2025 Indicators: SST's, MSLP, Shear, SAL, Steering, Instability (Day 16+ Climate Models)

[LarryWx]

While I still expect activity to pick up in the back of half of September, there's an increasing chance we go the entire first 10 days (or perhaps longer) of September without a single tropical cyclone. That has to be extremely rare. Two years in a row, we've seen an uncharacteristic lull near the peak of the season. Unlike last year though, we've seen practically no Gulf activity except the weak, short-lived Barry in late June. Erin has been the only hurricane so far. 2025 is on pace to have the latest second hurricane in the NATL since 2013.

Regarding the current active era seasons with no El Niño:
-In 2024, there were 0 TCs during the 19 days 8/21-9/8.
-In 2022, there were 0 TCs in August.
-In 2016, there were 0 TCs Sep 4-11 and 0 H Sep 3-28.
-In 2013, there was no H til 9/11.
-In 2001, there was no H til 9/8

[WeatherBoy2000]

While I still expect activity to pick up in the back of half of September, there's an increasing chance we go the entire first 10 days (or perhaps longer) of September without a single tropical cyclone. That has to be extremely rare. Two years in a row, we've seen an uncharacteristic lull near the peak of the season. Unlike last year though, we've seen practically no Gulf activity except the weak, short-lived Barry in late June. Erin has been the only hurricane so far. 2025 is on pace to have the latest second hurricane in the NATL since 2013.

Regarding the current active era seasons with no El Niño:
-In 2024, there were 0 TCs during the 19 days 8/21-9/8.
-In 2022, there were 0 TCs in August.
-In 2016, there were 0 TCs Sep 4-11 and 0 H Sep 3-28.
-In 2013, there was no H til 9/11.
-In 2001, there was no H til 9/8

Except for 2013, all those seasons had at least relatively busy late seasons.

[aspen]

While I still expect activity to pick up in the back of half of September, there's an increasing chance we go the entire first 10 days (or perhaps longer) of September without a single tropical cyclone. That has to be extremely rare. Two years in a row, we've seen an uncharacteristic lull near the peak of the season. Unlike last year though, we've seen practically no Gulf activity except the weak, short-lived Barry in late June. Erin has been the only hurricane so far. 2025 is on pace to have the latest second hurricane in the NATL since 2013.

Either Erin was a freak anomaly and not representative of what peak season has in store (what we all thought Beryl was during the 2024 lull), or we’re going to have yet another delayed peak. 2024-levels of activity are likely off the table even if the latter happens.

I’m thinking we could end the season with 2022 numbers. Which is kind of what I suspected early on seeing the lukewarm to slightly unfavorable indicators — relatively tame SSTAs, unenthusiastic CanSIPS precipitation forecasts, etc. It didn’t seem like we were looking at another 15+ NS, >120-140 ACE season.

[StormWeather]

While I still expect activity to pick up in the back of half of September, there's an increasing chance we go the entire first 10 days (or perhaps longer) of September without a single tropical cyclone. That has to be extremely rare. Two years in a row, we've seen an uncharacteristic lull near the peak of the season. Unlike last year though, we've seen practically no Gulf activity except the weak, short-lived Barry in late June. Erin has been the only hurricane so far. 2025 is on pace to have the latest second hurricane in the NATL since 2013.

Either Erin was a freak anomaly and not representative of what peak season has in store (what we all thought Beryl was during the 2024 lull), or we’re going to have yet another delayed peak. 2024-levels of activity are likely off the table even if the latter happens.

I’m thinking we could end the season with 2022 numbers. Which is kind of what I suspected early on seeing the lukewarm to slightly unfavorable indicators — relatively tame SSTAs, unenthusiastic CanSIPS precipitation forecasts, etc. It didn’t seem like we were looking at another 15+ NS, >120-140 ACE season.

It sounds impossible after facing 10 straight years of average (2022) to above average (2016, 2017, 2018, 2019, 2020, 2021, 2023 and 2024) that we could see our first below average season since 2014, and that strikes me as odd.

[REDHurricane]

While I still expect activity to pick up in the back of half of September, there's an increasing chance we go the entire first 10 days (or perhaps longer) of September without a single tropical cyclone. That has to be extremely rare. Two years in a row, we've seen an uncharacteristic lull near the peak of the season. Unlike last year though, we've seen practically no Gulf activity except the weak, short-lived Barry in late June. Erin has been the only hurricane so far. 2025 is on pace to have the latest second hurricane in the NATL since 2013.

Either Erin was a freak anomaly and not representative of what peak season has in store (what we all thought Beryl was during the 2024 lull), or we’re going to have yet another delayed peak. 2024-levels of activity are likely off the table even if the latter happens.

I’m thinking we could end the season with 2022 numbers. Which is kind of what I suspected early on seeing the lukewarm to slightly unfavorable indicators — relatively tame SSTAs, unenthusiastic CanSIPS precipitation forecasts, etc. It didn’t seem like we were looking at another 15+ NS, >120-140 ACE season.

It sounds impossible after facing 10 straight years of average (2022) to above average (2016, 2017, 2018, 2019, 2020, 2021, 2023 and 2024) that we could see our first below average season since 2014, and that strikes me as odd.

There's absolutely no way that this season will end up below average, and I'd be willing to bet money on it if I cared enough -- it's September 5th, the Atlantic is only ~8 ACE below average, and the scene looks like this:



Yeah no, I'd say there's still a better chance that this season will reach 200 ACE than fall below the long-term average of ~125 ACE. I'll happily eat my crow if I'm wrong, but I really don't see how this current SST setup results in anything other than an above-average season -- sure, SSTs are only one part of the equation, but we have more than a century of data to very strongly suggest that the next 2.5 months in a La Niña/+AMO/tropics solidly above average/subtropics near average Atlantic background state will produce a high amount of tropical activity. Way too early to even think about starting the "season cancel" musings in my humble opinion; at this point that only serves to tempt fate.

[StormWeather]

Either Erin was a freak anomaly and not representative of what peak season has in store (what we all thought Beryl was during the 2024 lull), or we’re going to have yet another delayed peak. 2024-levels of activity are likely off the table even if the latter happens.

I’m thinking we could end the season with 2022 numbers. Which is kind of what I suspected early on seeing the lukewarm to slightly unfavorable indicators — relatively tame SSTAs, unenthusiastic CanSIPS precipitation forecasts, etc. It didn’t seem like we were looking at another 15+ NS, >120-140 ACE season.

It sounds impossible after facing 10 straight years of average (2022) to above average (2016, 2017, 2018, 2019, 2020, 2021, 2023 and 2024) that we could see our first below average season since 2014, and that strikes me as odd.

There's absolutely no way that this season will end up below average, and I'd be willing to bet money on it if I cared enough -- it's September 5th, the Atlantic is only ~8 ACE below average, and the scene looks like this:

https://i.ibb.co/N6gVPNxC/ct5km-ssta-v3-1-global-current.png

Yeah no, I'd say there's still a better chance that this season will reach 200 ACE than fall below the long-term average of ~125 ACE. I'll happily eat my crow if I'm wrong, but I really don't see how this current SST setup results in anything other than an above-average season -- sure, SSTs are only one part of the equation, but we have more than a century of data to very strongly suggest that the next 2.5 months in a La Niña/+AMO/tropics solidly above average/subtropics near average Atlantic background state will produce a high amount of tropical activity. Way too early to even think about starting the "season cancel" musings in my humble opinion; at this point that only serves to tempt fate.

That definitely looks like a La Niña event trying to form. And the Atlantic subtropics could be cooler, but the correlation is there for an active season. Just have to wait and see I guess.

[Category5Kaiju]

I guess in a certain sense, it would be very natural to watch an invest like 91L (with multiple models consistently showing significant development of the system, only to abruptly drop it even as it reached 60/90% chance of formation per NHC, all during the month of September), and begin to question the season's potential and if there's something strange going on with the basin.

However, in this case I think it would be wise to take a step back and look at the broad picture to have a better understanding of what may be happening. What do we know? Well, we know that the Atlantic currently is in an unfavorable MJO pattern. This has been talked about quite a bit for the past days/weeks since Erin departed the picture. That, or something related, may be the reason why there's so much dry air, shear, and stability/sinking motion associated with the deep tropics and why despite initial model excitement for 91L, there were, retrospectively, red flags for such to really amount to anything huge.

However, what we do know is that the deep tropics are still very warm, the Nino 3-4 region is starting to exhibit signs that it may enter some degree of La Nina or cool neutral for this winter, and a more favorable MJO pulse is expected to enter the basin by mid-month. These are all key ingredients to possibly fueling late season action, and as we've learned from 2022 and 2024, sometimes early September can look radically different from late September. Instability naturally increases as we enter fall can really do wonders to facilitate tropical cyclogenesis.

Also...as I type this, the 00z GFS and CMC are both spitting out another wave into the MDR that looks to become a trackable feature/system around the September 12th timeframe (so basically a week from now). It remains to be seen if this is a phantom or now, but unlike 91L, this theoretical system would actually coincide with the predicted favorable MJO pulse, and by then who knows if whatever negative factors caused 91L's demise are still around....or not? My point in all this is, while 91L's bust was certainly eyebrow-raising, at this point in time, I don't think it was indicative of some larger, underlying problem that will plague the basin for the forseeable future. If we still struggle with producing tropical cyclones throughout this month, then yes I would reconsider my stance on this, but for now I guess our eyes should shift to long-range models for mid-September. As a reminder, even the abysmal 2013 season saw its two hurricanes during September, and the 1914 season saw its only storm during September. We say "September Remember" for a reason.

[AxaltaRacing24]

I guess in a certain sense, it would be very natural to watch an invest like 91L (with multiple models consistently showing significant development of the system, only to abruptly drop it even as it reached 60/90% chance of formation per NHC, all during the month of September), and begin to question the season's potential and if there's something strange going on with the basin.

However, in this case I think it would be wise to take a step back and look at the broad picture to have a better understanding of what may be happening. What do we know? Well, we know that the Atlantic currently is in an unfavorable MJO pattern. This has been talked about quite a bit for the past days/weeks since Erin departed the picture. That, or something related, may be the reason why there's so much dry air, shear, and stability/sinking motion associated with the deep tropics and why despite initial model excitement for 91L, there were, retrospectively, red flags for such to really amount to anything huge.

However, what we do know is that the deep tropics are still very warm, the Nino 3-4 region is starting to exhibit signs that it may enter some degree of La Nina or cool neutral for this winter, and a more favorable MJO pulse is expected to enter the basin by mid-month. These are all key ingredients to possibly fueling late season action, and as we've learned from 2022 and 2024, sometimes early September can look radically different from late September. Instability naturally increases as we enter fall can really do wonders to facilitate tropical cyclogenesis.

Also...as I type this, the 00z GFS and CMC are both spitting out another wave into the MDR that looks to become a trackable feature/system around the September 12th timeframe (so basically a week from now). It remains to be seen if this is a phantom or now, but unlike 91L, this theoretical system would actually coincide with the predicted favorable MJO pulse, and by then who knows if whatever negative factors caused 91L's demise are still around....or not? My point in all this is, while 91L's bust was certainly eyebrow-raising, at this point in time, I don't think it was indicative of some larger, underlying problem that will plague the basin for the foreseeable future. If we still struggle with producing tropical cyclones throughout this month, then yes I would reconsider my stance on this, but for now I guess our eyes should shift to long-range models for mid-September. As a reminder, even the abysmal 2013 season saw its two hurricanes during September, and the 1914 season saw its only storm during September. We say "September Remember" for a reason.

This is also the same season that just produced a monster cat 5 only weeks ago. This season might end up like 2014 where it is very MJO reliant, meaning that we will get quality canes, but not a high storm total.

[Teban54]

Current SST Anomalies

I know that SSTs aren't everything, but we can still look at them.

Here's how North Atlantic SSTAs evolved in the past month (source). MDR remains warmer than climo, while a lot of warmth in the subtropics has been wiped out by Erin (although that's starting to build back gradually). The western subtropics around 30N 60W is still a bit warm, but nowhere near as extreme as many recent years (including 2022 and 2024).



The Atlantic MDR (which includes the Caribbean in all charts below) has been running 0.5 C above average since August:



Here is an excellent interactive chart of how SSTs compare to different years:



The following years have higher SSTs than 2025 on September 5:

• 2023 and 2024, by more than 0.5 C
• 2005, 2010 and 2017, by about 0.2 C

And then it's 2025. At equal levels to this year are 2019 and 2020; just below them are 2008 and 2022 (0.2 C cooler).

Of course, with climate change and the rest of the basin/globe warming in tandem, the same SST in 2025 is less meaningful than 2005/2010/2017. But still.

[WeatherBoy2000]

Current SST Anomalies

I know that SSTs aren't everything, but we can still look at them.

Here's how North Atlantic SSTAs evolved in the past month (source). MDR remains warmer than climo, while a lot of warmth in the subtropics has been wiped out by Erin (although that's starting to build back gradually). The western subtropics around 30N 60W is still a bit warm, but nowhere near as extreme as many recent years (including 2022 and 2024).

https://i.postimg.cc/W1qxP4Hm/archive-crw-ssta-natl-1.gif

The Atlantic MDR (which includes the Caribbean in all charts below) has been running 0.5 C above average since August:

https://cyclonicwx.com/data/sst/crw_ssta_graph_atlmdr.png

Here is an excellent interactive chart of how SSTs compare to different years:

https://i.postimg.cc/cJwH60rw/image.png

The following years have higher SSTs than 2025 on September 5:

• 2023 and 2024, by more than 0.5 C
• 2005, 2010 and 2017, by about 0.2 C

And then it's 2025. At equal levels to this year are 2019 and 2020; just below them are 2008 and 2022 (0.2 C cooler).

Of course, with climate change and the rest of the basin/globe warming in tandem, the same SST in 2025 is less meaningful than 2005/2010/2017. But still.

The chart below is the mdr compared to the rest of the global tropics, right now it's about 0.3-04c above it:



Theoretically, TC activity should be more favored in the tropical Atlantic, but outside Erin it so far hasn't been happening.

[MarioProtVI]

 https://x.com/andyhazelton/status/1964463019590902090

[MetroMike]

In Joe Bastardi's free Saturday summery video he was making comparisons with last year mid to late September with the MJO placement in 2024 and this years predicted placement along with similar pressure placements.
Very similar moisture in the western basin also.
Seems any threats for the conus will come from the western basin and not the MDR.
Shall see if this pans out.

[cycloneye]

 https://x.com/RyanMaue/status/1964515653576187997

[chaser1]

In Joe Bastardi's free Saturday summery video he was making comparisons with last year mid to late September with the MJO placement in 2024 and this years predicted placement along with similar pressure placements.
Very similar moisture in the western basin also.
Seems any threats for the conus will come from the western basin and not the MDR.
Shall see if this pans out.

I would actually be very curious to go back in time and compare last years MJO for September '24 and this year for myself. I don't specifically recall if last year's MJO was rather muted (close to or within the circle) or significantly more heightened?

[NDG]

Caribbean shear during the month of August was the top ten lowest of all times. Mind boggling that this year the Atlantic will not produce a single hurricane since Erin in mid August until at least mid September while in the same period of 2023 the Atlantic produced 5 hurricanes in the middle of a developing strong El Nino.
I think with the changing climate they need to go back to the drawing boards to find the bigger factors that come into play more now other than ENSO conditions.
We'll see if the rest of the season will be busy.

[MetroMike]

In Joe Bastardi's free Saturday summery video he was making comparisons with last year mid to late September with the MJO placement in 2024 and this years predicted placement along with similar pressure placements.
Very similar moisture in the western basin also.
Seems any threats for the conus will come from the western basin and not the MDR.
Shall see if this pans out.

I would actually be very curious to go back in time and compare last years MJO for September '24 and this year for myself. I don't specifically recall if last year's MJO was rather muted (close to or within the circle) or significantly more heightened?

Yes if you watch Joe's video from Saturday he shows the MJO from late September last year and it was more muted but over South America and the conus.
This year’s MJO forecast looks to be less muted and centered over the western basin also.

[Kingarabian]

Models showing a TC breakout in the EPAC. This would favor some subsidence over the GOM and the Caribbean over this period of time. Of course the EPAC has had a really hard time spawning actual systems of significance. So could be short lived.

Just have to wait until the EPAC slows down

[MarioProtVI]

I think it’s even more troubling when the CFS doesn’t show any signs of an increase in activity - over the last several days has persistently shown only one or two weak short-lived systems tracking across the basin the entire run despite the supposed MJO coming around 9/20. At this point it seems very very likely we are heading for a below-average season, and it’s possible we don’t get past 75 ACE by seasons end.

[Category5Kaiju]

I think it’s even more troubling when the CFS doesn’t show any signs of an increase in activity - over the last several days has persistently shown only one or two weak short-lived systems tracking across the basin the entire run despite the supposed MJO coming around 9/20. At this point it seems very very likely we are heading for a below-average season, and it’s possible we don’t get past 75 ACE by seasons end.

Does the CFS also think late September onward is going to be inactive? Maybe it's just me, but after how 2022 and 2024, being -ENSO years as well, dramatically improved in activity during that timeframe, I'd have to imagine that getting at least 35 ACE or more by November 30 would be feasible despite how conditions currently appear, given stability normally and naturally improves as we enter autumn.

[MarioProtVI]

I think it’s even more troubling when the CFS doesn’t show any signs of an increase in activity - over the last several days has persistently shown only one or two weak short-lived systems tracking across the basin the entire run despite the supposed MJO coming around 9/20. At this point it seems very very likely we are heading for a below-average season, and it’s possible we don’t get past 75 ACE by seasons end.

Does the CFS also think late September onward is going to be inactive? Maybe it's just me, but after how 2022 and 2024, being -ENSO years as well, dramatically improved in activity during that timeframe, I'd have to imagine that getting at least 35 ACE or more by November 30 would be feasible despite how conditions currently appear, given stability normally and naturally improves as we enter autumn.

The CFS doesn’t really show much of anything in late September/early October. I don’t remember how CFS was at this point in those years but with 2022 I think it still showed a burst late month. There’s no such burst on the last 7 or 8 runs of the CFS.