Maximally active possible Atlantic hurricane season

[WalterWhite]

This post will seek to determine the maximally active possible Atlantic hurricane season both theoretically and practically. The most active year for each month in terms of storm count, hurricane count, and major hurricane count will be used. For instance, September 2020 was the most active September on record in terms of storm count with 10 storms, so the maximally active possible Atlantic hurricane season will be assumed to have 10 storms in September.

THEORETICAL LIMIT

For the theoretical limit, the following conditions must be met:

1. Extremely warm Atlantic SSTs to ensure storms have enough energy to form and intensify (beyond 2023 levels of warmth)
2. A strong, early-setting La Niña background state that prevents the Madden-Julian Oscillation from creating periods of inactivity
3. Extreme luck regarding subtropical cyclogenesis in the off-season

January: 1 storm, 1 hurricane, 0 major hurricanes (2016)
February: 1 storm, 0 hurricanes, 0 major hurricanes (1952)
March: 1 storm, 0 hurricanes, 0 major hurricanes (1908)
April: 1 storm, 0 hurricanes, 0 major hurricanes (2017)
May: 2 storms, 1 hurricane, 0 major hurricanes (2020 for storms, 1970 for hurricanes)
June: 3 storms, 2 hurricanes, 1 major hurricane (2023 for storms, 1968 for hurricanes, 1966 for major hurricanes)
July: 5 storms, 3 hurricanes, 2 major hurricanes (2005)
August: 8 storms, 5 hurricanes, 3 major hurricanes (2004)
September: 10 storms, 5 hurricanes, 4 major hurricanes (2020 for storms, 2005 for hurricanes, 2017 for major hurricanes)
October: 8 storms, 5 hurricanes, 3 major hurricanes (1950 for storms, 2010 for hurricanes, 2020 for major hurricanes)
November: 3 storms, 3 hurricanes, 2 major hurricanes (2020 for storms, 2001 for hurricanes, 2020 for major hurricanes)
December: 2 storms, 1 hurricane, 0 major hurricanes (1887)
Total: 45 storms, 21 hurricanes, 15 major hurricanes

PRACTICAL LIMIT

For the practical limit, the following conditions must be met:

1. Extremely warm Atlantic SSTs to ensure storms have enough energy to form and intensify (beyond 2023 levels of warmth)
2. A strong La Niña background state that prevents the the Madden-Julian Oscillation from creating periods of inactivity during the late season
3. Extreme luck regarding subtropical cyclogenesis in the off-season

Practically speaking, however, the Madden-Julian Oscillation will inevitably create areas of rising and sinking air during spring and summer in the Northern Hemisphere. Data indicates that favorable Madden-Julian Oscillation phases (i.e. Phases I-IV) are twice as active as unfavorable Madden-Julian Oscillation phases (i.e. Phases V-VIII). (Source: https://agupubs.onlinelibrary.wiley.com ... 23GL102762)

Because the Madden-Julian Oscillation has a full period of roughly two months during Northern Hemisphere spring and summer (i.e. the duration between two favorable periods is roughly two months) and because favorable MJO phases are generally twice as active as unfavorable MJO phases, the activity for the months of March, April, May, June, July, and August will each be reduced by 25%. The maximum theoretical Atlantic hurricane activity for these months is 19 storms, 11 hurricanes, and 6 major hurricanes. However, applying the reduction gives 15 storms, 9 hurricanes, and 5 major hurricanes. The other months are not affected because it is assumed the La Niñá background state would overpower the Madden-Julian Oscillation.

This reduction reduces the total storm count by 4, the total hurricane count by 2, and the total major hurricane count by 1, leading to a practical limit of 41 storms, 19 hurricanes, and 14 major hurricanes.

[Hurricane2022]

This post will seek to determine the maximally active possible Atlantic hurricane season both theoretically and practically. The most active year for each month in terms of storm count, hurricane count, and major hurricane count will be used. For instance, September 2020 was the most active September on record in terms of storm count with 10 storms, so the maximally active possible Atlantic hurricane season will be assumed to have 10 storms in September.

THEORETICAL LIMIT

For the theoretical limit, the following conditions must be met:

1. Extremely warm Atlantic SSTs to ensure storms have enough energy to form and intensify (beyond 2023 levels of warmth)
2. A strong, early-setting La Niña background state that prevents the Madden-Julian Oscillation from creating periods of inactivity
3. Extreme luck regarding subtropical cyclogenesis in the off-season

January: 1 storm, 1 hurricane, 0 major hurricanes (2016)
February: 1 storm, 0 hurricanes, 0 major hurricanes (1952)
March: 1 storm, 0 hurricanes, 0 major hurricanes (1908)
April: 1 storm, 0 hurricanes, 0 major hurricanes (2017)
May: 2 storms, 1 hurricane, 0 major hurricanes (2020 for storms, 1970 for hurricanes)
June: 3 storms, 2 hurricanes, 1 major hurricane (2023 for storms, 1968 for hurricanes, 1966 for major hurricanes)
July: 5 storms, 3 hurricanes, 2 major hurricanes (2005)
August: 8 storms, 5 hurricanes, 3 major hurricanes (2004)
September: 10 storms, 5 hurricanes, 4 major hurricanes (2020 for storms, 2005 for hurricanes, 2017 for major hurricanes)
October: 8 storms, 5 hurricanes, 3 major hurricanes (1950 for storms, 2010 for hurricanes, 2020 for major hurricanes)
November: 3 storms, 3 hurricanes, 2 major hurricanes (2020 for storms, 2001 for hurricanes, 2020 for major hurricanes)
December: 2 storms, 1 hurricane, 0 major hurricanes (1887)
Total: 45 storms, 21 hurricanes, 15 major hurricanes

PRACTICAL LIMIT

For the practical limit, the following conditions must be met:

1. Extremely warm Atlantic SSTs to ensure storms have enough energy to form and intensify (beyond 2023 levels of warmth)
2. A strong La Niña background state that prevents the the Madden-Julian Oscillation from creating periods of inactivity during the late season
3. Extreme luck regarding subtropical cyclogenesis in the off-season

Practically speaking, however, the Madden-Julian Oscillation will inevitably create areas of rising and sinking air during spring and summer in the Northern Hemisphere. Data indicates that favorable Madden-Julian Oscillation phases (i.e. Phases I-IV) are twice as active as unfavorable Madden-Julian Oscillation phases (i.e. Phases V-VIII). (Source: https://agupubs.onlinelibrary.wiley.com ... 23GL102762)

Because the Madden-Julian Oscillation has a full period of roughly two months during Northern Hemisphere spring and summer (i.e. the duration between two favorable periods is roughly two months) and because favorable MJO phases are generally twice as active as unfavorable MJO phases, the activity for the months of March, April, May, June, July, and August will each be reduced by 25%. The maximum theoretical Atlantic hurricane activity for these months is 19 storms, 11 hurricanes, and 6 major hurricanes. However, applying the reduction gives 15 storms, 9 hurricanes, and 5 major hurricanes. The other months are not affected because it is assumed the La Niñá background state would overpower the Madden-Julian Oscillation.

This reduction reduces the total storm count by 4, the total hurricane count by 2, and the total major hurricane count by 1, leading to a practical limit of 41 storms, 19 hurricanes, and 14 major hurricanes.

I think by 2030 - 2035 we're likely to see a season at or near these numbers, mostly due to damn global warming

[Category5Kaiju]

I will also mention that if we were to see these kinds of seasons with more than 40 named storms, then the Atlantic naming system is almost certainly going to have to become WPAC-like.

[Ianswfl]

This post will seek to determine the maximally active possible Atlantic hurricane season both theoretically and practically. The most active year for each month in terms of storm count, hurricane count, and major hurricane count will be used. For instance, September 2020 was the most active September on record in terms of storm count with 10 storms, so the maximally active possible Atlantic hurricane season will be assumed to have 10 storms in September.

THEORETICAL LIMIT

For the theoretical limit, the following conditions must be met:

1. Extremely warm Atlantic SSTs to ensure storms have enough energy to form and intensify (beyond 2023 levels of warmth)
2. A strong, early-setting La Niña background state that prevents the Madden-Julian Oscillation from creating periods of inactivity
3. Extreme luck regarding subtropical cyclogenesis in the off-season

January: 1 storm, 1 hurricane, 0 major hurricanes (2016)
February: 1 storm, 0 hurricanes, 0 major hurricanes (1952)
March: 1 storm, 0 hurricanes, 0 major hurricanes (1908)
April: 1 storm, 0 hurricanes, 0 major hurricanes (2017)
May: 2 storms, 1 hurricane, 0 major hurricanes (2020 for storms, 1970 for hurricanes)
June: 3 storms, 2 hurricanes, 1 major hurricane (2023 for storms, 1968 for hurricanes, 1966 for major hurricanes)
July: 5 storms, 3 hurricanes, 2 major hurricanes (2005)
August: 8 storms, 5 hurricanes, 3 major hurricanes (2004)
September: 10 storms, 5 hurricanes, 4 major hurricanes (2020 for storms, 2005 for hurricanes, 2017 for major hurricanes)
October: 8 storms, 5 hurricanes, 3 major hurricanes (1950 for storms, 2010 for hurricanes, 2020 for major hurricanes)
November: 3 storms, 3 hurricanes, 2 major hurricanes (2020 for storms, 2001 for hurricanes, 2020 for major hurricanes)
December: 2 storms, 1 hurricane, 0 major hurricanes (1887)
Total: 45 storms, 21 hurricanes, 15 major hurricanes

PRACTICAL LIMIT

For the practical limit, the following conditions must be met:

1. Extremely warm Atlantic SSTs to ensure storms have enough energy to form and intensify (beyond 2023 levels of warmth)
2. A strong La Niña background state that prevents the the Madden-Julian Oscillation from creating periods of inactivity during the late season
3. Extreme luck regarding subtropical cyclogenesis in the off-season

Practically speaking, however, the Madden-Julian Oscillation will inevitably create areas of rising and sinking air during spring and summer in the Northern Hemisphere. Data indicates that favorable Madden-Julian Oscillation phases (i.e. Phases I-IV) are twice as active as unfavorable Madden-Julian Oscillation phases (i.e. Phases V-VIII). (Source: https://agupubs.onlinelibrary.wiley.com ... 23GL102762)

Because the Madden-Julian Oscillation has a full period of roughly two months during Northern Hemisphere spring and summer (i.e. the duration between two favorable periods is roughly two months) and because favorable MJO phases are generally twice as active as unfavorable MJO phases, the activity for the months of March, April, May, June, July, and August will each be reduced by 25%. The maximum theoretical Atlantic hurricane activity for these months is 19 storms, 11 hurricanes, and 6 major hurricanes. However, applying the reduction gives 15 storms, 9 hurricanes, and 5 major hurricanes. The other months are not affected because it is assumed the La Niñá background state would overpower the Madden-Julian Oscillation.

This reduction reduces the total storm count by 4, the total hurricane count by 2, and the total major hurricane count by 1, leading to a practical limit of 41 storms, 19 hurricanes, and 14 major hurricanes.

I think by 2030 - 2035 we're likely to see a season at or near these numbers, mostly due to damn global warming

Why I also think We will see FL get more TS and hurricane in Nov, and maybe landfalling tropical storms in December sometimes. When the waters stay warmer longer.

[Hurricanehink]

I think by 2030 - 2035 we're likely to see a season at or near these numbers, mostly due to damn global warming

Why I also think We will see FL get more TS and hurricane in Nov, and maybe landfalling tropical storms in December sometimes. When the waters stay warmer longer.

We saw that when 2020 had two Category 4 hurricanes in November, when there were previously only a handful of majors in the month. And speaking of Eta in 2020, does it and Nicole in 2022 mean the start of a new trend for later storms affecting the US?

[CyclonicFury]

I think by 2030 - 2035 we're likely to see a season at or near these numbers, mostly due to damn global warming

Why I also think We will see FL get more TS and hurricane in Nov, and maybe landfalling tropical storms in December sometimes. When the waters stay warmer longer.

We saw that when 2020 had two Category 4 hurricanes in November, when there were previously only a handful of majors in the month. And speaking of Eta in 2020, does it and Nicole in 2022 mean the start of a new trend for later storms affecting the US?

It's interesting how, despite the later hurricanes we've seen in recent years and earlier storm formations, we aren't really seeing intense hurricanes any earlier. There hasn't been a June hurricane since 2012, or a June major hurricane since 1966. There also hasn't been a single major hurricane in the Atlantic basin before August 20th in over a decade.

[Category5Kaiju]

Why I also think We will see FL get more TS and hurricane in Nov, and maybe landfalling tropical storms in December sometimes. When the waters stay warmer longer.

We saw that when 2020 had two Category 4 hurricanes in November, when there were previously only a handful of majors in the month. And speaking of Eta in 2020, does it and Nicole in 2022 mean the start of a new trend for later storms affecting the US?

It's interesting how, despite the later hurricanes we've seen in recent years and earlier storm formations, we aren't really seeing intense hurricanes any earlier. There hasn't been a June hurricane since 2012, or a June major hurricane since 1966. There also hasn't been a single major hurricane in the Atlantic basin before August 20th in over a decade.

There are definitely speculations that the Atlantic hurricane season might be becoming more backloaded.

[Ianswfl]

We saw that when 2020 had two Category 4 hurricanes in November, when there were previously only a handful of majors in the month. And speaking of Eta in 2020, does it and Nicole in 2022 mean the start of a new trend for later storms affecting the US?

It's interesting how, despite the later hurricanes we've seen in recent years and earlier storm formations, we aren't really seeing intense hurricanes any earlier. There hasn't been a June hurricane since 2012, or a June major hurricane since 1966. There also hasn't been a single major hurricane in the Atlantic basin before August 20th in over a decade.

There are definitely speculations that the Atlantic hurricane season might be becoming more backloaded.

Mark Suddith has mentioned this too and theories. Could be because more heat in the summer. More sinking air due to more heat. While it makes the sst boil the air like drier. As it cools down and the sst cool a tad we have better conditions. Could be why hurricane season is more active later now.

[Teban54]

It's interesting how, despite the later hurricanes we've seen in recent years and earlier storm formations, we aren't really seeing intense hurricanes any earlier. There hasn't been a June hurricane since 2012, or a June major hurricane since 1966. There also hasn't been a single major hurricane in the Atlantic basin before August 20th in over a decade.

There are definitely speculations that the Atlantic hurricane season might be becoming more backloaded.

Mark Suddith has mentioned this too and theories. Could be because more heat in the summer. More sinking air due to more heat. While it makes the sst boil the air like drier. As it cools down and the sst cool a tad we have better conditions. Could be why hurricane season is more active later now.

A question I have with this kind of theories is: Is it actually a change in long-term pattern, or just sheer luck?

The years 2006-2015 saw no Cat 5s, no CONUS major hurricane landfalls, and no Florida hurricane landfalls. People were thinking that would be the new norm, and even thought we were moving to a -AMO era. But since 2016, we've had 8 Cat 5s, 8 CONUS MH landfalls and 7 Florida H landfalls.

Even earlier this year, some pro mets were suggesting theories like "hurricanes transfer heat from the tropics to the subtropics, but with the subtropics being so warm, is there still a need for that" to support their forecasts of a below-average hurricane season.

[Ianswfl]

There are definitely speculations that the Atlantic hurricane season might be becoming more backloaded.

Mark Suddith has mentioned this too and theories. Could be because more heat in the summer. More sinking air due to more heat. While it makes the sst boil the air like drier. As it cools down and the sst cool a tad we have better conditions. Could be why hurricane season is more active later now.

A question I have with this kind of theories is: Is it actually a change in long-term pattern, or just sheer luck?

The years 2006-2015 saw no Cat 5s, no CONUS major hurricane landfalls, and no Florida hurricane landfalls. People were thinking that would be the new norm, and even thought we were moving to a -AMO era. But since 2016, we've had 8 Cat 5s, 8 CONUS MH landfalls and 7 Florida H landfalls.

Even earlier this year, some pro mets were suggesting theories like "hurricanes transfer heat from the tropics to the subtropics, but with the subtropics being so warm, is there still a need for that" to support their forecasts of a below-average hurricane season.

I think that was luck too. Ike could been hell of a lot strong had it not decided to take a trip over Cuba. Isaac 2012 could have been a lot stronger as well if not for that land interaction. Ike could been a monster had it gone north or south of Cuba. I mean a cat4 or cat5. Had Ike went through the Fl Straits instead.

[tolakram]

It's all random in my opinion.. I also think that high number of majors is a fantasy. Here's a good reason storms will now be limited along the east coast, possibly for the rest of the season.

 https://x.com/RyanMaue/status/1703829389220147467

[Ianswfl]

It's all random in my opinion.. I also think that high number of majors is a fantasy. Here's a good reason storms will now be limited along the east coast, possibly for the rest of the season.

 https://x.com/RyanMaue/status/1703829389220147467

Besides that's the east coast, gets cooler anyway. What about the Gulf. We could have a Kate 1985 this year with the hot water temps if upper level winds are favorable.

[WalterWhite]

It's all random in my opinion.. I also think that high number of majors is a fantasy. Here's a good reason storms will now be limited along the east coast, possibly for the rest of the season.

 https://x.com/RyanMaue/status/1703829389220147467

It is not entirely random, though. Conditions obviously influence certain seasons to have more storms than others. You would obviously expect a higher storm count, hurricane count, major hurricane count, and ACE from a season with a warm Atlantic and a cool equatorial Pacific than you would from a season with a cool Atlantic and a warm equatorial Pacific.

[al78]

For a massively hyperactive season:

June-July conditions like 2005.
August-September conditions like 2004.
October-November conditions like 2020.
December conditions like 2005.

[Hammy]

There are definitely speculations that the Atlantic hurricane season might be becoming more backloaded.

Mark Suddith has mentioned this too and theories. Could be because more heat in the summer. More sinking air due to more heat. While it makes the sst boil the air like drier. As it cools down and the sst cool a tad we have better conditions. Could be why hurricane season is more active later now.

A question I have with this kind of theories is: Is it actually a change in long-term pattern, or just sheer luck?

The years 2006-2015 saw no Cat 5s, no CONUS major hurricane landfalls, and no Florida hurricane landfalls. People were thinking that would be the new norm, and even thought we were moving to a -AMO era. But since 2016, we've had 8 Cat 5s, 8 CONUS MH landfalls and 7 Florida H landfalls.

Even earlier this year, some pro mets were suggesting theories like "hurricanes transfer heat from the tropics to the subtropics, but with the subtropics being so warm, is there still a need for that" to support their forecasts of a below-average hurricane season.

There were two Cat 5's in 2007, both of which made landfall at that intensity

[Teban54]

Mark Suddith has mentioned this too and theories. Could be because more heat in the summer. More sinking air due to more heat. While it makes the sst boil the air like drier. As it cools down and the sst cool a tad we have better conditions. Could be why hurricane season is more active later now.

A question I have with this kind of theories is: Is it actually a change in long-term pattern, or just sheer luck?

The years 2006-2015 saw no Cat 5s, no CONUS major hurricane landfalls, and no Florida hurricane landfalls. People were thinking that would be the new norm, and even thought we were moving to a -AMO era. But since 2016, we've had 8 Cat 5s, 8 CONUS MH landfalls and 7 Florida H landfalls.

Even earlier this year, some pro mets were suggesting theories like "hurricanes transfer heat from the tropics to the subtropics, but with the subtropics being so warm, is there still a need for that" to support their forecasts of a below-average hurricane season.

There were two Cat 5's in 2007, both of which made landfall at that intensity

Oops, I misremembered. But 2008-2015 is still quite a long steak without Cat 5s (though it can be argued that Igor might have been one).

The Cat 5 drought resulted in posts like this. There were multiple similar threads during those years with these unusually long streaks, such as the AMO thread.

[Ptarmigan]

I have wondered how much storms the Atlantic can produce. I know West Pacific have the most storms. They can go as high as 39 storms. West Pacific is larger and the area of warm water is larger compared to the Atlantic.

I would not be surprised prior to satellite that there have been over 30 storms in the Atlantic.

[Ptarmigan]

A question I have with this kind of theories is: Is it actually a change in long-term pattern, or just sheer luck?

The years 2006-2015 saw no Cat 5s, no CONUS major hurricane landfalls, and no Florida hurricane landfalls. People were thinking that would be the new norm, and even thought we were moving to a -AMO era. But since 2016, we've had 8 Cat 5s, 8 CONUS MH landfalls and 7 Florida H landfalls.

Even earlier this year, some pro mets were suggesting theories like "hurricanes transfer heat from the tropics to the subtropics, but with the subtropics being so warm, is there still a need for that" to support their forecasts of a below-average hurricane season.

There were two Cat 5's in 2007, both of which made landfall at that intensity

Oops, I misremembered. But 2008-2015 is still quite a long steak without Cat 5s (though it can be argued that Igor might have been one).

The Cat 5 drought resulted in posts like this. There were multiple similar threads during those years with these unusually long streaks, such as the AMO thread.

2007 had Dean and Felix. Both made landfall as Category 5 hurricanes, which is a rarity.

I think there were Category 5 hurricanes between 2008 to 2015. I am thinking Gustav (2008), Igor (2010), and Joaquin (2015).

Same goes with before the 2000s.

[Ianswfl]

I have wondered how much storms the Atlantic can produce. I know West Pacific have the most storms. They can go as high as 39 storms. West Pacific is larger and the area of warm water is larger compared to the Atlantic.

I would not be surprised prior to satellite that there have been over 30 storms in the Atlantic.

1933 very likely had many more storms. Remember, no satellites back then so you know there were a lot of storms not counted.

Also 1969. that was still the early days of satellite so I'm sure there were weak storms in the open atl not counted because satellites were not good enough back then to examine low level structures like they are now where junk storms are now named.

[Ubuntwo]

I have wondered how much storms the Atlantic can produce. I know West Pacific have the most storms. They can go as high as 39 storms. West Pacific is larger and the area of warm water is larger compared to the Atlantic.

I would not be surprised prior to satellite that there have been over 30 storms in the Atlantic.

1933 very likely had many more storms. Remember, no satellites back then so you know there were a lot of storms not counted.

Also 1969. that was still the early days of satellite so I'm sure there were weak storms in the open atl not counted because satellites were not good enough back then to examine low level structures like they are now where junk storms are now named.

It's funny you mention that. By the 70s it was quite the opposite, where systems were designated depressions purely for convection. Scatterometer satellites had yet to be developed. This led to inactive years like 1973 netting a whopping 24 depressions (only 8 became storms officially).