Complex sentence: In contrast, if the index is low (NAO -), westerlies are suppressed, the aforementioned areas register cold winters and storms track southerly toward the Mediterranean Sea, bringing much above normal storm activity and rainfall to southern Europe and North Africa.
Split into simpler sentences: In contrast, if the index is low (NAO -), westerlies are suppressed, these areas suffer cold winters and storms track southerly toward the Mediterranean Sea. This brings increased storm activity and rainfall to southern Europe and North Africa.