Climate Statement for Autumn and November 2021

Autumn 2021 (September, October, November)

Very mild and relatively dry, especially in the Midlands and East

Autumn 2021 was very mild everywhere and relatively dry overall, especially in the Midlands and East, with below average sunshine for most. Absolute droughts4 were recorded in September and dry spells6 were recorded in September and November. A number of stations recorded their highest maximum temperature for autumn on record, with some recording their warmest autumn on record. Ireland stayed on the warmer, southern side of the Jetstream through most of autumn. High pressure to the south of Ireland dominated through much of September and November giving warmer and drier than average conditions, while low-pressure to the west of Ireland dominated through much of October, giving warmer and wetter than average conditions. There were a few cooler periods when Ireland lay on the northern side of the Jetstream, notably for a few days at the end of September and beginning of October, for a few days at the beginning of November and for several days towards the end of November. During these periods, high pressure set up to the west of Ireland, allowing polar maritime air masses from the north and northwest to dominate.

Rainfall: Below average in most places, driest in the East

The majority of seasonal rainfall totals across the country were below their Long-Term Average (LTA). Percentage of seasonal rainfall values ranged from 59% (the season’s lowest seasonal rainfall total of 126.1 mm) at Phoenix Park, Co Dublin (its driest autumn since 2007) to 123 % (the season’s highest seasonal rainfall total of 586.0 mm) at Newport, Co Mayo. The highest daily rainfall total was 64.7 mm at Valentia Observatory, Co Kerry on Friday 8th Oct. The number of rain days ranged from 38 days at Casement Aerodrome, Co Dublin to 77 days at Knock Airport, Co Mayo. The number of wet days2 ranged from 24 days at Dublin Airport, Co Dublin to 67 days at Newport, Co Mayo. The number of very wet days3 ranged from 1 day at Gurteen, Co Tipperary to 23 days at Newport, Co Mayo. Seven stations had absolute droughts4 between Sunday 22nd August and Wednesday 8th September. Fourteen stations had dry spells6 between Saturday 21st August and Wednesday 8th September. Two stations had dry spells6 between Friday 12th November and Monday 29th November (see monthly statements for more details). Along with Phoenix Park, Co Dublin, it was also the driest autumn since 2007 at Dublin Airport, Co Dublin with 133.7 mm (63% of its LTA) and Casement Aerodrome, Co Dublin with 135.7 mm (63% of its LTA).

Temperature: Above average everywhere

All mean air temperatures across the country were above their Long-Term Average (LTA) for the season. Deviations from mean air temperature ranged from 0.9 °C (12.8 °C the season’s highest mean temperature) at Sherkin Island, Co Cork to 1.8 °C (11.9 °C mean temperature) at Phoenix Park, Co Dublin. Mean tempera-tures for the season were lowest at Knock Airport, Co Mayo with 10.5 °C (1.5 °C above its LTA). The season’s highest temperature of 27.9 °C was reported at both Shannon Airport, Co Clare (its highest maximum temperature for autumn on record (length 75 years)) and Valentia Observatory, Co Kerry (its highest maximum tempera-ture for autumn since 1991), both on Tuesday 7th Sep. Both the season’s lowest air and grass minimum temperature were recorded on Monday 22nd Nov at Gurteen, Co Tipperary. The lowest air minimum was -3.1 °C while the lowest grass minimum was -7.9 °C. More than half of stations reported ground frost. The number of days with ground frost ranged from zero days at Newport, Co Mayo to 20 days at both Markree, Co Sligo and Mount Dillon, Co Roscommon. More than half of stations reported air frost, all in November. The number of days with air frost ranged from zero days at a few stations to 6 days at Casement Aerodrome, Co Dublin. Eight stations had their warmest autumn on record (record lengths ranging from 10 to 71 years). Along with Shannon Airport, nine other stations had their highest maximum temperature for autumn on record, all on Tuesday 7th September (record lengths ranging from 11 to 75 years).

Sunshine: Dullest in the Northwest, sunniest in the Southeast

All available sunshine totals were below their Long-Term Average (LTA) for the season. Percentage of seasonal sunshine values ranged from 90% (seasonal sun-shine total of 263.3 hours) at Casement Aerodrome, Co Dublin to 98% (seasonal sunshine total of 264.2 hours) at Shannon Airport, Co Clare. Seasonal sunshine totals ranged from 194.6 hours (no LTA comparison*) at Malin Head, Co Donegal to 298.2 hours (no LTA comparison*) Johnstown Castle, Co Wexford. The highest number of daily sunshine hours recorded this season was 13.0 hours at Malin Head, Co Donegal on Wednesday 1st Sep. The number of dull days2 ranged from 23 days at Dublin Airport, Co Dublin to 35 days at both Malin Head, Co Donegal and Valentia Observatory, Co Kerry.

Wind: Gales, strong gales and storm force winds reported and one named storm

Seasonal mean wind speeds ranged from 4.9 knots (9.1 km/h) at Moore Park, Co Cork to 15.0 knots (27.8 km/h) at Malin Head, Co Donegal. Gales were report-ed on numerous days with up to strong gales reported on Sunday 31st Oct and Saturday 27th Nov, with storm force winds reported on Friday 26th Nov. The number of days with gales ranged from zero days at a few stations to 11 days at Malin Head, Co Donegal. The number of days with up to strong gales ranged from zero days at most stations to 2 days at Malin Head, Co Donegal. The number of days with storm force winds was 1 day at Malin Head, Co Donegal. Both the season’s highest gust and 10-minute mean wind speed was reported at Malin Head, Co Donegal on the Friday 26th Nov during storm Arwen. The highest gust was 70 knots (130 km/h) while the season’s highest 10-minute mean wind speed was 52 knots (96 km/h), storm force 10.

The full report is available here

Gridded 2021 rainfall (%) on a monthly basis for Ireland so far

Recent Novembers in Ireland were mostly unsettled with occasional storm events.

2016 however, was dominated by anticyclonic conditions and the Azores high. Most stations reported below their Long-Term Averages (LTA) for rainfall and all stations were below their LTAs for temperatures.
2017 was changeable, cool and unsettled. Below average monthly rainfall and mean temperatures at most locations with above average sunshine totals.
2018 was dull and wet, with above average rainfall and monthly mean temperatures in most places. Storm Diana was a feature on the 28th with the highest recorded gust of 62 knots (115 km/h) at both Casement (its highest in 27 years) and at Roche’s Point (its highest in 13 years).
2019 was very wet and dull in the East and cool everywhere. Most monthly rainfall totals were above their LTAs and all stations had below average monthly mean temperatures.
2020 was mild, wet in the West and dominated by an Atlantic regime, with rainfall above average in most places and mean temperatures above average everywhere.

November 2021

Mild and dry for most of the month. Sunny in the South

November was a dry month dominated by high pressure. The first two thirds of the month were mild with the high pressure mostly centred to the south of Ireland. The final third of the month saw high pressure shift to the west of Ireland, allowing cooler air masses from the north to dominate. The beginning of the first week saw low-pressure pulling away to the north, leaving a northerly airflow. High pressure soon moved in from the west, establishing itself to the south of Ireland by the end of the first week, bringing a milder westerly airflow. The second and third weeks continued with low-pressure to the north and high pressure to the south maintaining a mostly mild westerly airflow. Some weak weather fronts traversed the country from time to time bringing bands of rain or showers from the west, interspersed with long dry periods. Rainfall amounts stayed relatively low, especially in the Midlands and East. For the final third of the month, a shift in the posi-tion of the high pressure to the west of Ireland, allowed a mostly north or north-westerly airflow to take hold. This brought cool air masses from the north but it stayed relatively dry overall. A depression of 976 hPa, named storm Arwen by the Met Office (UK), brought the strongest winds of the month on the 26th and 27th, as it moved south south-eastward along the east coast of the UK. The month finished milder with rain moving in from the West.

Rainfall: Below average nearly everywhere, driest in the East

Nearly all rainfall totals were below their Long-Term Average (LTA) for the month. Percentage of monthly rainfall values ranged from 16% (the month’s lowest monthly rainfall total of 11.9 mm) at Dublin Airport, Co Dublin (its driest November since 1942) to 108 % (the month’s highest monthly rainfall total of 183.3 mm) at Newport, Co Mayo. The month’s wettest day was also recorded at Newport, Co Mayo with 30.5 mm on Tuesday 30th. The number of rain days ranged from 9 days at Dublin Airport, Co Dublin to 28 days at both Belmullet, Co Mayo and Knock Airport, Co Mayo. The number of wet days1 ranged from 4 days at Dublin Airport, Co Dublin to 24 days at Newport, Co Mayo. The number of very wet days3 ranged from zero days at a few stations to 5 days at Newport, Co Mayo. Three stations had their driest November on record. These were Oak Park, Co Carlow with 20.9 mm (24% of its LTA) (record length 17 years), Mount Dillon, Co Roscommon with 49.6 mm (48% of its LTA) (record length 17 years) and Finner, Co Donegal with 74.8 mm (58% of its LTA) (record length 10 years). Along with Dublin Airport, Johnstown Castle, Co Wexford also had its driest November since 1942 with 27.9 mm (24% of its LTA). Phoenix Park, Co Dublin had its driest November since 1945 with 17.5 mm (23% of its LTA). Gurteen, Co Tipperary had its driest November since 1957 with 34.3 mm (38% of its LTA). Both Dunsany, Co Meath with 30.2 mm (36% of its LTA) and Casement Aerodrome, Co Dublin with 16.4 mm (22% of its LTA) had their driest November since 1983 and Mullingar, Co West-meath had its driest November since 1989 with 41.6 mm (47% of its LTA). Two stations had dry spells6 between Friday 12th and Monday 29th. These were Roches Point, Co Cork (lasting 15 days) and Dublin Airport, Co Dublin (lasting 18 days).

Temperature: Above average everywhere

All mean air temperatures across the country were above their Long-Term Average (LTA) for the month. Deviations from mean air temperature ranged from 0.2 °C (8.4 °C mean temperature) at Johnstown Castle, Co Wexford to 1.6 °C at both Finner, Co Donegal (9.2 °C mean temperature) and Belmullet, Co Mayo (10.0 °C mean temperature). Mean temperatures ranged from 7.6 °C at both Casement Aerodrome, Co Dublin (0.4°C above its LTA) and Dunsany, Co Meath (0.9°C above its LTA) to 10.1 °C (1.2 °C above its LTA) at Mace Head, Co Galway. The month’s highest temperature was reported at Shannon Airport, Co Clare on Sunday 14th with a temperature of 17.7 °C. Both the month’s lowest air and grass minimum temperature were recorded on Monday 22nd at Gurteen, Co Tipperary. The lowest air mini-mum was -3.1 °C while the lowest grass minimum was -7.9 °C. More than half of stations reported ground frost. The number of days with ground frost ranged from zero days at Newport, Co Mayo to 14 days at both Phoenix Park. Co Dublin and Mount Dillon, Co Roscommon. More than half of stations reported air frost. The number of days with air frost ranged from zero days at a few stations to 6 days at Casement Aerodrome, Co Dublin.

Sunshine: Sunny in the South, dull in the North and Northwest

Nearly all available sunshine totals were above their Long-Term Average (LTA). Percentage of monthly sunshine values ranged from 85% (monthly sunshine total of 55.6 hours) at Casement Aerodrome, Co Dublin to 125% (monthly sunshine total of 74.1 hours) at Shannon Airport, Co Clare. Monthly sunshine totals ranged from 31.7 hours (no LTA comparison*) at Malin Head, Co Donegal to 93.4 hours (no LTA comparison*) at Cork Airport, Co Cork. The highest number of daily sunshine hours recorded this month was 8.3 hours at Johnstown Castle, Co Wexford on Thursday 4th. The number of dull days2 ranged from 9 days at both Gurteen, Co Tipperary and Cork Airport, Co Cork to 13 days at Valentia Observatory, Co Kerry.

Wind: Storm force winds reported

Monthly mean wind speeds ranged from 5.1 knots (9.4 km/h) at Moore Park, Co Cork to 18.6 knots (34.4 km/h) at Malin Head, Co Donegal. Gales were reported on 10 days during the month, with strong gales reported on Saturday 27th and storm force winds reported on Friday 26th. The number of days with gales ranged from zero days at a few stations to 7 days at Malin Head, Co Donegal. The number of days with up to strong gales ranged from zero days at most stations to 2 days at Malin Head, Co Donegal. The number of days with storms force winds was 1 day at Malin Head, Co Donegal. Both the month’s highest gust and 10-minute mean wind speed were reported at Malin Head, Co Donegal on Friday 26th during storm Arwen. The highest gust was 70 knots (130 km/h) while the month’s highest 10-minute mean wind speed was 52 knots (96 km/h), storm force 10.