Boscastle – Weather (rain) hazard August 18 th 2004

What was the Weather Like? It was summer but it really poured down!

But if you are asked about a weather hazard you must say a rainstorm (a flood is not a weather event) We are reducing our case studies by using Boscastle as a weather hazard and also as a flood hazard …

On the run-up to the flood some 200 millimetres (mm) of rain fell in 24 hours.

Most of this fell in a 5 hour period on Monday, August 16th with peak intensities of over 300 mm per hour (5 mm per minute). However the storm was very localised and four of the nearest 10 rain gauges - all within a few miles of Boscastle - showed less than 3 mm.

Studies of extreme rainfall patterns have concluded that freak floods are more likely to occur in June, July and August than at any other month of the year. They are Convectional Thunderstorms. This is when atmospheric conditions, such as a warm ground surface, typically found during summer, lead to the uplift of air masses which subsequently cool, producing cloud and rainfall formations.

Bands of showers aligned themselves with winds that had converged along the coastal high ground around Boscastle, creating Cumulonimbus clouds 12192m (40,000ft) high and kept them stationary for many hours

At midday, on the 16th August 2004, heavy, thundery showers had developed across the South West, these were the remnants of Hurricane Alex which had crossed the Atlantic. August 04, 2004 Look Out Kirsty! It looks like Hurricane Alex is heading towards the UK. I know by then it won't technically be a hurricane, but you guys still might get some rain from it.

How were people affected? Short Term (hours, days) Medium Term (weeks, months) Long Term (months, years)

Immediate concern save lives – 100 airlifted to safety from rooftops. No accoimmodation.

The clear up – loss of tourist income – hardship and stress. Insurance claims but good for builders

Back to normality It was a freak one in 200 year rain event No special protection measures