Éowyn. This storm was caused by Arctic Air over North America merging with warm, moist tropical air from the Bay of Mexico together producing a strong temperature contrast fuelling a very powerful Jet Stream running at over 250mph. This deepened exceptionally quickly and dropped to a significant low pressure of 948mb in Mid-Atlantic on it way to the UK.
Storm Éowyn was quickly followed two days later by Storm Herminia, named by the Spanish Met Office. This arrived with a vengeance on the 26th with torrential rain followed by squall lines during the evening and through into the 27th and wind gusting up to 38mph. The daily precipitation of 26.8mm included hail at 07.47 early on the 27th. The centre of the storm moved very slowly across Ireland then the UK that maintained the disturbed weather for another twenty-four hours.
We had a glancing blow from Storm Ivo on the 29th that was far south over northern France, just gave us a blustery day with rain no closer than Salisbury on its northerly track.
We have had five named storms this year in the season that runs from September to the following August. The previous year of 2023/2024 gave us 12 named storms. In the UK, storms are named by the UK Met Office, in collaboration with the Irish Met Service and Dutch Met Service with names chosen from a public suggestion list, excluding letters like Q, U, X, Y and Z. Storms are listed alphabetically when the final section has been made. Storms are named when a deep depression is likely to cause significant impacts with strong winds, heavy rain or snow.
The letters Q, U, X, Y and Z are never used to name storms due to the paucity of names that begin with these letters. It is only recently that the Met Office started naming storms, the first year was 2015. The idea of naming storms was to improve communication about severe weather by making it easier for the public to track and understand the potential impacts of a specific storm.
The month finished with a ridge of high pressure giving us a fine sunny day on the 30th.
January was much colder than the long-term average being 1.0C below average, interestingly that applied both to the average maximum and average minimum. Analysis shows that there were 19 days when the maximum was below average and 17 nights below average. There was an extremely cold day on the 4th when the thermometer did not rise above 0.8C with the coldest night occurring in the early hours of the 11th when the thermometer dropped to -7.5C. It was the coldest January since 2010, which was a significant 2.2C colder.
Snow was observed falling on 4 days, fog was seen in the morning on 3 days and small hail fell on one day.
The monthly rainfall of 117.6mm was 131% of the long-term average or+28mm.
