The wave tracked generally westward, interacting with an upper-level low on August 15 in the western Caribbean Sea, and spawned a low-pressure area. Convective activity developed around the low, and by August 18 the system was over the Yucatán Peninsula. Later that day, the disturbance emerged into the Bay of Campeche and a Hurricane Hunter reconnaissance mission into the system revealed that it had matured into a tropical depression around 1:00 pm CDT (1800 UTC), the third of the 1999 season.[1] Initially, moderate wind shear prevented the depression from strengthening as it moved slowly and erratically in response to weak steering currents over the system.[1][2] By August 19, the wind shear relented, allowing deep convection to develop over the center; later that day, the National Hurricane Center (NHC) upgraded the system to a tropical storm, assigning it the name Bret.[1][3] A small tropical cyclone, Bret gradually strengthened for several days as it tracked towards the north.