One of the many weather events that certainly stand out in the hearts of Irish weather enthusiasts along with others like Winter 1947 and the Big Snow of 1982 is the thunderstorm of 25/26 July 1985.
According to Met Éireann:
Widespread and spectacular thunderstorm activity occurred throughout the evening of the 25th July 1985 and continued overnight and into the morning of the 26th. Hundreds of farm animals were killed by lightning and large hailstones damaged tillage crops and crops of apples and fruit. The flooding which accompanied the storm affected farm buildings, houses, supermarkets, and stores in worst hit areas.
At midday on 25th July 1985, much of Ireland was under a blanket of high cloud with pressure ranging from 1014 mb in the south of the country to 1016 mb up north. As the continental airflow attempted to displace the moist Atlantic air, pressure gradually fell. As pressure continued to drop, by midnight on the 26th, a shallow low was spotted moving slowly off the southeast coast of Ireland with winds generally slack. This shallow pushed northeastwards during the morning of the 26th clearing by the afternoon. You can see by the synoptics below that it was a very volatile setup indeed.
Naas, Co. Kildare recorded up to 30mm in the space of 30-40 minutes whilst 28mm fell at Oak Park, Co. Carlow within 30 minutes and 29mm at Coon, Co. Kilkenny within 30 minutes. At the same stations, 22mm fell at Oak Park and 21mm fell at Coon within 15 minutes! The return period for events like this is over 100 years showing you how uncommon and rare it is.
The July 1985 thunderstorm does not seem remarkable in comparison to the 11 June 1963 thunderstorm that gave more than 75mm of rainfall at Mount Merrion in Dublin within one hour. However, what stood out was the intensity of the large hailstones, the frequency of the lightning flashes and the amount of regions affected by the heavy rain and hail when in comparison, it was mainly that particular region of Dublin that was affected on 11 June 1963.
Other notable rainfalls from this thunderstorm include:
76.8mm at Castleshane, Co. Monaghan on 25 July
61.8mm at Emyvale, Co. Monaghan on 25 July
58.4mm at Coolgreany Castlewarren, Co. Kilkenny on 25 July
57.2mm at Naas C.B.S, Co. Kildare on 25 July
52.4mm at Kilmacthomas, Co. Waterford on 25 July
52.2mm at Skerries, Co. Dublin on 25 July
46.9mm at Curragh Racecourse, Co. Kildare on 25 July
46.2mm at Duleek, Co. Meath on 25 July
30.1mm at Tibradden Larch Hill, Co. Dublin on 26 July
This is an RTÉ Archive video on the thunderstorm of July 1985 featuring actual footage: https://www.rte.ie/archives/collections/news/21200391-freak-storm-causes-damage/
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