On September 9, the storm rapidly intensified, and within 24 hours, Edith strengthened from a minimal hurricane to a powerful 160 mph (260 km/h) Category 5 hurricane just off the coast of Nicaragua. The cause for the explosive deepening is unknown, though it is speculated that the transformation in the upper troposphere from an upper-level low to an anticyclone led to a release of baroclinic energy. Reconnaissance aircraft crews in the peak of the storm reported extreme turbulence, causing concern for the safety of the crews. At its peak intensity, the very well-defined "pinhole" eye was only 5 miles (8 km) in diameter. Late on September 9, Hurricane Edith made landfall on northeastern Nicaragua at Cabo Gracias a Dios.