The 1975 Atlantic hurricane season was the longest season on record, spanning 342 days from the formation of a subtropical storm on January 4 to the dissipation of a subtropical storm on December 12. It also featured the first tropical storm to be upgraded to hurricane status using only satellite imagery, as well at the first major hurricane that formed from a subtropical storm. In terms of activity, the 1975 season was near average, with twelve nameable storms forming, of which seven became hurricanes. Four of those seven became major hurricanes, which are Category 3 intensity or higher on the Saffir–Simpson scale. The season officially began on June 1 and lasted until November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic Ocean.

The first system, an unnamed subtropical storm, developed on January 4. Hurricane Amy, which formed six months later, caused minor beach erosion and coastal flooding from North Carolina to New Jersey in July, and killed one person when a ship capsized offshore North Carolina. Hurricane Blanche brought strong winds to portions of Atlantic Canada, leaving about $6.2 million (1975 USD) in damage. Hurricane Caroline brought high tides and flooding to northeastern Mexico and Texas, with two drownings in the latter. In late August, Doris became the first tropical storm to be upgraded to a hurricane based solely on satellite imagery, and the first major hurricane that formed from a subtropical storm.

The most significant storm of the season was Hurricane Eloise, a Category 3 hurricane that struck the Florida Panhandle at peak intensity, after bringing severe flooding to the Caribbean. Eloise caused 80 fatalities, including 34 in Puerto Rico, 7 in Dominican Republic, 18 in Haiti, and 21 in the United States, with 4 in Florida. The hurricane left about $560 million in damage in the United States. Hurricane Gladys, a Category 4 hurricane, was the most intense tropical cyclone of the season, but left little impact on land. Two tropical depressions also caused damage and fatalities. Collectively, the tropical cyclones of this season resulted in 87 deaths and about $564.7 million in damage. __TOC__

Season summary

The Atlantic hurricane season officially began on June 1, with the first tropical cyclone developing on June 24. Although 23 tropical depressions developed, only twelve of them reached tropical storm intensity; this was near normal compared to the 1950–2000 average of 9.6 named storms. Seven of these reached hurricane status, slightly above the 1950–2000 average of 5.9. Furthermore, four storms reached major hurricane status; above the 1950–2000 average of 2.3. Collectively, the cyclones of this season caused at least 87 deaths and over $564.7 million in damage.

The Atlantic hurricane season officially ended on November 30, though the final cyclone became extratropical on December 13.

Tropical cyclogenesis began in January, with the development of a subtropical storm on January 4, followed by Hurricane Amy six months later on June 27. Four systems originated in July, including Hurricane Blanche and an unnamed tropical storm. After Tropical Depression Six dissipated on July 30, tropical activity went dormant for over three weeks, ending with the development of a tropical depression that would later become Hurricane Caroline on August 24. Another cyclone, Hurricane Doris, also formed in August. September was the most active month of the season, featuring eight tropical cyclones, including hurricanes Eloise, Faye, and Gladys. In October, four systems formed, one of which intensified into Tropical Storm Hallie. Two tropical depressions developed in November. The last system, a subtropical storm, formed on December 9 and transitioned into an extratropical cyclone on December 12.

The season's activity was reflected with an accumulated cyclone energy (ACE) rating of 76. Broadly speaking, ACE is a measure of the power of a tropical storm multiplied by the length of time it existed. Therefore, a storm with a longer duration will have high values of ACE. It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of . Accordingly, tropical depressions are not included here. After the storm has dissipated, typically after the end of the season, the National Hurricane Center (NHC) reexamines the data. These revisions can lead to a revised ACE total either upward or downward compared to the operational value.

Systems

Unnamed subtropical storm

A previously unknown subtropical storm in January of 1975 was identified during modern reanalysis and designated 24L.

Hurricane Amy

Tropical Storm Amy originated from a weak trough on June 24 accompanied by scattered showers and thunderstorms over Florida. The system tracked westward in response to an upper-tropospheric low over Georgia. By June 26, a surface circulation developed north of the Bahamas and satellite imagery showed a significant increase in convective activity and the National Hurricane Center (NHC) classified the system as a tropical depression early on June 27. On June 28, the system attained tropical storm-status while tracking north-northeast off the coast of North Carolina. By June 29, a trough, moving through the westerlies, rapidly approached the storm, causing the newly designated Amy to turn sharply toward the east. Strong wind shear disorganized the system slightly, leading to Amy featuring subtropical characteristics. By the evening, the strongest winds were not located around the center, but were instead situated between 60 and 90 mi (95 and 140 km) from the center. Convection became displaced from the center of circulation but the storm continued to intensify. Over the following several days, Amy tracked generally northeastward but underwent eastward jogs in response to rapidly moving troughs to the north. Amy neared hurricane intensity several times, beginning on June 30 as maximum winds increased to 70 mph (110 km/h); however, the storm was unable to acquire enough tropical features, and remained predominately subtropical. Gale-force winds at this time extended roughly 125 mi (210 km) out from the center to the north and east. On July 2, a barometric pressure of 981 mbar (hPa; 28.97 inHg) was recorded, the lowest in relation to Amy, as it strengthened into a hurricane, although it was only marginally tropical. The following day, another trough caused the storm to accelerate northeastward. On July 4, Amy passed roughly 170 mi (270 km) southeast of Cape Race, Newfoundland before becoming an extratropical cyclone.

As a tropical depression, Amy produced scattered rainfall in Florida, peaking around near the Georgia border. Along the North Carolina coast, heavy rain fell as the center of Amy tracked nearby. Many coastal areas recorded more than with a peak amount of falling in Belhaven, North Carolina. Rough seas from the storm resulted in minor coastal flooding and beach erosion in North Carolina and Virginia. Small craft advisories were issued along the Virginia and North Carolina coastlines as waves up to affected the region. Several beaches were closed due to the rough conditions. In Hampton, Virginia, a funnel cloud spawned by a squall line associated with Amy formed just offshore. On June 30, schooner capsized in rough seas roughly 250 mi (400 km) east of Cape Hatteras, North Carolina, carrying a family of four people. The father, a diabetic, slipped into a coma and died after he was unable to find his insulin pen. The three kids were rescued on July 14.

Unnamed tropical depression

Hurricane Blanche

A tropical wave emerged into the Atlantic Ocean from the west coast of Africa on July 14. The system remained weak for about a week, before convection began increasing significantly on July 21. After wind shear decreased, the wave managed to develop into a tropical depression on July 24 about northeast of the Turks and Caicos Islands. It moved northwestward until early on July 26, when an approaching cold front and associated trough caused the depression to turn northeastward. Around that time, the cyclone intensified into Tropical Storm Blanche. A weakening cold front and baroclinic forces created an environment favorable for intensifying, allowing Blanche to become a Category 1 hurricane on July 27. Slightly further deepening occurred, with the storm peaking with winds of and a minimum barometric pressure of . Before 12:00 UTC on July 28, Blanche made landfall in Barrington, Nova Scotia, with winds of . The system quickly transitioned into an extratropical cyclone, which soon dissipated.

In Atlantic Canada, the remnants of Blanche produced high winds gusts up to , along with moderate rainfall, peaking at in Chatham, New Brunswick. The strong winds knocked over two mobile homes and destroyed a slaughterhouse, which was under construction. Additionally, trees and power lines were downed, leaving between 500 and 1,000 customers without electricity. The electrical corporation in Nova Scotia suffered about $196,600 in damage. Telephone services were also interrupted. The A. Murray MacKay Bridge was closed after an oil rig broke loose and threatened to strike the bridge. In Prince Edward Island, flights to and from the Charlottetown Airport were canceled, as was ferry service to Nova Scotia. In the province, many homes and businesses lost telephone service. Overall, damage in Canada reached about $6.2 million.

Unnamed tropical storm

Tropical Depression Six

Tropical Depression Six developed from a trough of low pressure in the northeastern Gulf of Mexico about southwest of Cape San Blas, Florida, on July 27. The depression moved west-northwestward and strengthened slightly to reach winds of , but remained below tropical storm intensity and made landfall in eastern Louisiana. Once inland, the depression slowly weakened and re-curved northwestward on July 30 into Mississippi. Around that time, the depression dissipated. The remnants persisted at least until August 3, at which time it was situated over Arkansas.

The tropical depression dropped heavy rainfall, with some areas of the Florida Panhandle experiencing more than of precipitation, with a maximum total of observed in DeFuniak Springs. Bay, Gulf, Holmes, Okaloosa, Santa Rosa, Wakulla, and Walton were hardest hit. Numerous roads were flooded and closed, with $3.2 million in damage to that infrastructure. About 500 homes suffered flood damage, 22 of which were destroyed. Damage is estimated to have reached $8.5 million in the state of Florida alone. In southern Alabama, overflowing rivers flooded several businesses and homes in Brewton and East Brewton. Damage in Alabama totaled approximately $300,000. In Mississippi, about 50 families in the vicinity of the Biloxi River were evacuated as the river threatened to exceed its banks, while at least 70 families fled their homes in Moss Point. Water entered about a dozen homes there. Further north, about 100 residences were evacuated in Canton, where some businesses suffered water damage. A total of 12 homes in Vicksburg were flooded. The storm left three fatalities, with two in Florida and one in Alabama.

Hurricane Caroline