The inner core of convection collapsed while over southeast Mexico, and upon moving northward and reaching the Gulf of Mexico again, it was a large but weak tropical storm. Conditions favored significant strengthening, but Isidore did not redevelop central convection until reaching the northern Gulf of Mexico. The strengthening system hit Grand Isle, Louisiana on September 26 with maximum sustained winds of , but weakened quickly into a tropical depression after moving inland. The system raced to the northeast, and became an extratropical cyclone on September 27 before becoming absorbed in a frontal zone over Pennsylvania that night.