After intensification slowed for a few hours , another round of rapid intensification occurred and Gustav was upgraded to a Category 4 hurricane during a hurricane hunter flight around 1 p.m. EDT ( 1700 UTC ) , with 145 mph ( 215 km\/h ) winds .
After strengthening slowed for a few hours , another round of quick strengthening happened and Gustav was upgraded to a Category 4 hurricane during a hurricane hunter flight around 1pm ( EDT ) , with 145 mph winds .