Tropical Storm Arlene (1999)

The 1999 Atlantic hurricane season had five Category 4 hurricanes – the highest number recorded in a single season in the Atlantic basin, previously tied in 1961, and later tied in 2005 and 2020. The season officially began on June 1, and ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Atlantic basin. It was a fairly active season, mostly due to a persistent La Niña that developed in the latter half of 1998. The first storm, Arlene, formed on June 11 to the southeast of Bermuda. It meandered slowly for a week and caused no impact on land. Other tropical cyclones that did not affect land were Hurricane Cindy, Tropical Storm Emily, and Tropical Depression Twelve. Localized or otherwise minor damage occurred from Hurricanes Bret, Gert, and Jose, and tropical storms Harvey and Katrina.

The most significant storm of the season was Hurricane Floyd, a strong Category 4 hurricane that caused devastating flooding along the East Coast of the United States, especially in North Carolina. Damage from the storm totaled approximately $6.5 billion (1999 USD) and there were at least 77 fatalities, making it the deadliest hurricane in the United States since Hurricane Agnes in 1972. Flooding from Floyd in North Carolina followed Hurricane Dennis, a slow and erratic–moving storm that dropped heavy rainfall in the eastern portion of the state. Tropical Depression Eleven in October contributed to extreme flooding in Mexico, which left 636 people dead and caused $491.3 million in damage, though impact could not be distinguished from the storm itself. Hurricane Irene caused extensive flooding in Cuba and Florida, with lesser effects in the Bahamas and North Carolina. Irene was the second–costliest storm of the season, with about $800 million in damage. Hurricane Lenny was an unusual eastward–moving storm in the Caribbean Sea and a strong late–season storm. It caused extensive damage in the Lesser Antilles in the month of November. Collectively, the storms of the 1999 Atlantic hurricane season caused at least 123 fatalities and $8.328 billion in losses.

Seasonal forecasts

Pre-season outlooks

Ahead of and during each hurricane season, various national meteorological services, scientific agencies, and noted hurricane experts issue forecasts of hurricane activity. These include forecasters from the United States National Oceanic and Atmospheric Administration (NOAA)'s National Hurricane and Climate Prediction Center's, William M. Gray and his associates at Colorado State University (CSU), as well as Weather Research Center (WRC) and Tropical Storm Risk (TSR), then known as TSUNAMI. The forecasts include weekly or monthly assessments of the significant factors that help determine the number of tropical storms, hurricanes, and major hurricanes within a particular year.

Gray and his team at CSU issued their initial season outlook on December 4, 1998, predicting fourteen named storms, nine hurricanes, and four major hurricanes. The three main factors for this above average season forecast cited included a continuation of abnormally warm sea surface temperatures, the probability that La Niña conditions would remain, and that the quasi-biennial oscillation (QBO) winds would be in a westerly phase. Early in 1999, WRC issued its forecast for the season, projecting ten named storms and six hurricanes, but no prediction on the number of major hurricanes. In subsequent outlooks from Gray and his associates in April, June, and August, the predictions were unchanged.

On April 7, CSU noted that the probability of a major hurricane landfall in the United States was 72%, including a 54% chance on the East Coast and a 40% likelihood on the Gulf Coast. In their outlook on May 27, experts at NOAA noted that an above average season was a strong possibility. An addition to a La Niña, vertical wind shear would be decreased across much of the Caribbean Sea and tropical Atlantic Ocean, and a favorable jet pattern for tropical waves to develop into tropical cyclones. On June 1, TSR predicted that there would be 12 named storms, 7 hurricanes, and 2 major hurricanes.

As stated by NOAA and CSU, an average Atlantic hurricane season between 1981–2010 contains roughly 12 tropical storms, 6 hurricanes, 3 major hurricanes, and an accumulated cyclone energy (ACE) Index of 66–103 units. NOAA typically categorizes a season as either above-average, average, of below-average based on the cumulative ACE Index; however, the number of tropical storms, hurricanes, and major hurricanes within a hurricane season is considered occasionally as well.

Seasonal summary

The Atlantic hurricane season officially began on June 1, 1999, and the first tropical cyclone developed on June 11. It was an above–average season in which 16 tropical cyclones formed. Twelve depressions attained tropical storm status, and eight of these became hurricanes. Five hurricanes intensified further into major hurricanes. The season featured a record-breaking five Category 4 hurricanes, later tied in 2005 and 2020. These were Bret, Cindy, Floyd, Gert, and Hurricane Lenny. The last storm of the season, Hurricane Lenny, dissipated on November 23, which was about a week before the official season ending on November 30, 1999.

A persistent La Niña that developed during the previous season was attributed to the above average activity. Between August and October, there was very low wind shear over the Caribbean Sea and western Atlantic Ocean, attributed to a combination of abnormal upper-level easterly winds and low-level westerly winds. Six hurricanes and two tropical storms made landfall during the season and caused at least 123 deaths and approximately $8.19 billion in damage. Hurricane Gert also caused damage and fatalities, despite not making landfall.

Overall, the season's activity was reflected with a high cumulative accumulated cyclone energy (ACE) rating of 177. 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 34 knots (39 mph, 63 km/h) or tropical storm strength.

Systems

Tropical Storm Arlene

Along a diffuse front, a broad area of low pressure in association with an upper-level low was noted several hundred miles northeast of Puerto Rico on June 8. After the circulation reformed within the area of stronger convection, the NHC estimated that Tropical Depression One developed at 18:00 UTC on June 11 about 535 mi (860 km) southeast of Bermuda. Initially, the system resembled a subtropical cyclone, due to its frontal characteristics. The nascent depression drifted northward for 24 hours, and during this time, it strengthened and was upgraded to Tropical Storm Arlene at 12:00 UTC on June 12, based on Dvorak satellite classifications. The storm intensified further to its peak intensity at 00:00 UTC on June 13, with estimated maximum sustained winds of 60 mph (95 km/h) and a minimum barometric pressure of , based on ship reports and satellite. Subsequently, weakening due to westerly wind shear, Arlene tracking westward on June 13 and turned northwest the following day. Because the steering current became poorly defined, it drifted starting on June 15, and executed a small cyclonic loop later that day. At 00:00 UTC on June 17, Arlene was downgraded to a tropical depression. Later that day, it passed about east of Bermuda, where gale-force winds and abnormally high tides were observed. The depression weakened further due to decreasing sea surface temperatures and dissipated early on June 18.

Tropical Depression Two

A tropical wave crossed the west coast of Africa on June 20. As the wave moved into the western Caribbean Sea on June 30, a broad cyclonic turning was noted. The system moved over the Yucatán Peninsula on July 1, a day before emerging into the Bay of Campeche as a weak low pressure area. Later on July 2, deep convection became more organized while the system was centered over the southwestern Gulf of Mexico. By 18:00 UTC, the low developed into Tropical Depression Two. Around 04:00 UTC on July 3, the depression made landfall about 40 mi (65 km) south-southeast of Tuxpan, Veracruz, with winds of 35 mph (55 km/h). Eight hours later, it dissipated over the mountains of Mexico. The depression dropped heavy rain on the area amounting to a maximum of at Tanzabaca, San Luis Potosí. In some areas, up to of precipitation fell in 24 hours.

Hurricane Bret

Late on August 18, a tropical wave in the Bay of Campeche spawned Tropical Depression Three. The depression drifted and was initially hampered by wind shear. By late on August 19, the depression was upgraded to Tropical Storm Bret amid more favorable atmosphere conditions. Bret then moved generally northward and strengthened into a hurricane early on August 21. Bret strengthened significantly over the next 36 hours, peaking as a 145 mph (230 km/h) Category 4 hurricane with a minimum barometric pressure of on August 22. Thereafter, the storm began to weaken while curving west-northwestward. At 00:00 UTC on August 23, Bret made landfall in central Padre Island, Texas, as a Category 3 hurricane with winds of 115 mph (185 km/h). After moving inland, the storm weakened quickly, falling to tropical depression status on August 24. Early the following day, Bret dissipated near the border of Coahuila and Chihuahua.

Bret was a small tropical cyclone that made landfall in a sparsely–populated region of Texas, resulting in relatively little damage. Heavy rainfall in the area peaked at in Sarita. At least 200 homes and large agricultural fields were flooded in Duval County. Strong winds left approximately 64,000 people without electricity in South Texas. Four people died after a truck and a tractor collided near Laredo due to slick roads. In Mexico, the storm brought flooding to Coahuila, Nuevo Leon, and Tamaulipas, with an estimated of rain falling in Nuevo Leon. Numerous homes in the affected regions were damaged or destroyed, leaving roughly 150 people homeless. Three people died in Mexico – one was trampled to death during evacuation, another was electrocuted, and the third drowned. Overall, the storm caused $15 million in damage.

Hurricane Cindy

On August 18, a tropical wave moved westward off the coast of Africa. With low pressures and gradually organizing convection, Tropical Depression Four developed west of Senegal early on August 19. Initially it failed to intensify due to wind shear, and the center became ill-defined on August 20. After passing south of Cape Verde, the depression intensified into Tropical Storm Cindy as the convection became concentrated around the center. Due to a strong ridge, Cindy moved westward, before turning northwestward by August 21. Banding features gradually increased as outflow improved, and late on August 21, Cindy became a hurricane. Afterward, increased wind shear dislocated the convection from the center, which weakened Cindy to a tropical storm.

By August 23, high wind shear remained, and the storm's winds decreased to 60 mph (100 km/h). The shear decreased on August 24, and the convection increased over the center. By late on August 25, Cindy regained hurricane status. A ragged eye appeared on satellite imagery on August 27, and early the next day it attained major hurricane status. Cindy turned north-northwestward, now showing a well-defined eye, and reached Category 4 intensity with winds of 140 mph (220 km/h) on August 28. Turning northward, the storm remained at peak intensity until August 30, when prominent wind shear weakened Cindy again. On August 31, Cindy was downgraded to a tropical storm, and later that day it merged with a large extratropical storm northwest of the Azores.

Hurricane Dennis

Tropical Depression Five developed from a tropical wave about 220 mi (355 km) east of the Turks Islands on August 23. On the following day, the depression strengthened into Tropical Storm Dennis despite unfavorable westerly shear, which became a hurricane by August 26. After striking the Abaco Islands in the Bahama, conditions improved, allowing for Dennis to strengthen into a Category 2 by August 28. Around this time, Dennis began to move parallel to the Southeastern United States. Early on August 30, the storm peaked with maximum sustained winds of 105 mph (165 km/h) and a minimum barometric pressure of . By the following day, steering currents collapsed and the storm interacted with a cold front, causing Dennis to move erratically offshore North Carolina. Wind shear and cold air associated with the front weakened Dennis to a tropical storm on September 1 and removed some of its tropical characteristics. Eventually, warmer ocean temperatures caused some re-strengthening. By September 4, Dennis turned northwestward and made landfall in Cape Lookout, North Carolina, as a strong tropical storm. The storm slowly weakened inland, before transitioning into an extratropical cyclone over western New York on September 7.

In the Bahamas, Dennis produced moderate winds, rain, and storm surge on San Salvador, Crooked Island, Eleuthera, and Abaco Islands, resulting in damage to roofs and coastal properties. Dennis brought waves to the east coast of Florida, causing minor erosion and four drowning deaths. The waves left severe erosion and coastal flooding along the Outer Banks of North Carolina. An deep channel created along Highway 12 isolated three towns on Hatteras Island. In Carteret, Craven, and Dare counties, the storm damaged at least 2,025 homes and businesses to some degree. Heavy rainfall, peaking at at Ocracoke, fell in eastern North Carolina. Although the precipitation was generally beneficial due to drought conditions, it also damaged crops. Two indirect deaths occurred in Richlands during a weather-related car accident. Similar inland flooding occurred in northern and eastern Virginia, with precipitation reaching near Lawrenceville. A tornado in Hampton severely damaged five apartment complexes, three of which were condemned completely, as well an assisted living facility; about 460 people were forced to evacuate from the buildings, and as many as 800 vehicles may have been damaged. Overall damage in North Carolina and Virginia totaled about $157 million. Generally minor flooding occurred in the Mid-Atlantic and New England.

Tropical Storm Emily

A tropical wave ahead of Hurricane Cindy exited the west coast of Africa on August 15. Minimal development occurred initially, although the structure gradually organized as it approached the Windward Islands. By 06:00 UTC on August 24, the NHC estimated that a tropical depression developed about east-northeast of Tobago. The depression strengthened into Tropical Storm Emily six hours later. At 1800 UTC on August 24, Emily attained its peak intensity with maximum sustained winds of 50 mph (85 km/h) and a minimum barometric pressure of . The NHC did not initiate advisories until 2100 UTC, when a reconnaissance aircraft observed winds of in association with the small circulation of Emily. The agency initially predicted that the storm would intensify into a hurricane near the Windward Islands. Increased wind shear generated by Hurricane Cindy caused Emily to weaken slightly on August 25. Emily began moving slowly northwestward and progressively became more influenced by Cindy, developing occasional convective bursts. Later on August 26, the movement turned northward, well offshore the Lesser Antilles. Eventually, the storm no longer produced convective bursts, and by 12:00 UTC on August 28, Emily weakened to a tropical depression. Six hours later, the storm was absorbed into Cindy northeast of the Leeward Islands.

Tropical Depression Seven

Interaction between a strong monsoon-type flow and a tropical wave in the Bay of Campeche resulted in the development of Tropical Depression Seven on September 5. By 00:00 UTC on September 6, the depression attained maximum sustained winds of 35 mph (55 km/h) and a minimum barometric pressure of . Shortly thereafter, the center of circulation of the depression became difficult to locate, but was likely heading north-northwestward. Due to warm ocean temperatures, the SHIPS model predicted further intensification, despite the storm having almost no deep convection and being close to land.

At 12:00 UTC on September 6, the depression made landfall near La Pesca, Tamaulipas, with winds of 35 mph (55 km/h). The depression quickly weakened inland, and dissipated about twenty-four hours after landfall. Due to forecasts that the depression would strengthen to a tropical storm, the government of Mexico issued a tropical storm warning for Tampico to Matamoros, Tamaulipas. The storm caused heavy rainfall in Mexico, with as much as falling in Ciudad Mante in the state of Tamaulipas. In Texas, the depression produced light rainfall, peaking at in Harlingen.

Hurricane Floyd

A westward moving tropical wave developed into a tropical depression while located about 1,000 mi (1,600 km) east of the Lesser Antilles on September 7. The depression strengthened and was upgraded to Tropical Storm Floyd on the following day. Floyd became a hurricane on September 10, while curving northwestward, before the storm resumed its initial west-northwestward course late on the following day. Significant intensification occurred on September 12 and September 13. At 12:00 UTC on the latter date, Floyd peaked with maximum sustained winds of 155 mph (250 km/h) and a minimum barometric pressure of . Thereafter, the storm began weakening while approaching the Bahamas, decreasing to Category 3 intensity at 06:00 UTC on September 14. Six hours later, Floyd made landfall near Alice Town

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