EPS based probabilistic forecasts and verification at Finnish Meteorological Institute (FMI)

EPS based probabilistic forecasts and verification at Finnish Meteorological Institute (FMI)

Janne Kauhanen Juha Kilpinen

Matias Brockman

Finnish Meteorological Institute

[email protected]@fmi.fi

[email protected]

mailto:[email protected]



Outline• Introduction

• About RAVAKE-project

• Some verification results

20.04.23ECAM 2011 Kauhanen-Kilpinen-Brockman


Introduction

The example of spesific treshold of wind (11m/s) in local SmartMet workstation at FMI.

EPS forecasts been used widely at FMI since mid 1990’ies. However, the data has been mostly used as guidance information. Now FMI is moving towards more direct and operational use of probabilistic information also for customer products and warnings. Computations of the probabilities of accumulated precipitation forecasts (and also many other parameters) of ECMWF EPS system are performed at FMI to allow the determination of user specific thresholds.


Introduction (continues)

A probabilistic rainfall warning system is under development at FMI (with an interactive user-interface).

The aim is to produce a solid probabilistic rainfall forecast from +15 min to +5 days combining all available data sources (radar observations and extrapolations, deterministic NWP output with post-processing (PEPS, etc.) and ECWMF EPS)

The main focus is to offer the end-users an interface where they can modify the products for their own needs.

Verification of this data has also started and at first ECMWF EPS data is considered. Some results are shown here.

24h and 12 hours probability forecasts for rain over 10 mm in 6 hours and observed precipitation measured by radar network.

20.04.23Juha Kilpinen RAVAKE-projekti 5

RAVAKE – project plan

Lead time

ECMWF deterministic /EPS/GFS?

PEPS/NEIGHBOURHOOD METHODGLAMEPS

HIRLAM/RCR/MBEHIRLAM/RCR/MBE

AROMEAROME

RADAR EXTRAPOLATION


Convective rain in Pori

August 2007:~120 mm in 3 hoursdamage 15-20 M€



An example of heavy precipitation causing flooding in Helsinki Area was some weeks ago. Two convective cells hit Helsinki Metropolitan area causing a flash flood with substantial harm to property and traffic. The measured maximum precipitation was 50-70 mm in about 90 minutes.

The NWP models did not capture the cells well. Only high resolution Harmonie (2.5 km) was able forecast the phenomenon reasonably well. The case was also difficult to observe by the radar due to the strong attenuation.

Helsinki 22.8.2011

Verification of ECMWF EPS precipitation forecasts

• Two data sets:

• Years 2007-2010: 12h and 24h accumulative precipitation forecasts for about 130 stations.

• Year 2010: 6 hourly accumulative precipitation up to +66h4 stations (02981, 02974, 02935, 02836)



Examples of the present verification products


ROC and Brier Score

Annual results for daily (24h) probability of precipitation (>= 10 mm) and group rain gage precipitation stations with 00 UTC analysis hours and using arrival time as lead time basis

Results: 6 hourly accumulative precipitation


ROC AREA

ROC curves


RR>1.0mm

RR>0.1mm

RR>5.0mm

RR>0.5mm

Results: 6 hourly accumulative precipitation


Brier Score


Conclusions

Due to small data sample and the coarse resolution of ECMWF EPS (compared to the scale of a typical convective system) the verification of heavy precipitation did not give very promising results. But for early warning use in longer time ranges ECMWF EPS provides a good data to start.

For time ranges between extrapolated radar data and ECMWF EPS the up-scaled AROME and PEPS products offers an interesting challenge for near future.

Originally calibration of EPS was on the work list but it had to be postponed to some later project.

The combination/merging of different data sources on daily and hourly basis is enough challenging.

Thank You for your attention !


Documents

EPS based probabilistic forecasts and verification at Finnish Meteorological Institute (FMI)