Concentric eyewall cycle
From AMS Glossary
concentric eyewall cycle
When a tropical cyclone exhibits concentric eyewalls, the outer eyewall often contracts and replaces the inner one.
A cycle typically takes about one day to complete and is accompanied by significant fluctuations in central surface pressure and maximum wind speed, with maximum winds exceeding 50 m s-1 (96 knots). The cycle may repeat indefinitely.