Armagh Observatory, 5th December 2023.
Armagh Observatory reports that November 2023 was slightly warmer, sunnier and drier than average. Taking September, October, and November together the meteorological autumn at Armagh was much wetter, and warmer and sunnier than average.
Total precipitation was 60.05 mm (2.36 inches) including 7 trace values, or 59.7 mm if trace values are ignored. This is approximately 81% of the 183-year (1838–2020) long-term average November precipitation at Armagh (73.85 mm) and 73% of the most recent (1991– 2020) 30-year average (81.87 mm). The wettest day was the 12th with 21.6 mm (0.85
inches) of rainfall followed by the 19th with 6.9 mm and the 17th with 6.0 mm.
There were two named storms this month, namely Storm Ciarán and Storm Debi. Northern Ireland was fortunate in finding itself located nearly centrally between two very deep areas of low pressure during the first two days of the month, leading to comparatively quiet conditions and very little wind or precipitation associated with the violent Storm Ciarán.
This caused havoc to northern France and southern Britain as it drove through the southern approaches before swinging north and weakening as it moved into the North Sea. By contrast, Storm Debi later in the month brought heavy rain and wind to Armagh on the night of the 12th/13th, with winds approaching near gale force on the morning and early afternoon of the 13th.
Partial rainbows were observed on the afternoons of the 3rd and 7th, and a complete rainbow on the 8th. The 4th was noteworthy in having an unusually low atmospheric pressure for November, the lowest at Armagh for 13 years. Astronomers also observed the daylight occultation of Venus by the Moon on the morning of the 9th. An aurora borealis was seen from near Armagh and across the UK and Ireland on the night of the 5th/6th. Around 6.30pm on the evening of the 5th, auroral activity included the very rare short-lived space weather phenomenon known as STEVE, that is, a Strong Thermal Emission Velocity Enhancement. The visual appearance of STEVE, which is often described as cometary and is occasionally bright, is poorly understood but is thought to be produced by a ribbon of high-temperature (several thousand degrees Celsius), high velocity (several kilometres per second), low-density, ionised gas at great heights in the Earth’s atmosphere. Images of this phenomenon, together with a video posted on the internet by Mr Davy Patton, can be found on the internet.
The mean temperature this November was 7.5 degrees Celsius (45.5 Fahrenheit), nearly 1.3 C warmer than the 225-year (1796–2020) long-term average November temperature at Armagh (6.22 C) and 0.2 C warmer than the most recent (1991–2020) 30-year average (7.33 C). It is interesting to note that when we consider the difference between the (1961–
1990) 30-year average at Armagh and the most recent (1991–2020) interval November shows the greatest warming, approximately 1.2 C in thirty years or 0.4 C per decade. Such a change is noticeable even without a thermometer. For example, leaves are now remaining on trees until quite late in November, and lawns still need to be cut right up to the end of the month and sometimes into early December. Such phenomena would have been almost unheard of 30 years ago.
The highest maximum temperature or warmest day was 14.8 C on the afternoon of the 18th followed by 13.1 C, which occurred on the afternoons of the 22nd and 23rd. The weather became much cooler towards the end of the month, leading to the coolest day or lowest maximum air temperature being 3.4 C on the 29th followed by 6.0 C on the 30th. The warmest night or highest minimum air temperature was 11.1 C, conventionally attributed to the 23rd, followed by 10.3 C in the early hours of the 19th. The coolest night or lowest minimum air temperature was -1.8 C on the 30th followed by -1.6 C on the 29th. There were 16 nights with ground frost, the coldest three of which occurred on the 30th (- 8.8 C), the 25th (-7.7 C) and the 29th (-7.6 C). Unlike November 2022 when there were no nights with air frost, this November recorded three nights when the air temperature fell below freezing, namely the 30th (-1.8 C), the 29th (-1.6 C), and the 25th (-1.5 C). There were 82.6 hours of strong sunshine this November, approximately 39% more than the 140-year (1881–2020) long-term average November sunshine at Armagh (59.5 hours) and nearly 34% more than the most recent (1991–2020) 30-year average (61.6 hours).
This was the ninth sunniest November on record at Armagh. The sunniest day was the 15th with 7.0 hours of strong sunshine followed by the 10th with 6.5 hours and the 5th and 30th with 6.0 hours. Taking the three autumn months September, October and November together, September was the third warmest September on record at Armagh and wetter and sunnier than average, and October was the wettest October on record and very mild and sunnier than average. As a result, the meteorological autumn at Armagh was much wetter than average, and both warmer and sunnier than average. Total autumn precipitation was 347.2 mm, approximately 56% more than the 140-year (1838–2020) long-term average at Armagh (223.2 mm) and 52% than the most recent (1991–2020) 30-year average (227.9 mm). Autumn 2023 is now the fourth wettest autumn on record at Armagh. The mean autumn temperature was almost 11.5 C, approximately 2.0 C warmer than the 225-year (1796–2020) long-term average autumn temperature at Armagh (9.41 C) and 1.1 C warmer than the most recent (1991–2020) 30-year average (10.40 C). This being the fifth warmest autumn on record at Armagh, all the top seven warmest autumns at Armagh have occurred in the 2000s. There were 304.3 hours of strong sunshine this autumn, nearly 18% more than the 140-year (1881–2020) long-term average at Armagh (259.0 hours) and 14% more than the most recent (1991–2020) 30-year average (61.6 hours).
These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.
FOR FURTHER INFORMATION PLEASE CONTACT:
Mark Bailey at the Armagh Observatory, College Hill, Armagh, BT61 9DG.
Tel.: 028-3752-2928
mark.bailey@armagh.ac.uk;
http://climate.armagh.ac.uk/
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