F. Grazzini, Forecast Products Users Meeting June 2005 SEVERE WEATHER FORECASTS F. Grazzini, F. Lalaurette

F. Grazzini, Forecast Products Users Meeting June EFI definition and properties - Definition of extreme weather in the observations - EFI Verifications results - A case study - Two new products for severe weather forecasting OUTLINE

F. Grazzini, Forecast Products Users Meeting June 2005 It is a normalised distance of an ensemble forecast from a climate distribution 0=forecast distribution identical to the climate one 1= forecast distribution is a perfect outlier EFI definition

F. Grazzini, Forecast Products Users Meeting June 2005 EFI: a measure of anomaly and spread Solid lines/current formulation, dashed lines pre 2003 formulation

F. Grazzini, Forecast Products Users Meeting June 2005 EFI verification: the need of a local climatology Climate Atlas of Europe (Météo-France) The atlas contains monthly normals of temperature, precipitation, wind and sunshine duration for ~ 700 selected European stations. In addition statistical information for these parameters and for the occurrence of phenomena such as fog, thunderstorm, hail and snow are reported. The computation period is More information at

F. Grazzini, Forecast Products Users Meeting June 2005 Extreme event if 24h TP > Tsh Tsh=max(20,RRQ4/5) RRQ4 = Upper quintile of monthly precipitation (per station, per month) Using GTS synop 2622 extreme events were found during the period October 2003 – May 2005 Extreme event definition

F. Grazzini, Forecast Products Users Meeting June 2005 Extreme precipitation thresholds

F. Grazzini, Forecast Products Users Meeting June 2005 Frequency of extreme daily precipitation TP > Tsh

F. Grazzini, Forecast Products Users Meeting June 2005 EFI verification: total events, 2622 extreme events False Alarm Ratio POFD=F/(Z+F) FAR=F/(H+F) FC / OBSYESNO YESHF NOMZ

F. Grazzini, Forecast Products Users Meeting June 2005 False Alarm Ratio Verification of prob of TP > 20 mm/24h

F. Grazzini, Forecast Products Users Meeting June 2005

Frequency of EFI > 0.6 Medium-Range

F. Grazzini, Forecast Products Users Meeting June 2005 Frequency of EFI > 0.45 Medium-Range

F. Grazzini, Forecast Products Users Meeting June 2005 Frequency of EFI > 0.6 Short-Range

F. Grazzini, Forecast Products Users Meeting June 2005 A case study: heavy precip between UTC – UTC D+5

F. Grazzini, Forecast Products Users Meeting June 2005 A case study D+4

F. Grazzini, Forecast Products Users Meeting June 2005 A case study D+3

F. Grazzini, Forecast Products Users Meeting June 2005 A case study D+2

F. Grazzini, Forecast Products Users Meeting June New global EFI multi-parameter map for anomalous weather - A simultaneous (synoptic) view of the flow pattern and associated weather parameters can provide a better understanding of possible scenarios. - EFI provides a concise and selective information about deviation of the forecast from the climate

F. Grazzini, Forecast Products Users Meeting June 2005 Global EFI Map

F. Grazzini, Forecast Products Users Meeting June 2005 Global EFI Map D+5

F. Grazzini, Forecast Products Users Meeting June 2005 Global EFI Map D+4

F. Grazzini, Forecast Products Users Meeting June 2005 Global EFI Map D+3

F. Grazzini, Forecast Products Users Meeting June 2005 Global EFI Map D+2

F. Grazzini, Forecast Products Users Meeting June 2005 Global EFI Map

F. Grazzini, Forecast Products Users Meeting June 2005 Freak wave prediction -It is important to detect possible deviation from linear theory of wave interaction (Gaussian distribution of surface elevation) -In particular condition nonlinear interaction of waves became stronger (focussing). The distribution of surface elevation may deviate from the Normal with increase in probability of anomalous waves (compared to the median) -Additional wave parameters characterizing extreme events have been introduced in to the system in October 2003: BFI and the wave spectra kurtosis

F. Grazzini, Forecast Products Users Meeting June 2005 Freak wave prediction: kurtosis analysis

F. Grazzini, Forecast Products Users Meeting June 2005 Freak wave prediction: kurtosis analysis

F. Grazzini, Forecast Products Users Meeting June 2005 Freak wave prediction: kurtosis forecast T+36

F. Grazzini, Forecast Products Users Meeting June 2005 A step forward towards an EFI validation against observations Verification could provide useful guidance for calibration EFI verification for daily precipitation : mixed feelings, however it seem to provide better results than probabilities. Global multi-parameter EFI maps may be useful to provide a synoptic view of weather anomalies to users Progress in wind induced ocean freak waves Summary