2nd SRNWP Workshop on Short Range EPS 78 April 2005, Bologna

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2nd SRNWP Workshop on Short Range EPS7-8 April
2005, Bologna

• Aula Prodi
• Piazza San Giovanni in Monte

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Severe weather on the synoptic scale

• Examples
• December 1999 storms (France, Switzerland, South
  of Germany)
• August 2002 (Western Germany, Czech Republic,
  Austria)

• Emphasis towards this aim has improved
• the EPS technique should improve the forecast of
  severe weather.
• Example Always mentioned in connection with
• LEPS and Short-range LEPS (SLEPS)
• NORLAMEPS

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Severe weather convective flash floods
Only possible with models of 1-2 km
resolution The Boscastle floods in Cornwall
(England) which happened the 16th of August 2004
was produced by exceptionally heavy localised
rain (152.2mm in 4.5 hours at one
location). This event has been simulated with 3
different resolutions at the UK Meteorological
Office by the mesoscale version of the Unified
Model.
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Severe weather convective flash floods
But we progress towards the km-scale faster than
foreseen 2 years ago in Madrid We shall attain
the necessary resolution for an operational EPS
presumably not before 10 years
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Specific models for severe weather EPS?

• For example by using very active models,
• i.e. tuned for producing strong gradients?
• The answer is still No (fortunately!)

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Stochastic Physics

• Today an important EPS technique, equally
  justified for LAM and global models
• Main argument for its introduction were the
  errors caused by imperfect parameterizations.
• Equally important today, stochastic physics
  should account for the errors caused by finite
  resolution

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Problem of the finite resolution
ECMWF model Large domain (T95) 1.5 x 1.5
small domain (T799) 0.15 x 0.15
L. Hermanson and B. Hoskins (2004)
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Singular vectors

• In Madrid (2002)
• Todays singular vectors are computed only for a
  dry atmosphere. This should be changed by
  computing the singular vectors of an integrated
  system consisting of the moist atmosphere and the
  soil model
• We were too optimistic!

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Weather forecasts in probabilistic form how to
approach the users?

• Still a very important point.
• Are today probabilistic forecasts better accepted
  by the forecasters than 2½ years ago?
• And by the media?
• I have the feeling that it is not the case.

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FIRST WORLD CONFERENCE ON BROADCAST
METEOROLOGY 3-5 June 2004, Barcelona (Spain)
Steven Tracton, NOAA Ensemble Systems in
Forecasting and the Communication of Uncertainty
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Between October 2002 and April 2005 (1)

• EPS for severe weather on the synoptic scale
  progress follows the improvement in NWP
• EPS for local severe weather not yet possible,
  but pace to its realisation faster than foreseen
• EPS tuned for severe weather no longer mentioned
• Stochastic physics its importance has increased

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Between October 2002 and April 2005 (2)

• Singular vectors (operational) not yet
  comprehensive for a soil-atmosphere system
• Multi-model ensembles have gained in importance
  (SRNWP-PEPS, INM, UKMO-PEPS)
• EPS and end-users
• Forecasters method now known, but not much
  used
• Media (man in the street) no change
• General importance of the EPS technique in the
  NWS has increased

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I wish you a very interesting, fruitful and
friendly workshop