2013 Atlantic hurricane season

A season that never took off

Measured by energy rather than storm count, 2013 was a remarkably feeble year. The season's ACE of 36.1 sat far below the 1981 to 2010 median of about 92 and was the lowest since 1994. The number of tropical storms was close to normal, yet only two of them became hurricanes, neither climbed beyond Category 1, and no storm came near major hurricane strength. Fifteen systems appear in the archive, fourteen of which reached tropical storm force, including a subtropical storm near the Azores in December; the fifteenth, Tropical Depression Eight, never did.

The main culprit was an unexpected, sharp weakening of the Atlantic thermohaline circulation during late winter and spring, the largest drop in its strength in the reanalysis record. Colder air and water spread south across parts of the subtropical Atlantic, cooling sea surface temperatures, and the spring pattern simply persisted into the heart of the season: strong vertical wind shear, dry air in the middle levels of the atmosphere and unusually stable conditions. Slightly stronger trade winds and weaker convergence along the Intertropical Convergence Zone further starved developing disturbances.

How the season unfolded

Activity began early. Tropical Storm Andrea formed in the eastern Gulf of Mexico on 5 June and crossed northern Florida, and less than two weeks later Tropical Storm Barry developed from a disturbance that had drifted across Central America, crossed Belize and later came ashore near Veracruz. July brought two fast-moving systems from the deep tropics: Tropical Storm Chantal, one of the quickest-moving storms observed in the tropics in the satellite era, raced through the Lesser Antilles, and Tropical Storm Dorian formed south of the Cape Verde Islands and lasted, on and off, into early August, making it the longest-tracked storm of the year in the archive.

August stayed quiet. Tropical Storm Erin weakened in dry air west of Cape Verde, and Tropical Storm Fernand lived barely a day in the Bay of Campeche before striking Veracruz state. September was the season's only burst. Tropical Storm Gabrielle revived north of the Caribbean and passed just east of Bermuda, Tropical Depression Eight formed and moved inland near Tampico within hours, and Humberto and Ingrid became the year's only hurricanes within days of each other. Tropical Storm Jerry followed at the end of the month over the open central Atlantic.

The autumn produced only scattered, short-lived storms. Tropical Storm Karen threatened the northern Gulf Coast in early October before falling apart offshore, and Tropical Storm Lorenzo spun briefly east-southeast of Bermuda later that month. After nearly four weeks without a cyclone, Tropical Storm Melissa began as a subtropical storm in mid-November and turned tropical before racing toward the Azores. The last system, an unnamed subtropical storm south of the Azores, formed on 5 December and faded on 7 December, a week after the official end of the season.

Two modest hurricanes

Hurricane Humberto was the strongest storm of the year. It formed west-southwest of Dakar on 8 September, strengthened as it passed south of the Cape Verde Islands and became a hurricane on 11 September while turning north over the eastern Atlantic, peaking later that day with one-minute winds of 80 kt (Category 1) and a pressure of 979 hPa. Shear, cooler water and stable air knocked it down to a remnant low by 14 September, but it regenerated the next day and lingered south of the Azores until it became subtropical and dissipated on 19 September. Its arrival as a hurricane on 11 September tied 2002 for the latest first hurricane of the satellite era.

Hurricane Ingrid formed in the Bay of Campeche on 12 September and became a hurricane on 14 September, peaking early on 15 September with winds of 75 kt and a pressure of 983 hPa, estimates backed by reconnaissance flights and dropsonde data. Wind shear then eroded its thunderstorms, and a trough over eastern Mexico and a ridge over the southeastern United States steered it west toward land. Among the weaker storms, Andrea, Chantal, Gabrielle, Karen and Melissa all peaked at 55 kt, and Melissa's central pressure fell to 980 hPa, almost as low as Humberto's.

Landfalls and impacts

Eastern Mexico bore the brunt of the season. Ingrid came ashore just south of La Pesca, Tamaulipas, on 16 September, weakened to a 55 kt tropical storm by landfall, and struck within a day of Eastern Pacific Hurricane Manuel's landfall on Mexico's Pacific coast. Together the two storms flooded much of the country. The NHC report cites Mexican agencies attributing 32 deaths to Ingrid, mostly from heavy rain and mudslides, without a direct and indirect breakdown, and Aon Benfield data putting insured property damage in Mexico at about US$230 million. Broader estimates of Ingrid's total losses run to roughly US$1.5 billion (2013 dollars).

Three weaker systems had already soaked the same coast. Tropical Storm Barry, whose rains also reached Honduras, Belize and El Salvador, caused five direct deaths according to the NHC, two in El Salvador and three in eastern Mexico. Tropical Storm Fernand came ashore north of Veracruz city on 26 August with a 63 kt gust measured at Veracruz Harbor, and its 5 to 9 inches of rain triggered landslides that the Veracruz governor said killed 13 people, with a fourth death by drowning in Oaxaca. Tropical Depression Eight moved inland near Tampico on 6 September, and the NHC received no reports of damage or casualties from it.

Elsewhere, impacts were limited. Tropical Storm Andrea made landfall about 10 nautical miles south of Steinhatchee, Florida, on 6 June at 50 kt; the NHC counts one direct death, a surfer lost off Horry County, South Carolina, and three indirect deaths in traffic accidents in Virginia and New Jersey, with insured US damage below the US$25 million catastrophe threshold. Tropical Storm Chantal unroofed houses in Dominica and caused one direct death in the Dominican Republic, where a firefighter was swept away by floodwater. Gabrielle brought minor damage and power cuts to Bermuda, Humberto caused minor flooding in the southern Cape Verde Islands, and Karen prompted evacuations on the Louisiana coast before dissipating without landfall and without reported damage or casualties.

A forecast bust and other records

Every major seasonal outlook had called for an above-average year, citing warm Atlantic waters, weak trade winds and the absence of El Niño. Colorado State University forecast 18 named storms, nine hurricanes and four major hurricanes in April and June, and NOAA's May outlook gave ranges of 13 to 20 named storms and three to six major hurricanes. All groups trimmed their numbers in August, but even the revised forecasts proved far too high, and CSU's Phil Klotzbach later described 2013 as probably the biggest forecast bust in three decades of the team's predictions.

The season set several low marks. It was the first since 1994 without a major hurricane and had the fewest hurricanes since 1982, and reconnaissance aircraft flew just 45 missions totalling 435 hours, the fewest flight hours since 1966. Tropical Depression Eight, forming at 97.4°W near Tampico, has the westernmost genesis point in the Atlantic hurricane database. The December subtropical storm was not advised on in real time; the NHC identified it only in its post-season review, having treated the marginal system operationally as a marine feature. The name Ingrid was retired in 2014 because of the storm's toll in Mexico and replaced with Imelda.