Hurricane Helene (1958)

Hurricane Helene was the most intense tropical cyclone of the 1958 Atlantic hurricane season. 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 and a minimum barometric pressure of . The intense hurricane came within 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 , 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 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 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 .

Moving on a west-northwest track at roughly 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 intensified 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 and a central minimum pressure of . 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 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 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 . Moving slowly towards The Carolinas, the hurricane rapidly intensified. A recon flight reported a minimum pressure of , a drop of 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 . However, Helene's lowest barometric pressure of was recorded earlier during the day. Still moving northwestward due to the influence of the Azores High, the hurricane came within 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 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.

Preparations

Upon the storm's formation, the Weather Bureau cautioned ships in Helene's path of the impending conditions, and did so throughout the storm's duration. As the storm moved west on September 23, advisories specified for small craft in northern islands of The Bahamas to remain in "protected places." After Helene was forecast to remain north of the archipelago, notifications were lifted except for small craft along the coast of the South Atlantic States. Nearing the US East Coast, the Weather Bureau began to issue special bulletins for press radio and television stations early on September 24. At the same time, small craft were warned of the storm from The Carolinas southward. The following day, the weather forecast office (WFO) in Charleston, South Carolina began to issue local statements regarding the hurricane, while small craft alerts were shifted northward to coastal regions between Cape Hatteras, North Carolina and Daytona Beach, Florida. The first hurricane watch was issued on 1000 UTC on September 26 for the entirety of the Georgian coast to Charleston, South Carolina. A gale warning was posted at the same time for coastal areas from Daytona Beach, Florida to Wilmington, North Carolina. Small craft alerts continued to shift northwards along with Helene.

As the storm began to quickly intensify on September 26, areas of the watch from Savannah, Georgia to Cape Fear, North Carolina were upgraded to a hurricane emergency area at 1600 UTC. Affected communities were advised to begin precautionary measures immediately and evacuate. Shipping and small craft were told to exercise "extreme caution." Gale warnings were changed to warn areas between Fernandina, Florida to Cape Hatteras, North Carolina. The heightened warnings caused WFOs to issue local bulletins regarding the impending hurricane. At the time, the Weather Bureau projected Helene to make landfall in South Carolina. These landfall forecasts shifted further north along the coast over time, before they were stopped after Helene recurved away from the coast entirely. At 0400 UTC on September 27, hurricane warnings were extended to include areas between Cape Fear and Cape Hatteras, North Carolina. Gale warning issuance reflected the changes and were too shifted northwards to the Virginia Capes area, while hurricane watches covered both warning areas. At 1600 UTC later that day, hurricane emergency and gale warnings were extended north to Manteo, North Carolina, while hurricane watches were continued for coastal regions from Savannah, Georgia to Myrtle Beach, South Carolina. After Helene began recurving away from the coast, all warnings south of Wilmington, North Carolina were discontinued at 2200 UTC on September 27. As Helene passed certain areas, warnings were discontinued upon the storm's passage. At 1000 UTC the next day, all onshore hurricane warnings were either downgraded to gale warnings or discontinued. However, offshore gale warnings were still issued for oceanic regions from the Virginia Capes to Cape Cod, Massachusetts. Shortly after, all warnings, with the exception of the offshore gale warnings, were discontinued. Remaining warnings lasted until 2200 UTC on September 28. Despite not issuing any warnings, the Weather Bureau cautioned interests in Newfoundland, and forecasted hurricane-force winds to effect the island.

Due to the potential impacts from Helene, the Weather Bureau began to advise prompt emergency evacuation in their advisories. Areas between Beaufort, South Carolina and Cape Fear, North Carolina were urged to begin evacuation procedures immediately. The Southeastern American Red Cross sent ten field staff warnings to locations in Georgia and South Carolina in order to assist in setting up emergency shelters. The Red Cross held 27 hurricane preparation conferences to plan preparation procedures. Other civil defense organizations also mobilized hurricane preparation staff and equipment. The Weather Bureau sent a mobile weather station to Charleston, South Carolina in order to monitor weather conditions and alert surrounding populations with short-range radio equipment. Beaches on North Carolina's coast, including Wrightsville Beach and Carolina Beach, were completely evacuated during the night of September 27. In Wilmington, North Carolina, 100 members of the United States National Guard