Antonio Jesus Robles Fernández, Universidad Complutense de Madrid, Facultad de Ciencias Fisicas, Madrid, Spain, Belen Rodriguez-Fonseca, Complutense University of Madrid, Facultad de Fisicas, Madrid, Spain, Teresa Losada, Universidad Complutense de Madrid, Facultad de CC Física, Madrid, SPAIN, Antje Weisheimer, University of Oxford, Department of Physics, National Centre for Atmospheric Science (NCAS), Oxford, United Kingdom and Magdalena Balmaseda, European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom