2nd SRNWP Workshop on

Short Range EPS

7-8 April 2005, Bologna

Aula ProdiPiazza San Giovanni in Monte

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

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.

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”

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!)

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

L. Hermanson and B. Hoskins (2004)

ECMWF model

Large domain (T95): 1.5° x 1.5° ; small domain (T799): 0.15 ° x 0.15 °

Problem of the finite resolution

Singular vectors

In Madrid (2002):

“Today’s 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!

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.

FIRST WORLD CONFERENCE ON BROADCAST METEOROLOGY

3-5 June 2004, Barcelona (Spain)

Steven Tracton, NOAA

Ensemble Systems in Forecasting and the Communication of Uncertainty

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

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

I wish you a very interesting, fruitful and friendly workshop