Hurricane Humberto (2001)

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 mi 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.

Meteorological history
Hurricane Humberto originated from a trough that extended southwestward from Hurricane Gabrielle, which had previously moved across Florida into the western Atlantic Ocean. The trough interacted with an upper-level low, resulting in an increase of convection, or thunderstorms, in the region. A surface low developed on September 19, and it gradually organized as it moved westward. After deep convection developed over the center, it is estimated the system reached tropical depression strength (39 mph) on September 21, about halfway between Puerto Rico and Bermuda. The National Hurricane Center (NHC) first published an advisory on the storm at 11 AM EDT, identifying it as Tropical Depression Ten. Upon its formation, the depression moved northwestward toward a break in the mid-level ridge. On satellite imagery, the depression looked well-organized, with banding features, outflow, and convection, although Hurricane Hunters had difficulty locating a closed center of circulation. The unfavorable conditions were from the upper-level low to its southwest, which was producing wind shear over the storm; nevertheless, the NHC anticipated strengthening.

On September 22, the surface circulation rapidly became better organized, and based on confirmation from the Hurricane Hunters, the NHC upgraded the depression to Tropical Storm Humberto. Throughout its life, the storm was smaller than average, and as it moved around the subtropical ridge, it gradually intensified. Tropical Storm Humberto developed an eye feature on September 23. Shortly thereafter, the storm reached hurricane status about 175 mi west-southwest of Bermuda. After passing about 140 mi west of Bermuda, Hurricane Humberto turned more to the northeast, and reached Category 2 status on the Saffir–Simpson scale. Subsequently, strong upper-level westerlies began affecting the storm, which caused a marked decrease in intensity; by September 25, the winds decreased to 75 mph, or minimal hurricane status. At that time, the NHC expected Humberto to continue weakening due to the shear, as well as steadily decreasing water temperatures.

Unexpectedly, the weakening trend stopped, as the steering winds came from the same direction behind the hurricane. It slowed down slightly, and on September 26 the eye of the hurricane became much more distinct. Humberto quickly re-intensified and reached peak winds of 105 mph, while located about 200 mi south-southeast of Sable Island, off the coast of Nova Scotia. Just as quickly it strengthened, the hurricane began weakening again. The eye became distorted as the convection became asymmetrical, due to the cooler waters and stronger westerlies. Initially, the NHC forecast Humberto to become extratropical. On September 27, it turned more eastward and later to the east-southeast, and Humberto weakening to tropical storm status about 400 mi southeast of Newfoundland. The cloud pattern became increasingly elongated and removed from the center, and late on the 27th, the circulation of Humberto degenerated into an open trough in the far northern Atlantic Ocean. The remnants were expected to be absorbed quickly by a larger extratropical storm to its north.

There were three major aircraft flights into the hurricane over a three-day period which, according to NASA, "were the most comprehensive measurements of the structure of the hurricane ever recorded." The flights were designed to obtain data for better hurricane forecasting.

Impact
Prior to its passage by Bermuda, the National Hurricane Center advised the residents "should monitor the progress of Humberto until it is safely past." On September 23 when the hurricane passed the island, the hurricane-force winds extended 30 mi from the center, while tropical storm force winds only extended 105 mi from the center. As a result, Bermuda only experienced peak sustained winds of 27 mph, with gusts to 43 mph. During its passage, the island also recorded 1.69 in of rainfall.

Only two ships recorded tropical storm-force winds, both of which were away from the center. Some higher surf was recorded along the New Jersey coastline. In September 2001, two men sought to break the record for sailing the quickest time from New York City to Melbourne, Australia; Humberto disrupted their early path slightly, but they ultimately broke the record by 28 hours. Later in its path, there were several marine warnings issued for offshore Newfoundland, although no severe weather affected coastal Atlantic Canada. Overall, there were no reports of casualties or damage from the hurricane.