Hurricane Ophelia (2017)

Hurricane Ophelia, known as Storm Ophelia while extratropical, was regarded as the worst storm to affect Ireland in 50 years, and was also the easternmost Atlantic major hurricane on record. The tenth and final consecutive hurricane and the sixth major hurricane of the very active 2017 Atlantic hurricane season, Ophelia had non-tropical origins from a decaying cold front on 6 October. Located within a favourable environment, the storm steadily strengthened over the next two days, drifting north and then southeastwards before becoming a hurricane on 11 October. After becoming a Category 2 hurricane and fluctuating in intensity for a day, Ophelia intensified into a major hurricane on 14 October south of the Azores, brushing the archipelago with high winds and heavy rainfall. Shortly after achieving peak intensity, Ophelia began weakening as it accelerated over progressively colder waters to its northeast towards Ireland and Great Britain. Completing an extratropical transition early on 16 October, Ophelia became the second storm of the 2017–18 European windstorm season. Early on 17 October, the cyclone crossed the North Sea and struck western Norway, with wind gusts up to 70 kilometres per hour (43 mph) in Rogaland county, before weakening during the evening of 17 October. The system then moved across Scandinavia, before dissipating over Norway on the next day.

Three deaths can be directly attributed to Ophelia, all of which occurred in Ireland. Total losses from the storm were less than initially feared, with a minimum estimate of total insured losses across Ireland and the United Kingdom of US$87.7 million.

On 3 October, a broad low-pressure area had formed along a stationary front about 740 km (460 mi) west of the Azores. The low meandered over the north Atlantic for days. On 6 October, a large wind field had formed associated with the low. The low only developed shallow, weak convection, along with a long, curved cloud band, and a cold-core center—typical characteristics of an extratropical low. The system began to acquire subtropical characteristics on the next day, benefits from warm sea surface temperature of 27 °C (81 °F), thus the National Hurricane Center (NHC) noted for a high chance of tropical cyclogenesis. Although the system lost some of its organization due to dry mid-level air, it managed to develop gale-force winds and a well-defined center. Deep convection continued to develop near the center early on 9 October, and the NHC classified the system as Tropical Storm Ophelia at 06:00 UTC, about 1,410 km (875 mi) west-southwest of the Azores.

Despite moving over marginally warm waters of 26.5 °C (79.7 °F), the effects of cold air temperatures aloft and decreasing wind shear allowed Ophelia to gradually strengthen. At the same time, Ophelia drifted several hundred miles southwest of the Azores due to the cut off from mid-latitude westerlies. In addition, the large temperature contrast between the unusually-warm ocean surface and the extremely cold temperatures in the upper atmosphere provided instability for Ophelia's thunderstorms, which allowed the storm to continue strengthening, despite marginally warm ocean temperatures. Late on 10 October, Ophelia began to move southeastwards as it embedded in a mid-to upper-level trough. A slight degradation of the structure of the storm resulted in some weakening early on 11 October, but this was short-lived as deep convection wrapped around the entire storm. After developing a ragged eye, the NHC upgraded Ophelia to a hurricane at 18:00 UTC about 1,225 km (760 mi) south of the Azores. Upon the upgrade, Ophelia becoming the record-tying tenth consecutive hurricane to form during the 2017 hurricane season; this was the fourth such occurrence after 1878, 1886, and 1893 seasons. Afterwards, Ophelia steadily intensified as it became nearly stationary, intensifying to a Category 2 hurricane late on 12 October, as the eye became better defined. Ophelia achieved its initial peak intensity at 06:00 UTC on 13 October, with maximum sustained winds of 169 km/h (105 mph) and a central pressure of 966 mbar (966 hPa; 28.5 inHg).

The hurricane accelerated to the northeast, under the influence of the large mid-latitude trough. Ophelia weakened slightly later that day. The cloud tops warmed due to moderate vertical wind shear, but wind shear decreased shortly afterwards, allowed Ophelia to strengthen once again. Its eye became better defined, and the NHC upgraded Ophelia to a Category 3 hurricane at 12:00 UTC on 14 October; at 27.7°W, this was the farthest east that a storm of such intensity had been observed in the satellite era. It attained its peak intensity simultaneously with maximum sustained winds of 185 km/h (115 mph) and a central pressure of 959 mbar (959 hPa; 28.3 inHg) while located approximately 925 km (575 mi) southwest of the Azores. Early on 15 October, increasing wind shear and cold waters of 20 °C (68 °F) caused Ophelia to gradually weaken. Embedded within a fast southwesterly flow, Ophelia raced to the north-northeast with a speed of 61 km/h (38 mph). After losing all of its deep convection and becoming attached to a warm front and a cold front, the storm became extratropical at 00:00 UTC on the next day, about 500 km (310 mi) southwest of Mizen Head. The extratropical low then made landfall in southwestern Ireland, near Valentia Island, with winds of 121 km/h (75 mph), at 11:00 UTC. Afterwards, Ophelia's extratropical remnants tracked over Ireland and made its second landfall in Soay, Inner Hebrides with winds of 97 km/h (60 mph), at 23:45 UTC. On 17 October, the extratropical low turned to the east-northeast, and tracked over the North Sea. The storm made its third and final landfall in Våge, Austevoll, with winds of 72 km/h (45 mph), at 17:30 UTC, before dissipating over Norway early on 18 October.

The Portuguese Institute of the Sea and the Atmosphere issued a red warning for heavy rainfall for the eastern group of the Azores—São Miguel, Santa Maria and Formigas—on 14 October from 17:59 UTC to 23:59 UTC. An orange gale warning was issued for the eastern group for the afternoon through night of 14–15 October, as well as a yellow alert for high seas. Rainfall alerts were also issued for the central group—Terceira, Graciosa, São Jorge Island, Pico and Faial.

The President of the Regional Service of Civil Protection of the Azores, Lieutenant-Colonel Carlos Neves, announced there was no serious damage. High winds downed four trees on São Miguel, three in the Ponta Delgada district and one in Povoação. The island also experienced some minor flooding. In the central group of the Azores, there were a few instances of light damage, with one home suffering a roof leak.

Starting on 15 October 2017, winds from Ophelia fanned wildfires in both Portugal and Spain. The wildfires have claimed the lives of at least 49 individuals, including 45 in Portugal and four in Spain, and dozens more were injured. In Portugal, more than 4,000 firefighters battled around 150 fires. The National Hurricane Center's Tropical Cyclone Report on Hurricane Ophelia makes no mention of the fires, thus the associated fatalities are not included as part of the storm total.