28/29 Mar 2021 – Rainfall on Scafell Pike

Rainfall accumulations from weather radar

The heaviest of the orographic rain that fell yesterday was concentrated over the Cumbian fells once again. Despite this the Met Office had no warning in place for heavy rain either here or for Snowdonia. I’m sure they’ll argue that the impacts of flooding from the event weren’t severe enough to warrant one. A total 88.4 mm of rain was reported from Shap, and 69.6 mm from Capel Curig, in the 24 hours ending at 06 UTC this morning. Western Scotland, which is covered by a yellow warning, did get a drenching with over a 125 mm on the highest hills, but it was even wetter across the Lake District with extremes close to 200 mm in a little over 24 hours if my estimates are anything to go by. Here’s the pseudo hyetograph for the highest mountain in England as an example, and don’t forget it had been raining here since 18 UTC on Saturday evening.

Estimates from weather radar

4 thoughts on “28/29 Mar 2021 – Rainfall on Scafell Pike”

  1. Warnings issued as a part of a multi-agency analysis. I’m going to assume at this point that the EA ran their models and decided that the Cumbrian catchments were able to cope with 200 mm, and SEPA did the same and assessed that the river response in Scotland would be potentially impactful – hence a warning. Has that part of Scotland had above average rainfall in the days leading up to this event? Warnings these days are not threshold-based, so issue will depend on input from a number of sources.

    1. I can’t deny that I am critical of the UKMO and their impact based warnings system. But I only flag up a warning when I think they get it wrong, especially when they can clearly see it’s going wrong and don’t do anything about putting it right, as was the case with the heavy rain in the NW of England on Sunday. They don’t do that of course because that would draw attention to themselves – when did you last hear the Met Office apologising? I have delusions of grandeur and imagine myself, for the purposes of xmetman blog, as a kind of AC-12 to find out what went wrong and find the bent copper. The UKMO can always hide behind the “impacts” of an event as their get out of jail card when it appear that they may have got it wrong, and that’s why they should stick to a threshold based system, and leave the impacts to the experts at the EA or SEPA to quantify.
      Latest SEPA & EA Flood status

      1. “and leave the impacts to the experts at the EA or SEPA to quantify”. But that is exactly what happens – MO has the weather models, SEPA/EA the river catchment models. Joint conference where SEPA/EA assess impacts of MO-supplied rain forecast. Warning issued or not issued based on this.

        1. I can’t see what the problem is here.
          The UKMO have a super-computer which churns out hourly mesoscale (1 km?) forecasts of rainfall intensity from the NWP models for the next x number of hours.
          They run this model every six hours (or even more frequently) and pass this product they have created directly to the EA and SEPA.
          The EA and SEPA plug this data into their river catchment model which then generates the various flood alerts and warnings to disseminate nationally.
          There is no need for ‘experts’ to intervene and decide whether their respective models are right, because if these models are in any way accurate, they have already decided about the risk of flooding at any particular location in real time.
          When a river level reaches a certain level it will break its banks and flood the surrounding land, that land could be a water meadow in a flood plain, or it could contain roads and houses in a steep sided valley.
          They know the level at which this will start to occur, so there is little need to ‘assess the impacts’ it should be automatic.
          How severe the flooding event will be is totally dependent on the river level itself and not by any impact assigned to it by SEPA or the EA after consultations with the UKMO.
          I can always see a need for enhancements and improvements to these models in the future, but joint conferences and cosy chats on the phone between the two organisations should be totally unnecessary.
          We have been deluding ourselves for too many years using terms such as ‘forecaster’, because everyone knows forecasts are spit out by NWP models run on supercomputers, and when the lights go out so do the forecasts.
          It’s about time the government merged both organisations into one and reaped the cost savings from the duplication and bureaucracy that would bring.

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