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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 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 • Resolution of strong convection • Some problems of false alert • Gust and thunderstorm • Heavy rainfall
05 utc 14 utc 14.45 utc Sea breeze: example in the gulf of Valencia
Precipitation feature: example of a narrow band of cold front
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
Orography and rainfall: example of storm Dirk 1. synoptic background
2. Continuous rain over Britanny during 18 hours with intensity about 3-4 mm/h
Orogrophic wave and foehn storm: example of storm Xynthia 27th February 2010 (synoptic background)
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
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
Strong convection When deep convection is prevailing, AROME is able to produce forecast that differ from its global model ARPEGE
Pmer and Wet Bulb Température 850 hPa A stormy front moves to the SE of France
18 3 hours rainfall from 03 to 18Z
Strong convection example 2 :heavy rains and strong convection on the SW France 25/7/14 24 hours rainfall forecast by ARPEGE
Gusts under thunderstorms Formula is ok most of the time But what happen under strong convection?
Thunderstorm and gusts, example1 18/7/14 Strong convective structure (bow echo) forecast between 18/19UTC
Gust and wind forecast by AROME between 18/19 UTC Gust= max during previous hour Wind=at the time step
Observation: strong convection OK but smaller structures than forecast
Last run before the event! Example 2 case 28/6/2014 Forecast of gusts by three successive runs of AROME
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
At 14 UTC, more than 60 mm in 3 hours forecast, 5 mm observed
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