One of the main challenges for a skilful Limited Area Model Ensemble Prediction System (LAMEPS) is the generation of appropriate initial perturbations. In most operational LAMEPSs, the initial perturbations are provided by a global Ensemble Prediction System (EPS). Molteni et al. (2001) proposed clustering analysis as an objective selection criterion to choose a member from the global European Centre for Medium-range Weather Forecasts (ECMWF)-EPS model as initial perturbations in LAMEPS. In this article, another strategy for using the clustering method is investigated which ensures that initial perturbations are centred on the control analysis. The main purpose of this article is to study the benefit of cluster analysis and to validate the effect of different clustering strategies on the performance of a 17-member LAMEPS. The system used in this study is the operational Aire Limitée Adaptation Dynamique Développement InterNational-Limited-Area Ensemble Forecasting (ALADIN-LAEF) model.Three experiments were carried out over a 50-day period to validate different clustering strategies: i) representative members of 16 clusters from the 50-member ECMWF-EPS, where initial perturbations are not necessarily centred; ii) representative members from eight clusters and the symmetric pairs from ECMWF singular vector analysis; and iii) eight arbitrarily chosen ECMWF-EPS singular vector pairs. Results of the verified experiments show that the statistical reliability of ALADIN-LAEF improves when clustering is applied, but no clear improvement can be seen in the skill of LAMEPS. A case study of a heavy precipitation event confirms the result of the 50-day verification. The validation shows that none of the clustering strategies outperforms any other. Nous avons mené trois expériences sur une période de 50 jours pour valider différentes stratégies de groupement: i) membres représentatifs de 16 groupements d'un ECMWF-EPS de 50 membres, où les perturbations initiales ne sont pas nécessairement centrées; ii) membres représentatifs de huit groupements et les paires symétriques issues de l'analyse par vecteurs singuliers du ECMWF; et iii) huit paires issues de l'analyse par vecteurs singuliers du ECMWF-EPS choisies au hasard. Les résultats des expériences vérifiées montrent que la fiabilité statistique du ALADIN-LAEF s'améliore lorsqu'un groupement est appliqué, mais on ne perçoit aucune amélioration nette dans l'habileté du LAMEPS. Une étude de cas d'un événement de fortes précipitations confirme le résultat de la vérification de 50 jours. La validation montre qu'aucune des stratégies de groupement ne surpasse les autres.
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