Scotland suffered from the worst storm, the Barbet storm this year on the 20th and 21st of October with Red, Amber and Yellow warnings being issued over the two days.
I again monitored the rainfall in my area of the North of Scotland during the Babet storm. Although there was high winds on the 20th October, there was only limited rainfall. By the 21 October my area of the North of Scotland was included in an Amber warning for heavy rain issued by the Met Office.
The rainfall started at 3:50 am on the morning of the 21st October 2023. It continued until 11:23 pm the same day, approximately 20 hours. During this time there was a total of 41.2mm of rain. The maximum intensity over the 20 hours as 5.2mm/hour and an average intensity of 2.06mm/hour.
Annual Exceedance Probability
Based on the data above it suggests that the storm event that occurred between the 21st October had an Annual Exceedance Probability (AEP) of 3.33% This means that there is only a 3.33% chance of a rainfall event being exceeded annually.
Another way of explaining this is a 1 in 30 year rainfall event, although this does not suggest that this event will not occur for another 30 years.
There was a similar 1 in 30 year rainfall event earlier this month on the 6th – 8th of October. See my previous blog page.
For further reading, more information about flood estimation is available from the website below: