The 1984 Atlantic hurricane season was the most active since 1971, though the season was below average in hurricanes and major hurricanes. It officially began on June 1, 1984, and lasted until November 30, 1984. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. The 1984 season was an active one in terms of named storms, but most of them were weak and stayed at sea. Most of the cyclones tracked through the northwest subtropical Atlantic west of the 50th meridian to near the Eastern coast of the United States between mid-August and early October. The most damaging storm was Hurricane Klaus, which caused $152 million (1984 dollars) in damage in Puerto Rico. Hurricane Diana was the first hurricane to strike a nuclear power plant without incident; it was also the first major hurricane to strike the U.S. East Coast in nearly 20 years. Also of note was Hurricane Lili, which lasted well after the official end of the season. It was downgraded from a named storm on December 24. Damage overall from the tropical cyclones in 1984 totaled $228.7 million (1984 USD). Unusually, no hurricanes developed from tropical waves in 1984, which usually are the source of the strongest storms in an Atlantic hurricane season.

Predictions of tropical activity in the 1984 season

Source	Date	Named storms	Hurricanes	Major hurricanes	Ref
Average (1981–2010)		12.1	6.4	2.7
Record high activity		30	15	7†
Record low activity		1	0†	0†
CSU	July 23, 1983	11	8	N/A
WRC	Early 1984	7	4	N/A
CSU	May 24, 1984	10	7	N/A
CSU	July 30, 1984	10	7	N/A
	Actual activity	13	5	1

Forecasts of hurricane activity are issued before each hurricane season by noted hurricane experts such as Dr. William M. Gray and his associates at Colorado State University (CSU). A normal season, as defined by the National Oceanic and Atmospheric Administration (NOAA) in the period from 1981 to 2010, has approximately 12 named storms, with 6 of those reaching hurricane status. About 3 hurricanes strengthen into major hurricanes, which are tropical cyclones that reach at least Category 3 intensity on the Saffir–Simpson scale.

On July 23, 1983, forecasters at CSU predicted an above-average season in 1984 with a total of 11 tropical storms developing, 8 of which would reach hurricane status, under the assumption that sea-level pressures over the Caribbean Sea and Gulf of Mexico would be normal. Early in 1984, the Weather Research Center (WRC) forecast on the other hand called for a below-average season with seven named storms, with four of those strengthening into a hurricane. on May 24, 1984, forecasters at CSU revised their prediction downwards to a total of 10 tropical storms, 7 of which would reach hurricane status, as the easterly Quasi-biennial oscillation cycle had lasted longer than expected and the previously expected La Niña event in 1984 had yet to form and was now not expected until the autumn or winter, On the other hand, sea-level pressures over the Caribbean Sea and Gulf of Mexico were more favorable than expected. These numbers were unchanged in CSU's next season outlook, issued on July 30. None of these predictions included a forecast for the number of major hurricanes. Ultimately, the predictions issued by CSU proved to be too high for hurricanes and too low for tropical storms, with 13 subtropical or tropical storms forming in 1984 and 5 of those reaching hurricane status. CSU attributed the overforecast of hurricanes to the easterly QBO cycle not changing during the hurricane season as was expected and the sea-level pressures from August to October being less favorable than expected, and the underforecast of tropical storms to the unusual amount of formation in the subtropics from mid-latitude residual frontal activity.

Six storms during the season had subtropical characteristics at some point in their track, those being Subtropical Storm One, Tropical Storm Cesar, Hurricane Hortense, Hurricane Josephine, Hurricane Klaus, and Hurricane Lili.

The season's activity was reflected with a cumulative accumulated cyclone energy (ACE) rating of 84, which is classified as "near normal". ACE is, broadly speaking, a measure of the power of the hurricane multiplied by the length of time it existed, so storms that last a long time, as well as particularly strong hurricanes, have high ACEs. It is only calculated for full advisories on tropical systems at or exceeding 39 mph (63 km/h), which is the threshold for tropical storm strength.

Tropical depression (SSHWS)
Duration	June 11 – June 14
Peak intensity	35 mph (55 km/h) (1-min); ≤1016 mbar (hPa)

By June 11, an upper-level low caused thunderstorm development off the Florida coast, which caused the formation of a tropical depression. Moving westward, the depression moved into St. Augustine, causing a total of 5.02 inches (128 mm) of rainfall at Jacksonville Beach, Florida, as its main thunderstorm activity was concentrated north of the center. It dissipated as a tropical cyclone on June 14 while moving through the Florida panhandle. The small remnant low continued moving westward inland of the Gulf coast, causing occasional redevelopment of thunderstorm activity as the system moved into Louisiana, before both the thunderstorm activity and low-pressure area dissipated by June 17.

Tropical depression (SSHWS)
Duration	June 18 – June 20
Peak intensity	35 mph (55 km/h) (1-min); 1008 mbar (hPa)

An upper-level low-pressure area traversing the southern Gulf of Mexico spawned convective activity over the Isthmus of Tehuantepec on June 16. This convective area waxed and waned somewhat in intensity, until becoming a larger disturbance on June 18. A surface low soon formed, and around 12:00 UTC that day, the system developed into a tropical depression over the Bay of Campeche. With vertical wind shear preventing significant further intensification, the depression made landfall near Tampico, Tamaulipas, with winds of 35 mph (55 km/h). The depression quickly dissipated over the mountainous terrain of eastern Mexico. The cyclone and its precursor dropped heavy rainfall in some areas, including a peak total of 11.43 in (290 mm) of precipitation in San Lucas Ojitlán, Oaxaca.

Tropical depression (SSHWS)
Duration	July 24 – July 26
Peak intensity	35 mph (55 km/h) (1-min); 1000 mbar (hPa)

A tropical depression formed about 800 mi (1,285 km) east of the Windward Islands on July 24. Moving west-northwestward, the depression passed between Martinique and Saint Lucia early on the following day. On the latter, the storm dropped up to 8 in (200 mm) of precipitation. The Castries River overflowed its banks, washing away three homes in the eastern section of Castries. Two commercial fisherman were reported missing. Barbados recorded up to 6 in (150 mm) of rainfall in association with the system. The depression entered the Caribbean Sea and failed to intensify further, dissipating about halfway between the Dominican Republic and Venezuela late on July 26.

Subtropical storm (SSHWS)
Duration	August 18 – August 21
Peak intensity	60 mph (95 km/h) (1-min); 1000 mbar (hPa)

A weak frontal trough generated a low-pressure system that organized into a subtropical depression north of Bermuda on August 18. The depression headed northeast and strengthened to a subtropical storm. It is believed to have merged with a front on August 21. The history of Subtropical Storm One is not entirely certain, as satellite images were largely unavailable due to a failure of the VISSR unit on GOES EAST (then GOES-5), and this system remained at the fringe of the GOES WEST and Meteosat throughout its existence. Wind gusts up to 65 mph (105 km/h) were reported on the southwest coast of Newfoundland. In addition, a weather office on the island reported rainfall at 2.1 in (53 mm).

Tropical storm (SSHWS)
Duration	August 28 – September 5
Peak intensity	50 mph (85 km/h) (1-min); 1004 mbar (hPa)

A well-defined tropical wave emerged into the Atlantic from the west coast of Africa on August 23. Moving westward and later northwestward, the system remained to the south of a persistent shearing pattern that inhibited the development of several tropical waves. A reconnaissance aircraft flight indicated that a tropical depression formed late on August 28 roughly 700 mi (1,100 km) east of Trinidad. On the next day, another reconnaissance flight recorded tropical storm conditions, and thus, the depression intensified into Tropical Storm Arthur. The cyclone attained its peak intensity several hours later with maximum sustained winds of 50 mph (85 km/h) and a minimum barometric pressure of 1,004 mbar (29.6 inHg). Arthur was downgraded to a depression on September 1 after being negatively impacted by vertical wind shear, and dissipated on September 5 about halfway between the Bahamas and Bermuda. Despite its close proximity to the Lesser Antilles, Arthur caused no significant impact on land as it was a tropical depression at the time.

Tropical storm (SSHWS)
Duration	August 30 – September 4
Peak intensity	40 mph (65 km/h) (1-min); 1007 mbar (hPa)

On August 26, a tropical wave emerged into the Atlantic from the west coast of Africa. Tracking westward, the wave developed into a tropical depression about 1,170 mi (1,885 km) west-southwest of the southwesternmost islands of Cape Verde and in close proximity to the east of Arthur. A reconnaissance flight into the depression on August 31 indicated that it strengthened into Tropical Storm Bertha. Later that day, Bertha peaked as a minimal tropical storm with maximum sustained winds of 40 mph (65 km/h) and a minimum barometric pressure of 1,007 mbar (29.7 inHg). The system moved northwestward due to a weakening high pressure ridge to the north. Based on observations from reconnaissance flights on September 1, Bertha was downgraded to a tropical depression. On September 2, Bertha turned north-northeastward into response to an approaching cold front. The cold front then eroded the high pressure ridge, causing the cyclone to accelerate northeastward. Bertha later merged with the cold front on September 4.

Tropical storm (SSHWS)
Duration	August 31 – September 2
Peak intensity	60 mph (95 km/h) (1-min); 994 mbar (hPa)

A second storm formed on August 31 as a non-tropical low strengthened into Tropical Storm Cesar off the East Coast of the United States. Cesar traveled east-northeast and strengthened gradually until it became extratropical and merged with another system off the coast of Newfoundland on September 2.

Tropical depression (SSHWS)
Duration	September 6 – September 8
Peak intensity	35 mph (55 km/h) (1-min);

A tropical wave moved across Central America into the far eastern north Pacific Ocean by August 28. The system moved westward with no signs of development until September 1, when an upper-level low to its north across the Gulf of Mexico caused an area of thunderstorms to form just south of the Mexican coastline. An upper trough developed across the southern Plains of the United States, which slowly lured the northern portion of this increasingly large disturbance northward through the Mexican Isthmus. The southern portion moved westward, developing into Hurricane Marie. For a short while, Marie acted as a source of vertical wind shear from the west for this system, halting further development.

By September 6, the disturbance had emerged into the southwest Gulf of Mexico and consolidated into a smaller system which had enough organization to be classified as a tropical depression, the seventh of the season. The depression moved north-northwest into northeast Mexico on the afternoon of September 7, dissipating completely on September 8.

Category 4 hurricane (SSHWS)
Duration	September 8 – September 16
Peak intensity	130 mph (215 km/h) (1-min); 949 mbar (hPa)

On September 8, an extratropical cyclone organized into Tropical Storm Diana north of the Bahamas. Diana proved difficult for meteorologists to forecast, initially moving westward towards Cape Canaveral, but then turned to the north and paralleled the coastline. On September 11, the storm reached hurricane strength, and continued to intensify to a Category 4 hurricane, peaking with maximum sustained winds of 130 mph (215 km/h) and a minimum barometric pressure of 949 mbar (28.0 inHg). Diana moved north-northeast, and performed a small anti-cyclonic loop before striking near Cape Fear, North Carolina, as a minimal Category 2 hurricane on September 13. A weakened Diana curved back out to sea and headed northeast until it became extratropical near Newfoundland on September 16.

Severe beach erosion impacted Horry County, South Carolina, damaging 90 residences, 40 multi-family dwellings, 8 mobile homes, and a few businesses. In North Carolina, precipitation peaked at 18.98 in (482 mm) near Southport. Many areas in southeastern North Carolina reported freshwater flooding, with parts of Duplin, Pender, and Sampson counties experiencing 100-year flood events. High winds damaged some buildings and homes, especially in coastal areas of Brunswick and New Hanover counties. Throughout the state, Diana destroyed 68 homes and substantially damaged 325 others. Damage estimates were set at $65.5 million, with about $26.5 million of that figure dealt to agriculture. Three deaths, all due to indirect causes, occurred in relation to the storm. Diana became the first hurricane to strike a nuclear power plant — the Brunswick Nuclear Generating Station, which recorded sustained hurricane-force winds but no damage to the facility.

Tropical storm (SSHWS)
Duration	September 14 – September 15
Peak intensity	65 mph (100 km/h) (1-min); 998 mbar (hPa)

The origins of Tropical Storm Edouard are unclear, but an area of persistent organized storms formed in the Bay of Campeche, which strengthened into a tropical storm on September 14. Edouard rapidly intensified, with wind speeds reaching 65 miles per hour (105 km/h) in 18 hours as a faint eye feature became visible. Following its strengthening, Edouard dissipated even more quickly, degenerating into an area of thunderstorms the next day. The remnants of Edouard moved over land near the port of Veracruz.

Tropical storm (SSHWS)
Duration	September 15 – September 20
Peak intensity	65 mph (100 km/h) (1-min); 994 mbar (hPa)

On September 14, a well-defined tropical wave exited the coast of Africa. The next day, it had rapidly organized into a tropical depression. On the afternoon of September 16 the depression attained tropical storm strength, and it was given the name Fran. It turned to the northwest, and passed very near the Cape Verde. 31 people were killed in the country. Fran continued between the northwest and west-northwest on September 17–18 as it continued to organize. During this period satellite imagery indicated that Fran peaked with winds of 65 mph (105 km/h) and a minimum surface pressure of 994 mbar (29.35 inHg). As Fran passed the Cape Verde islands weather stations reported 35 miles per hour (55 km/h) winds, which is tropical depression force. During the period of September 19–20 Fran turned towards westward and began to encounter strong upper-level wind shear, which caused Fran to dissipate on September 20.

Tropical storm (SSHWS)
Duration	September 16 – September 19
Peak intensity	50 mph (85 km/h) (1-min); 1006 mbar (hPa)

Gustav spent most of its life as a well-organized tropical depression, which formed on September 16 in the open Atlantic south of Bermuda. The depression moved north, and its motion stalled over Bermuda on September 17. A day later, the depression had strengthened to a tropical storm and was named Gustav. Tropical Storm Gustav headed northeast until it was absorbed by a front on September 19.

Category 1 hurricane (SSHWS)
Duration	September 23 – October 2
Peak intensity	75 mph (120 km/h) (1-min); 993 mbar (hPa)

A large frontal system spawned a subtropical depression early on September 23, about 385 miles (620 km) east of Bermuda. Ship and satellite data confirmed its development, and indicated the system intensified into a subtropical storm later on September 23. Initially the cyclone moved toward the south-southwest, although on September 24 it turned to the west. That day, the hurricane hunters reported that the system transitioned into a tropical cyclone; as such, it was named Tropical Storm Hortense. The newly-tropical storm quickly intensified while turning to the northwest, and late on September 25 Hortense attained hurricane status, about 300 miles (475 km) southeast of Bermuda.

Twelve hours after reaching hurricane status, Hortense began a sharp weakening trend while passing east of Bermuda. By September 27 it was a minimal tropical storm, and subsequently it executed a clockwise loop to the southwest. The intensity of Hortense fluctuated slightly over the subsequent few days, although it never regained its former intensity. On September 30, after turning to the west and later to the north, the storm passed just 7 miles (11 km) west of Bermuda. As the storm was so weak, the island only reported winds of 18 miles per hour (29 km/h). Hortense accelerated to the northeast, moving rapidly across the north Atlantic before being absorbed by a larger extratropical storm late on October 2, northwest of the Azores.

Tropical storm (SSHWS)
Duration	September 25 – October 1
Peak intensity	60 mph (95 km/h) (1-min); 999 mbar (hPa)

A tropical depression formed on September 25 off the southeastern Bahamas. The depression headed west, and was upgraded to a tropical storm in the central Bahamas on September 26. It struck the US coast near Jupiter, Florida. Retaining tropical storm strength, Isidore curved to the northeast, emerging over water near Jacksonville, Florida. Isidore continued northeast until it was absorbed by a front on October 1. Total damages were estimated at over $750,000 (1984 US dollars). One death from electrocution was reported.

Category 2 hurricane (SSHWS)
Duration	October 7 – October 18
Peak intensity	105 mph (165 km/h) (1-min); 965 mbar (hPa)

Josephine became a named storm on October 8 while northwest of Puerto Rico. It briefly moved west then turned almost due north. While it stayed well away from the U.S. coast, Josephine was a large storm and sustained tropical storm winds were measured at the Diamond Shoals of Cape Hatteras. When it passed 36°N latitude (roughly level with Norfolk, Virginia), Josephine curved to the southeast, then back to the northeast. It continued on this path until it made a cyclonic loop beginning on October 17 while becoming extratropical. The storm lost its identity on October 21. The hurricane caused wave damage to coastal areas, but primarily posed a threat to the shipping lanes of the North Atlantic.

Offshore, a sailboat with six crewmen on it became disabled due to high waves, estimated to have exceeded 15 ft (4.6 m), produced by the hurricane. All of the people on the ship were quickly rescued after issuing a distress signal by a nearby tanker vessel. In Massachusetts, one man drowned after falling off his boat on North River amidst large swells produced by the storm. In Long Island, New York and parts of New Jersey, tides between 2 and 4 ft (0.61 and 1.22 m) above normal resulted in minor coastal flooding.

Tropical depression (SSHWS)
Duration	October 25 – October 28
Peak intensity	35 mph (55 km/h) (1-min); 1013 mbar (hPa)

This system was recognized as the seventeenth tropical depression of the season by the National Hurricane Center after the season ended. A retrograding upper-level low spurred the development of a low east of the Bahamas on October 25. The system tracked westward with limited shower and thunderstorm activity, crossing Florida on October 26 before moving into the Gulf of Mexico. Once the system moved into the north-central Gulf, deep convection began to develop near its center, expanding in intensity and coverage near and after landfall in extreme southeast Mississippi. The small system accelerated rapidly to the north and northeast ahead of an approaching cold front, moving across the Tennessee Valley and central Appalachians before linking up with the front and becoming a weak extratropical cyclone. The non-tropical cyclone then moved through coastal New England.

Category 1 hurricane (SSHWS)
Duration	November 5 – November 13
Peak intensity	90 mph (150 km/h) (1-min); 971 mbar (hPa)

Forming from a broad area of low pressure on November 5, Klaus maintained a northeast movement throughout much of its path. After making landfall on extreme eastern Puerto Rico, it passed to the north of the Leeward Islands, resulting in strong southwesterly winds and rough seas. Klaus attained hurricane status and reached peak winds of 90 miles per hour (145 km/h) before becoming extratropical over cooler waters on November 13. The storm dropped heavy rainfall in Puerto Rico, causing minor flooding and light damage. Klaus caused heavy marine damage in the Leeward Islands, including wrecking at least three ships. The Virgin Islands experienced heavy damage, as well. Damage from the storm totaled to $152 million (1984 USD), and the hurricane killed two on Dominica.

Tropical depression (SSHWS)
Duration	November 22 – November 29
Peak intensity	35 mph (55 km/h) (1-min); 1005 mbar (hPa)

A low-pressure system formed east of Florida on November 22 and rode up the East Coast of the United States producing heavy rain before curving back out to sea and dissipating on November 26. The storm left one fatality and $7.4 million (1984 USD) in damage. There has been evidence that the November storm may have become a subtropical cyclone east of Bermuda. The remnants of the cyclone contributed to formation of a potent nor'easter.

Category 1 hurricane (SSHWS)
Duration	December 12 – December 24
Peak intensity	80 mph (130 km/h) (1-min); 980 mbar (hPa)

In the second week of December, a frontal trough stalled south of Bermuda. An upper-level disturbance moved over the area on December 9, and produced widespread convection along the frontal wave. The system moved to the northeast, and based on a developing circulation within the convection, the National Hurricane Center classified it as a subtropical cyclone on December 12 while located 275 miles (443 km) northeast of Bermuda. A day later, a ridge forced the storm to the southeast and later to the south for a few days. A break in the ridge allowed the storm to turn back to the northeast on December 16, followed by a turn northwestward a day later. Another ridge halted the storm's movement, turning it back to the southwest on December 18, and later to the south. During this time, the subtropical storm intensified, with satellite-estimated hurricane-force winds by December 19. On the next day, a nearby ship recorded winds of 72 mph (117 km/h), along with a minimum pressure of 982 mbar (29.0 inHg). Based on the observations, as well as the appearance of a well-defined eye, the NHC reclassified the storm as Hurricane Lili on December 20, estimating peak winds of 80 mph (130 km/h) and a pressure of 980 mbar (29 inHg). At the time, Lili was located about 730 miles (1,170 km) east of Bermuda. Lili was only one of six Atlantic hurricanes on record during the month of December.

After becoming a tropical cyclone, Lili accelerated to the southwest, completing a large cyclonic loop by December 22, after crossing over the same location one week prior. That day, a hurricane watch was issued for Puerto Rico and the Virgin Islands on December 22. However, Lili weakened due to increased wind shear, degrading to a tropical storm on December 23 while 430 miles (690 km) northeast of Antigua. The storm rapidly lost organization as it approached the Leeward Islands, dissipating near the northern coast of the Dominican Republic on December 24. The storm brought light rainfall to the region.

The following list of names was used for named storms that formed in the north Atlantic in 1984. Most names were used for the first time, except for Bertha and Fran, which were previously used under the old naming convention. No names were retired following the season, so the list was used again in the 1990 season.

Arthur Bertha Cesar Diana Edouard Fran Gustav

Hortense Isidore Josephine Klaus Lili Marco (unused) Nana (unused)

Omar (unused) Paloma (unused) Rene (unused) Sally (unused) Teddy (unused) Vicky (unused) Wilfred (unused)

This is a table of all of the storms that formed in the 1984 Atlantic hurricane season. It includes their name, duration, peak classification and intensities, areas affected, damage, and death totals. Deaths in parentheses are additional and indirect (an example of an indirect death would be a traffic accident), but were still related to that storm. Damage and deaths include totals while the storm was extratropical, a wave, or a low, and all of the damage figures are in 1984 USD.

Saffir–Simpson scale
TD	TS	C1	C2	C3	C4	C5

• 1984 Pacific hurricane season
• 1984 Pacific typhoon season
• 1984 North Indian Ocean cyclone season
• Australian cyclone seasons: 1983–84, 1984–85
• South Pacific cyclone seasons: 1983–84, 1984–85
• South-West Indian Ocean cyclone seasons: 1983–84, 1984–85
• South Atlantic tropical cyclone
• Mediterranean tropical-like cyclone

• Monthly Weather Review
• U.S. Rainfall information for tropical cyclones from 1984