As usual, November 30 marks the official end of the Atlantic and Eastern Pacific hurricane seasons. Activity this season spanned approximately five months, with Tropical Storm Alberto forming as a subtropical depression May 25 over the Northwestern Caribbean, and ending on October 31 with the extratropical transition of Hurricane Oscar over the central Atlantic. The 2018 Atlantic hurricane season produced 16 tropical cyclones, 15 named storms, 8 hurricanes, and 2 major (Category 3+) hurricanes, with an approximate Accumulated Cyclone Energy (ACE) of 127 units. The most memorable storms of the season were Hurricanes Florence and Michael, which caused major damage to the Carolinas and the Florida Panhandle, respectively. The names Florence and Michael should certainly be retired when the World Meteorological Organization meets in Spring 2019.

2018 Atlantic hurricane season storms

Storm Name	Classification	Formed	Dissipated	Maximum 1-minute sustained winds (mph)	Minimum pressure (mbar)
Alberto	Tropical Storm	May 25	May 31	65	990
Beryl	Category 1 hurricane	July 4	July 16	80	991
Chris*	Category 2 hurricane	July 6	July 12	105	970
Debby*	Tropical Storm	August 7	August 10	50	1000
Ernesto*	Tropical Storm	August 15	August 18	45	999
Florence*	Category 4 hurricane	August 31	September 17	140	939
Gordon*	Tropical Storm	September 3	September 8	70	997
Helene*	Category 2 Hurricane	September 7	September 16	110	966
Isaac*	Category 1 Hurricane	September 7	September 15	75	993
Joyce*	Tropical Storm	September 12	September 29	50	997
Eleven*	Tropical Depression	September 22	September 23	35	1007
Kirk*	Tropical Storm	September 22	September 29	60	998
Leslie *	Category 1 Hurricane	September 23	October 13	90	969
Michael*	Category 4 Hurricane	October 7	October 12	155	919
Nadine*	Tropical Storm	October 9	October 13	175	908
Oscar*	Category 2 Hurricane	October 27	October 31	105	970

* These storms have not yet had post-season analysis completed by the National Hurricane Center (NHC) and their dates and intensities are not final. 

For the fourth consecutive season, the Atlantic basin produced a pre-season tropical cyclone. Tropical Storm Alberto (operationally assessed as a subtropical storm) formed in the Northwestern Caribbean Sea as a subtropical depression on May 25. Alberto made landfall over the western Florida Panhandle on Memorial Day, causing moderate damage and heavy rainfall. Alberto surprisingly maintained its tropical characteristics all the way inland until northern Indiana. For the first time since 2014, no tropical cyclones formed in the Atlantic in June. This is not unusual as approximately one of every two years does not have an Atlantic named storm form in the month.

July was more active than usual, with the formation of two hurricanes – Beryl and Chris. July 2018 was the first July to feature two hurricanes in the North Atlantic basin since 2008. Beryl formed over the eastern tropical Atlantic on July 4, and the tiny storm rapidly intensified into a Category 1 hurricane two days later. Beryl then became an open wave just two days after reaching its peak intensity, though later regenerated into a subtropical storm over the northern Atlantic on July 14. At the same time Beryl was a hurricane, a new tropical cyclone – Chris – formed off the United States east coast. Chris stalled out over the western Atlantic, and did not make landfall as a tropical cyclone. Chris reached its peak intensity as a Category 2 hurricane on July 11, and transitioned into an extratropical cyclone the following day. The rest of July was quiet, with no new tropical cyclones.

The month of August was very quiet with only two weak tropical storms – Debby and Ernesto – being named during the month. Both Debby and Ernesto formed as subtropical cyclones and transitioned into tropical storms. Debby did not affect any land areas, though Ernesto’s post-tropical remnants did bring some rain to the British Isles. No hurricanes formed in the Atlantic during August for the first time since the 2013 season.

A much more active period of Atlantic activity began on August 31 with the formation of a new tropical depression southeast of the Cabo Verde Islands. This depression strengthened into Tropical Storm Florence the following day. Florence fluctuated in intensity for the first few days of its life, but unexpectedly rapidly intensified into the first major hurricane of the season on September 5, reaching Category 4 intensity over the central tropical Atlantic. Strong wind shear briefly weakened Florence back to a tropical storm, though a second period of rapid intensification occurred from September 9-10, bringing Florence to its peak intensity with maximum sustained winds of 140 mph and a minimum pressure of 939 mb. Florence made landfall near Wrightsville Beach, North Carolina on the morning of September 14 as a Category 1 hurricane. The cyclone slowed down its forward speed shortly after making landfall, causing major flooding to areas in the eastern Carolinas. Florence then transitioned into a post-tropical cyclone on September 17, ending the cyclone’s long life. Hurricane Florence caused an estimated 53 fatalities and approximately $17.9 billion in damage, making it the costliest storm of the season.

Over a week prior to Florence’s landfall in North Carolina, Tropical Storm Gordon formed near South Florida and made landfall near the Alabama-Mississippi border late on September 4 as a strong tropical storm. Gordon, much like Alberto, caused only minor damage overall.

Helene and Isaac both formed over the tropical Atlantic at the same time on September 7. Helene peaked just below major hurricane status as a Category 2 hurricane three days later, and Isaac reached minimal hurricane intensity on the same day. Neither Isaac nor Helene caused any significant damage. However, on September 10, the Atlantic had three simultaneously active hurricanes for the second year in a row: Florence, Helene and Isaac.

The second half of September featured a series of weak, low-impact tropical cyclones. Subtropical Storm Joyce formed on September 12, giving the Atlantic a very rare occurrence of four active tropical cyclones at the same time. Joyce later transitioned to a tropical storm, but did not affect any land areas. Joyce persisted for a week, dissipating on September 19. On September 22, a sheared, poorly organized Tropical Depression – Eleven – formed over the tropical Atlantic, but dissipated east of the Lesser Antilles the following day. Also on September 22, Tropical Storm Kirk formed over the eastern tropical Atlantic at an unusually low latitude of 8.3 degrees North, making it the southernmost Atlantic named storm on record. Kirk briefly opened up into a wave and later regenerated into a tropical storm, peaking on September 26 with maximum sustained winds of 60 mph. Kirk opened up into a tropical wave three days later.

Perhaps the strangest storm of the season was the erratic Hurricane Leslie. Leslie formed as a subtropical storm over the central Atlantic on September 23. Only two days after formation, Leslie merged with a frontal system, eventually becoming a powerful hurricane-force extratropical cyclone. Leslie then started to take on subtropical characteristics once again, redeveloping into a Subtropical Storm on September 28. The following day, Leslie transitioned into a fully tropical storm, gradually intensifying into a Category 1 hurricane on October 3. Leslie weakened back to a tropical storm the following day, and did not change much in intensity for the following several days. Leslie regained hurricane intensity on October 10, reaching its peak intensity with maximum sustained winds of 90 mph the following day. Leslie then transitioned into a hurricane-force extratropical cyclone just prior to moving inland into the Iberian Peninsula on October 13. Leslie outlived the following two named storms that formed after it.

The strongest storm of the season, Hurricane Michael, formed on October 7 over the Northwestern Caribbean Sea. Despite moderate wind shear, Michael rapidly intensified over the next three days, making landfall near Mexico Beach, Florida on October 10 with maximum sustained winds of 155 mph and a minimum pressure of 919 mb. It is possible Michael may have reached Category 5 intensity. Michael caused an estimated $14.6 billion in damage, and 60 fatalities. Tropical Storm Nadine formed over the eastern Tropical Atlantic on October 9, making it the easternmost tropical storm to form in the tropical Atlantic that late in the season. Michael transitioned into a post-tropical cyclone on October 12, and Nadine dissipated the following day on October 13.

The final named storm of the season, Oscar, formed over the central Atlantic as a Subtropical Storm on October 27. Oscar reached its peak intensity as a Category 2 hurricane two days later with maximum sustained winds of 105 mph. Oscar transitioned into a post-tropical cyclone on Halloween. Barring an unlikely December development, Oscar was the last named storm of the 2018 Atlantic hurricane season. No tropical cyclones formed in the Atlantic basin in November during 2018 for the first time since 2014.

The 2018 Atlantic hurricane season significantly exceeded most seasonal forecasts. Although early predictions called for a near or above average season from most forecasting groups, forecasts were lowered by the start of the season due to well below average sea surface temperatures over the tropical Atlantic and the possible development of El Niño late in the season. The Atlantic was likely more active than expected due to the high amount of subtropical storms as well as a strong West African Monsoon (WAM) present during the peak of the season. Although my final forecast was too low predicting 9-13 named storms, 5-7 hurricanes, 1-3 major hurricanes, and 80 ACE, it was more accurate than the Colorado State University and Tropical Storm Risk predictions, both of which called for well below average activity. The 2018 Atlantic hurricane season should be a lesson to those who wrote off the season due to colder than normal tropical Atlantic water temperatures in August: it only takes one storm for a season to be memorable (and 2018 had two significant hurricanes). My first outlook at the 2019 Atlantic hurricane season will be released in late December.