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February’s Rainfall Accumulations

Latest February Analysis 2020 updated at 10am, Wednesday 27th February 2020 by Paul Moore, Aidan Murphy and Sandra Spillane, Climate Services

A strong Stratospheric Polar Vortex, coupled with the troposphere, has led to the North Atlantic Oscillation being in a strongly positive phase during February 2020. This has resulted in a zonal pattern across the Atlantic with a strong Polar Jetstream, further south than normal, bringing a series of vigorous Atlantic depressions, towards or just to the north of Ireland. These depressions, including two named storms, Ciara and Dennis, brought prolonged periods of heavy rainfall and stormy weather leading to extensive flooding in places, particularly along the Shannon catchment. Heavy rainfall falling on already saturated ground and with low evaporation rates in winter exacerbated the flooding.
The position and strength of the Polar Jetstream has resulted in 1.5 to 3 times the normal monthly rainfall so far for February throughout the country (a month usually associated with one of the least rainfall amounts).
The highest monthly rainfall total during the period 1-26 February was observed at Newport, Co Mayo with 306.6 mm (242 % of its February LTA). The Lowest monthly rainfall total during the period 1-26 February was observed at Dublin Airport, Co Dublin with 120.7 mm (247% of its February LTA). While the highest daily rainfall total was 51.5 mm on Saturday 8 February 2020 at Knock Airport, Co Mayo (50% of its monthly LTA).

So far this month, ten synoptic stations have already had their wettest February on record, including Phoenix Park, Co Dublin (records going back to 1850), Shannon Airport, Co Clare (record length 74 years), Newport, Co Mayo (record length 60 years), Claremorris, Co Mayo (record length 19 years), Casement, Co Dublin (record length 56 years) and Knock Airport (record length 23 years).

Full report <<here>>

 

Meteorologist’s Commentary at 12 noon, Monday, 25th February 2020 by Sandra Spillane PhD, Climatologist and Aidan Murphy, Climate Services 

The Weather and Climate Statements for February 2020 and Meteorological Winter 2020 (December 2019, January 2020 and February 2020) will be published on the 2nd working day and 3rd working day of March 2020 respectively. For these publications, and more, see: www.met.ie/climate/past-weather-statements.

The recent rainfall is above average at all our SYNOPTIC stations when compared to the 1981-2010 climatological long-term-average period (LTA, the World Meteorological Organisation’s standard period range for weather comparisons). The provisional rainfall totals for 1-24 February are currently at 225% of Ireland’s average. For comparison, December 2015 (Storms Desmond on Sat 5th,  Eva on Thu 24th and Frank Tue 29th), was around 245% of normal.

Note: the provisional value may go up or down by the end of the month, as quality control is completed on the data and as more rainfall observations come into Met Éireann. You might spot in the February 2020 maps below that there are gaps in mountain regions, the reason for this is due to their location and that rainfall totals at mountain stations are generally read once a month.

A series of vigorous Atlantic depressions affected the country in February, tracking closer to Ireland than usual and bringing prolonged periods of heavy rainfall and stormy weather leading to extensive flooding in places. The Polar jet stream extended across the Atlantic right over Ireland for most of the month, marking the tracks of successive storms resulting in 1.5 to 2.5 times the normal rainfall so far this month throughout the country.

The highest monthly rainfall total during the period 1-24 February was observed at Newport, Co Mayo with 283.5 mm (224% of its LTA). While the highest daily rainfall total was 51.5 mm on Saturday 8 February 2020 at Knock Airport, Co Mayo (50% of its monthly LTA).

Be aware of flooding and keep up to date with the latest warnings and weather forecasts for your area: www.met.ie/warnings.

The following graph illustrates Newport’s cumulative daily rainfall graph for the last 20 days together with the Forecast Ensembles going into the coming week.

It is not unusual for a single highest monthly total rainfall accumulation to be in this range and higher.

Recent Highest February Rainfall Totals

  • 2019: 569.9 mm at in the Cummeragh Mountains (gauge no.3), Co Kerry (216% of its LTA), 81.9 mm on Tuesday 19 February 2019 at this station
  • 2018: 305.9 mm at in the Cummeragh Mountains (gauge no.3), Co Kerry (116% of its LTA)
  • 2017: 400.1 mm at Beenreagh Mountains, Co Kerry (164% of its LTA)
  • 2016: 550.0 mm at Beenreagh Mountains, Co Kerry (225% of its LTA) with 99.5 mm on Tuesday 16 February (41% of its monthly LTA)

What is unusual is the lowest monthly rainfall total, observed at a rainfall station, to be this high. During the period 1-24 February 2020 at Roches Point, Co Cork there has been 115.7 mm total rainfall, this value is 155% of its monthly LTA (result is provisional until quality control is completed). The following graph illustrates Roches Point’s cumulative daily rainfall graph for the last 20 days together with the Forecast Ensembles going into the coming week.

Recent Lowest February Rainfall Totals

  • 2019: 15.8 mm at Ringsend, Co Dublin (37% of its LTA)
  • 2018: 19.0 mm at Ringsend, Co Dublin (44% of its LTA)
  • 2017: 28.5 mm at Clogher Head (Port), Co Louth (54% of its LTA)
  • 2016: 43.6 mm at Malahide Castle, Co Dublin (100% of its LTA)

The following maps are for (provisional) 1-24 February 2020 and December 2015 when up to 943.5 mm of rainfall fell at Gernapeka, Co Cork. The lowest during that month was 149.0 mm at Malahide Castle, Co Dublin (219% of its LTA).

The following gridded maps show the observed rainfall totals across the last four February’s for comparison.

Feb 2016 Feb 2017 Feb 2018 Feb 2019

To read more on the national weather records, see www.met.ie/climate/weather-extreme-records.

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