Hurricane Humberto was a moderately powerful hurricane that briefly affected Bermuda in September 2001. It was the eighth named storm of the season, as well as the fourth hurricane. It formed on September 21 between Puerto Rico and Bermuda, partially related to previous Hurricane Gabrielle. Humberto passed about 140 miles (225 km) west of Bermuda, which spared the island with its strongest winds. After weakening and believed to be on the verge of dissipating, Humberto unexpectedly restrengthened to the southeast of Atlantic Canada. The intensification was short-lived and the storm dissipated on September 27. There were a series of significant observational flights into the hurricane that produced a wealth of data on the structure of hurricanes.