The rainfall from storm Dennis started in some places in the southwest of England as early as 06 UTC this morning so it’s surprising to see that the amber warning only comes into force at 12 UTC today. As you can see from the weather radar estimates for the 18-12 period it’s been particularly wet in Galway Ireland, the west of Scotland and southwest England already, with accumulations of over 32 mm and in Galway exceeding 50 mm. The Met Office obviously think that it will get even wetter after 12 UTC.
They have cleverly toned down their amber warnings for heavy rain in this mornings updates by splitting out a separate warning for south Wales and the valleys, and reducing the highest expected accumulations from 120-140 mm to 100-120 mm, and in the remaining amber alert areas for England and Wales reducing it from 120-140 mm down to 50-80 mm. Because the state of their warnings board is so confused by multiple layered warnings, it’s not at all easy to see what’s what. It’s still a fair amount of rain, and they have generated a lot of media attention with all their shenanigans this week, and maybe if they had given themselves that extra six hours at the start of the amber warnings they might have achieved those higher totals.