Met Éireann is the National Meteorological Service of Ireland and one of its most important roles is to issue weather forecasts and warnings for Ireland. The Public Weather Service provided by Met Éireann prioritises the protection of life and ensuring citizen safety. The service also supports the activities of the citizen and other agencies to mitigate damage to property and reduce disturbance to economic activity and so enhance support for impact-based decision making for weather events.
Met Éireann’s main suite of warnings are issued by the duty forecaster between 10am and midday and are updated as necessary as new information becomes available. In general, warnings will not be issued more than 60-hours ahead of the expected adverse weather but advisories on potential hazards are issued up to a week in advance.
The weather forecast for Tuesday night (1 September) and daytime Wednesday (2 September) was for spells of heavy rain and spot flooding.
A Status Yellow Rainfall warning was in operation for daytime Wednesday 5am to 5pm for the northwest (issued 4pm Tuesday, 1st). This yellow rainfall warning was extended to Connacht, Donegal, Cavan and Monaghan on Wednesday morning valid from 10am to 9pm Wednesday (issued 9am Wednesday, 2nd).
While the general forecast was for heavy rain and a risk of spot flooding the rain was much heavier than forecast, further south than forecast and also occurred earlier than forecast. The heavy rain was expected to be in the northwest during Wednesday with the cold front whereas it was in the west with the warm front on Tuesday night.
Intense rainfall in west Galway resulted in the Owenglin River breaking its banks and flooding 17 houses. Rainfall totals of 70mm in a 24hr period were recorded at Connemara national park (CAMP station). The flood was short lived.
A number of local factors may have contributed to the magnitude of the event including that the river is very flashy and responds quickly to heavy rain, and the backup of water at a small bridge in the town.
There was a wet end to August, with soils being in a saturated state. This would result in rainfall running directly to the river.
It is noted that this catchment area does not have any Office of Public Works (OPW) river gauges which could be used to monitor river levels. As part of the development of the National Flood Forecasting and Warning Service, Met Éireann is engaged in a program of fluvial model development, trials of which are expected to begin in Q3 2021. The Owenglin is included in this phase of development.
Any analysis to establish the reason for the flooding or the impact on the conversion of land use is a matter for the OPW who lead and co-ordinate the implementation of Ireland's National Flood Risk Policy.
