revisiting the synoptic-scale predictability of severe european winter storms using ecmwf ensemble reforecasts
;F. Pantillon;P. Knippertz;U. Corsmeier
anziam journal2017Vol. 17pp. 1795-1810
201
pantillon2017naturalrevisiting
Abstract
New insights into the synoptic-scale predictability of 25 severe European
winter storms of the 1995–2015 period are obtained using the homogeneous
ensemble reforecast dataset from the European Centre for Medium-Range Weather
Forecasts. The predictability of the storms is assessed with different
metrics including (a) the track and intensity to investigate the storms'
dynamics and (b) the Storm Severity Index to estimate the impact of the
associated wind gusts. The storms are well predicted by the whole ensemble up
to 2–4 days ahead. At longer lead times, the number of members predicting
the observed storms decreases and the ensemble average is not clearly defined
for the track and intensity. The Extreme Forecast Index and Shift of Tails
are therefore computed from the deviation of the ensemble from the model
climate. Based on these indices, the model has some skill in forecasting the
area covered by extreme wind gusts up to 10 days, which indicates a clear
potential for early warnings. However, large variability is found between the
individual storms. The poor predictability of outliers appears related to
their physical characteristics such as explosive intensification or small
size. Longer datasets with more cases would be needed to further substantiate
these points.