Issac becomes a hurricane
Live Updates: Hurricane Isaac, Heading Toward Louisiana(AccuWeather)
Isaac has crossed the threshold at 12:20 p.m. EDT Tuesday, becoming a hurricane, while rolling toward the southern coast of Louisiana.
An eye has formed with thunderstorms wrapping around the center of Isaac by noon Tuesday. During Monday afternoon and evening, dry air worked its way into Isaac, cutting off its flow of deep moisture, which put a halt to the thunderstorm activity on the north side of the storm.
Dry air entrainment has been an issue with Isaac even as it entered the Caribbean.