The mid August stormy period of 2004

A wrap around occlusion with associated heavy rain swirled around a low pressure centred over Northern Ireland during the day and left those to the south of it, in England and Wales, in a showery regime. The heavy rain associated with the occlusion barely moved throughout the day causing flooding across the south of Shetland and the NE of Scotland with a total of 75mm recorded at Lerwick in the 24 hours to 12Z on the 19th. The storms also left over 25,000 homes in the NE of Scotland without power.

To the south, in England and Wales, widespread heavy showers and thunderstorms developed during the day, and during the afternoon these cells became more potent giving some torrential downpours and atrocious conditions in many areas. More flooding occurred and some of the worst areas affected were much of Northern Ireland (including Londonderry from the previous evening), North and West Cornwall (from the morning) and much of Central Scotland.

In Central Scotland several hours of torrential rainfall caused several landslides in Stirlingshire. The RAF and emergency services were called out to rescue trapped motorists on the A85 after thousands of tons of debris were swept down the hillside and onto the main road, dragging a mechanical digger down with them. You can see the news story from the BBC on the day just here :http://news.bbc.co.uk/2/hi/uk_news/scotland/3578566.stm

During the evening a small secondary low pressure area developed SW of Brest, with an estimated central pressure of 984mb at 18Z; the tightly wrapped isobars around its southern flank produced, at times, severe gales across Northern France which eased up through the Channel Islands, and then across exposed southern coastal regions. Bands of heavy showers swung NE into Brest whilst others developed over Cherbourg and Normandy, these later moving NE into the SE of England. By 19Z on the 18th pressure falls over Brittany were large, down 7.2mbs in 3 hrs at Ushant at 20Z and down 3.1mbs from the previous hour as the winds picked up rapidly too. Slightly further south at the Pointe Du Raz (an exposed coastguard station in Western Brittany) the winds increased still further, the wind gusting as high as 60 knots. An hour later at 20Z the wind became even more extreme, a mean wind of 54 knots was recorded along with a gust to 68 knots (78mph). Even inland the wind become strong with gusts to the mid 40 knot level. At 21Z, the station of La Tulet (an island off the south coast of Brittany) saw a gust to 62 knts, however there were no significant pressure falls to report in the region prior to the wind increasing - it seems that the small tight circulation did not move near enough to cause a fall in the pressure, however it was falling rapidly 60miles to the NW and so a large pressure gradient became established across this region.

The low tracked east during the night. At 23Z the pressure tendency at Ushant lighthouse had risen as much as 11.4mbs in 3 hours. A huge gradient  existed between the Channel Islands to the east and Quessant to the west. The low continued its track east, with the large pressure rises continuing to its rear. The strongest winds seem have been located just to the SE of the main low, Boulogne gusting to 54 knts at 06Z and 07Z. However, the very highest gust recorded appears to have been in the Dover Straits with Sandettie Light vessel reporting 74 knots (85mph) at 05Z. An hour later the mean wind was 49 knots -or storm force 10. Storm force 10 warnings were hastily issued for the corresponding sea areas (Dover and Thames) as the low tracked east.

The low continued to fill through the morning, whilst maintaining a tight centre. The lowest pressure at the Sandettie Light Vessel was 995.4mbs. Had the low tracked slightly further to the north, over the SE of England with such winds and gradients, then the story might have been a very different one- and deemed rather more newsworthy! The low quickly filled as it moved ENE to eventually lie in the Thames estuary with central pressure 993mb by 06Z. A yachtsman was rescued in the Channel Isles and the cross channel ferries were disrupted but generally any damage was limited due to its sea passage.