1. Operationnal use of high resolution model AROME image source: Sander Tijm, KNMI

2. Abstract  Advantages of AROME versus global model ARPEGE  Examples of mesoscale structures: see breeze, precipitation features, fog and low clouds, etc…  Orography: precipitations and winds  Resolution of strong convection  Some problems of false alert  Gust and thunderstorm  Heavy rainfall

3. Sea breeze: example in the gulf of Valencia 05 utc 14 utc 14.45 utc

4. Precipitation feature: example of a narrow band of cold front

6. Fog and low clouds Thanks to its high density levels close to the surface and its microphysics, AROME forecast of fog/low clouds is often better than ARPEGE

7. Orography and rainfall: example of storm Dirk 1. synoptic background

8. 2. Continuous rain over Britanny during 18 hours with intensity about 3-4 mm/h

9. 3. Comparison between models ECMWF/ARP/AROME

10. Orogrophic wave and foehn storm: example of storm Xynthia 27 th February 2010 (synoptic background)

11. AROME 2.5km ALADIN ZOOM Vent 10m (km/h) 21H Max=129km/h Pic du Midi = 124km/h Source C.Lac et all CNRM Meteo France Max=104km/h Max=110 km/h=Pic du Midi 10m wind (km/h) 21H Relief Strong winds downstream of relief

12. Gust 10m (km/h) 21H AROME 2.5km OBS Max=209km/h Max=213km/h Pic du Midi=195km/h Source C.Lac et all CNRM Meteo France

13. Strong convection When deep convection is prevailing, AROME is able to produce forecast that differ from its global model ARPEGE

14. Example 1: ZT 500 hPa from 18 th July to 21 th July 2014

15. Pmer and Wet Bulb Température 850 hPa A stormy front moves to the SE of France

16. RR03 forecast by ARPEGE from 03 to 18 UTC on 20 th

17. RR03 forecast by AROME from 03 to 18 UTC

18. 18 3 hours rainfall from 03 to 18Z

19. comparison

20. Mesoscale structure: bow echo

22. Mesoscale structure: bow echo (zoom)

23. Strong convection example 2 :heavy rains and strong convection on the SW France 25/7/14 24 hours rainfall forecast by ARPEGE

24. 24 hours rainfall forecast by AROME

25. 24 hours rainfall by radar

26. Gusts under thunderstorms Formula is ok most of the time But what happen under strong convection?

27. Thunderstorm and gusts, example1 18/7/14 Strong convective structure (bow echo) forecast between 18/19UTC

28. Gust and wind forecast by AROME between 18/19 UTC Gust= max during previous hour Wind=at the time step

29. Observation: strong convection OK but smaller structures than forecast

30. Observed gusts

31. Example 2 case 28/6/2014 Forecast of gusts by three successive runs of AROME Last run before the event!

32. False alert of heavy rainfall At 12 utc, more than 40 mm in 3 hours forecast, 3.4 mm observed Example of 28/7/14 on the Pyrénéees

33. At 14 UTC, more than 60 mm in 3 hours forecast, 5 mm observed

34. Conclusion  Positive balance sheet of AROME use by forecasters (previous synoptic study still required!)  Wishes  Extending the forecast period to 48 hours  More realistic convection (could be achieved with lower resolution?)  Next challenge for forecasters: work with the ensemble forecast AROME