Status:Ongoing analysis Material from: Linus
1. Impact
In 23-24 November windstorm Bert hit Ireland and Great Britain, with extreme rainfall and strong winds. The rainfall caused floodings in South Wales (https://www.bbc.co.uk/news/articles/cgj7qvj097po) and around Northampton.
2. Description of the event
The evaluation of the rainfall will focus on 48-hour rainfall on 23 November 00UTC - 25 November 00UTC for a 0.25x0.25 degree box over South Wales (centred on 51.8N, 3.3W).
For the wind speed will focus on 24-hour mean 10-metre wind speed on 23 November 12UTC - 24 November 12UTC for a 0.125x0.125 degree box centred on Heathrow (centred on 51.5N, 0.5W).
The plots below show analyses of MSLP and 6 hour rainfall from 21 November 00UTC to 25 November 00UTC, every 12th hour.
The plots below show analyses of T850 and z500 from 20 November to 25 November.
The table below list the maximum observations between 0400 on 23 November to around 1200 on 24 November.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show 48-hour precipitation in observations (first plot), concatenated short forecasts (second plot). Note that no observations were available from inside the box over South Wales.
The plots below show 48-hour precipitation in ENS control forecasts with different lead times.
The plots below show 48-hour precipitation in DestinE 4.4km with different lead times.
The plots below show 48-hour precipitation in AIFS with different lead times.
The plots below show 48-hour precipitation in AIFS-ENS member 1 with different lead times.
3.3 ENS
The plots below shows EFI for 3-day precipitation valid 23-25 November (as we do not have 2-day EFI). The forecast from 17-18 November had the atmospheric river feature shifted somewhat to the south.
The plots below show the same as above but for integrated water vapour flux.
The plot below shows the forecast evolution plot for 48-hour precipitation for the box over South Wales.
Analysis - green dot
ENS control–red
ENS - blue box-and-whisker
AIFS - cyan dot
Desint4.4km - evergreen dot
AIFS-ENS - grey box-and-whisker
Model climate – cyan box-and-whisker
Ensemble mean as black diamonds. Triangle marks the maximum in the model climate based on 600 forecasts.
The plot below shows the forecast evolution plot for 24-hour mean wind for London-Heathrow.
Observation - green hourglass
Analysis - green dot
ENS control–red
ENS - blue box-and-whisker
AIFS-ENS - grey box-and-whisker
Model climate – cyan box-and-whisker
Ensemble mean as black diamonds. Triangle marks the maximum in the model climate based on 600 forecasts.
The plot below shows the 10-metre wind speed in forecast from 23 November 00UTC for ENS-CF (red), ENS-PF (blue) and observations from Heathrow and Northolt (black).
3.4 Monthly forecasts
3.5 Comparison with other centres
4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event