The low mountains of western Cuba disrupted Hurricane Gustav's low-level circulation.
Although it crosses the island in only a few hours, the brief interaction caused the storm's eye to partially cloud-over and its wind speeds fell to 140 mph (230 km/h) as it entered that southeastern Gulf of Mexico that night.
Through that night and into the morning of August 31 it continued moving northwestward across the Gulf, its winds weakening to 125 mph (201 km/h) as the damage from its interaction with Cuba continued to take its toll.
That morning the eye, which was expanding as the storm weakened, completely clouded over.
Some mid- to upper-level dry air was drawn into the cyclone and a trough to the south added a slight vertical shear, but these interferences were short lived.
Under the continued influence of the ridge over the western Atlantic and southeastern United States Hurricane Gustav accelerated into the central gulf.
Here the storm tracked over a warm eddy in the loop current, but the high oceanic heat content failed to induce strengthening.
Deep convection continued to be asymmetric and the eyewall opened to the southeast as wind speed continued to fall into Category 2 status.
However by the afternoon of August 31 the hurricane's ragged appearance began to improve.
The eye returned properly and its minimum central pressure fell even as its outer bands came ashore on the northern Gulf Coast.
Its asymmetric appearance improved and its wind radius expanded, but by that night Gustav had moved off the eddy of the loop current and over slightly cooler water.
It could not restrengthen here, despite its more impressive presentation.

In the pre-dawn hours of September 1, while 170 mi (270 km) from the Gulf Coast, the hurricane's wind field expanded and tropical storm force winds extended 220 mi (350 km) from its center.
Dry air intrusion from the south broke up the hurricane's eye, completely dissolving the eyewall as heavy rain bands came ashore in the state of Louisiana.
As the eye approached the Louisiana coast, the storm weakened to 105 mph.
Making landfall near Cocodrie, Louisiana at 1430 UTC the eye briefly reformed but was not associated with any strengthening.
The low mountains of western Cuba disrupted Hurricane Gustav's low-level circulation. Although it crosses the island in only a few hours, the brief interaction caused the storm's eye to partially cloud-over and its wind speeds fell to 140 mph (230 km/h) as it entered that southeastern Gulf of Mexico that night. Through that night and into the morning of August 31 it continued moving northwestward across the Gulf, its winds weakening to 125 mph (201 km/h) as the damage from its interaction with Cuba continued to take its toll. That morning the eye, which was expanding as the storm weakened, completely clouded over. Some mid- to upper-level dry air was drawn into the cyclone and a trough to the south added a slight vertical shear, but these interferences were short lived. Under the continued influence of the ridge over the western Atlantic and southeastern United States Hurricane Gustav accelerated into the central gulf. Here the storm tracked over a warm eddy in the loop current, but the high oceanic heat content failed to induce strengthening. Deep convection continued to be asymmetric and the eyewall opened to the southeast as wind speed continued to fall into Category 2 status. However by the afternoon of August 31 the hurricane's ragged appearance began to improve. The eye returned properly and its minimum central pressure fell even as its outer bands came ashore on the northern Gulf Coast. Its asymmetric appearance improved and its wind radius expanded, but by that night Gustav had moved off the eddy of the loop current and over slightly cooler water. It could not restrengthen here, despite its more impressive presentation.
In the pre-dawn hours of September 1, while 170 mi (270 km) from the Gulf Coast, the hurricane's wind field expanded and tropical storm force winds extended 220 mi (350 km) from its center. Dry air intrusion from the south broke up the hurricane's eye, completely dissolving the eyewall as heavy rain bands came ashore in the state of Louisiana. As the eye approached the Louisiana coast, the storm weakened to 105 mph. Making landfall near Cocodrie, Louisiana at 1430 UTC the eye briefly reformed but was not associated with any strengthening.
Meteorological history of Hurricane Gustav