Status: Ongoing analysis Material from: Linus
1. Impact
On 12-14 January western-central Norway and parts of the Swedish mountains were hit by heavy precipitation. In the mild air it fell as rain in my places. The event was caused by a strong atmospheric river hitting the mountain range.
2. Description of the event
The plots below show analyses of MSLP and 6-hour forecasts of precipitation from 11 January 00UTC to 15 January 00UTC, every 12 hour.
The plots below show analyses of z500 (contour) and T850 (shade) from 9 January 00UTC to 15 January 00UTC, every 24 hour.
3. Predictability
3.1 Data assimilation
3.2 HRES
The plots below show observations from SYNOP (first plot) and HRES forecasts of 72-hour precipitation valid 12 January 00UTC - 15 January 00UTC, from different initial dates. The black box marks a region south of Trondheim, Norway.
3.3 ENS
The plots below show EFI for 3-day precipitation 12-14 January, from different initial times.
The plots below show the same as above but for integrated water-vapor flux as a measure for atmospheric river features.
The plot below shows the forecast evolution plot for 72-hour precipitation valid 12-14 January centered south of Trondheim, Norway (0.5x0.5 degree box). Mean of observations - green, HRES –red, ENS CF – purple, ENS blue box-and-whisker, Model climate – red box-and-whisker. Triangle marks the maximum in the model climate based on 1200 forecasts, The black square marks the ensemble/climate median and diamond ensemble/climate mean. The ensemble started to pick up the event more than 10 days before the end of the accumulation period.
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
- Very good signal in early medium-range. Probably due to the connection to an atmospheric river