2025 NATL hurricane season is here

[cycloneye]

 https://x.com/NHC_Atlantic/status/1964741805569699844

[Travorum]

https://x.com/AndyHazelton/status/1964658176609116561

Interesting…I knew climate change is predicted to cause stronger storms and more rapid intensification, but I assumed the total number of storms would remain the same.

I've seen some suggestions that since climate change results in greater warming in the subtropics compared to the tropics, the decreased temperature gradient results in atmospheric conditions being a little less likely on average to be conducive to cyclogenesis. But when conditions are supportive, SSTs and OHC are present to support very high end hurricanes and so the net result is slightly fewer storms but more high end storms and more RI cases. Andy actually mentions this mechanism a little lower in that thread:

 https://x.com/AndyHazelton/status/1964664384132931822



Of course observationally right now we really don't have enough data to draw significant conclusions, but that's the theory.

[Category5Kaiju]

https://x.com/AndyHazelton/status/1964658176609116561

Interesting…I knew climate change is predicted to cause stronger storms and more rapid intensification, but I assumed the total number of storms would remain the same.

I've seen some suggestions that since climate change results in greater warming in the subtropics compared to the tropics, the decreased temperature gradient results in atmospheric conditions being a little less likely on average to be conducive to cyclogenesis. But when conditions are supportive, SSTs and OHC are present to support very high end hurricanes and so the net result is slightly fewer storms but more high end storms and more RI cases. Andy actually mentions this mechanism a little lower in that thread:

 https://x.com/AndyHazelton/status/1964664384132931822



Of course observationally right now we really don't have enough data to draw significant conclusions, but that's the theory.

It's a very intriguing theory for sure, and in a grand sense I guess it does make sense. However, I agree that we need more years to definitively conclude something like that, because a sample size of 3 years (let alone 3 years nearly back-to-back) is still quite small. As far as we may know, the phenomenon with -ENSO years displaying very quiet climatological peaks may very well just be a 2022/2024/2025 thing. If we reach the 2030s and still continue to see something like this, then perhaps we could have greater confidence to say that this kind of seasonal behavior may be a new norm.

But then again, I'm sure there were those who wondered if we would ever see an Atlantic Category 5 hurricane again. Until Matthew happened. Or, a major CONUS landfall. Until Harvey happened. Or, a Caribbean cruiser. Until Beryl happened. Or, a strong mid-August hurricane. Until Erin happened. When we think something's set in stone in terms of Atlantic seasonal behavior, we get a surprise or a reminder of the past every once in a while. This goes either way, and the way I see it we could easily see a -ENSO year in the very near future that exhibits a more "normal" seasonal timeline with multiple storms happening around September 10.

[Travorum]

I've seen some suggestions that since climate change results in greater warming in the subtropics compared to the tropics, the decreased temperature gradient results in atmospheric conditions being a little less likely on average to be conducive to cyclogenesis. But when conditions are supportive, SSTs and OHC are present to support very high end hurricanes and so the net result is slightly fewer storms but more high end storms and more RI cases. Andy actually mentions this mechanism a little lower in that thread:

[url]https://x.com/AndyHazelton/status/1964664384132931822[url]

Of course observationally right now we really don't have enough data to draw significant conclusions, but that's the theory.

It's a very intriguing theory for sure, and in a grand sense I guess it does make sense. However, I agree that we need more years to definitively conclude something like that, because a sample size of 3 years (let alone 3 years nearly back-to-back) is still quite small. As far as we may know, the phenomenon with -ENSO years displaying very quiet climatological peaks may very well just be a 2022/2024/2025 thing. If we reach the 2030s and still continue to see something like this, then perhaps we could have greater confidence to say that this kind of seasonal behavior may be a new norm.

But then again, I'm sure there were those who wondered if we would ever see an Atlantic Category 5 hurricane again. Until Matthew happened. Or, a major CONUS landfall. Until Harvey happened. Or, a Caribbean cruiser. Until Beryl happened. Or, a strong mid-August hurricane. Until Erin happened. When we think something's set in stone in terms of Atlantic seasonal behavior, we get a surprise or a reminder of the past every once in a while. This goes either way, and the way I see it we could easily see a -ENSO year in the very near future that exhibits a more "normal" seasonal timeline with multiple storms happening around September 10.

Oh yeah I definitely agree with all of this, and to be clear I'm not suggesting that this is a definite thing we're seeing right now but rather behavior that could possibly emerge over the next several decades. As you mentioned drawing concrete conclusions of patterns from data on a yearly scale—or even decade-order scale in the case of the Category 5/US landfalling MH droughts—is generally poor practice. And the 2020s in general have basically been a case study in how individual years can be downright weird when viewed in the context of climatological averages or inter-seasonal forcing factors like ENSO.

[cycloneye]

:team:

Now we wait for the first invest.

Or even better yet........... the 1st Season Cancel

That was post #19 of this thread on May 19th from chaser1 and it turns out that those kind of posts are all around social media on the peak days of the season. Who have thought that would occur but here we are as mother nature dictates how the weather and the tropics will be. I continue to see a backloaded rest of season.

[USTropics]

I've seen some suggestions that since climate change results in greater warming in the subtropics compared to the tropics, the decreased temperature gradient results in atmospheric conditions being a little less likely on average to be conducive to cyclogenesis. But when conditions are supportive, SSTs and OHC are present to support very high end hurricanes and so the net result is slightly fewer storms but more high end storms and more RI cases. Andy actually mentions this mechanism a little lower in that thread:

[url]https://x.com/AndyHazelton/status/1964664384132931822[url]

Of course observationally right now we really don't have enough data to draw significant conclusions, but that's the theory.

It's a very intriguing theory for sure, and in a grand sense I guess it does make sense. However, I agree that we need more years to definitively conclude something like that, because a sample size of 3 years (let alone 3 years nearly back-to-back) is still quite small. As far as we may know, the phenomenon with -ENSO years displaying very quiet climatological peaks may very well just be a 2022/2024/2025 thing. If we reach the 2030s and still continue to see something like this, then perhaps we could have greater confidence to say that this kind of seasonal behavior may be a new norm.

But then again, I'm sure there were those who wondered if we would ever see an Atlantic Category 5 hurricane again. Until Matthew happened. Or, a major CONUS landfall. Until Harvey happened. Or, a Caribbean cruiser. Until Beryl happened. Or, a strong mid-August hurricane. Until Erin happened. When we think something's set in stone in terms of Atlantic seasonal behavior, we get a surprise or a reminder of the past every once in a while. This goes either way, and the way I see it we could easily see a -ENSO year in the very near future that exhibits a more "normal" seasonal timeline with multiple storms happening around September 10.

Oh yeah I definitely agree with all of this, and to be clear I'm not suggesting that this is a definite thing we're seeing right now but rather behavior that could possibly emerge over the next several decades. As you mentioned drawing concrete conclusions of patterns from data on a yearly scale—or even decade-order scale in the case of the Category 5/US landfalling MH droughts—is generally poor practice. And the 2020s in general have basically been a case study in how individual years can be downright weird when viewed in the context of climatological averages or inter-seasonal forcing factors like ENSO.

This is a really interesting topic that is still being heavily researched (i.e., various climate models are attempting to forecast this). This is something I’ve worked on with a professor analyzing data, and I’ll discuss some of our findings, create some interactive graphs, and talk about limitations.

Let’s start by looking at the Atlantic basin, and we’ll extend the database to include all data from 1850-2024 first. Here are the plots for named storms, hurricanes, major hurricanes, maximum wind speed (adjusted by 1/10 of actual values for best fit to graph), and ACE (also adjusted by 1/10 of actual value).



Interactive chart: https://docs.google.com/spreadsheets/d/ ... nteractive

Observationally, as you noted, we’re dealing with limited data—TC records are noisy due to detection biases, especially pre-satellite era (before ~1960), and natural variability (e.g., Atlantic Multidecal Variability) can dominate short-term trends. Do the trends in the Atlantic change if we just isolate the years after the pre-satellite era?



https://docs.google.com/spreadsheets/d/ ... nteractive

Here is the issue though, we are trying to isolate basin-specific signals (like the Atlantic), and that is difficult to do. If we look at global trends (which has its own inherent limitations due to how various agencies track and validate data), there is a trend in less hurricanes but more intense events.



https://docs.google.com/spreadsheets/d/ ... nteractive

I think where Andy potentially is misleading here is he attributes a decrease in tropical cyclone activity due to a spatial temperature gradient reduction. This may play a role in weakening large scale circulations like the Hadley and Walker circulations, but it more ‘delays’ genesis (both in terms of seasonality and position).

There is a temperature gradient that is important here though, and that’s in the vertical—a lessening vertical temperature gradient directly relates to vertical lift and the lapse rate. The lapse rate is essentially the vertical temperature gradient (i.e., how quickly temperature drops with altitude, typically ~6.5 C/km in the troposphere).

In a warming climate, the upper troposphere in the tropics warms faster than the surface due to enhanced moist convection and latent heat release aloft. This "lessens" the gradient -> increasing static stability -> the atmosphere becomes more resistant to vertical displacement of air parcels.

Less instability means reduced CAPE, weaker updrafts, and thus less vertical lift, making it harder for thunderstorms to cluster and organize into TCs. This vertical stabilization is another key reason models project fewer TCs overall, complemented by meridional gradient effects. It's not the only factor—changes in humidity, shear, and vorticity also play in (see 99L and 91L)—but it directly ties to why genesis might become rarer even as intensity potential grows.

This AMS journal article does a great job of showing possible outcomes using climate model projections. Their findings are we will see an increase in occurrences of slow-moving storms near land in the Atlantic and eastern North Pacific, as well as an increase in polewarm LMI (meaning lifetime maximum intensity will occur further north), but a decrease in TC frequency.

https://journals.ametsoc.org/view/journ ... 0452.1.xml

[chaser1]

:team:

Now we wait for the first invest.

Or even better yet........... the 1st Season Cancel

That was post #19 of this thread on May 19th from chaser1 and it turns out that those kind of posts are all around social media on the peak days of the season. Who have thought that would occur but here we are as mother nature dictates how the weather and the tropics will be. I continue to see a backloaded rest of season.

Of course they are
It may very well be our favorite meme that YOU know will begin spreading around no matter how active hurricane season was. To some, hurricane season will never meet their expectations LOL.

[Category5Kaiju]

Or even better yet........... the 1st Season Cancel

That was post #19 of this thread on May 19th from chaser1 and it turns out that those kind of posts are all around social media on the peak days of the season. Who have thought that would occur but here we are as mother nature dictates how the weather and the tropics will be. I continue to see a backloaded rest of season.

Of course they are
It may very well be our favorite meme that YOU know will begin spreading around no matter how active hurricane season was. To some, hurricane season will never meet their expectations LOL.

What's even funnier is that there are some on social media who are like "yeah, no more NSs this year," and if you bring up 2022 or 2024, let alone 100+ recorded Atlantic years where at least something formed in September, they're like "well, 2025 could be the first year for such to happen."

I mean, maybe it's just me, but expecting a total outlier by default is...wild

[caneman]

That was post #19 of this thread on May 19th from chaser1 and it turns out that those kind of posts are all around social media on the peak days of the season. Who have thought that would occur but here we are as mother nature dictates how the weather and the tropics will be. I continue to see a backloaded rest of season.

Of course they are
It may very well be our favorite meme that YOU know will begin spreading around no matter how active hurricane season was. To some, hurricane season will never meet their expectations LOL.

What's even funnier is that there are some on social media who are like "yeah, no more NSs this year," and if you bring up 2022 or 2024, let alone 100+ recorded Atlantic years where at least something formed in September, they're like "well, 2025 could be the first year for such to happen."

I mean, maybe it's just me, but expecting a total outlier by default is...wild

Each year is in fact wholly and uniquely different. Just because it's never happened in the past doesn't mean it it cant or won't happen in the future. Especially given our data set for historical cyclone events is relatively small in comparison. Further, if I were a betting man, after just 6 days in September gone, I'd lay odds on storm development by end month. Of course, I would have also laid the odds on the Bulls pulling a massive upset of the Gators which had never happened before.

[al78]

I think before trying to attribute climate change to the lack of activity globally, if not just the Atlantic, this year, we ought to first find out what physical mechanisms are causing tropical cyclone suppression, then question if those physical mechanisms are more likely to be present with continual warming. Everything has cause and effect. If you have no idea why it is quiet against all expectations, how can you link it to climate change?

[caneman]

I think before trying to attribute climate change to the lack of activity globally, if not just the Atlantic, this year, we ought to first find out what physical mechanisms are causing tropical cyclone suppression, then question if those physical mechanisms are more likely to be present with continual warming. Everything has cause and effect. If you have no idea why it is quiet against all expectations, how can you link it to climate change?

Excellent point. Especially since recently we've been told with some level of certainty that the increase in cyclones and intense cyclones was most assuredly due to climate change and that we are to expect even more. You can't now also state that the lack of activity is also due to climate change and expect any one to take you seriously. Far more likely in my mind is that each year is wholly unique and different and can't just rely on history. If that were true as example that things must happen based solely on history then you would never see for example the Bulls upsetting the Gators because it had never happened before in history. There are always new firsts in everything in life.

[cycloneye]

Mr Webb is not surprised about where is the season going and that is lower ACE than normal.

 https://x.com/webberweather/status/1965029411822223450

[al78]

Mr Webb is not surprised about where is the season going and that is lower ACE than normal.

 https://x.com/webberweather/status/1965029411822223450

Every time something unusual happens that goes against predictions, there is always someone who comes out of the woodwork claiming they saw it coming, and it is always someone I've never heard of. I wonder why these people don't start doing their own seasonal foreecasts, they'd blow the current crop of experts out of the water if they are as good as they imply they are.

TSR does take into account April-June NAO when doing its seasonal forecast for the Atlantic. The NAO signal was very mixed with April negative, May near-neutral and June positive. It is possible the cooling of the MDR anomaly in June was related to the +NAO; however, SST have recovered since then, so I would question if the June NAO is a significant link to the current hiatus.

[WeatherBoy2000]

Mr Webb is not surprised about where is the season going and that is lower ACE than normal.

 https://x.com/webberweather/status/1965029411822223450

Every time something unusual happens that goes against predictions, there is always someone who comes out of the woodwork claiming they saw it coming, and it is always someone I've never heard of. I wonder why these people don't start doing their own seasonal foreecasts, they'd blow the current crop of experts out of the water if they are as good as they imply they are.

TSR does take into account April-June NAO when doing its seasonal forecast for the Atlantic. The NAO signal was very mixed with April negative, May near-neutral and June positive. It is possible the cooling of the MDR anomaly in June was related to the +NAO; however, SST have recovered since then, so I would question if the June NAO is a significant link to the current hiatus.

Eric Webb is a meteorologist, but I feel like this is a retread of 2024 again. People at this time last year were screaming about 2024 being a massive bust, and then things picked up big time once the mjo came into phase late September. For all we know, something like that happens again and CSU's forecast largely verifies.

[storm_in_a_teacup]

I think before trying to attribute climate change to the lack of activity globally, if not just the Atlantic, this year, we ought to first find out what physical mechanisms are causing tropical cyclone suppression, then question if those physical mechanisms are more likely to be present with continual warming. Everything has cause and effect. If you have no idea why it is quiet against all expectations, how can you link it to climate change?

Excellent point. Especially since recently we've been told with some level of certainty that the increase in cyclones and intense cyclones was most assuredly due to climate change and that we are to expect even more. You can't now also state that the lack of activity is also due to climate change and expect any one to take you seriously. Far more likely in my mind is that each year is wholly unique and different and can't just rely on history. If that were true as example that things must happen based solely on history then you would never see for example the Bulls upsetting the Gators because it had never happened before in history. There are always new firsts in everything in life.

To be fair, contradictory effects are a common thing in scientific research. Like in my field, I study the supermassive black holes at the centers of galaxies. When they consume matter, they generate a ton of energy that then gets deposited in the host galaxy. Simulations and observations show that this energy can suppress star formation in the galaxy, but they *also* show it can enhance star formation. It is unclear which effect dominates, or whether they have equal magnitude, or whether one or the other applies to different types of galaxies, or the same galaxy at different times.

...But this doesn't make supermassive black holes any less real

[caneman]

I think before trying to attribute climate change to the lack of activity globally, if not just the Atlantic, this year, we ought to first find out what physical mechanisms are causing tropical cyclone suppression, then question if those physical mechanisms are more likely to be present with continual warming. Everything has cause and effect. If you have no idea why it is quiet against all expectations, how can you link it to climate change?

Excellent point. Especially since recently we've been told with some level of certainty that the increase in cyclones and intense cyclones was most assuredly due to climate change and that we are to expect even more. You can't now also state that the lack of activity is also due to climate change and expect any one to take you seriously. Far more likely in my mind is that each year is wholly unique and different and can't just rely on history. If that were true as example that things must happen based solely on history then you would never see for example the Bulls upsetting the Gators because it had never happened before in history. There are always new firsts in everything in life.

To be fair, contradictory effects are a common thing in scientific research. Like in my field, I study the supermassive black holes at the centers of galaxies. When they consume matter, they generate a ton of energy that then gets deposited in the host galaxy. Simulations and observations show that this energy can suppress star formation in the galaxy, but they *also* show it can enhance star formation. It is unclear which effect dominates, or whether they have equal magnitude, or whether one or the other applies to different types of galaxies, or the same galaxy at different times.

...But this doesn't make supermassive black holes any less real

That in no way addresses the multitide of different types of seasons that have occurred and will occur going forward nor does it mean it's climate change.