The eyewall collapsed somewhat , and Helene weakened into a Category 2 hurricane , where it levelled off for about 48 hours until September 20 because of a lengthy eyewall replacement cycle and a stretched out cloud pattern . The eyewall collapsed somewhat , and Helene weakened slightly to a Category 2 hurricane , where it leveled off for about 48 hours until September 20 due to a lengthy eyewall replacement cycle and an elongated cloud pattern .