Long ribbon of damp damaging air

When disasters happen we look for an explanation. This week's extreme rainfall in the north-west of the UK will be no exception. Honister, in Cumbria, had a record-breaking 341mm of rainfall within 24 hours, breaking the previous record of 316mm set at nearby Seathwaite in November 2009. More than 5,200 properties have been affected by the recent flooding, and insurers estimate a bill of as much as 250m to clean up the mess.

Just like November 2009, Cumbria this season has been affected by an "atmospheric river", a narrow ribbon of very moist air, stretching back over thousands of kilometres. About 10 potentially damaging atmospheric rivers pummel the UK each winter, but this one was particularly strong.