2024 Season Summary

The 2024 Atlantic hurricane season was well above average in activity, with a total of

18 cyclones attaining tropical depression status,
18 cyclones attaining tropical storm status,
11 cyclones attaining hurricane status, and
5 cyclones attaining major hurricane status.

Before the beginning of the season, I predicted that there would be

24 cyclones attaining tropical depression status,
22 cyclones attaining tropical storm status,
12 cyclones attaining hurricane status, and
6 cyclones attaining major hurricane status.

The average numbers of tropical storms, hurricanes and major hurricanes (over the 30 year period 1991-2020) were 14.4, 7.2, and 3.2, respectively. The eventual numbers for 2024 fell short of my predictions for a historically active season, but the (preliminary) Accumulated Cyclone Energy value for 2024 was 162, enough to qualify as a "hyperactive" season, since it exceeded 165% of the median for hurricane seasons since 1950. Most predictions for the 2024 season were extremely high due to several favorable pre-season indicators. The main reason the true activity didn't quite reach this ceiling was an anomalous gap in storm formation near peak season; this will be discussed further below.

The most basic requirement for hurricane formation is warm ocean water. 2024 had this in spades.

A majority of the tropical Atlantic, Caribbean, and Gulf of Mexico experienced its warmest hurricane season on record. This is of course part of the worrying trend of climbing ocean temperatures globally due to anthropogenic global warming, but previous recent seasons had also seen very high ocean temperatures. The difference this year was where they were concentrated: the highest anomalies were in the heart of the main formation regions, rather than in the subtropical Atlantic.

During the heart of hurricane season, the average vertical wind shear was the lowest on record; since shear disrupts tropical cyclone formation, this also should contribute to higher activity. Both high ocean temperatures and low wind shear were well anticipated, hence the sky-high forecasts. And indeed, 2024 got off to a roaring start, with Hurricane Beryl became the most powerful hurricane ever recorded so early in a season. After the formation of Ernesto on August 13, however, no more storms were named until September 9, nearly a month-long gap. Since the climatological peak of hurricane season is mid-September, this was very unusual. As a point of comparison, the last time no named storms formed in that span of dates was 1968. After September 9, things switched to high gear again for the rest of hurricane season. For instance, 7 hurricanes formed on or after September 25, the first time this has ever happened on record. What happened in that gap?

A few factors likely contributed, but the main reason was that hurricane activity was cut off at the spigot, in a way: the north African monsoon shifted unusually far north. This caused tropical waves entering the Atlantic to quickly curve rightward into cooler and more stable environments. Meanwhile, dry air and high upper-level atmospheric temperatures over the tropical Atlantic quelled thunderstorm activity, making it difficult for disturbances to gain a foothold on the way to development. In short, tropical cyclone formation is complex; even when a couple factors are extremely favorable, other ingredients are still needed.

The following snapshot on October 6 highlights how busy that month was. Kirk (top right), Leslie (bottom right), and Milton (left) were all hurricanes simultaneously on that day. This was the first time such an occurrence had been recorded in October or later.

As far as more localized predictions go, land impacts were most common around the Gulf of Mexico, while U.S. east coast and greater Antilles impacts were somewhat less than I predicted. Unfortunately, a total of five hurricanes made landfall in the conintental United States, continuing a recent streak of bad hurricane seasons for the country. The most devastating of these was Hurricane Helene, which due to its size and strength caused widespread damage in the U.S. southeast and southern Appalachia, leading to the largest death toll in the mainland U.S. since Hurricane Katrina. Hurricane Milton also caused substantial damage in Florida, and was notable for being the strongest hurricane by minimum pressure since 2005, with a minimum central pressure of 897 mb.

Some other notable facts and figures from 2024 include:

• Beryl became the earliest category 4 and later the earliest category 5 recorded in the Atlantic; it also became the second southermost major hurricane formation, at 10.6° N
• Kirk became the easternmost forming hurricane in the tropical Atlantic after September, at 40.1° W, until this record was crushed immediately after by Leslie at 34.2° W
• Milton strengthened from a tropical depression to a category 5 hurricane in 49 hours, the fastest this had ever been observed
• Rafael was the second ever November major hurricane in the Gulf of Mexico on record

The 2024 hurricane season was very active and damaging, despite slightly underachieving statistically relative to pre-season predictions. Sources: https://yaleclimateconnections.org/2024/12/the-weirdly-hyperactive-2024-atlantic-hurricane-season-ends/, https://newsmediarelations.colostate.edu/2024/11/26/csu-researchers-slightly-over-predict-extremely-active-2024-atlantic-hurricane-season/,

Tropical Storm Sara (2024)

Storm Active: November 14-18

A tropical wave moved through the Caribbean sea during the second week of November and began to interact with a large gyre located near central America. This combination produced heavy rainfall in Jamaica and Hispaniola as it passed by and began to organize. The system was designated Tropical Depression Nineteen just northeast of Honduras early on November 14. Conditions in the southwest Caribbean were very favorable for strengthening, but the cyclone was very close to land and the circulation was quite large, preventing quick intensification.

Unfortunately, the depression still managed to intensify into Tropical Storm Sara that day and slowed down to a crawl just off the northern coast of Honduras. This led to a prolonged flooding event for the country, and surrounding areas. Eventually, a ridge built to the northeast of Sara and finally got the cyclone moving to the west-northwest again. It managed to maintain tropical storm strength until its landfall in Belize during the morning of November 17. Once inland, the storm weakened quickly, and it dissipated by the time it reached the Bay of Campeche early on November 18.

The image above shows Sara near the northern coast of Honduras on November 15.

Land interaction limited Sara from intensifying further, but this same prolonged proximity to mountainous Honduras led to extreme rainfall totals exceeding 40 inches at some locations.

Hurricane Rafael (2024)

Storm Active: November 4-10

Around the beginning of November, a broad area of low pressure formed in the southwestern Caribbean, a typical occurrence for that time of year. The disturbance gradually consolidated over the following few days and a closed center appeared on satellite imagery on November 3. On the 4th, enough convection had developed near the center for the system to be designated Tropical Depression Eighteen. Favorable conditions allowed it to strengthen into Tropical Storm Rafael later the same day.

Rafael turned northwest and passed just west of Jamaica during the morning of November 5. Steady intensification continued as the storm's organization increased, but it was kept in check by some dry air entering the circulation from the north. That night, Rafael managed to build a more complete eyewall and strengthen more rapidly. It reached hurricane status while passing the Cayman Islands. An eye cleared out occasionally on satellite the next morning, and Rafael peaked as a major hurricane early in the afternoon with winds of 115 mph and a central pressure of 956 mb. Very soon after, the hurricane made landfall in western Cuba.

Passage over land weakened the storm a little, but it soon entered the Gulf of Mexico as a category 2. Ocean temperatures remained very warm in the Gulf and Rafael made a comeback on November 7 when its eye made another appeareance and deep convection surrounded the center. That night, the hurricane reached its overall peak intensity of 120 mph winds, also matching its previous minimum pressure of 956 mb. This also matched the record for strongest winds recorded in a November hurricane in the Gulf of Mexico that was set by Hurricane Kate in 1985.

A developing ridge turned the hurricane west across the Gulf, where it soon encountered moderate wind shear and an extremely dry air mass. Though the storm had plenty of ocean heat content to work with, dry air steadily devoured Rafael and it weakened quickly from that point. By the evening of the 8th, it was a tropical storm. The storm slowed down and began a tight clockwise loop as it continued weakening. Rafael became a remnant low on November 10. The low dissipated soon afterwards.

The image above shows Rafael near peak intensity in the Gulf of Mexico.

Rafael had a destructive landfall as a category 3 in Cuba before moving into the Gulf of Mexico. Unusually (and fortunately), the storm dissipated over the Gulf rather than making any further landfall.

Tropical Storm Patty (2024)

Storm Active: November 1-4

Near the end of October, shower and thunderstorm activity began to concentrate near the center of a non-tropical low pressure system located over the open subtropical Atlantic. The system moved eastward and separated from the surrounding frontal boundaries. By November 1, it had the characteristics of a subtropical cyclone. Since it was already producing gale-force winds, it was named Subtropical Storm Patty. Patty had a small core where vertical instability supported some deep convection, but the entire cyclone was embedded in a cold air mass, contributing to the "subtropical" designation.

The system strengthened a little and veered south of east, reaching peak sustained winds of 65 mph. On November 2, the storm reached the Azores, passing just south of the western islands before turning east and directly over the eastern islands the following day. Wind shear over the storm increased on November 3 and Patty's strength gradually diminished as it finished its passage over the Azores. Rather unexpectedly, the cyclone transitioned into a fully tropical storm that night. The overall trends did not change, though. Progressively chillier water and high shear snuffed out Patty's remaining thunderstorm activity and it dissipated on November 4. By that time, the system was not far from western Europe; what was left of it brought some rain to Spain and Portugal soon after.

The image above shows Patty as a small subtropical storm on November 2.

Patty brought tropical storm conditions to portions of the Azores.

Hurricane Oscar (2024)

Storm Active: October 19-22

A tropical wave moved off of Africa on October 10. A low pressure center soon formed in association with the wave and the system trekked steadily across the tropical Atlantic. Along its journey, the low had a pretty well-defined center and was on the verge of tropical cyclone status multiple times, but was unable to muster enough convection to get there in a dry atmospheric environment. On October 18, the low passed just north of the greater Antilles and found another opportunity north of Hispaniola. It was finally named Tropical Storm Oscar during the morning of October 19.

Making up for lost time, Oscar ramped up quickly. Aircraft reconaissance found that the small storm had launched to category 1 hurricane strength by the same afternoon. A ridge north of the cyclone pushed it west-southwestward and the hurricane passed among the Turks and Caicos that evening, including a direct landfall on Great Inagua island early on October 20. The storm slowed down as it approached eastern Cuba that afternoon and made landfall near the country's eastern tip with maximum sustained winds fo 80 mph and a central pressure of 986 mb.

After landfall, Oscar stalled as the steering ridge was replaced by a trough that slowly turned it back toward the north. Its interaction with mountainous terrain weakened it quickly to a tropical storm and disrupted the circulation. During the afternoon of October 21, the storm finally reentered the Atlantic as a minimal tropical storm. It moved northeast into the Bahamas and brought some rain there, but atmospheric conditions had become much more hostile and Oscar was unable to improve its poorly defined structure. The cyclone ultimately dissipated the next day.

The image above shows tiny Oscar just after being upgraded to a category 1 hurricane. The storm was small but made multiple direct landfalls.

The track above shows the full path Oscar and its progenitor system (points where it was not a tropical cyclone are triangles). The system finally developed only near the end of its journey of thousands of miles.

Tropical Storm Nadine (2024)

Storm Active: October 19-20

Around October 15, a broad low pressure system formed in the southwestern Caribbean just east of Nicaragua. The system drifted northwest only very slowly over the next few days, but brought heavy rains to a broad swath of central America. In the early hours of October 19, it became organized enough to be designated Tropical Storm Nadine east of Belize. Nadine organized rapidly but was quickly running out of water as it moved due west. Just before noon, the storm made landfall in Belize with peak winds of 60 mph. After landfall, the storm weakened steadily. It weakened to a tropical depression over Guatemala and turned west-southwest until dissipation on October 20.

The image above shows a strengthening Nadine just before landfall in Belize.

Nadine was a short-lived but large tropical storm which had significant flooding impacts.

Hurricane Milton (2024)

Storm Active: October 5-11

Around the end of September, a tropical wave moving through the Caribbean interacted with a broad area of rotation over central America to produce a large area of disturbed weather. This disturbance moved northwest into the Bay of Campeche over the next couple of days. After that, it remained mostly stationary just off the western coast of the Gulf of Mexico. On October 4, the system suddenly coalesced quickly around a nascent center of circulation. The next morning, it was designated Tropical Depression Fourteen.

The depression had low shear and warm water to work with and quickly strengthened into Tropical Storm Milton during the afternoon of the 5th. The system was rather small at first, but this allowed it to ramp up quickly, especially once an inner core became established early on October 6. Milton rapidly intensified into a hurricane that day. The system embarked on an unusual motion just south of east across the Gulf of Mexico. Overnight, the storm began a historic burst of strengthening. At 0900 UTC on October 7, the storm was upgraded to a category 2. Just two hours later it became a major hurricane, and after another two hours, a strong category 4. A little before 1600 UTC, it reached category 5 intensity. At 0000 UTC October 8, peaked at a historic intensity of 180 mph sustained winds and a central pressure of 897 mb. This was the lowest pressure recorded in an Atlantic hurricane since 2005 and made Milton the fifth most intense Atlantic hurricane on record by minimum pressure. The cyclone's ascent from tropical depression to category 5 hurricane took 49 hours, the fastest such a feat had ever been observed.

The storm remained incredibly compact throughout this explosion of intensification. A small but very symmetric eye had first appeared the morning of the 7th, and it contracted further after Milton reached category 5 strength until it was under 5 miles in diameter by that evening. The center was surrounded by an area of exceptionally cold cloud tops, the likes of which are seldom seen in the Atlantic basin. The storm's heading took it eastward across the Gulf just north of the Yucatan peninsula, and close enough to bring tropical storm conditions to the northern coastline. Overnight, Milton underwent an eyewall replacement cycle as the tiny eye filled in and the original eyewall was slowly replaced by a secondary larger one. This caused the storm's maximum winds to weaken back to category 4 and minimum pressure to rise temporarily, but it did expand the area of hurricane force winds.

The system recovered well on October 8 though and regained category 5 strength during the afternoon. By that time, Milton was on a faster east-northeastward path toward the central coast of western Florida. It reached an impressive secondary peak intensity of 165 mph winds and a minimum pressure of 902 mb that evening. Fortunately, shear began to increase quickly after that time and the cyclone weakened fairly rapidly from that point. It was down to a category 4 by early on the 9th, and became increasingly disheveled on satellite imagery. Nevertheless, Milton was still at category 3 strength when it made landfall in Florida that evening. The storm's days as a powerful hurricane led to significant storm surge impact, and its quick movement brought wind damage across a swath of the state. Milton was still a category 1 hurricane when it emerged on the Atlantic side of Florida early on October 10. By that time, the storm was interacting with a frontal zone and losing tropical characteristics. It became post-tropical early that evening and continued to gradually spin down as it pushed generally eastward out to sea.

The image above shows Milton near peak intensity on October 7. The cyclone exhibited a "pinhole eye" of only 5 miles across, a feature common for the Atlantic's top few strongest hurricanes. Milton's lowest pressure reading of 897 mb was the lowest observed in the Atlantic for 19 years.

Milton achieved category 5 status twice en route to a category 3 landfall in Florida.

Hurricane Leslie (2024)

Storm Active: October 2-12

Near the end of September, a late season tropical wave entered the Atlantic, cruising slowly westward at a low latitude. The disturbance was dwarfed by the strengthening Tropical Storm (and soon Hurricane) Kirk to its northwest, but it still managed to steadily organize and become Tropical Depression Thirteen on October 2. The cyclone had plenty of moisture to work with, but was buffeted by the outflow of Kirk for another few days, so its intensification was gradual. Nevertheless, it strengthened into Tropical Storm Leslie that night and continued to improve its satellite presentation over the coming days.

The storm found a pocket of conditions favorable enough to reach hurricane strength late on October 4. Leslie surpassed nearby Kirk and again set the mark for easternmost formation of a hurricane in the tropical Atlantic post-September, at a longitude of 34.2° W, further evidence of the anomalous warmth of the Atlantic basin. Leslie turned west-northwest and then northwest over the next couple of days and encountered some mid-level try air. It had some success battling off this dry air intrusion for a time, and managed to intensify a bit more on October 6, reaching its first peak intensity of 90 mph winds and a pressure of 982 mb.

The next day, Leslie's structure began to slowly degrade. Although the storm was still producing very deep convection, the core became more lopsided and the maximum winds decreased. The system was downgraded to a tropical storm early on October 8. It rebuilt its eyewall and made a comeback later in the day however, regaining hurricane status. Leslie remained surprisingly resilient and deepened more on October 9. Its eye partially cleared out and it beat its previous strength mark that evening, reaching a new peak intensity as a category 2 hurricane with 105 mph winds and a central pressure of 972 mb.

Upper-level winds from a disturbance to the storm's west increased markedly over Leslie on the 10th, however. This initiated rapid weakening, an the storm also began curving north and then northeast out to sea. By October 11, the cyclone was down to moderate tropical storm strength and was producing convection only sporadically. The next day, Leslie dissipated altogether.

The image above shows Leslie near its second peak intensity as a category 2 hurricane on October 9.

Leslie did not affect land as a tropical cyclone.

Hurricane Kirk (2024)

Storm Active: September 29-October 7

Around September 25, a large tropical wave entered the Atlantic. After passing through the Cape Verde islands, the disturbance began more organized; it was classified Tropical Depression Twelve on September 29. The next day, it strengthened into Tropical Storm Kirk. The storm was moving west at first, but soon began to arc very gradually toward the north. Kirk was a sprawling storm and was a little disheveled on satellite imagery due to some wind shear, but it nevertheless intensified steadily. On October 1, it became a hurricane. Kirk was located at 40.1° W when it reached hurricane strength, far surpassing the previous record easternmost tropical Atlantic hurricane formation in October (a record previously shared by Jose of 1999 and Tammy of 2023). That record stood for all of three days until it was again far surpassed by Hurricane Leslie.

Kirk didn't stop there, however. The large hurricane deepened much further over the following days, especially during a rapid burst of intensification beginning on the evening of October 2, when the eye quickly cleared on satellite imagery and became a major hurricane. The following afternoon, it reached category 4, and late on October 3, Kirk achieved a powerful peak intensity of 145 mph winds and a central pressure of 934 mb. The next day, the storm's steady northwest heading brought it into an area of higher shear from an upper-level low to the northwest. A gradual weakening trend began. The storm turned north and began to accelerate as it felt the tug of the mid-latitude westerlies.

Even as the core lost its definition and the peak winds decreased, Kirk's windfield grew as it gained latitude, pushing large waves to coasts all around the Atlantic. It lost major hurricane status on October 6 and turned northeast. Increasingly hostile upper-level winds soon began extratropical transition. The storm became post-tropical during the morning of October 7. What was left of Kirk eventually brought rain and strong winds to parts of western Europe a few days later.

The image above shows Kirk as a category 4 hurricane over the open Atlantic on September 4.

Despite being a large hurricane, Kirk did not directly affect land as a tropical cyclone.

Tropical Storm Joyce (2024)

Storm Active: September 27-30

On September 22, another tropical wave left Africa and entered the eastern tropical Atlantic. Within a few days, the disturbance was close to tropical storm status, but the center was not well-defined enough. It took a few more days for the system to clear the final hurdle and become Tropical Storm Joyce on September 27, when it was located around halfway between Africa and the Leeward Islands. Joyce intensified modestly in the day after its formation and turned northwest into a weakness in the subtropical ridge. However, the system soon encountered increasing wind shear and began to weaken by September 29.

Late that same day, it weakened to a tropical depression. Though the storm continued to produce bursts of thunderstorm activity, the center became less and less defined and eventually dissipated late on September 30.

Joyce was a small tropical storm; the image above shows a satellite image from September 27.

Joyce was a short-lived tropical storm that did not affect any land areas.