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

[chaser1]

In other words, if a wave gets into Western Caribbean like the 0z Euro and 6z GFS show... Watch out.

Could be a Mitch redux?

[galaxy401]

The Caribbean has been dead due to how active the EPAC has been consistently. The storms over there pushes all the wind shear over the Caribbean.

This feels right, but shear over the Caribbean has been below average almost all season. Part of the issue seems to be a lack of tropical waves. Andy Hazleton has talked about this a few times. The waves either develop too early, are pulled north, or get desiccated by SAL before arriving. It’s just that the very few solid waves to track through the Caribbean have lined up with shear from the EPAC or dry conditions. So ‘bad luck’ (good luck?) has played a part.

Only question I have regarding that is the EPAC itself. The majority of storms that form in that basin originate from tropical waves. Considering the high number of storms there, that seems to imply there were many tropical waves that made it there. Most of these must have failed to develop in the Atlantic.

If there weren't a lot of tropical waves, then shouldn't there be less storms to form in the EPAC? Probably more reasons for that but it's just a surface-level observation.

[Teban54]

The Caribbean has been dead due to how active the EPAC has been consistently. The storms over there pushes all the wind shear over the Caribbean.

This feels right, but shear over the Caribbean has been below average almost all season. Part of the issue seems to be a lack of tropical waves. Andy Hazleton has talked about this a few times. The waves either develop too early, are pulled north, or get desiccated by SAL before arriving. It’s just that the very few solid waves to track through the Caribbean have lined up with shear from the EPAC or dry conditions. So ‘bad luck’ (good luck?) has played a part.

From Michael Lowry:

Interestingly, wind shear in the Caribbean has been running historically low through the heart of the season – consistent with a budding La Niña in the eastern equatorial Pacific. Since September, wind shear across the Caribbean has been the third lowest since 1979.

https://i.imgur.com/tPz1pmi.png

In other words, if a wave gets into Western Caribbean like the 0z Euro and 6z GFS show... Watch out.

Could be a Mitch redux?

No comment.

[Teban54]

Onto more serious stuff:

MJO is currently in the Maritime Continent and will move towards WPac, which may explain the WPAC invest and model storms. Looks like models have it either go strongly into WPAC or come back to the circle.

Around mid to late November, some favorable intraseasonal forcing could return to the Caribbean. This could provide one last chance for activity there (not that we need it).

[Category5Kaiju]

To say that I'm concerned about the future of this season is....an understatement.

With Erin already reaching Category 5 status by mid-August and with rumblings of yet another storm originating in the deep tropics in the coming days/weeks that potentially looks to be more of a land threat than Erin, there's no telling what September and October are going to look like. The fact that we're getting such formidable activity in what recently has been a relatively dead period in the Atlantic, combined with the expected -ENSO trend, makes me think that we still have a lot of season left and that Erin may not be the only Category 5 hurricane we see this season.

I know there's been a lot of mixed signals early on this hurricane season, but at this point I think the tropics have really shown how they would like to proceed forward in terms of activity. Buckle up, and be prepared.

Wow....I really said that.

[WaveBreaking]

To say that I'm concerned about the future of this season is....an understatement.

With Erin already reaching Category 5 status by mid-August and with rumblings of yet another storm originating in the deep tropics in the coming days/weeks that potentially looks to be more of a land threat than Erin, there's no telling what September and October are going to look like. The fact that we're getting such formidable activity in what recently has been a relatively dead period in the Atlantic, combined with the expected -ENSO trend, makes me think that we still have a lot of season left and that Erin may not be the only Category 5 hurricane we see this season.

I know there's been a lot of mixed signals early on this hurricane season, but at this point I think the tropics have really shown how they would like to proceed forward in terms of activity. Buckle up, and be prepared.

Wow....I really said that.

The more I think about it the more I realize Erin was this season’s Beryl in the sense that it was a preview of how favorable the season was going to be, despite both seasons having a period of downtime.

[MEANINGLESS_NUMBERS]

So what do we think? Done for the year? On average, November has 1 named storm. No likely candidates in the short term though.

[Category5Kaiju]

So what do we think? Done for the year? On average, November has 1 named storm. No likely candidates in the short term though.

Maybe one or two weak storms mid to late month, but otherwise, I think it's a wrap. Or at least, I hope. Melissa was enough.

[LarryWx]

So what do we think? Done for the year? On average, November has 1 named storm. No likely candidates in the short term though.

Since the start of the current active era, there have been 76% (16 of 21) of non-Nino seasons with at least one NS with TCG in the Nov-Dec period. The only ones without any TCG in Nov-Dec were 1995, 2000, 2010 (Thomas’ TCG was Oct 29), 2012, and 2021 (Wanda started Oct 30th).

So, I’m giving it ~75% chance for at least one more NS in 2025. And there may be a strong storm included based on 2024, 2020, 2016, 2008, and 1999. So, if I were a betting man, I’d bet we haven’t seen the last NS yet. But there’s ~25% chance I’d lose that bet based on these stats. So, we’ll see!

[CFLHurricane]

So what do we think? Done for the year? On average, November has 1 named storm. No likely candidates in the short term though.

CONUS is done, but the Caribbean or Central America are still in danger of a finale storm. Otherwise it would be baryclonic storm in the open Atlantic that may endanger Bermuda or the Azores, at most.

[Category5Kaiju]

Did you know that there was a high-end, extremely slow-moving Category 5 hurricane in the Western Caribbean Sea just a little less than a week ago?

Rhetorical question, of course.

[LarryWx]

https://www.star.nesdis.noaa.gov/pub/socd/mecb/crw/data/5km/v3.1_op/image_browse/daily/ssta/png/2025/ct5km_ssta_v3.1_global_20251101.png

Did you know that there was a high-end, extremely slow-moving Category 5 hurricane in the Western Caribbean Sea just a little less than a week ago?

Rhetorical question, of course.

Indeed as one can clearly see the cold wake (at to just above 0 C anomaly) near the track of Melissa vs +1+ C to the SW and over much of the Gulf.

Where it hardly moved for a long time to the S of Jamaica one can see a gray area (0C anomaly).

[Team Ghost]

Despite the near-record breaking number of Category V storms this season produced (Erin, Humberto, and Melissa), is it surprising, at least to me, that this season only produced 13 storms, only 5 of which became hurricanes. Perhaps someone more knowledgeable than me can explain why there are relatively so few storms and hurricanes; but either I would have expected a season with 3 Category V hurricanes to rival 2005 or 2020 in activity, or I would have expected a season with 13 storms and 5 hurricanes to have at most 1 Category V. Is there any precedent to this?

[Category5Kaiju]

Despite the near-record breaking number of Category V storms this season produced (Erin, Humberto, and Melissa), is it surprising, at least to me, that this season only produced 13 storms, only 5 of which became hurricanes. Perhaps someone more knowledgeable than me can explain why there are relatively so few storms and hurricanes; but either I would have expected a season with 3 Category V hurricanes to rival 2005 or 2020 in activity, or I would have expected a season with 13 storms and 5 hurricanes to have at most 1 Category V. Is there any precedent to this?

Basically, the season as a whole had various unfavorable factors (whether it be wind shear imparted by a TUTT, peak season stability, or a drier than usual African wave belt) that caused many potential storms to simply not form, and the ones that did were fairly weak in strength. This explains the slightly below average number of named storms. These conditions were intraseasonal, so the usual generic seasonal forecasts that are based on stuff like sea surface temperature anomalies, ENSO warmth, etc. weren't really able to detect this nuanced behavior.

However....this season also featured pockets of favorable conditions at given points in time, and one such area in particular happened to be the southwestern open Atlantic/Sargasso Sea. This is where storms like Erin and Humberto exploded in strength. Melissa happened in part due to the October/-ENSO late season climatology of activity naturally shifting into the Caribbean Sea. With extremely warm waters and a very favorable upper-level wind pattern, it's no surprise that Melissa became the titan that it did.

So, to sum things up, this season had two tales. Either a storm didn't form at all or formed and ended up very weak, falling victim to unfavorable ambient conditions.....or a storm found a pocket of very favorable conditions and took the utmost advantage of such.

Seasons like this aren't new (but also rare in the grand scheme of things). 2007 and 1999 come into mind. 1999 had 12 named storms in total, yet there were 8 hurricanes (3 Category 2 hurricanes and 5 Category 4 hurricanes, with Floyd and Lenny being the most notable storms of that year). 2007 had 15 named storms, of which 6 became hurricanes. 4 peaked only at Category 1 strength, but 2 became powerful, Caribbean-cruising Category 5 hurricanes (Dean and Felix). However, the unprecedented aspect of this season is that it's the first recorded season to feature more than 2 Category 5 storms and still finish with a below average number of named storms.

[Team Ghost]

I suppose these two maps explain the oddly low storm counts of 2025 and to a lesser extent 2024. There is no negative velocity potential in West Africa!





Honestly, without much justification, I assumed the African Standing Wave was one of the more minor impacts of global warming and that this negative velocity potential pattern would serve to keep storm counts high. That the standing wave survived the El Niños of 2018-19 and 2023-24 only further solidified that for me.

How else are you supposed to explain a year with not-so-stellar Atlantic SSTs and an El Niño (2018) having above-average activity? How else are you supposed to explain a year with a record-breaking El Niño (2023) having solidly above-average activity with 20 storms to boot? How else are you supposed to explain every season from 2018 to 2023 regardless of ENSO having this pattern.

Compared to expectations, 2024 and 2025 definitely underdelivered in terms of raw activity, but I think forecasters are adjusting to the suppression of the African Standing Wave these past few seasons. If anyone knows why this standing wave has been suppressed the last two seasons, that would be great.

[zzzh]

African standing wave from June to Sep was the most suppressive in this AMO+ period (since 1995). The level of sinking air in Africa-tropical Atlantic is comparable to some of the most inactive seasons in -AMO period.

[WeatherBoy2000]

African standing wave from June to Sep was the most suppressive in this AMO+ period (since 1995). The level of sinking air in Africa-tropical Atlantic is comparable to some of the most inactive seasons in -AMO period.

It'll be interesting to see if this year was just a one-off fluke or the start of a more suppressive period for the Atlantic. Ignoring majors/ace, this season only produced five hurricanes and 13 storms, the lowest since 2015.

[Team Ghost]

African standing wave from June to Sep was the most suppressive in this AMO+ period (since 1995). The level of sinking air in Africa-tropical Atlantic is comparable to some of the most inactive seasons in -AMO period.

It'll be interesting to see if this year was just a one-off fluke or the start of a more suppressive period for the Atlantic. Ignoring majors/ace, this season only produced five hurricanes and 13 storms, the lowest since 2015.

As shown above, 2024 also had positive velocity potential in Africa, and it produced 18 storms and 11 hurricanes. (This is still above average, but it is less than what some previous seasons with similar conditions produced.)

I remember looking at SST anomaly maps the spring of that year: the whole Atlantic was lit bright red, and off the heals of a Strong El Niño, a La Niña was forecast. With the combination of a record-warm Atlantic, an oncoming La Niña, and satellites allowing mets to detect more storms than ever before, I legitimately thought 2024 was very likely to exceed 200 ACE and exhaust the main naming list.

I was of course wrong, and I wonder if the suppressed African Standing Wave was the culprit. Something clearly changed in the Atlantic in 2024; that season, compared to every season from 2015 to 2023, started abnormally late, and August and September had relatively few storms. (Combined August and September 2024 had 8 storms, as opposed to 13 for 2023, 6 for 2022 (another season less active than expected), 15 for 2021, 14 for 2020, 10 for 2019, and 9 for 2018 (a year with an all-around awful Atlantic pattern that overperformed massively).) For how many storms 2023, a Strong El Niño year produced, it is surprising that 2024, a -ENSO year, produced fewer storms.