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Finalized Material from: Tim , Linus, Lisa Bengtsson (SMHI), Mike Bush (UKMO)

Discussed in the following Daily reports:

http://intra.ecmwf.int/daily/d/dreport/2014/09/01/sc/




1. Impact

 

Excerpt

Significant flooding, due to a relatively short-lived burst of convective activity, affected both Copenhagen and Malmo in the morning of 31 August. Many roads were closed and buildings were flooded.

 

2. Description of the event

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The plots above show 12-hour accumulation for forecasts from 31 August 00UTC from CF (left), HRES (middle) and 2.8 km AROME (right), provided by SMHI. While the both ECMWF forecast missed the event over Malmo-Copenhagen, AROME had intensive rainfall in the region. 

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The plot above shows the accumulated precipitation (12-hour) from the MetOffice Euro4 model (4 km resolution) from 31 August 00z provided by Mike Bush, UKMO. The black cross indicates Copenhagen.  The forecast has a maximum of more than 100 mm over Mamlo and another maximum north-west of Copenhagen with a maximum of 80 mm.


3.3 ENS

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titleEFI for total precipitation 31 August
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The plots above shows EFI for rainfall valid for 31 August. The first plot is from 28 31 August 00UTC and the following from 29, 30 and 31 August. 3 days before (top left) there was by 12 hours apart backwards in time. Already the forecast from 27 August 00UTC a hint of heavy rain, whilst . The signal got stronger for later forecasts and the 2 and 1 day before forecasts had a notable EFI and SOT (>1) signal. The 'day 0' forecast (first panel) backtracked a little, though is of no relevance for forecasting given issue time.

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Below we compare different ensembles retrieved from the TIGGE archive.

Probability maps

Probability for .20 mm/12 hours for the 31 August 00-12UTC

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titleECMWF

ECMWF (32 km)

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titleDMI-HIRLAM

DMI-HIRLAM (5.5 km)

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titleCOSMO-LEPS

COMSOCOSMO-LEPS (10 km)

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titleCOSMO-DE-EPS

COSMO-DE-EPS (2.8 km)

 

Stamp maps

For all ensemble, a maximum of 20 members are plotted. These plots should be compared to the 12-hour accumulation shown above.

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ECMWF (32 km)

NCEP (55 km)

DMI-HIRLAM -DMI (11 5.5 km?)

COSMO-LEPS (10 km)

COSMO-DE-EPS (2.8 km)

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  • Increased EFI values from 3 days before the event.
  • Clearly underestimated values in the global models.
  • Extreme rainfall predicted by ~3 km limited area models (both AROME, COSMO and COSMO4km  UKMO model)
  • A good example of the value of limited area models.

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