...
The plots below show EFI for 3-day temperature 3-5 January. All forecast from 28 December and onwards captured the general structure of the cold event.
The plot below shows the forecast evolution for the 3-day (3-5 January) 2-metre temperature in the 1x1 degree box in northern Sweden between Vidsel and Alvsbyn. The evolution plot includes:
Analysis - green dot
Mean of observations - green hourglass
Medium-range ensemble blue box-and-whisker
ENS control - red dot
IFS DestinE 4.4km - purple dot
AIFS (1 degree) - pink
Graphcast - grey
PangyWeather - cyan
Model climate based on medium-range (cyan) based reforecasts with 1800 fields. Climate maximum as triangle (to be added).
The ensemble gained the signal of the extreme from 25 December to 27 December. The machine-learning models (especially PanguWeather) struggled with the magnitude of the extreme in the medium-range. All forecasts were warmer than the mean of the observations (based on the stations in Alvsbyn and Vidsel).
The plot below shows the forecast evolution for the 3-day (3-5 January) 2-metre temperature in the 1x1 degree box in northern Sweden between Vidsel and Alvsbyn, going back 30 days before the event. The evolution plot includes:
Analysis - green dot
Mean of observations - green hourglass
Extended-range ensemble purple box-and-whisker
The plot below shows the same as above but for a 1x1 degree box in Estonia.
3.4 Monthly forecasts
The plots below show forecasts of weekly temperature anomalies for 1-7 January.
...
5. Good and bad aspects of the forecasts for the event
...
- Early signal for cold over northern Sweden in the extended-range. Might connect to cold autumn and start of the winter
- The stronger signal appeared between 25 to 27 December
- Machine-learning models struggled with this case
- Destine 4.4km somewhat warmer than 9 km version of IFS