Mid-season shutdowns and active late seasons in the Atlantic: A trend or a blip?

[Teban54]

Alright, time for a discussion.

Three of the four most recent Atlantic hurricane seasons, 2022, 2024 and 2025, behaved in similarly unexpected and atypical ways.

• All three seasons were expected to be active by professionals. CSU's forecasts issued in July had 180, 230 and 140 ACE, respectively, all of which were above the 1991-2020 mean of 122.5.
• A La Nina was expected to develop in all three years, contributing to the high expectations.
• Two of the three years had active early seasons with Cat 5s: Beryl 2024 in July, and Erin 2025 in mid-August.
• All three years had significant, atypical, and sometimes record-breaking lulls in activity that lasted through the conventional "peak season". The exact timings and activity levels (underperformance or no formation at all) were different, but in all three cases, the basin was anomalously quieter than climo. "Season cancel" comments, and discussions of inactivity (2022, 2024), became more and more realistic and grounded.
• All three years made a major comeback in late September (and possibly later), with multiple major hurricanes. Many users found them utterly surprising and unexpected, given the hostile conditions that preceded.

An irony is that 2023, which ended above-average despite a strong El Nino, actually had a "typical" peak-season schedule. Four storms formed on or close to the "bell ringing day" of August 20 itself (which was frequently used to compare to 2024 and 2025), and all three MHs of that season occurred in late August and early September.

Of course, it could have just been a coincidence, similar to "there won't be a Cat 5 ever again" or "CONUS won't be hit by an MH ever again".

But it also naturally makes you wonder... Could this be the start of a trend?

[Teban54]

A recap of how this applies to each season:

2022

• Peak season lull: No storms existed for almost two months between July 3 - August 31 (first time since 1941).
  
  • August was storm-free: First since 1997, and first in a La Nina.
  • Multiple MDR waves and "model storms" failed to develop, eroding confidence of storm watchers.
  • Even when TC genesis resumed, storms continued to underperform by peak-season standards. Earl in particular was forecast to peak as a Cat 4, but only managed Cat 2 after struggling with dry air. Many people wrote off the season afterwards.
• Late season comeback: The "switch" flipped on September 14 when Fiona formed. The season went 9/6/2 afterwards, including the two major hurricanes that defined the season: Fiona and Ian.
  
  • Both MHs were very destructive, making 2022 the third costliest Atlantic hurricane season at the time. (It has since dropped to the 4th.)
  • Even October and November produced 4 hurricanes, including 3 in November alone, albeit all as Cat 1s.

2024

• Active early season: 2024 produced the earliest Cat 4 and Cat 5 hurricane on record, Beryl, which became a Cat 5 on July 1. Because of it and widespread active indicators, expectations of hyperactivity were widely agreed upon -- right until the peak season.
• Peak season lull: The exact boundaries are debatable, but there was widespread consensus that 2024 was surprisingly inactive from late August to early or mid-September, especially given the high expectations.
  
  • No storms formed between August 13 (after Ernesto) and September 8 (before Francine). The only other such occurrence in the satellite era was 1968.
  • Even after Francine formed, the season still underwhelmed. Until September 23, the conventional peak season only produced one Cat 2 hurricane (Francine) and one TS (Gordon).
  • "Model storm" failures again contributed: pre-Francine was repeatedly expected to form much earlier than it actually did, and Gordon was initially hyped to be a significant CV hurricane.
• Late season comeback: The "switch" flipped indisputably on September 24, when Helene formed (and eventually did major damage to southeast US). The season went 11/7/4 afterwards, and displayed one of the most extraordinary late seasons on record with multiple records broken, rivaling 2020.
  
  • Kirk was an unusually late CV major, and shattered just about every record for MDR storms in October: easternmost hurricane, Cat 3, and Cat 4.
  • October 6, 2024 was the first time in record that three simultaneous hurricanes existed in October.
  • Milton was the first sub-900 storm since 2005, the fourth most intense hurricane on record, and the most intense hurricane in the Gulf (both tied with Rita). Most storms of similar strength occurred either in the Western Caribbean or earlier in the season.
  • Rafael was the strongest November Gulf hurricane on record, and one of the only two MHs known at that date and time (the other being Kate 1985).
  • The season was also very destructive with Helene and Milton, and is now the third costliest season (replacing - coincidentally - 2022).

2025

• Active early season: While not nearly as anomalous as last year, 2025 got a significant head start with Erin before the "bell ringing" day. Not only was it the most active mid-August since 2010, but very few Cat 5s existed earlier in this month, with Allen as the only close comparison. When Erin dissipated, 2025 had the 15th highest ACE-to-date.
• Peak season lull: No storms formed between August 24 - September 17. Again, there was only one other such occurrence in the satellite era: 1992.
  
  • You can argue that the lull continued for a few days beyond September 17, as Gabrielle's early life was uninspiring -- soon after forming, it was devoid of convection for a full day. Some were skeptical that it would become a MH or even a hurricane.
  • 2025 took "model storm failures" on steroids: Invest 91L got up to 60/90, with every model locked in for a significant hurricane, before it suddenly poofed on all models.
• Late season comeback: Obviously its story is still being written, but 2025 has already exceeded people's expectations given the lull.
  
  • Gabrielle reached Cat 4 on September 22 (at an unusually high latitude), massively outperforming expectations.
  • Humberto became the second Cat 5 of the season today, September 27. The first three hurricanes of the season all became major hurricanes; the only other such occurrence was 1935.

[al78]

Not nearly enough data to determine whether this is a trend or a blip. It reminds me of the talk about the record 11 consecutive years of absence of major hurricane landfalls in the U.S., look how that panned out! The problem is that humans have this tendency to try and attribute cause and effect to what may, and sometimes is, random noise, and is why it is possible to tell given two sequences, which one is truly random and which one someone has generated and tried to simulate randomness (the latter will have very little clustering compared to the former).

Maybe if these heavily backloaded seasons become more frequent, we'll see an end to season write-off and seasonal forecast bust claims when we are barely half way through the season, but I won't hold my breath.

[REDHurricane]

Not nearly enough data to determine whether this is a trend or a blip. It reminds me of the talk about the record 11 consecutive years of absence of major hurricane landfalls in the U.S., look how that panned out! The problem is that humans have this tendency to try and attribute cause and effect to what may, and sometimes is, random noise, and is why it is possible to tell given two sequences, which one is truly random and which one someone has generated and tried to simulate randomness (the latter will have very little clustering compared to the former).

Maybe if these heavily backloaded seasons become more frequent, we'll see an end to season write-off and seasonal forecast bust claims when we are barely half way through the season, but I won't hold my breath.

I agree with your assessment, though I do wonder how climate change factors into the way we should interpret short-term changes like this going forward. If we're talking about "normal" Earth climatological patterns, then yeah, 5 years means absolutely nothing and 50 years registers as a blip at most -- but given how insanely quickly the Earth as a whole is changing, it's starting to look like there may actually be an attributable cause behind some of these anomalous weather swings, and hopefully we'll be able to figure out exactly what those causes are (i.e., something more specific than just "everything is getting warmer") at some point to assist with seasonal forecast accuracy.

But yes, I think it's still a bit too soon to conclude that future years will follow this trend unless we're able to identify a distinct reason as to why this is happening, which I'm guessing we don't have the data/technology to successfully do quite yet.

[Hammy]

This seems like a longer term trend, but due to as of yet inconclusive (potentially short-term, potentially long term/relating to climate change) reasons, the break has gotten later, and deeper into the peak of the season, but there is precedent over the last 40ish years, albeit somewhat off and on, with inactive seasons pre-active period exluded:

1979 had nothing in August until the 25th
1981 had nothing form between Dennis (Aug 7) and Emily (Aug 31)
1984 had nothing until August 20
1985 actually had nothing after Elena for two weeks, Sep 4-17
1988 was quiet from Aug 10-28 except for several depressions
1990 while Isidore was long-lasting, nothing formed (or at least got named) Sep 7-23
1996-1999 were all quiet for almost a whole month between late July and August 19
1996, like 1990 (again, with Hortense this time being active) had a lull of no new storms being named from September 8-26
2002 had nothing between August 7-29
2006 nothing between August 7-22
2010 was quiet from August 6-22
2018 had a dead tropics for two months from early July until September 1 when Florence formed--while it wasn't completely quiet, only two short lived, high latitude storms formed
2019 had the six weeks between Barry and Chantal, July 16-Aug 20
2022 all of August was quiet
2023 was quiet from late July until August 21
2024 was quiet August 20-Sep 9
2025 quiet between August 28-September 17

So while there's a clear shift over the last two years, 2022 also stands out (ironic the only 'normal' quiet period in the last four years was an El Nino) and this seems like lateward shift in the normal pattern--and I cant help but personally wonder if Tonga (which did contribute significantly to upper atmospheric warming) may have played a role in this, though this is also theory as nothing has confirmed this

But there's been an observed trend for the last decade or two of increasingly backloaded seasons, this could likewise be the natural end result of that as well--as the activity shifts towards later in the season (for whatever undetermined reasons), the peak--along with the preceding quiet period--may be shifting later with it

[canebeard]

Although i want to, or try to accept new interpretations of relatively short term climatolgical changes, i would guess these type of seeming repeated patterns, are the result of most every other "apparent" meteorological trend--- pure chance.

[canebeard]

Although i want to, or try to accept new interpretations of relatively short term climatolgical changes, i would guess these type of seeming repeated patterns to some, have the same cause that results in most every other "apparent" meteorological trend--- pure chance.

As far as activity before July 25th; there is very likely still no corellation whatsoever betwen that period in a given year, and what happens after July 26th that year.

[MarioProtVI]

I think it really just boils down to unfortunate timing due to a variety of factors, though I will note the northward migration of the monsoon trough to unusually high latitudes has been a persistent feature of these shutdowns. Even 2020 had this issue as well, and because of this the waves that come off just get thrown northwestward into the colder waters and much drier air, shutting down any potential development or they just become huge elongated messes that don’t develop until they get further west into better conditions (Isaias, Laura, Gabrielle, etc).

The background forcing also appears to be a big factor in this as well, as we saw with the first half of this month and other periods, sometimes there is just too much subsidence that basically squashes any chances for development. This also ties into the ASW which was a persistent player since 2016 but appears to have shut off this year, where it would lead us to having a storm active usually. Finally there’s the issue of anticyclonic wavebreaking which seems to have also become a bigger issue recently and could probably be influenced by the persistent Niña-like state the basin has been in with the amount of northern ridging that’s occurred up there (leading to well above SSTAs there which influences ridge building as seen in 2022). That leads to the dry African air getting advected off and into the Atlantic leading to increased gradients IIRC, making the MDR more hostile.

Altogether I’m not quite sure if this has a common link, but there’s a good shot that as AGW continues to increase, that could influence the pattern to where these negative factors occur more frequently then they did say in 1995-2010.

[caneman]

Not nearly enough data to determine whether this is a trend or a blip. It reminds me of the talk about the record 11 consecutive years of absence of major hurricane landfalls in the U.S., look how that panned out! The problem is that humans have this tendency to try and attribute cause and effect to what may, and sometimes is, random noise, and is why it is possible to tell given two sequences, which one is truly random and which one someone has generated and tried to simulate randomness (the latter will have very little clustering compared to the former).

Maybe if these heavily backloaded seasons become more frequent, we'll see an end to season write-off and seasonal forecast bust claims when we are barely half way through the season, but I won't hold my breath.

Thank you. I've been preaching the same thing here for years. People keep wanting to blame this that and other as to cause. Climatology works only to a degree. We don't have enough history and each year is different and unique. Past performance does not equal future results.