Invest 91L developed in the Caribbean this week, first as a tropical disturbance and the National Hurricane Center is tracking it over Mexico.

The colors make it visibly clear how likely a system could develop, with yellow being low, orange medium, and red high. The National Hurricane Center generally doesn't issue tropical advisories until there is a named storm, but there is an exception.

The National Hurricane Center (NHC) is closely monitoring a disturbance in the western Caribbean Sea that could develop as it moves into the southern Gulf of Mexico over the coming days. Forecasters currently give the system a 20 percent chance of tropical development.