Former chief forecaster reflects on the 'unique' hailstorm of 2008
- Credit: Alex Walton
In collaboration with Nick Grahame ex-Chief Forecaster at the Met Office
How many times before, when talking about Ottery St Mary, have we used the word “unique”? This time it brings us back to the memories of certainly a “unique” meteorological event that took place in Ottery in 2008 and is well known as the Great Ottery Hailstorm. We have been asked many times about this strange phenomenon, even mentioned at the House of Commons in 2008, mainly by newcomers eager to know the truth behind it. We were very fortunate to know that Nick Grahame, an Ottery resident and ex-Chief Forecaster working at the Met Office at that time, was holding the key that would allow us to provide everybody with a fully-backed and professional version of why this happened. We thank Nick for his valuable collaboration. This is what we learned:
“The impending drama began to unfold just before midnight on Wednesday, October 29 with the first clap of thunder and some heavier rain developing,” said Nick. “However, this was just a portent of things to come with the rain becoming very intense soon after midnight and then the hail came down, which just went on and on for around two hours. The sheer volume of water accumulating in the town and cascading down the surrounding slopes of the Otter Valley led to rapidly swollen watercourses, flash flooding and intense erosion of supporting roadside banks. Meanwhile, the large amounts of hail blocked watercourses and draining ditches and exacerbated the problems. The River Otter soon burst its banks, with Ottery and nearby villages being particularly affected. As a consequence of floodwaters rising to around 4-5ft in places, emergency services received a vast number of calls from residents concerned about their homes and loss of livestock. By 5am on Thursday, October 30, Ottery was cut off and more than 100 people had to be evacuated, with some residents airlifted to safely by coastguard helicopter.
“The hailstones themselves were of generally low density and roughly pea-sized, and this allowed them to be transported ‘en-masse’ by the intense run-off of rainwater and swollen streams and dumped at the lowest points in the town. The ‘freak’ element of the event is very much related to reports of ice floes through parts of Ottery during the early hours of that Thursday. Once dawn broke, there was also the visual impact of 3-4ft banks of hail; misreported by the descending media as snowdrifts, perhaps understandably.
“Some meteorological facts – on the night of 29/30 October 2008, the forecast charts showed a weather front becoming slow-moving as it reached East Devon. There were reasons as to why thunder clouds could develop along the front but the exceptional nature of what followed was due to a combination of local effects, such as the alignment of hill ridges on either side of the Otter Valley and a funnelling of moist air from the English Channel to maintain the ‘fuel’ to keep the storm going. Rainfall totals in the period of midnight to 3am were truly exceptional with the King’s School rain-gauge recording 160mm, the highest since records began there in 1961. The epicentre of the storm itself, based on Met Office radar data, was located around Toadpit Lane and subsequent analysis of this data concluded that 177mm of rain actually fell there (more than twice the October average in just three hours!). This is an unconfirmed record for a three-hour period in the UK and has a return period of more than 200 years. Meanwhile, the localised nature was emphasised by the fact that Exeter Airport only reported 6mm of rain that night”.
There are records showing that at the Council Meeting of November of 2008, councillors expressed their concerns and others were quick to allay fears of a repeat of the events, but as Nick said: “Although the event had shocked the town and many were caught up in the mayhem, the Carnival Procession went ahead and townsfolk turned out to cheer on the floats two days later. Meanwhile, the funfair relocated to the Canaan Way car park and the famous bonfire was lit, as usual, on Tar Barrels night.
“Looking back, 13 years last October, it is remarkable that no-one died as floodwaters rose dramatically through the early hours of Thursday, October 30, 2008, and once again that was thanks to our emergency services, responsible agencies and people helping others”.
Giving us another example of that “unique” Ottregian community spirit.