A deep area of low pressure with a centre of 973mb approached from the south of England and pushed northwards during the evening of the 23rd September 2012. This lingered in the central and northern swave of the UK as well as affecting northern and east parts of Ireland nearly all day on the 24th with persistent heavy rainfall in gusty easterly winds, later veering to northwesterly to northerlies. Further heavy rainfall occurred over the same places on the 25th before finally starting to clear southeastwards into south England during the afternoon of the 26th. This was the deepest September storm since 1981 and it was so unusual to be seeing a low as deep as this in September especially considering that much of September 2012 up to that point was sunny and dry. This was a reminder that Mother Nature wasn't done with us just yet in delivering a poor to atrocious period of weather that began in April that year and would only end in the third to last week of May 2013 with very few breaks.
Rainfall totals (mm) for Irish stations during the period, 24th-26th September 2012.
Malahide Castle's daily total of 70.5mm on the 24th was over 2/3 of its September 2012 monthly rainfall total of 106.8mm - its wettest September since 1975. In contrast, Ballineen, Co. Cork recorded only 5.7mm of rainfall throughout September 2012 making it the driest September here on record since its records began in 1994. All parts of Cork received under 30% of their average September rainfall whilst places like Malahide Castle had up to 181% of their September rainfall and the main reason for this was this event or storm of the period 23rd-26th.
It wasn't only the rain that was notable, it was also how cold for the time of year it was. According to the BBC, several Met Office stations recorded their coldest September day on record on the 24th. They include Glenanne (Armagh), Altnahinch (Antrim), and Lough Fea (Tyrone), all in Northern Ireland. Slieve Bloom Mts (Nealstown) recorded a maximum of 9.2°C on the 24th whilst Dublin Airport recorded a max of 10.4°C under the heavy rain on the same day.
Impacts for the UK from the UK Met Office:
An unusually vigorous area of low pressure brought very unsettled weather to most parts from the 23rd to the 26th, giving particularly high rainfall totals (most notably 130 mm at Ravensworth, North Yorkshire, over a 3-day period) and some strong winds. Prolonged heavy rainfall across SW England overnight 23rd / 24th resulted in some transport disruption, with localised flooding of roads, and main rail routes closed for a time. During the 24th, the heavy rain moved north, bringing disruption to road and rail journeys in the West Midlands, North Wales and northern England. On the 25th, strong winds in eastern Scotland resulted in fallen trees, power cuts, and restrictions on road bridges. Rail services on the East Coast mainline and roads and properties in NE England were further affected by flooding. By the 26th, there were concerns about the rising levels of rivers across northern England, such as the River Ouse at York, and also across north Wales. Around 600 homes and businesses were reported to have been flooded across England and Wales since the 23rd.
Satellite on 24th September 2012, the main day of the event.
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