Operationnal use of high resolution model AROME image source: Sander Tijm, KNMI.
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Transcript of Operationnal use of high resolution model AROME image source: Sander Tijm, KNMI.
Operationnal use of high resolution Operationnal use of high resolution model AROMEmodel AROME
image source: Sander Tijm, KNMI
AbstractAbstract
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
Sea breeze: example in the gulf of ValenciaSea breeze: example in the gulf of Valencia
05 utc14 utc14.45 utc
Precipitation feature: example of a narrow band of cold front
Fog and low cloudsFog 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
3. Comparison between models ECMWF/ARP/AROME
Orogrophic wave and foehn storm: example of storm Xynthia 27th February 2010 (synoptic background)
AROME 2.5km
ALADIN
ZOOMVent 10m
(km/h)21H
Max=129km/hPic 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
Gust 10m (km/h) 21H AROME 2.5km
OBS
Max=209km/hMax=213km/hPic du Midi=195km/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
Example 1: ZT 500 hPa from 18th July to 21th July 2014
Pmer and Wet Bulb Température 850 hPa
A stormy front moves to the SE of France
RR03 forecast by ARPEGE from 03 to 18 UTC on 20th
RR03 forecast by AROME from 03 to 18 UTC
1818
3 hours
rainfall from 03 to 18Z
comparison
Mesoscale structure: bow echo
Mesoscale structure: bow echo
Mesoscale structure: bow echo (zoom)
Strong convection example 2 :heavy rains and strong convection on the SW France 25/7/14
24 hours rainfall forecast by ARPEGE
24 hours rainfall forecast by AROME
24 hours rainfall by radar
Gusts under thunderstormsGusts under thunderstorms
5.34110
ou
TKEURafales erNiveaum
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
Observed gusts
Example 2 case 28/6/2014
Forecast of gusts by three successive runs of AROME
Last run before the event!
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
ConclusionConclusion
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