The 1990 Atlantic hurricane season was the most active Atlantic hurricane season since 1969, with a total of 14 named storms. The season also featured eight hurricanes, one of which intensified into a major hurricane. It officially began on June 1, 1990, and lasted until November 30, 1990. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. However, tropical cyclogenesis can occur prior to the start of the season, as demonstrated with Tropical Depression One, which formed in the Caribbean Sea on May 24.

Though active, the season featured relatively weak systems, most of which stayed at sea. The 1990 season was unusual in that no tropical cyclone of at least tropical storm strength made landfall in the United States for the first time since the 1962 season, although Tropical Storm Marco weakened to a depression just before landfall.

Only a few tropical cyclones caused significant impacts. Hurricane Diana killed an estimated 139 people in the Mexican states of Veracruz and Hidalgo, while also causing approximately $90.7 million in damage. Hurricane Klaus brought flooding to Martinique and caused torrential rainfall across the southeastern United States after combining with Tropical Storm Marco and a frontal boundary. As a result of effects from Diana and Klaus, both names were retired following the season. Overall, the storms of the season collectively caused 171 fatalities and approximately $157 million in damage.

Seasonal forecasts +Predictions of tropical activity in the 1990 seasonSourceDateNamedstormsHurricanesMajorhurricanesNOAAApril 20, 1990146UnknownCSUJune 5, 19901173Record high activity30157 (Tie)Record low activity10 (tie)0Actual activity 14 8 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), has eleven named storms, of which six reach hurricane strength, and two major hurricanes. In April 1990, it was forecast that six storms would reach hurricane status, and there would be "three additional storms" from the previous year, which would indicate 14 named storms. The forecast did not specify how many hurricanes would reach major hurricane status. In early June 1990, CSU released their predictions of tropical cyclonic activity within the Atlantic basin during the 1990 season. The forecast from CSU called for 11 named storms, seven of which to intensify into a hurricane, and three would strengthen further into a major hurricane.

Seasonal summary

The Atlantic hurricane season officially began on June 1, but activity in 1990 began five days earlier with the formation of Tropical Depression One on May 25. It was an above average season in which 16 tropical depressions formed. Fourteen depressions attained tropical storm status, and eight of these attained hurricane status. There was only one tropical cyclone to reach major hurricane status (Category 3 or higher on the Saffir–Simpson Hurricane Scale), which was slightly below the 1950–2005 average of two per season. Unusually, the season featured no landfalling tropical storms in the United States. This was only the sixth such occurrence known, the other seasons being 1853, 1862, 1864, 1922, and 1962. Overall, the storms of the season collectively caused 171 deaths and approximately $153 million in damage. The last storm of the season, Hurricane Nana, dissipated on October 21, over a month before the official end of the season on November 30.

The activity in the first two months of the season were limited in tropical cyclogenesis, with the second tropical depression of the season not developing until July 22. Following that, the season was very active, and there was a quick succession of tropical cyclone development from late-July to mid-August. The Atlantic briefly remained dormant, and activity resumed on August 24 with the development of Tropical Depression Eight (Hurricane Gustav). Although August was a very active month, there were only two named storms in September, both of which became hurricanes. Activity in October was higher than average, with five tropical cyclones either forming or existing in that month. Following an active October, no tropical cyclogenesis occurred in November.

The season's activity was reflected with an accumulated cyclone energy (ACE) rating of 97, which is slightly above the mean value of 96. 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 , which is the threshold for tropical storm strength.

Systems Tropical Depression One

Tropical Depression One formed on May 24 from a weak low pressure area to the west of Jamaica, which had been producing scattered showers over the island during the preceding days. The depression moved across Cuba shortly after forming, although the convection was located to the east of its poorly defined center. As it headed toward Florida, it was absorbed by an approaching cold front.

The depression did not cause significant damage. In Florida, the depression was forecast to ease drought conditions that persisted for about two years. While crossing Cuba, the depression dropped heavy rainfall, and predictions stated that precipitation amounts could reach as high as , but the greatest amount measured was at east of Havana. Heavy rainfall also occurred across much of south Florida, peaking at at the Royal Palm Ranger Station in Everglades National Park. While the depression was affecting south Florida, the National Weather Service issued "urban flood statements" warning of flooded streets in mainly low-lying areas, especially in Dade and Broward counties. Standing water on many Florida expressways caused automobile accidents, especially in Dade County, where 28 accidents were reported.

Tropical Storm Arthur

The second tropical depression of the season developed on July 22 from a tropical wave nearly midway between the Lesser Antilles and Cape Verde. The depression slowly intensified, and was eventually upgraded to Tropical Storm Arthur, two days later. On July 25, Tropical Storm Arthur crossed the Windward Islands chain, and it was noted that the storm made landfall on Tobago. Emerging into the Caribbean Sea, Arthur nearly attained hurricane status on July 25. Thereafter, wind shear began increasing over Arthur, and a weakening trend began after peak intensity. As Arthur headed further into the Caribbean Sea, it significantly weakened and was downgraded to a tropical depression on July 27. Later that day, Air Force reconnaissance and satellite imagery did not show a low-level circulation, indicating that Arthur had degenerated into open tropical wave southeast of Kingston, Jamaica.

Shortly after Arthur became a tropical storm on July 24, a tropical storm warning was issued for Trinidad, Tobago, and Grenada; six hours later, it was extended to the Grenadines. About 24 hours later, all of the tropical storm warnings were discontinued. As Arthur headed further into the Caribbean Sea, a tropical storm watches and warnings were issued for Hispaniola and Puerto Rico on July 26. All of the tropical storm watches and warnings were discontinued after Arthur weakened to a tropical depression. After Arthur made landfall on Tobago, several landslides occurred, and a major bridge had collapsed; electrical and water services were significantly disrupted. Damage was also reported on Grenada, where two bridges were damaged, electricity and telephone service was disrupted, and crops were affected as well. In addition, Arthur caused damage to four hotels and hundreds of houses. Wind gusts on the island of Grenada reportedly reached . As Arthur passed south of Puerto Rico, there were reports of strong winds and heavy rainfall. Heavy rainfall was also reported on the south coast of Haiti as Arthur approached the country.

Hurricane Bertha

A tropical wave emerged off the coast of Africa, and after interacting with a cold front and an area of low pressure, developed into a subtropical depression on July 24, offshore of North Carolina near Cape Hatteras. The subtropical depression slowly acquired tropical characteristics, and was reclassified as Tropical Depression Three on July 27. On the following day, the National Hurricane Center upgraded the depression to Tropical Storm Bertha. It drifted northeast and became a hurricane west-southwest of Bermuda on July 29. As Bertha continued parallel to the East Coast of the United States, it had experienced strong wind shear and was downgraded back to a tropical storm later on July 29. However, by July 30, Air Force reconnaissance flights reported at hurricane-force winds, and Bertha had re-intensified into a hurricane at that time. After becoming a hurricane again, Bertha continued northeastward, but transitioned into an extratropical cyclone over Nova Scotia on August 2.

Nine deaths were attributed to Bertha, including six crew members of the Greek freighter Corazon who perished off the Canadian coast after their ship broke up. Another fatality was caused when one person fell off the ship Patricia Star and into the Atlantic; the other two deaths were from two people drowning in north Florida. Damage to crops and a suspension bridge were reported from Nova Scotia and Prince Edward Island; this damage totaled to $4.427 million (1990 CAD; $3.912 million 1990 USD).

Tropical Storm Cesar

While Bertha was approaching Atlantic Canada, a tropical wave emerged into an Atlantic from the west coast of Africa, and quickly developed into Tropical Depression Four approximately south of Cape Verde. The depression headed northwestward due to the weakness of a subtropical ridge and slowly intensified. While the depression was well west of Cape Verde, it intensified into Tropical Storm Cesar on August 2. Cesar continued on the generally northwestward path and no significant change in intensity occurred, as it peaked at shortly after becoming a tropical storm. Later in its duration, wind shear significantly increased, causing the low-level circulation to be removed from the deep convection on August 6, and Cesar weakened back to a tropical depression as a result. As it was weakening to a tropical depression, Cesar became nearly stationary, and turned abruptly eastward. On the following day, Cesar dissipated almost east-southeast of Bermuda.

Tropical Storm Edouard

A frontal wave formed near the Azores in early August. When thunderstorm activity grew near its center, it was deemed a subtropical depression on August 2 just east of the Azores. Associated with an upper-level cold low, it intensified into a subtropical storm on August 3, although water temperatures were cooler than what is usually required for tropical cyclogenesis. It tracking westward and passed near Graciosa before weakening back to a depression on August 4. The depression executed a small cyclonic loop, developing deep and organized convection near the circulation. Late on August 6, it transitioned into Tropical Depression Six. The depression moved northeastward toward the Azores, intensifying into Tropical Storm Edouard on August 8. Shortly thereafter it reached peak winds of , and subsequently it moved past the northern Azores. On August 10, Edouard weakened again to depression status, and became extratropical on the following day. The remnants of Edouard dissipated on August 13, a few hundred miles west of Portugal.