This animation layer shows precipitation accumulations forecasted for the upcoming five days. For the first few hours of the forecast, the timestep is 1 hour, thereafter the timestep is 6 hours.
These precipitation accumulations have been obtained by seamless blending of the:
- 20-members ensemble of 1-h accumulation generated with the algorithm for probabilistic nowcasting by extrapolation of radar observations SBMcast (Berenguer et al., 2011) applied to the gauge-adjusted OPERA radar composites over Europe (2 km, 15 minutes; Park et al. 2019)
- 51-members ensemble of 1-h accumulation forecasts obtained by Numerical Weather Prediction (NWP) with the ECMWF Ensemble Prediction System (EPS)
The blending technique (Wong et al. 2009) is applied for the first 6 hours, and applies a phase shift and bias correction to blend radar nowcasts into NWP using a hyperbolic tangent weighting function. For lead times beyond 6 hours, the product relies only on the NWP forecasts.
The displayed accumulations correspond to the forecasts obtained with the control member, and are of the 80th percentile of rainfall.
Figure 1. 80th percentile of the hourly blended precipitation ensemble forecast at 15:00 UTC on 2022-09-05
References
Berenguer, M., Sempere-Torres, D. and Pegram, G, 2011: SBMcast - An ensemble nowcasting technique to assess the uncertainty in rainfall forecasts by Langrangian extrapolation. Journal of Hydrology, 404(3), 226-240
Park, S., Berenguer, M. and Sempere-Torres, D, 2019: Long-term analysis of gauge-adjusted radar rainfall accumulations at European Scale. Journal of Hydrology, 573, 768-777
Wong, W., Yeung, L., Wang, Y. and Chen, M, 2009: Towards the Blending of NWP with Nowcast - Operation Experience in B08FDP. WMO Symposium on Nowcasting, 30 Aug- 4 Sep, Whistler, Canada.