Debby formed from the southern part of a tropical wave that became Tropical Storm Chris. In the mid-tropical Atlantic, the northern area of convection detached and became Tropical Depression Seven. The southern portion continued moving westward as a disorganized area of showers. The system did not develop until the low-level center emerged from the Yucatán into the Bay of Campeche on August 31. It is estimated that the storm became Tropical Depression Eight just offshore at around 12 p.m. local time.