DRY JANUARY, COOLER AND SUNNIER THAN AVERAGE

Armagh Observatory reports that January 2024 was drier, cooler, and sunnier than average. There were four named storms this month, bringing the total number of such storms to have affected Northern Ireland to a greater or lesser extent this 2023/2024 storm season to 13. Total precipitation was 39.15 mm (1.54 inches) including 7 trace values, that is, 38.8 mm if trace values are ignored. This is slightly more than half the 183-year long-term (1838–2020) average January precipitation at Armagh (72.8 mm) and the most recent (1991– 2020) 30-year average (72.7 mm). The wettest day was the 1st with 8.7 mm associated with a complex weather system announcing the arrival of Storm Henk, a storm that primarily affected southern and central parts of England and Wales. The second and third wettest days were the 22nd with 6.8 mm and the 23rd with 4.7 mm, associated with storms Isha and Jocelyn. With just 13 rain days, that is, days with precipitation greater than or equal to 0.2 mm, this January was the driest at Armagh for four years, that is, since January 2020 (38.65 mm
including 9 trace values).

There was an extended cool dry spell during the second and third week of the month, which produced snowflakes and some light snow on four days, namely the 14th, 15th, 16th, and 18th. This resulted in a thin partial covering of snow at Armagh on the 18th that persisted until the following day. A faint rainbow was seen on the morning of the 8th. Gale force winds associated with Storm Isha were observed on the evening of the 21st. These damaging winds continued into the small hours of the 22nd with strong winds also on the afternoon and evening of the 23rd associated with Storm Jocelyn, named after the famous astrophysicist Dame Jocelyn Bell Burnell. Although these storms produced the second and third wettest days of the month, neither caused significant rainfall at Armagh.

Strong winds approaching gale force also occurred on the 31st associated with an exceptionally deep depression passing several hundred miles north of Scotland named Storm Ingunn by the Norwegian Meteorological Institute. In contrast to the 2022/2023 storm season, which produced only two UK Met Office named storm systems, Antoni and Betty both in August 2023, this was the 13th named storm to affect Northern Ireland to some degree since September 2023.The average temperature, namely 4.8 C (40.6 Fahrenheit), was approximately 0.6 C warmer than the 225-year long-term (1796–2020) average January temperature at Armagh (4.2 C) but 0.2 C cooler than the most recent (1991–2020) 30-year average (5.0 C). This was the first month since July 2023 to have a lower mean temperature than the most recent 30-year average and the coolest January at Armagh for three years, that is, since January 2021 (3.1 C)

The highest maximum air temperature, notionally the warmest meteorological day, that is, the 24-hour period beginning at 09:00 GMT the day before the 09:00 GMT manual readings are taken each day, was 14.2 C on the 23rd. This was the warmest January day at Armagh since the 24th of January 2016 (15.0 C) and is now the fourth warmest January day on record at Armagh. Although January 2024 was cooler than average, there were several other very mild days towards the end of the month, namely 13.7 C on the 25th, 13.5 C on the 21st, and 13.0 C on the 27th, each with maximum air temperatures more than 5.0 degrees Celsius above the most recent 30-year average January maximum at Armagh (7.8
C). The lowest maximum air temperature, notionally the coolest day, was 2.2 C on the 17th followed by 3.3 C on the 15th and 3.6 C on both the 8th and 12th. It was during this relatively cool spell around the middle of the month that snow fell.

The highest minimum air temperature, notionally the warmest night, was 7.6 C on the 24th, followed by 6.8 C on the 28th (though actually occurring around 09:40 GMT the previous calendar day), and 6.5 C on both the 3rd and 21st. The lowest minimum air temperature, or coolest night, was -4.6 C on the 18th followed by -4.0 C on the 8th and -3.6 C on the 17th and 19th (though the latter occurred around 09:00 GMT the previous calendar day). In January at Armagh the lowest temperature during any given meteorological day occurs the previous calendar day roughly half the time.

This month there were 11 days with night frosts, with minimum air temperatures less than or equal to zero degrees C, and 21 days with ground frost, that is, days when the minimum grass temperature fell to zero C or less. The coldest of these ground frosts were -10.5 C on the 18th, followed by -9.9 C on the 17th and -8.4 C on the 30th. With 68.6 hours of strong sunshine this was the sunniest January at Armagh for 13 years, that is, since January 2011 (71.8 hours) and the eighth sunniest January at Armagh on record. January 2024 was approximately 49% sunnier than the 140-year long-term (1881–
2020) January average at Armagh (46.2 hours) and 45% sunnier than the most recent (1991–2020) 30-year average (47.4 hours). The sunniest day was the 30th with 7.1 hours of strong sunshine, followed by the 6th (6.3 hours) and the 4th (5.9 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; URL: http://climate.arm.ac.uk/.


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