Calum Baugh Christel Prudhomme Marc Berenguer WaiKin Wong calumbaughecmwfint Aim To translate rainfall nowcasts WP 2 into probabilistic flash flood hazard nowcasts Existing Methods ID: 780582
Download The PPT/PDF document "Work Package 3: Transforming Rainfall N..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Work Package 3: Transforming Rainfall Nowcasts into Flash Flood Hazard Products
Calum Baugh, Christel Prudhomme, Marc Berenguer, Wai-Kin Wong
calum.baugh@ecmwf.int
Slide2Aim:
To translate rainfall nowcasts (WP 2) into (probabilistic) flash flood hazard nowcastsExisting Methods:
2
European Centre for Medium-Range Weather Forecasts
ERICHA:
WP 3.1 & 3.4 Transformation of Blended Nowcasts into FF Hazard Predictions
Limitations:
Deterministic only
Short lead time (4 hours)
Real world thresholds difficult to exceed when using radar accumulations
Slide3Aim:
To translate rainfall nowcasts (WP 2) into (probabilistic) flash flood hazard nowcastsExisting Methods:
3
European Centre for Medium-Range Weather Forecasts
EPIC:
(pre-cursor to current ERIC method on EFAS)
WP 3.1 & 3.4 Transformation of Blended Nowcasts into FF Hazard Predictions
COSMO-LEPS ensemble precipitation forecast
Twice daily
6-hourly time steps
5 days lead time
7 × 7 km
Maximum accumulated precipitation
Over all 3 accumulation periods
Accumulated precipitation
Grid cells with upstream area <2000 km
2
6, 12 & 24-hour accumulations
Mean annual maximum
From 19-year climatology (COSMO-LEPS reforecast)
EPIC flash flood indicators
Twice daily6-hourly time steps5 days lead time1 × 1 km
Advantages:
Probabilistic
Warnings account for NWP bias
Limitations:
No short range detail for first 4 hours
Slide4WP 3.1 & 3.4 Transformation of Blended Nowcasts into FF Hazard Predictions
Solution:
Combine ERICHA and EPIC Methodologies
Probabilistic information
Extended lead time up to 5 days (whilst preserving detail in first 4 hours)
Warnings not affected by biasInput: Blended probabilistic rainfall nowcasts (WP2)Output: Probabilistic flash flood hazard nowcasts
4
European Centre for Medium-Range Weather Forecasts
0h
6h
120h (5 days)
Blending Window
ECMWF NWP only
(1 hourly timestep)
(6 hourly timestep)
At each timestep show probability of exceeding mean annual maximum
Probabilistic product:
Slide5WP 3.3 Simplified Rapid Risk Forecasts
Currently no way of knowing which locations will have the most impactPopulation density is a key driver
Solution:
Intersect probabilistic flash flood hazard with population density
5
European Centre for Medium-Range Weather Forecasts
1km Probabilistic FF Hazard
100m Population Density
pop/km
2
1km Rapid Risk Product