Why is the 2024 Atlantic hurricane season underperforming expectations?

[Hammy]

My expectation for Sep 10-Nov 30 is: ACE 75-100
5-6 hurricanes
3 MH

We'll see!

I think a new 2024 Remainder of 2024 Atlantic season Forecast poll with a short fuse 3 day deadline, for Sept. 10 - Nov 30 would be fascinating given the extreme unknown and disparity of opinion regarding what the remainder of the season will bring

This would put us about 2000-01 final numbers but with higher ACE I believe?

[toad strangler]

A seemingly epic bust of a seasonal forecast yet we are staring at possibly the third hurricane landfall in the CONUS. Bizzare!

[chaser1]

My expectation for Sep 10-Nov 30 is: ACE 75-100
5-6 hurricanes
3 MH

We'll see!

I think a new 2024 Remainder of 2024 Atlantic season Forecast poll with a short fuse 3 day deadline, for Sept. 10 - Nov 30 would be fascinating given the extreme unknown and disparity of opinion regarding what the remainder of the season will bring

Yep, even if the overall numbers prove out to not to be gang-buster I'm also still thinking a similar outcome in terms of strong intensities.
My guestimate at this time would probably be 10/7/4 (going forward, beginning today)

[chaser1]

My expectation for Sep 10-Nov 30 is: ACE 75-100
5-6 hurricanes
3 MH

We'll see!

I think a new 2024 Remainder of 2024 Atlantic season Forecast poll with a short fuse 3 day deadline, for Sept. 10 - Nov 30 would be fascinating given the extreme unknown and disparity of opinion regarding what the remainder of the season will bring

This would put us about 2000-01 final numbers but with higher ACE I believe?

Pretty decent comparison. Like a juiced-up version of 2000

[WeatherBoy2000]

My expectation for Sep 10-Nov 30 is: ACE 75-100
5-6 hurricanes
3 MH

We'll see!

This would put us about 2000-01 final numbers but with higher ACE I believe?

Pretty decent comparison. Like a juiced-up version of 2000

Interestingly, 2001 ended with 9 hurricanes and 4 majors but didn't see hurricane activity until the second week of September.

[FireRat]

My expectation for Sep 10-Nov 30 is: ACE 75-100
5-6 hurricanes
3 MH

We'll see!

This would put us about 2000-01 final numbers but with higher ACE I believe?

Pretty decent comparison. Like a juiced-up version of 2000

2000 huh, that would be interesting.
That year was pretty tame for the CONUS, hopefully the same is the case later this season, though I think we'll get hit a few more times after Francine!

[Category5Kaiju]

With Francine and what looks to potentially be a long tracking Cape Verde hurricane on the horizon, I’m fairly confident in saying that the two week lull we saw, while occurring during a time when hurricane activity is present in typical seasons and, thus, seemingly indicative of a strange early season shutdown, was just a temporary speed bump.

[tolakram]

With Francine and what looks to potentially be a long tracking Cape Verde hurricane on the horizon, I’m fairly confident in saying that the two week lull we saw, while occurring during a time when hurricane activity is present in typical seasons and, thus, seemingly indicative of a strange early season shutdown, was just a temporary speed bump.

I might agree if a second storm develops.

[chaser1]

What continues to occur out in the Atlantic between the African coastline and 60W reminds me of the early season EPAC. Models kept advertising development, only to be dashed away. Until proven otherwise and a tropical storm actually develops in the Eastern/Central Atlantic, or perhaps a clear near to mid-term MJO signal favoring Atlantic condition favorability occurs, then I have to believe that the Mt. Everest sized speedbump will continue to be a formidable obstacle for the Atlantic Wave train to overcome.

[MarioProtVI]

What continues to occur out in the Atlantic between the African coastline and 60W reminds me of the early season EPAC. Models kept advertising development, only to be dashed away. Until proven otherwise and a tropical storm actually develops in the Eastern/Central Atlantic, or perhaps a clear near to mid-term MJO signal favoring Atlantic condition favorability occurs, then I have to believe that the Mt. Everest sized speedbump will continue to be a formidable obstacle for the Atlantic Wave train to overcome.

Models are notoriously poor with handling monsoon trough interactions. The GFS especially has a tendency to string out vorticity from this waves and form gyre-like systems which indicates they do not have a solid grasp at all. For example, the GFS has played the string out method more then the EURO has (which seems to be having a better grip on the interactions). So I’m more inclined to believe the EURO and the GEFS ensembles which still support development into a strong hurricane down the road.

[chaser1]

What continues to occur out in the Atlantic between the African coastline and 60W reminds me of the early season EPAC. Models kept advertising development, only to be dashed away. Until proven otherwise and a tropical storm actually develops in the Eastern/Central Atlantic, or perhaps a clear near to mid-term MJO signal favoring Atlantic condition favorability occurs, then I have to believe that the Mt. Everest sized speedbump will continue to be a formidable obstacle for the Atlantic Wave train to overcome.

Models are notoriously poor with handling monsoon trough interactions. The GFS especially has a tendency to string out vorticity from this waves and form gyre-like systems which indicates they do not have a solid grasp at all. For example, the GFS has played the string out method more then the EURO has (which seems to be having a better grip on the interactions). So I’m more inclined to believe the EURO and the GEFS ensembles which still support development into a strong hurricane down the road.

Very true and that certainly applies to a significant overreach on the part of the GFS. In fact, this especially makes sense with regard to those model storms that conveniently suggest development well to the east. Beyond the African monsoonal low however, there are very clearly visible areas of low to mid levels of vorticity well west of any influence by the African monsoon which inevitably are fighting far more localized conditions preventing them from maintaining their convection and/or structure. We'll see if those conditions are slowly improving as the EURO depicts in roughly 138 hr's when the EURO brings 92L to sub 1000 mb pressures as well.

[toad strangler]

Speaking of baffling, per a recent Phil Klotzbach tweet, in the last 123 years (since 1900) only eight Atlantic Basin seasons have seen 3 or more US landfalling hurricanes by the date of 9/11
1915, 1916, 1933, 1934, 1985, 2004, 2005, 2020 and now 2024 makes 9 seasons.

Check out the back to back years that show up not once, not twice, BUT THREE TIMES in this small number of instances... now THAT's baffling So this season may not reach pre-season forecasted storm count or ACE totals (we shall see) but the word BUST is getting a little smaller and a little less bold as we move on here ..

[ConvergenceZone]

It looks like after Gordon and maybe the east coast possible weak disturbance, it's going to go quiet once again. Who would have thought this would be the case at the heart of September.

[WeatherBoy2000]

Interesting thread by Eric Webb about why this season failed to live up to expectations. He points to the +NAO that developed this summer as being a big factor behind the season under performing. Apparently a strong +NAO during the summer correlates with less active -enso Atlantic hurricane seasons and a very strong one developed this year:

 https://x.com/webberweather/status/1834675543817732353



 https://x.com/EricBlake12/status/1834697261491929430



 https://x.com/webberweather/status/1834705353340240154



The only hyperactive season listed is 1996. The other seasons ranged from average to below average and includes the infamous 2013 season.

[tolakram]

I wonder if that's really enough data to make a conclusion?

[Teban54]

Interesting thread by Eric Webb about why this season failed to live up to expectations. He points to the +NAO that developed this summer as being a big factor behind the season under performing. Apparently a strong +NAO during the summer correlates with less active -enso Atlantic hurricane seasons and a very strong one developed this year:

[...]

The only hyperactive season listed is 1996. The other seasons ranged from average to below average and includes the infamous 2013 season.

Interesting thoughts. I'm sure Larry would jump in with "NAO can be measured in different ways, and while one measure gives record +NAO, another measure that NOAA uses is nowhere near as anomalous".

But other than that: I just feel that the correlation between +NAO and less activity is something that had never been discussed before. Past discussions typically associate NAO way more with tracks than with overall activity levels (unlike AMO). +NAO seasons were typically considered more dangerous, as they steer systems further west and closer to land. (2023 and 2010 are the exact opposite, since both years had a persistent -NAO during peak season, and almost all CV storms recurved.)

This is not to say the correlation doesn't exist or is mere coincidence -- it's just as likely to be another case of "we still have a lot to learn for seasonal forecasts".

Also, NAO has now become neutral and will be well into negative territory in a few days. Will this help with dry air intrusions? Or will this be another 2023 situation, where CV storms move north too quickly and thus have limited time to intensify?

[Hypercane_Kyle]

Going forward, I'm just going to assume strong +NAO means an average hurricane season regardless of how favorable the background state is.

[Category5Kaiju]

There's a lot of rich discussions going on regarding this topic. It's really fascinating, to be honest.

But I do have a point I'd like to share, and that is: is there a possibility that the inhibitory factors in the Atlantic we're seeing now is somewhat associated with the El Nino from last year? I've noticed that some -ENSO seasons that occur right after a traditional El Nino tend to struggle in some shape or form. Since the +AMO era in 1995, here are the patterns I've seen:

1995: Right after the moderate El Nino of 1994. This is perhaps a classic example of a hyperactive year post-El Nino. No comment otherwise.

1998: Right after the very strong El Nino of 1997. While hyperactive, activity was heavily backloaded, and the two significant storms of the season (Georges and Mitch) happened after mid-September.

2007: Right after the weak El Nino of 2006. Aside from Category 5 twins Dean and Felix, activity was fairly weak and basically a slightly more juiced-up version of 2013 as there were no hurricanes that reached Cat 2-4 strength.

2010: Right after the moderate El Nino of 2009. While hyperactive, Wikipedia notes that "In spite of the high number of tropical cyclones, mid-level dry air dominated the tropical Atlantic throughout the peak of the season, perhaps hindering the season from being even more active."

2016: Right after the very strong El Nino of 2015. The season featured a fairly inactive July-August and even a September where only tropical storms formed. Then by the tail end of the month, Category 5 Matthew happened, followed by Category 4 Nicole and Category 3 Otto in the latter months of hurricane season.


** I will also add that in quite a few of these cases, the following year, assuming it also ended up as -ENSO, actually ended up being more active, especially if the first year failed to reach hyperactivity. 1999 featured more major hurricanes than 1998, 2008 was simply a much more impactful and active year than 2007, and 2017 ended up being the legendary hurricane season we remember it as. Pre-1995 examples of this include 1932/1933 and 1954/1955. Almost gets you wondering if 2025, assuming it is also a -ENSO year, may end up being what we initially thought 2024 would be.

[WeatherBoy2000]

Interesting thread by Eric Webb about why this season failed to live up to expectations. He points to the +NAO that developed this summer as being a big factor behind the season under performing. Apparently a strong +NAO during the summer correlates with less active -enso Atlantic hurricane seasons and a very strong one developed this year:

[...]

The only hyperactive season listed is 1996. The other seasons ranged from average to below average and includes the infamous 2013 season.

Interesting thoughts. I'm sure Larry would jump in with "NAO can be measured in different ways, and while one measure gives record +NAO, another measure that NOAA uses is nowhere near as anomalous".

But other than that: I just feel that the correlation between +NAO and less activity is something that had never been discussed before. Past discussions typically associate NAO way more with tracks than with overall activity levels (unlike AMO). +NAO seasons were typically considered more dangerous, as they steer systems further west and closer to land. (2023 and 2010 are the exact opposite, since both years had a persistent -NAO during peak season, and almost all CV storms recurved.)

This is not to say the correlation doesn't exist or is mere coincidence -- it's just as likely to be another case of "we still have a lot to learn for seasonal forecasts".

Also, NAO has now become neutral and will be well into negative territory in a few days. Will this help with dry air intrusions? Or will this be another 2023 situation, where CV storms move north too quickly and thus have limited time to intensify?

https://i.postimg.cc/SRh7XbGj/image.png

Yeah there still needs to be more research into this because it is just one of the numerous theories out there for why this season is failing. Whether a strong +NAO suppresses the Atlantic could be dependent on other factors, in certain cases it may not have a negative effect at all but in others it does. 1996 is listed for having a very strong +NAO during the summer and it was a hyperactive season with 9 hurricanes and 6 majors.

[WeatherBoy2000]

There's a lot of rich discussions going on regarding this topic. It's really fascinating, to be honest.

But I do have a point I'd like to share, and that is: is there a possibility that the inhibitory factors in the Atlantic we're seeing now is somewhat associated with the El Nino from last year? I've noticed that some -ENSO seasons that occur right after a traditional El Nino tend to struggle in some shape or form. Since the +AMO era in 1995, here are the patterns I've seen:

1995: Right after the moderate El Nino of 1994. This is perhaps a classic example of a hyperactive year post-El Nino. No comment otherwise.

1998: Right after the very strong El Nino of 1997. While hyperactive, activity was heavily backloaded, and the two significant storms of the season (Georges and Mitch) happened after mid-September.

2007: Right after the weak El Nino of 2006. Aside from Category 5 twins Dean and Felix, activity was fairly weak and basically a slightly more juiced-up version of 2013 as there were no hurricanes that reached Cat 2-4 strength.

2010: Right after the moderate El Nino of 2009. While hyperactive, Wikipedia notes that "In spite of the high number of tropical cyclones, mid-level dry air dominated the tropical Atlantic throughout the peak of the season, perhaps hindering the season from being even more active."

2016: Right after the very strong El Nino of 2015. The season featured a fairly inactive July-August and even a September where only tropical storms formed. Then by the tail end of the month, Category 5 Matthew happened, followed by Category 4 Nicole and Category 3 Otto in the latter months of hurricane season.


** I will also add that in quite a few of these cases, the following year, assuming it also ended up as -ENSO, actually ended up being more active, especially if the first year failed to reach hyperactivity. 1999 featured more major hurricanes than 1998, 2008 was simply a much more impactful and active year than 2007, and 2017 ended up being the legendary hurricane season we remember it as. Pre-1995 examples of this include 1932/1933 and 1954/1955. Almost gets you wondering if 2025, assuming it is also a -ENSO year, may end up being what we initially thought 2024 would be.

Next year being more active would be a strong possibility if this level of inactivity keeps up for the rest of the season.