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Hurricane Helene was the most intense tropical cyclone of the 1958 Atlantic hurricane season, as measured by minimum barometric pressure. The eighth tropical storm and fourth hurricane of the year, Helene was formed from a tropical wave east of the Lesser Antilles on September 21, 1958. Moving steadily westward, the storm slowly intensified, attaining hurricane strength on September 24. As conditions became increasingly favorable for tropical cyclone development, Helene began to rapidly intensify. Nearing the United States East Coast, the hurricane quickly attained Category 4 intensity on September 26, before it subsequently reached its peak intensity with maximum sustained winds of 135 mph (215 km/h) and a minimum barometric pressure of 934 mbar (hPa; 27.84 inHg). The intense hurricane came within 10 mi (15 km) of Cape Fear, North Carolina before recurving out to sea. Accelerating northward, Helene gradually weakened, and transitioned into an extratropical cyclone as it passed over Newfoundland on September 29. Helene's extratropical remnants traversed eastwards across the Atlantic Ocean before dissipating near Great Britain on October 4. Despite not making landfall on North Carolina, its close proximity to land caused extensive damage across the US East Coast. Strong winds resulted in widespread power outages, cutting telecommunications along the coast. A weather station in Wilmington, North Carolina reported a wind gust of 135 mph (215 km/h), setting a new record for fastest wind gust reported there. Though mostly concentrated in North Carolina, rainfall was widespread, reaching as far north as Maine. In the United States, damages reached $11.2 million and there was one indirect death. After impacting the US, Helene produced strong winds and heavy rain across much of Atlantic Canada. In Cape Breton Island on Nova Scotia, the storm was considered the worst in at least 21 years. Power outages cut most communications from the island to the mainland, and property damage in Sydney, Nova Scotia totaled to C$100,000. At Helene's landfall in Newfoundland, strong gusts peaking at 82 mph (132 km/h) in Naval Station Argentia were reported, and loss of power severed communications. Damage across there totaled to at least C$100,000. Total damages associated with Helene in the United States and Canada amounted to $11.4 million, making Helene the costliest storm of the season. ==Meteorological history== The origins of Hurricane Helene can be traced back to an easterly wave that formed near Cape Verde on September 16. Moving towards the west due to trade winds associated with the Hadley cell, the disturbance gradually intensified. On September 20, ships in the system's vicinity reported widespread shower activity and generally low barometric pressures.〔 Early the following day, a reconnaissance flight reported evidence of a weak circulation,〔 with gusts of 35 mph (55 km/h) in heavy squalls surrounding the circulation center. At 0200 UTC later that day, the United States Weather Bureau office in San Juan, Puerto Rico began issuing bulletins on the system for public interests.〔 In HURDAT, the tropical wave was first classified as a tropical depression at 0600 UTC on September 21, well east of the Leeward Antilles. At the time, the depression had maximum sustained winds of 30 mph (50 km/h). Moving on a west-northwest track at roughly 20 mph (30 km/h) early on September 22, the storm initially changed little in intensity. However, a large upper tropospheric anticyclone developed over the southern Atlantic coast, producing the favorable wind shear needed for tropical cyclone development.〔 A second reconnaissance flight reported an intensifed tropical cyclone, indicating that the storm system had reached tropical storm strength.〔 At 0000 UTC on September 23, the depression attained tropical storm strength, with maximum winds of 40 mph (65 km/h) and a central minimum pressure of 1013 mbar (hPa; 29.92 inHg). The US Weather Bureau issued their first advisory on the newly developed tropical storm at 1600 UTC later that day, giving the storm the name ''Helene''. Despite the storm's poor organization, Helene gradually intensified in favorable conditions generated by the large anticyclone.〔 Throughout the day, a second anticyclone moved eastward until it was situated off of the Mid-Atlantic states, while a mean trough in the lower levels of the atmosphere became situated over the United States East Coast. This would set up a path for Helene to pass very close to the United States.〔 The tropical storm attained hurricane intensity by 2200 UTC on 2200 UTC on September 24, while located 425 mi (685 km) east of Fort Pierce, Florida.〔 However, in post-season analysis, it was found that Helene reached hurricane intensity earlier that day, by 1200 UTC. At the time, gale-force winds extended up to 220 mi (355 km) out from the storm's center of circulation.〔 The hurricane steadily strengthened as it moved towards the northwest around the western periphery of the Azores High on September 25. Encountering the anticyclone situated off of the Mid-Atlantic states, Helene began to curve slightly towards the west. The lack of strong steering currents in the storm's vicinity caused the hurricane to move very slowly throughout the day, giving the hurricane time to significantly intensify.〔 By 0000 UTC on September 26, Helene strengthened to the equivalent of a modern-day Category 2 hurricane, with a minimum pressure of 980 mbar (hPa; 28.94 inHg). Moving slowly towards The Carolinas, the hurricane rapidly intensified. A recon flight reported a minimum pressure of 948 mbar (hPa; 28.00 inHg), a drop of 40 mbar (hPa; 1.18 inHg) from the previous day.〔 As the hurricane neared the coast, its eye became apparent on coastal long-range WSR-57 weather radar images.〔 By 1800 UTC on September 26, Helene strengthened to a Category 3 hurricane and then to a Category 4 hurricane the following day. The major hurricane continued to strengthen before reaching its peak intensity on September 27 with winds of 135 mph (215 km/h). However, Helene's lowest barometric pressure of 934 mbar (hPa; 27.84 inHg) was recorded earlier during the day. Still moving northwestward due to the influence of the Azores High, the hurricane came within 10 mi (15 km) of the US East Coast before recurving towards the northeast out to sea.〔 As Helene recurved and accelerated towards more northerly latitudes, it steadily weakened. By 1200 UTC on September 28, Helene was no longer a major hurricane. The hurricane's wind field also expanded from the storm's center as it weakened.〔 By midday on September 29, Helene had weakened to minimal hurricane strength, and later transitioned into an extratropical cyclone by 1800 UTC that day, though it still maintained hurricane-force winds. At roughly the same time, Helene passed over Newfoundland, with gale force winds having expanded 500 mi (800 km) from the system's center, coinciding with the US Weather Bureau's final advisory on the system.〔 Helene's extratropical remnants continued eastward across the Atlantic, becoming a dominant synoptic feature,〔 before entirely dissipating by 0600 UTC on October 4 just west of Great Britain. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hurricane Helene (1958)」の詳細全文を読む スポンサード リンク
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