Status:Ongoing analysis Material from: Linus
1. Impact
During the first week of January northern Europe was hit by extreme cold, with temperatures reaching below 40C. Two stations in Sweden even had a 3-day mean temperature below -40C (Nikkaloukta and Kvikkjokk), which has only happened two times before in the observation history (https://www.smhi.se/bloggar/vaderleken-2-3336/stora-temperaturkontraster-tre-i-rad-och-vinter-i-hela-sverige-1.203412). Kvikkjokk set a new record for the station with -43.6C, with the previous record being from 1918.
One can note that due to the strong surface inversion nearby stations in the mountains had very different temperature, with difference between Nikkaloukta and Tarfala (11 km apart) being almost 35 degrees.
During this period southern Sweden and Denmark had a severe snow storm (202401 - Snowfall - Southern Sweden) and several parts of western Europe (e.g UK) was hit by flooding.
2. Description of the event
The plots below show analyses of T850 and z500 from 31 December to 6 January.
The plot below shows the 2-metre temperature anomaly from ERA5 for 3 to 5 January.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show analysis of 3-day temperature 3-5 January forecasts from 30 December from IFS (ENS control), AIFS, PanguWeather and Graphcast. The box outlines a region between Vidsel and Alvsbyn.
3.3 ENS
The plots below show EFI for 3-day temperature 3-5 January.
3.4 Monthly forecasts
The plots below show forecasts of weekly temperature anomalies for 1-7 January.
The plots below show forecasts of weekly z500 anomalies for 1-7 January.
The plots below show forecasts of weekly total precipitation anomalies for 1-7 January.
3.5 Comparison with other centres
4. Experience from general performance/other cases
5. Good and bad aspects of the forecasts for the event