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Operationnal use of high resolution model AROME

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

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Operationnal use of high resolution model AROME

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

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

  5. 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

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

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

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

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

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

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

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

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

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

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

  16. RR03 forecast by AROME from 03 to 18 UTC

  17. 18 3 hours rainfall from 03 to 18Z

  18. comparison

  19. Mesoscale structure: bow echo

  20. Mesoscale structure: bow echo

  21. Mesoscale structure: bow echo (zoom)

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

  23. 24 hours rainfall forecast by AROME

  24. 24 hours rainfall by radar

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

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

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

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

  29. Observed gusts

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

  31. 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

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

  33. 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

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