NEW ORLEANS (AP) — If a remnant of Hurricane Isaac becomes a tropical system in the Gulf of Mexico — which forecasters say could happen — it would be a rare event.

In 2005, a remnant from a tropical depression that dissipated near Puerto Rico became part of a new depression, which evolved into Hurricane Katrina.

National Hurricane Center forecaster Todd Kimberlain said Katrina was the only modern example he could find of a system’s partial remains regenerating and getting a different tropical designation.

If the Gulf system becomes a tropical storm, it probably would be named Nadine. At midday Thursday, forecasters gave it a 40 percent chance of developing. An approaching cold front could influence its future.

The Gulf Coast is cleaning up after Isaac made landfall the night of Aug. 28-29.