Status:Ongoing analysis Material from: Linus, Esti
1. Impact
Storm Darragh, which struck the UK and Ireland on December 7–8, 2024, brought severe weather conditions, including wind gusts of up to 93 mph (150 km/h) and heavy rainfall. The storm caused widespread damage, leaving hundreds of thousands without power and tragically resulting in two fatalities due to fallen trees in Lancashire and Birmingham. Coastal regions, particularly in Wales and southwestern England, experienced significant structural damage, with roofs torn off buildings and major disruptions to travel due to blocked roads and suspended train services. In Wales, communities like Builth Wells faced flooding, and approximately 21 flood warnings were issued. The Met Office issued a red weather warning for wind, indicating a high risk to life and property. The storm's heavy rainfall led to localized flooding, particularly in western regions, with some areas recording over 80 mm (3.1 inches) of rain. On Saturday, December 7, 2024, there were three red weather warnings in place in total across Europe: one for wind in Wales, another for wind in Croatia, and a third for snow in northern Spain. In addition, orange and yellow warnings were widespread across the continent.
2. Description of the event
The evaluation will focus on 24-hour maximum wind gusts on 7 December for a point (51.7N, 4.4W) near Pembrey in South Wales.
The plots below show analyses of MSLP and 6 hour rainfall from 5 December 00UTC to 9 December 00UTC, every 12th hour.
The plots below show analyses of T850 and z500 from 5 to 9 December.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show 24-hour maximum wind gusts in observations (first plot), concatenated short forecasts (second plot). Note that different countries was different reporting standards for wind gusts.
The plots below show 24-hour maximum wind gusts in ENS control forecasts with different lead times.
The plots below show 24-hour maximum wind gusts in DestinE 4.4km with different lead times.
3.3 ENS
The plots below show EFI and for 24-hour maximum wind gusts on 7 December.
The plot below shows the forecast evolution plot for 24-hour maximum wind gusts over Pembrey in South Wales.
Observation - green hourglass
Analysis - green dot
ENS control–red
ENS - blue box-and-whisker
Desint4.4km - evergreen dot
Model climate – cyan box-and-whisker
Ensemble mean as black diamonds. Triangle marks the maximum in the model climate based on 600 forecasts.
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
- Drop in signal around 3 December 12UTC due to a prediction of a more southerly track of the cyclone.