Hurricane Frederic, known in Latin America as Federico, was an intense and destructive tropical cyclone that carved a path of destruction from the Lesser Antilles to Quebec, in particular devastating areas of the United States Gulf Coast. Though only five were killed directly, the US$1.77 billion in damage accrued by Frederic made it the Atlantic basin's costliest tropical cyclone on record at the time. Prior to its final landfall, the threat that Frederic imposed on areas of the U.S. Gulf Coast triggered a mass exodus from the region larger than any other evacuation in the past. While the storm primarily impacted the U.S. states of Mississippi and Alabama, lesser effects were felt throughout the Greater and Lesser Antilles, as well as inland North America.

Frederic was the thirteenth tropical cyclone, sixth named storm, third hurricane, and second major hurricane of the 1979 Atlantic hurricane season. It developed from a tropical depression south of the Cape Verde Islands on August 28. Tracking at a steady clip westward, the primitive cyclone reached tropical storm intensity the next day. Favorable conditions in the open Atlantic allowed for Frederic to reach hurricane intensity on September 1. However, outflow from nearby Hurricane David began to inhibit further intensification and would continue to do so for roughly a week, weakening Frederic as it tracked across the Greater Antilles. The tropical cyclone nearly dissipated over Cuba before redeveloping on September 9 near the Isle of Youth. From then on, Frederic moved northwestward, intensifying to its peak intensity in the Gulf of Mexico with winds of on September 12, shortly before making landfall at Dauphin Island, Alabama just below the state line between Alabama and Mississippi. Inland over the United States, Frederic rapidly weakened before becoming extratropical in Pennsylvania on September 14 and dissipating the next day.

Frederic is estimated to have inflicted at least $5 million in both Puerto Rico and the U.S. Virgin Islands, with an additional $2.22 billion in damage on the mainland United States. The Federal Emergency Management Agency (FEMA), which had been established only three months before Frederic hit, was the focal point for nearly $250 million in federal aid for recovery, $188 million of which went to Alabama. In southern Alabama, the landscape was changed for years, with thousands of tall pine trees tilted and leaning northwest.

Meteorological history

The precursor to Hurricane Frederic emerged as a loosely defined tropical wave off the west coast of Africa late on August 27. The following day, satellite images indicated that the tropical wave had become more defined, and was beginning to show signs of cyclonic rotation. At 0600 UTC on August 29, the National Hurricane Center (NHC) classified the system as a tropical depression based on observational data from ships nearby in conjunction with satellite images. Upon developing into a tropical cyclone, the depression moved at an unusually rapid pace westward, gradually curving towards the west-northwest and slowly intensifying in ideal conditions. At 1200 UTC on August 30, the tropical depression was upgraded to tropical storm status and thus named Frederic. Intensification continued after the storm's upgrade, and early on September 1, Frederic developed an eye, prompting the NHC to further upgrade the tropical cyclone to hurricane status at 0600 UTC that day.

Frederic only maintained hurricane intensity for roughly eighteen hours over the open waters of the Atlantic on September 1 before outflow from nearby Hurricane David began to adversely affect the tropical cyclone. At 0000 UTC on September 2, Frederic weakened back to tropical storm strength while it was still well east of the Lesser Antilles. This weakening phase continued as Frederic began to assume a more westerly track and slow in forward motion. On September 4, Frederic tracked over the Virgin Islands before making landfall on Puerto Rico later that day with maximum sustained winds of . Frederic's interaction with Puerto Rico greatly disrupted the low-level circulation contained within the tropical cyclone, enhancing the weakening effects of Hurricane David's outflow. After passing over the island, the tropical storm briefly took a southwest course before curving into Hispaniola on September 6, inducing additional disruption within Frederic. At 1800 UTC that day, Frederic was downgraded to tropical depression status north of Haiti. Frederic remained a tropical depression for two days as it tracked into and then parallel to the southern coast of Cuba beginning on September 7. During this time, Hurricane David had tracked far into the Northeastern United States, and as a result its inhibiting effects of intensification ceased. At 0000 UTC on September 9, Frederic regained tropical storm intensity while located roughly /h) east of the Isle of Youth. The following day, the cyclone tracked over western Cuba as it gradually curved towards the northwest.

Favorable conditions, marked by very warm sea surface temperatures as high as 86 °F (30 °C) and the presence of a large anticyclone over the system, allowed Frederic to strengthen to hurricane status for a second time while just northwest of Cuba, despite proximity to land. Frederic took a northwesterly course throughout its trek across the Gulf of Mexico in early September, intensifying in a highly conducive environment. By 1800 UTC on September 10, the hurricane became stronger than it had ever been over the central Atlantic. At 0000 UTC on September 12, Frederic attained major hurricane status over the eastern Gulf of Mexico, and twelve hours later reached peak intensity with a minimum barometric pressure of 943 mbar (hPa; 27.85 inHg) and sustained winds of , making the cyclone a Category 4 hurricane on the Saffir–Simpson hurricane wind scale. Moving gradually faster in the Gulf of Mexico, Frederic eventually made two landfalls – one on Dauphin Island and the other near the border between Alabama and Mississippi – with a virtually unchanged intensity. Tracking rapidly northward, Frederic began to weaken due to land interaction, and was downgraded to tropical storm status while it was near Meridian, Mississippi on September 13. At around the same time, the cyclone began to curve northeastward, eventually merging with an extratropical cyclone in southwestern Pennsylvania by 1800 UTC on September 14. These extratropical remnants proceeded to track through the Mid-Atlantic states and New England before they were last officially documented by the NHC in New Brunswick on September 15. However, the Canadian Hurricane Centre still considered the cyclone active up until the storm entered the Labrador Sea on September 16.

Preparations

The first tropical cyclone watches and warnings issued in association with Frederic were on September 3, when the National Hurricane Center issued a hurricane warning and gale warning for several islands of the Lesser Antilles stretching from Dominica to the northern Leeward Islands. Residents of Charlotte Amalie in the United States Virgin Islands were urged by governor Juan Francisco Luis to move to 24 emergency shelters. Luis also mobilized a company of the Virgin Islands National Guard to expedite evacuations and protect emptied residences and other buildings from looting. Further south in Dominica, Melville Hall Airport was forced to close due to the presence of gale-force winds, delaying relief efforts following Hurricane David.

Despite having weakened to a tropical storm by the time Frederic moved over the Virgin Islands, the National Hurricane Center issued a hurricane watch for Puerto Rico on September 4. As precautionary measures, the Luis Muñoz Marín International Airport and schools closed for the duration of the storm. Hundreds of residents were ordered to evacuate from Toa Baja for the second time in just four days due to the threat of flooding rivers. In Trujillo Alto, a dike was relieved in order to mitigate potential flooding. After its track across Puerto Rico, gale warnings were issued for portions of the Dominican Republic and Haiti, as well as the Turks and Caicos Islands. No watches or warnings were issued by the NHC for any areas while Frederic was classified as a tropical depression over the Greater Antilles. However, small craft warnings were posted for some coastal regions off of Miami, Florida due to strong winds caused by the nearby tropical cyclone.

After Frederic reattained hurricane status in the Gulf of Mexico on September 10, a gale warning was issued for the Dry Tortugas; this was the first NHC warning issued in association with Frederic. Not long after, a hurricane watch was issued for coastal areas extending from Panama City, Florida to Vermilion Bay in Louisiana. Although forecasts showed that Frederic posed no threat to Sarasota, Florida, the city readied barrels of water if distribution was necessitated to Sarasota County's 58 emergency shelters. Municipality managers were asked to place their respective emergency personnel on standby. In Key West, Florida, city workers had shortened workdays while the storm moved close by.

At Keesler Air Force Base (AFB) in Biloxi, the staff declared HURCON 1 on the morning of September 12. Personnel at the base sand-bagged low lying areas and boarded up windows in preparation for the storm. Most aircraft on the base were flown out of the storm's path.

Impact Lesser Antilles and Puerto Rico Effects from Frederic were first felt on the outward facing Leeward Islands. In Antigua, the threat of widespread power outages forced the insular government to shut down power. A peak gust of was documented on the island as a result of the storm. These strong winds also unroofed some buildings. Strong winds and rain were felt in Guadeloupe, Barbuda, and a number of other islands, but no damaging effects from the passing tropical cyclone occurred in those locations.

In St. Maarten, these strong winds toppled a radio antenna. Flowing floodwaters washed away plentiful food crops in the island. Some homes were damaged and others destroyed on the adjacent Sint Maarten. Off of the island, seven Japanese people were killed after their fishing boat sank during the storm.

Power outages knocked out electricity to half of Tortola in the British Virgin Islands and downed telephone lines. Rainfall and downed trees blocked several roads. Offshore, the yacht Princess blew out into sea, prompting a coast guard rescue of the ship and its crew.

As a tropical storm, Frederic dropped heavy rain across the U.S. Virgin Islands and Puerto Rico. Despite having weakened from its prior hurricane intensity, the storm still brought gale-force winds coupled with gusts as strong as to the area. Three buildings in an apartment complex on St. Thomas were unroofed, displacing roughly 50 families. Electricity was deliberately cut during the late night hours as a preventive measure. The entirety of the U.S. Virgin Islands reported numerous felled trees and downed utility lines as a result of the strong winds. Wind damage on nearby Puerto Rico was of only minor extent and much less severe than in the Virgin Islands. However, torrential precipitation accounted for most of the damage, as the passage of Hurricane David less than a week earlier saturated soils, priming the area for floods induced by the passage of Frederic. Rainfall peaked at around in 12 hours in Puerto Rico and in 30 hours in St. Croix.