Gustav developed from Sub-Tropical Depression Eight northeast of
The Bahamas. It was classified as a Sub-Tropical Storm until the morning of
September 10, 2002, when it acquired tropical characteristics and was re-classified
as a Tropical Storm. On September 11, it became a hurricane.
A sub-tropical cyclone is a low pressure system that is
a hybrid between a tropical cyclone and a mid-latitude
extratropical cyclone. While it has regions of deep convection like a
tropical cyclone, it generally exhibits the milder horizontal temperature
gradients of a mid-latitude cut-off low (once it has developed). These storms have the
potential to become tropical storms by concentrating the strongest winds close to the
center and developing a warm core. See NHC Glossary
for more information.