Ok so this post is going to be looking at the general history of Ireland's thunderstorms since 1983, the ones that really stand out, with some stats to back up the summaries. I will likely do detailed posts on some of them in future if possible.
To start off, let's briefly discuss how thunderstorms occur and what they are exactly.
Thunderstorms are very basically storms or heavy rain showers with the combination of lightning and thunder. They occur in the unstable atmospheric conditions favourable for the development of heavy showers but their unique and spectacular features are thunder and lightning. Lightning is an enormous electrical spark caused by the discharge of static electricity either from one cloud to another within a cloud or between a cloud and the ground. The lightning strike causes a sudden and intense heating of the air along its path which in turn causes an explosive expansion producing the loud noise known as thunder. Because a lightning strike can be up to 2km long, the sound from different parts of the flash reaches you at slightly different times which, together with echoes, accounts for the rumbling sounds of thunder that we're familiar with. While the light from the flash reaches you almost instantaneously (since the speed of light is extremely fast at 299,792,458 m/s), the sound from the thunder travels through the air much more slowly at 1km every 3 seconds. Thunder can often be heard up to 15km away. The amount of energy involved in a thunderstorm is enormous. The potential difference just before a lightning strike occurs is estimated at between 100 million and 1000 million volts, and during its most active phase, a thunderstorm will produce about one strike every 20 seconds. A small thunderstorm of about 1km radius is equivalent in terms of energy to ten nuclear bombs of the type that dropped on Hiroshima.
2013 - Following two weeks of very warm to hot weather courtesy of a stubborn area of high pressure with the jet stream well to the north, low pressure approached from the Atlantic on the 22nd into the 23rd July. This came into the warm air already entrenched over Ireland and as the low pushed in, it forced the winds to a southerly direction dragging up some extremely humid and unstable air with nightime temperatures not getting below 15°C widely and even 20°C in England on the 23rd July in particular. The month went out with a bang as a result bringing thundery downpours to many and high daily rainfalls leading to a wet July for some regardless of the drought that occurred for much of the month. On the evening of the 24th July, heavy thundery showers moved into Leinster and Munster. These brought lightning and heavy rainfall including a daily fall of 62.5mm at Ballincurrig, Co. Cork. This same station had only 2.5mm of rainfall from the 1st to the 20th July. Further thunderstorms occurred days afterwards in continuous high humidity conditions with a daily rainfall of 35.0mm at Merrion Square, Co. Dublin on the 26th.
Could only find one good video of the thunderstorm in Cork. The second two are Dublin.
2012 - June 2012 was a very wet month with a lot of rainfall and for some, the wettest June on record. It was also quite a cool month with daytime temperatures being well below average for much of the month stuck in the 13-16°C range. However, near the end of the month, a warm front pushed northwards on the 26th introducing some much warmer air all the way from Spain. Temperatures peaked at 24.8°C in Dún Laoghaire, Co. Dublin on the 27th which whilst not a remarkable temperature felt very warm because we had not seen such temperatures since the end of May at that point, mixed with the humid nature of the southerly winds. The warm front brought light rain northwards whilst another band of rain pushed into the south on the night of the 26th into the 27th. This rain was more intense than the previous band but worse was yet to come. On the night of the 27th into the 28th, very heavy thundery rain associated with an active cold front moved northwards over the country with further thunderstorms behind it on the 28th and yes, another band of rain pushed into the south during the evening. In all this time, there was plenty of flash flooding and thunderstorms contrasting with the warm, humid air. Accumulations of 50mm or more were recorded between 21:00 on the 27th and 03:00 on the 28th with Cork being particularly affected. At Cork Airport, 36.1mm of rainfall fell within 3 hours and this sort of event has a return period of 20-30 years showing you how extreme it was. Cork newspapers reported that more than 50 homes and numerous businesses were damaged by floodwater with several thousand homes left without power. All of this thundery rain of course was falling on already saturated ground especially from the first week of June. These were some of the worst thunderstorms to hit Cork in recorded history.
I remember the June 2012 thunderstorms very well. Whilst I didn't hear any thunder where I am, the rain was very heavy and it was the second heaviest rainfall I have experienced after the morning of 18 November 2015.
Here's some videos from the June 2012 thunderstorms.
The lightning happens near the end of this video.
2009 - July 2009 was the wettest July on record for a large part of Ireland. On the 2nd, heavy thunderstorms brought exceptional falls of rain resulting in localised flooding. During the period from midnight to 09:00, thundery rain affected the east and northeast of Ireland, especially Dublin. Rainfall totals for the 9-hour period were around 40-50mm in parts of the city with 26.5mm being recorded within the hour 04:00 to 05:00 at Dublin Airport, the largest hourly rainfall total on record at Dublin Airport. During the afternoon and evening of the same day, another narrow band of thunderstorms or thundery rain affected Clare, Galway and Mayo bringing even heavier falls. Newport, Co. Mayo recorded up to 67mm with 41.6mm of this falling within one hour!
July 2009 had frequent thunderstorms with hail being observed at Cork Airport on the 29th. The 2nd July was the most notable of all the thunderstorms.
After a band of heavy rain passed through on the 20th October 2009, isolated thunderstorms were recorded in gusty southeasterly winds on the 21st including a daily rainfall of 28.5mm at Oak Park, Co. Carlow and 40.1mm at Mount Russell, Co. Limerick.
This picture is of cumulonimbus clouds over Dublin on 21st October 2009.
2008 - Like June 2012 and July 2009, August 2008 was a very wet month with absolute exceptional rainfalls and for some, the wettest August on record including at Phoenix Park whilst for others, not as wet as August 1986. On the 6th, Shannon Airport recorded an HOURLY rainfall of 38.4mm between 16:00 and 17:00 under a thunderstorm with hail, with almost 30mm of this being recorded within half an hour! This became Ireland's highest hourly rainfall total on record at a synoptic station for any month.
On the 9th, a cold front moved eastwards with a very unstable airmass immediately behind the front facilitating the development of thunderstorms in the east of Ireland following the frontal passage. Outbreaks of rain had affected the area earlier in the day from around 03:00 to 08:00 bringing totals of around 6-8mm. During the early afternoon, convective rain developed in the midlands. From approximately 13:30 onwards, a thunderstorm cell developed over west Offaly which then spread to north Kildare and eventually covered most of county Dublin and south Meath. Dublin Airport and Casement Aerodrome were reporting thunderstorms with further bursts of heavy rain continuing in the Greater Dublin Area until 22:30. Dublin Airport recorded a daily rainfall of 76.2mm under this thunderstorm, its second highest for any month and its wettest August day on record at that point (now second wettest August day and third wettest day after the 2nd August 2014). 68.3mm of this fell within a 5 hour period at the station. At Celbridge, Co. Kildare, 73.6mm of rainfall fell within the 5 hours whilst 77.8mm fell at Leixlip, Co. Kildare within the 5-hour period. Such rainfalls have return periods of between 150-240 years!
Here's some videos from the August 2008 thunderstorms. The first one is a place that I know very well and have been through all my life so to see it badly flooded like that is mad to look at.
2007 - June 2007 was a very wet month in the east and south with it being Kilkenny's wettest June on record before the station closed in April 2008. Many of the showery days in the second half of the month were associated with thunderstorms.
Active fronts over Ireland on the 13th separated warm and humid air of tropical origin to the south and a cool arctic airstream to the north. As a result, some heavy thundery falls of rain occurred with a particular emphasis on the midlands. Mullingar measured an hourly rainfall between 14:00 and 15:00 on the 13th of 29mm with a return period of 50 years.
The 22nd brought heavy showers in from the west in a northerly wind direction. These showers, associated with thunderstorms, became unusually intense in parts of the east. Phoenix Park recorded a daily rainfall of 51.6mm on this day with 26mm of this falling within 90 minutes.
Here's a picture of Galtymore, Co. Tipperary on the 24th under a funnel cloud. Picture courtesy of Des Loughney.
2006 - Much of Summer 2006 was dry, settled and warm with a particularly warm start to June and mid-July period. Therefore, there wasn't much convection that took place but on the 9th/10th June, some localised thunderstorms took place out to the west and south. These weren't all that heavy however.
Here's a video from June 2006.
Not sure when this one was exactly in Summer 2006.
2005 - Heavy thunderstorms developed during the evening of the 29th June 2005 over many parts of Ireland giving some torrential falls locally and leading to flooding in parts of Munster and west Dublin. These showers were associated with a shallow depression which moved close to the southeast of Ireland during the day. Phoenix Park recorded a daily rainfall total of 41.2mm on this day according to Met Éireann's historical data but their June 2005 monthly weather summary states the station had 47mm in the hour of 17:35 to 18:35 on the day which included a 10-minute fall of 16.8mm. I am not sure which one is correct but nevertheless, both rainfalls are high. Cork Airport had recorded 13.5mm in thunderstorms.
On the 12th July, severe thunderstorms developed over the southern part of Ireland during the evening giving some torrential rainfalls and a tornado developed the same evening near Myshall, Co. Carlow. The 10th-12th brought hot and sunny weather everywhere over Ireland with temperatures getting as high as 30.3°C on the 12th, you have to go back to July 1983 to see a higher temperature for July in Ireland up to that point. However, during the afternoon of the 12th, convective clouds developed producing heavy showers with thunderstorms in the southwest and southeast. Falls of between 20-25mm within a 3-hour period were recorded over Kerry, Cork and Tipperary.
Courtesy of Liam Clarke, this picture shows the tornado near Myshall, Co. Carlow on 12th July 2005.
2004 - The first part of July produced widespread thunderstorm activity over various parts of Ireland but there were no notable rainfalls.
August was a very warm month though not as warm as 2003 and unusually for such a warm Summer month, it was very wet for some. This was down to the fact that it was a showery month with regional variations. It was the wettest August in the east since 1986 at this time whilst the driest since 1995 in the northwest. Heavy showers were associated with numerous thunderstorms through August. On the 12th, Kilkenny recorded thundery rain with a daily rainfall of 32.2mm. Meanwhile, on the 18th, thunderstorms produced 32.8mm at Dublin Airport. Another notable thunderstorm occurred in Dublin on the evening of the 23rd resulting in flash or localised flooding, see the photo below (courtesy of Matthew Carrigan) of Clontarf, Co. Dublin on said evening.
2003 - Before the Summer really took off in August with warm, dry and sunny conditions, June/July were very warm but wet months. June contained some isolated thunderstorms but nothing really notable. However, on 20th July, slow moving thunderstorms brought localised flooding to parts of the west with Galway city being the worst affected. The station at NUIG measured a daily total of 39mm whilst in the east and even other parts of the northwest, there was little to no rain on that day. In general, July was a very humid and thundery month with easterlies being the prevalent wind direction dragging in a lot of cloud with these thundery showers. Another band of thunderstorms on the 29th July produced a tornado near Mullinavat, Co. Kilkenny causing some property damage.
Thunder was recorded during the heatwave of August 2003 but was mostly isolated with the exception of the 5th when thunderstorms were widespread over the east and south coasts and heavy causing disruption to power supplies.
2002 - The second week of July was very showery with hail and thunder being recorded in parts on the 10th. Funnel clouds or tornadoes not reaching ground level, were observed in parts of the south, west and northwest on the 9th.
2001 - A depression moved northwards from the Bay of Biscay on the 26th June introducing very warm and humid conditions with spells of thundery rain or showers. Some heavy thunderstorms affected the southeastern half of Ireland on this day which are indicated by the lightning symbol on the synoptic chart below for the 26th June 2001.
A line of thundery rain or showers associated with a frontal trough moved slowly eastwards over Ireland on the 13th July 2001. By afternoon, some heavy thunderstorms had developed over Munster and south Leinster but did not reach county Wexford until after nightfall. At Johnstown Castle, just south of Wexford town, rain commenced just before 23:00. Over the next two hours, a thunderstorm became almost stationary over the area giving continuous heavy rain at the station amounting to 65mm in the 2-hour period up to 01:00 on the 14th. This kind of event has a return period of more than 100 years. The 24-hour total at the station of 84.5mm was the second highest daily rainfall at the station in its 84-year history surpassed only by the fall of 111mm on August 3rd 1997. At nearby Clonroche, 63mm was recorded in the 24-hour period up to 09:00 on the 14th but Rosslare, less than 10 miles from Johnstown Castle, recorded a daily rainfall total of only 2.2mm.
The first part of August brought heavy and thundery rain to places leading to localised flooding. For example, on the afternoon of the 2nd, Cork Airport received 22mm in the space of 2 hours.
Radar at 23:45 on 13th July 2001.
2000 - Thunderstorms on the 30th June produced some very heavy falls in Mayo and Galway. Straide measured 39.6mm on this day whilst Crossmolina recorded 45mm in a 3-hour period on the evening of the same day.
The first week of July was dominated by very showery weather. Humid air circulating around an area of low pressure which moved slowly eastwards near the south coast brought a mixture of heavy, sometimes thundery, showers and sunny spells. Whilst some areas received over 20mm between the 1st and 5th, other areas were virtually dry. There were some particularly heavy thunderstorms in parts of the south and west on the 4th and 5th along with the midlands on the 3rd, when lightning damaged power lines and there was localised flooding. Near Westport, Co. Mayo, 22mm was recorded in an hour during the evening of the 4th. Nealstown, Co. Laois in the Slieve Bloom mountains recorded 63.6mm in a 2-hour thunderstorm on the 3rd. Near the end of July, a shallow depression became established over Ireland following a spell of settled weather. Showers became heavy and more widespread between the 27th-29th. Around 50mm was measured in the Clare/Limerick area during a thunderstorm on the 27th. A number of thunderstorms produced a daily total of 39mm at Shannon Airport on the same day.
Throughout August 2000, there were some localised heavy showers which were often accompanied by thunder and with some occasional torrential downpours. It was unusual just how frequent thunderstorm activity was during the month. Thunderstorms in the period 15th-20th around the middle of the month were accompanied by tornadoes. At Coolavin, Co. Sligo, a funnel cloud was observed on the afternoon of the 17th whilst around the same time, a waterspout or miniature tornado over water, was observed from an Air Corps helicopter over Clew Bay. A hailstorm over Skerries, Co. Dublin gave a covering of over 10cm of hail on the morning of the 20th giving the appearance of snowfall. The following day, a tornado at Toome Bridge, Co. Antrim, produced hailstones of 13mm diameter while at Aldergrove Airport near Belfast, there was a total of 7 days during the month with thunder - around its usual number for an entire year and the highest for any month at the station for exactly 50 years. Widespread thunderstorms were recorded on the 25th especially over the eastern half of Ireland giving falls of over 20mm to parts.
Irish Independent article from August 24 2000 stating how good of a month August 2000 was for thunderstorms and hail:
https://www.independent.ie/irish-news/august-is-a-wicked-month-for-hailstorms-26112260.html
Skerries, Co. Dublin on 20th August 2000. Picture is taken from the August 2000 monthly weather bulletin thus why it's black and white.
1999 - Much of August was mainly influenced by areas of low pressure giving spells of locally heavy rain. Some of this rain was accompanied by severe thunderstorm activity leading to reports of tornadoes from a number of locations during the month. The very warm, sunny weather of late July extended into the 1st of August in most places but the first of the month's frontal troughs was already approaching the west coast. These bands of thundery rain became slow moving over Ireland over the following days as the associated depression lay just off the southwest coast. Rain was particularly heavy in the south and east between the 4th and 6th where falls of over 50mm were measured during the period whilst a tornado struck the Sligo village of Ballisodare on the 6th. The weather around mid-month became showery as a depression lay to the north between the 14th-16th and some of the showers were very thundery in the fresh northwesterly airstream. Shower activity increased further as low pressure became centred over us on the 17th and 18th. Tornadoes were reported from Ballina and Portumna on the 17th whilst severe thunderstorms over southern Wexford on the 18th produced golfball sized hail and knocked out power supplies. Rosslare measured 27.5mm in a 2-hour period during the early afternoon of the 18th.
1998 - There was a very wet start to what was going to be one of the wettest Junes on record over the southern half of Ireland as bands of thundery rain or showers, associated with a depression crossing Munster, gave 2-day rainfalls of 20mm or more. A tornado struck near Dungarvan, Co. Waterford on the 1st. Two families staying at Ballyclamper Holiday Park were fortunate to escape without serious injury when the tornado destroyed the mobile homes in which they were staying. Dr. John Tyrell of University College Cork, who visited the area, reports that the tornado followed a southeast to northwest track for approximately 2.8km, commencing about 200m from the shoreline and had a width of 10m. The tornado developed during a 3 to 4-hour spell of heavy rain. Carriglea about 10km distant recorded 15mm of rain between 01:00 and 04:00 on the 1st. Some of the contents of the caravans were found over a kilometre away! On the 6th, a funnel cloud was observed at Lyreacrumpane, Co. Kerry as a frontal trough crossed the country giving some very heavy rain and squalls. That same afternoon, 18mm was recorded within 20 minutes at Birr. Birr remarkably enough faced a nine degree drop from 20c to 11c that afternoon within the space of 2 hours.
August wasn't a very thundery month but nevertheless, thundery downpours affected northern areas during the afternoon of the 11th. At Malin Head, flash flooding followed showers producing 15mm within the space of 2 hours, a maximum rate of 36mm/hr was recorded. Paddy Delaney, the head of the synoptic station at Malin Head at this time, reports that damage was widespread in the Malin Head area. Houses were flooded, stone walls ruptured and the tarmac surface removed from many stretches of road with the force of the water. Within a couple of hours, the only obvious evidence of anything unusual having happened was the large amounts of debris on the roads.
1997 - Heavy rain associated with thunder fell in western regions on the 10th and 12th July 1997. The rainfall recording at Bangor Erris measured 50mm of rain in 2 hours on the 12th whilst Belmullet's daily total of 29mm on the same day was its highest for July since 1987.
There were widespread thunderstorms on the 10th and 11th August with up to 34mm recorded at Valentia Observatory.
Here's a video of Baldoyle in August/September 1997.
1996 - Thundery rain over Ireland on the 28th July brought some local downpours particularly in western counties. Worst affected was Boyle, Co. Roscommon where 83mm was recorded in an hour and a quarter by John McPherson, the observer at the rainfall station in Marian Road. This was one of the highest rainfall totals in a short period ever recorded in Ireland. Elsewhere on the 28th, torrential rain in the Erris Peninsula caused a landslide resulting in the deaths of 50 sheep while in east Galway, there were reports of a number of cattle killed by lightning during the evening of the 28th. A daily total of 63.4mm was recorded at Kingscourt, Co. Meath. These heavy rainfalls were in stark contrast to the dry spell from the 7th-20th July which had no measureable rainfall at all at Cork Airport.
1995 - A depression brought thunderstorms on the 16th July resulting in some heavy rainfalls to parts including Dublin Airport where 39.0mm was recorded on the day.
August 1995 began with a very warm easterly flow dragging in hot continental air and some sufficient instability for thundery showers to localised areas. This included 31.4mm falling at Birr on the 1st day of the month.
1994 - A depression moved slowly northeastwards on the 24th June bringing frequent thunderstorms, especially in the north and east of the country. On this day, Clones recorded 38.5mm.
1992 - June was a dry month generally and indeed much of the rain that did fall can be accounted for a few heavy, often thundery, rainfalls on particular days. 100mm of the monthly rainfall total for June 1992 of 125mm at Cloosh in Connemara was recorded on the 29th. Similarily, 37mm was recorded during June at Dublin Airport and 26mm of this fell on the 2nd (over 20mm of that within an hour) whilst a drought occurred at the station from the 6th to the 29th (24 days).
1986 - June brought a very thundery start to the Summer of 1986 and we would have to wait 'til August 2000 to see a month as thundery as such. The first half of the month was dominated by westerly winds leading to generally cool and unsettled conditions but high pressure developed to the east around the middle of the month and low pressure that affected us tended to come from Europe than the Atlantic. Therefore, the temperatures rose and brought quite a lot of thunderstorm activity. The most notable of the thunderstorms occurred on the 27th and 28th causing widespread damage and destruction. In Dublin, about a dozen houses were struck by lightning and at least one was gutted by the resulting fire. Power supplies, transport and communications were disrupted and computers, cable television and other electrical equipment knocked out. 26.5mm fell at Birr on the 28th.
Here's RTÉ Archive coverage on June 1986 thunderstorms for 27th/28th.
https://www.rte.ie/archives/collections/news/21219093-thunder-and-lightning-storm-damage/
1985 - For this one, I'll leave you with just the RTÉ Archive coverage on it for the July 25th/26th 1985 thunderstorm for now (I will do a more detailed post on it in future).
https://www.rte.ie/archives/collections/news/21200391-freak-storm-causes-damage/
1983 - A hot spell in July that led to water shortages was followed by a severe thunderstorm to parts of the southeast with Kilkenny in particular. On the morning of the 17th July, this thunderstorm moved up the Nore valley. Nearly 1 inch of rain was recorded within 15 hours at the Kilkenny synoptic station on the day and this remains one of the highest on record for that space of time. The thunderstorm was quite slow moving, local to the Kilkenny area and not accompanied by hail. The ground was parched and hard beforehand and as the rain bucketed down it behaved like concrete, with little absorption. Just when things were beginning to reach crisis levels and cause untold damage, the rain subsided and widespread flash flooding was avoided. Here are the accumulative rainfall totals (mm) for Kilkenny on 17th July 1983 with the 66.4mm daily rainfall making it Kilkenny's wettest day on record in what was otherwise a very dry July!
15 mins - 23.5
30 mins - 31.6
1 hour - 37.9
2 hours - 56.7
6 hours - 65.7
12 hours - 66.4
24 hours - 66.4
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