Hurricane Humberto (2019)

Hurricane Humberto was a large and powerful tropical cyclone that caused extensive wind damage in Bermuda during September 2019. It was the eighth named storm, third hurricane, and second major hurricane – Category 3 or higher on the Saffir–Simpson scale – of the 2019 Atlantic hurricane season. Humberto formed on September 13 from the prolonged interaction of a tropical wave and an upper-level trough, then paralleled the eastern coastline of Florida through September 16 before turning sharply northeastward. A generally favorable environment allowed Humberto to become a hurricane that day, and the storm further strengthened to reach peak intensity as a Category 3 hurricane on September 18. After its center passed within 65 miles (100 km) of Bermuda around 00:00 UTC on September 19, the system encountered stronger wind shear and drier air. Stripped of its deep thunderstorm activity, the system transitioned to a potent extratropical cyclone early on September 20.

Forming on the heels of Hurricane Dorian two weeks prior, Humberto proved far less destructive throughout the Bahamas, producing only some squally weather. The eastern coastline of Florida saw tropical storm-force wind gusts, choppy seas, and light rainfall. Rip currents caused one death in Florida and another in North Carolina. In Bermuda, coastal flooding and rainfall were limited by low astronomical tides and Humberto's quick forward motion. However, peak surface winds of around 110 mph (177 km/h), with higher gusts, caused widespread damage to trees, roofs, crops, and power lines, most notably on the western end of the island chain. Some 90% of Bermuda's banana crop was lost. As many as 600 buildings suffered roof damage, while 27,900 customers were left without power; though most of the network was quickly repaired, some electric outages persisted for at least 10 days. L.F. Wade International Airport and the Bermuda Weather Service campus both suffered property damage. In total, the hurricane wrought over $25 million in damage throughout Bermuda. Hurricane Jerry to the south briefly posed a threat to the territory as cleanup from Humberto got underway, but it ultimately dissipated with no ill-effects.

Meteorological history

The origins of Hurricane Humberto trace back to a tropical wave that exited the western coast of Africa on August 27, 2019. Accompanied by little convective activity, the disturbance moved westward across the Atlantic for several days. On September 4, the wave encountered a mid- to upper-level trough of low pressure several hundred miles east of the Lesser Antilles. Resistance from the trough split the wave in two; the southern portion proceeded through the Windward Islands, while the northern portion of the wave moved toward the northwest in tandem with the trough. As the trough became negatively tilted, or oriented northwest-to-southeast, strengthening anticyclonic flow on its east side promoted periods of enhanced convection close to the tropical wave. These convective bursts, largely driven by diurnal cycles, led to the development of a broad surface low on the morning of September 12 as the disturbance turned north-northwest through the Turks and Caicos Islands. At 21:00 UTC, the National Hurricane Center (NHC) upgraded the disturbance to a potential tropical cyclone, given that it posed a threat to land but its circulation did not yet meet the organization necessary to designate a tropical cyclone. This facilitated the issuance of tropical storm warnings in the Bahamas. Observations from ships and nearby islands early on September 13 indicated that the low-level center had become better defined, and satellite imagery depicted the formation of a narrow curved spiral band in the disturbance's northeastern quadrant. Based on this evidence, the NHC estimated that a tropical depression formed around 18:00 UTC on September 13, approximately 85 miles (140 km) east of Eleuthera in the Bahamas. It intensified into Tropical Storm Humberto six hours later.

The newly formed storm slowly turned northwestward as it tracked toward a weakness in the Azores High. Dry air and wind shear imparted by the trough that contributed to Humberto's genesis now inhibited organization, and the tropical storm more closely resembled a subtropical cyclone rather than a fully tropical one during September 14. As the day progressed, reconnaissance missions found a more aligned storm center, an indication that upper-level winds were beginning to relent. Banding features flourished, upper-level outflow expanded, and a formative inner core became apparent. By 00:00 UTC on September 16, Humberto intensified into the season's third hurricane as it temporarily stalled about 175 miles (280 km) east-northeast of Cape Canaveral, Florida. From that point, a broad upper-level trough over the East Coast of the United States steered the cyclone sharply toward the northeast. While moving over sea surface temperatures of around 84° F (29° C), Humberto intensified during the next day. The hurricane developed a large eye, 35–40 miles (55–65 km) in diameter, surrounded by very cold cloud tops, a hallmark of intense thunderstorm activity. Data from a reconnaissance aircraft mission on the evening of September 17 was used as the basis for upgrading Humberto to a Category 3 hurricane around 00:00 UTC on September 18. This upgrade was applied despite a broad and asymmetric wind field that was most expansive in the southern semicircle.

As Humberto passed about 65 miles (100 km) northwest of Bermuda around 00:00 UTC on September 19, it reached maximum sustained winds of 125 mph (205 km/h). Some satellite intensity estimates supported Category 4 status, and a dropsonde in the southern eyewall measured winds aloft of 159 mph (256 km/h), in addition to surface winds of 131 mph (211 km/h). However, these values were recorded at two-second intervals and, consequently, were not representative of sustained winds. Additionally, weather radar imagery from Bermuda indicated a quickly eroding eyewall. Therefore, the strongest winds were likely the result of extratropical processes producing a wind maximum akin to a sting jet, which would not be indicative of Humberto's true strength as a tropical cyclone. As Humberto accelerated ahead of the encroaching upper-level trough to its west, it encountered even stronger upper-level winds and drier air that together triggered a weakening trend. By 00:00 UTC on September 20, the system had become devoid of organized deep convection, marking its transition to an extratropical cyclone while located 575 miles (925 km) south-southwest of Cape Race, Newfoundland. The post-tropical cyclone continued to produce a large area of gale

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