Monthly Weather
Summary
The Weather of December 2011
Wet in places; dull and windy everywhere
Rainfall for the month was above average along the Atlantic coast and in the northwest, with most stations
in the west reporting their wettest December in 5 years and an above normal number of wetdays (days with
1mm or more) recorded. Malin Head had the highest rainfall relative to normal in December, with 179 % of
its long-term average and its wettest December since 1999 (12 years). The rest of Ireland reported a dry
month with below average rainfall. Casement Aerodrome received only 72% of its monthly rainfall total and
recorded its driest December since 2004 (7 years). The majority of the month’s highest daily falls were on
the 12th and 19th, but were relatively small, with some stations reporting it as their lowest December daily
rainfall for a number of years. At Dublin Airport and Mullingar, it was the lowest daily rainfall at the sites in
December since 1963 (48 years) and 1970 (41 years), respectively. Mean temperatures for December were
above average or average for the time of year. Mean maximum temperatures for the month were above
normal everywhere, but almost all stations reported their maximum temperatures, mostly recorded on the
25th and 26th, were not as high as December 2007. Minimum air temperatures were warmer than normal
almost everywhere, leading to a below average number of air frosts recorded, of between zero and eight.
Malin Head and Belmullet both reported that their minimum air temperature’s for December of 2.0°C and
1.6°C, respectively, were the warmest minimum temperatures recorded since 1988 (23 years). Sunshine
during December was below average nearly everywhere, with Casement Aerodrome recording 26.2 hours of
sunshine and the dullest December on record since the station opened in 1964 (47 years). Other stations
across the country reported it was their dullest December for between six and 20 years.
1st to 10th: The start of the month was cool with light rain, drizzle and some fog at western inland locations. Deep
depressions with associated frontal systems followed, bringing a few bright, sunny spells, but mainly scattered
showers of snow and rain, some of which were heavy, with thunder and hail. Winds were gusty, mainly fresh to
strong, with gales recorded along western coasts.
11th to 18th: Frontal activity brought bands of rain and drizzle before wintry showers and gale force winds affected
most areas on the 13th. Gales generated a large swell off the Donegal coast and the M4 weather buoy measured a
maximum wave height of 20.4 m, the highest wave ever recorded in Irish waters. Temperatures became cooler due
to a northerly airflow, and weather was dry and bright, with few scattered showers, some heavy with hail and thunder.
Some air frost was recorded along southern coasts and at inland stations.
19th to 31st: At the start of the period, rain and snow showers were observed in the west, with some bright spells
and patches of light rain elsewhere. Temperatures rose and became milder due to warm front activity and a southerly
airflow, with rain and drizzle becoming more widespread. Showers of rain, some heavy with hail and periods of rain
and drizzle, followed. Mainly dull overall, with few sunny periods. Winds were mainly light to moderate at the start,
becoming moderate to strong, with gales reported along Atlantic coasts.
Wind and elements: Mean windspeeds for the month were above normal, between 10 and 22 knots (19 and
40km/h) and the highest for 12 and 37 years in most places. Gale gusts were recorded on all days with gales reported
on the 7th, 8th,12th,13th,14th, 22nd, 26th, 27th and 28th. The month’s highest gust of 74 knots (137km/h) was
observed at Malin Head on the 13th. Thunderstorms were reported on the 1st, 8th, 10th, 14th and 20th with
numerous days with hail reports, especially during the first two weeks of the month. Fog was reported in the west on
the 2nd, 10th, 19th, 20th, 21st and 27th and in the south on the 30th.
EXTREME VALUES AT SYNOPTIC STATIONS
Rainfall
Highest total: 188.0mm at Valentia Observatory
Lowest total: 49.1mm at Phoenix Park
Highest daily rainfall: 23.0mm at Valentia Observatory on the 12th (its lowest daily fall for December since 2004)
Temperature
Highest mean monthly temperature: 8.7°C at Sherkin Island
Lowest mean monthly temperature: 4.9°C at Knock Airport
Highest temperature: 13.7°C at Carlow (Oak Park) on 25th
Lowest air temperature: -4.9°C at Mullingar on 16th
Lowest grass minimum temperature: -10.1°C at Mullingar on 16th
Sunshine
Highest monthly total: 57.8 hours at Dublin Airport (its dullest December since 2005)
Lowest monthly total: 16.7 hours at Valentia Observatory(its dullest December since 1993)
Highest daily sunshine: 6.7 hours at Dublin Airport on 17th
December 2011 Daily values at selected synoptic stations
Rainfall (mm)
25
20
15
10
5
0
1
2
3
4
5
6
7
8
9
10 11 1 2 13 14 1 5 1 6 17 1 8 19 20 2 1 22 23 2 4 25 26 2 7 2 8 29 3 0 3 1
8
9 10 1 1 12 1 3 14 1 5 16 1 7 18 1 9 2 0 21 2 2 23 2 4 25 2 6 27 2 8 29 3 0 31
Sunshine (hourrs)
8
6
4
2
0
1
2
3
4
5
6
7
Maximum temperature (°°C)
15
10
5
0
1
2
3
4
5
6
7
8
9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 28 29 30 31
Minimum temperature (°°C)
15
10
5
0
-55
1

2
3
4
5
6
7
Valentia Observatory
8
9 10 11 12 13 14 15 16 17 18 19 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 29 30 31

Dublin Airport

Belmullet
December 2011 Percentage / Difference from 1961-90 monthly normals
Rainfall (% of normal for period 1961-1990)
Belmullet
145
123
Ballyhai se
65
Carlow
72
Casement Aero
135
Claremorris
60
Cork Airport
76
Johnstown Castle
179
Malin Head
95
Mullingar
146
Shannon Airport
118
Valentia Observatory
50
75
T em per atu re
100
125
150
175
200
(°C difference from normal for period 1961-1990)
Belmullet
0.9
Carl ow
0.8
Casement Aero
0.4
Clarem orri s
0.8
Cork Airport
0
Johnstown Castle
0.1
Malin Head
0.5
Mull ingar
0.3
Shannon Airport
0.8
Valentia Observatory
0.8
-0.5
0
Sunshine
0.5
1
(% of normal for period 1961-1990)
Belmullet
78
Casement Aero
56
Cork Airport
86
Dublin Airport
112
Shannon Airport
58
45
Valentia Observatory
30
55
80
105
130
Issued by the Climatology and Observations Division of Met Éireann on 3rd January 2012
This report is based on preliminary data from the synoptic weather stations operated by Met Éireann
A detailed summary is available in the Monthly Weather Bulletin
For more information, contact Met Éireann at 01-8064200 or e-mail: [email protected] website: www.met.ie