Original estimates recorded that Katrina had made this landfall as a Category 4 hurricane, with 135 mph (220 km/h) winds; however, as mentioned above, the storm weakened just before landfall to Category 3 intensity. The reasons for this weakening are not completely understood yet; while the eye-wall replacement cycle played a part, slightly increasing shear, dropping sea surface temperatures, dry air on the western semicircle of the storm and interaction with the continental landmass also may have played a role in weakening the cyclone. This follows the trend of previous strong cyclones in the Gulf of Mexico: all cyclones with minimum central pressures of 973 mbar (28.73 inHg) or less have weakened over the 12 hours before making landfall in the Gulf Coast of the United States.