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

[CyclonicFury]

Truly a rare sight. For the first time in the history of GTWOs, there is an empty GTWO on the peak day of Atlantic hurricane season. Unbelievable

[Pelicane]

Truly a rare sight. For the first time in the history of GTWOs, there is an empty GTWO on the peak day of Atlantic hurricane season. Unbelievable

https://i.imgur.com/p7LpB7P.png

Given all the major landfalls we've had in the last 10 years, I'd be nice to get a year where we just don't get anything.

[wwizard]

Truly a rare sight. For the first time in the history of GTWOs, there is an empty GTWO on the peak day of Atlantic hurricane season. Unbelievable

https://i.imgur.com/p7LpB7P.png

Doing a little research, had those maps existed in 1992, that would be the last time it likely would have been clean. That year on September 10th, it was 13 days after Andrew and 7 days before Bonnie formed. Unless there were low percentage areas of interest somewhere out there the map likely would have been clean.

1992 is also the last time there were no TCs forming in the first 15 days of September.

[MarioProtVI]

Truly a rare sight. For the first time in the history of GTWOs, there is an empty GTWO on the peak day of Atlantic hurricane season. Unbelievable

https://i.imgur.com/p7LpB7P.png

And now we have a 0/20 now

[CrazyC83]

With these frequent peak-season lulls make me wonder, is there something weird happening back in Africa? If we get a lot of storms in October and November, that could suggest that we might be moving towards a North Indian style cycle?

Also, at this time of year, it's quite uncommon to get storms from non-tropical sources.

[Hypercane_Kyle]

And I thought September 2024's lull was tame... September 2025 is an actual ghost town out there.

[kevin]

Look at the SST change over the last two months. The enormous heat anomalies in the subtropics are pretty much gone with now a lot more SST anomalies in the deep tropics: the MDR, Caribbean and the Gulf. Kinda shocking how extremely quiet the season has been the last few weeks considering this, but the truth remains that there is massive untapped potential in the deep tropics.

The North Atlantic as a whole now has a +0.31C anomaly wrt 1991-2020 climatology which is far removed from the record years 2024 (+0.80C) and 2023 (+1.22C). But this is mainly due to the cooler subtropics and near-polar regions. The MDR is the third-warmest on record (of course behind 2023, 2024) with an anomaly of +0.70C and is at a similar level as 2010, 2017 & 2020 this time of year. The Gulf is even warmer than 2024 with an average anomaly of +0.93C (only behind 2023 which had +1.32C this time of year). Other years I remember the argument that a lot of heat build-up in the subtropics prevented deep tropics TCs. But now the deep tropics are on fire SST-wise and it's been all crickets the last few weeks. Maybe the rest of the season will change that.

September


July

[rockice]

I would like to know which causing Atlanta hurricane season to be so dead lately ?

[StormWeather]

I would like to know which causing Atlanta hurricane season to be so dead lately ?

Dry air spilling over the east side of a high pressure ridge (wave breaking) and consistent Troughing off of North America

[WeatherBoy2000]

Look at the SST change over the last two months. The enormous heat anomalies in the subtropics are pretty much gone with now a lot more SST anomalies in the deep tropics: the MDR, Caribbean and the Gulf. Kinda shocking how extremely quiet the season has been the last few weeks considering this, but the truth remains that there is massive untapped potential in the deep tropics.

The North Atlantic as a whole now has a +0.31C anomaly wrt 1991-2020 climatology which is far removed from the record years 2024 (+0.80C) and 2023 (+1.22C). But this is mainly due to the cooler subtropics and near-polar regions. The MDR is the third-warmest on record (of course behind 2023, 2024) with an anomaly of +0.70C and is at a similar level as 2010, 2017 & 2020 this time of year. The Gulf is even warmer than 2024 with an average anomaly of +0.93C (only behind 2023 which had +1.32C this time of year). Other years I remember the argument that a lot of heat build-up in the subtropics prevented deep tropics TCs. But now the deep tropics are on fire SST-wise and it's been all crickets the last few weeks. Maybe the rest of the season will change that.

September
https://i.imgur.com/Im1pZV8.png

July
https://i.imgur.com/4ZwA88R.png

I wonder if the relatively cool Canary Current/North Atlantic might have something to do with the suppressed activity. Although the MDR/Caribbean are warm, the ssts further north are not that of a favorable +amo configuration for TC activity.

Here's an example of a classic +amo pattern:



Ssts south of Greenland and in the Eastern Atlantic are warm as well, along a cool western subtropics. We're seeing the opposite of this right now north of the tropical Atlantic.

The more notable mdr years of the +amo era tended to have a configuration that looked like this:

[TomballEd]

With these frequent peak-season lulls make me wonder, is there something weird happening back in Africa? If we get a lot of storms in October and November, that could suggest that we might be moving towards a North Indian style cycle?

Also, at this time of year, it's quite uncommon to get storms from non-tropical sources.

Non-tropical to sub or tropical systems seems more common early/late than during peak season, but the A storm of 1983, the last major to landfall in HGX county warning area, formed on the tail end of a frontal trough.

Odd fact to that- if I recall correctly, 1014 mb when the system became a named TS is the highest pressure in the basin (and probably the world) of any TS. Made it to 962 mb/100 knots at landfall

[Teban54]

Look at the SST change over the last two months. The enormous heat anomalies in the subtropics are pretty much gone with now a lot more SST anomalies in the deep tropics: the MDR, Caribbean and the Gulf. Kinda shocking how extremely quiet the season has been the last few weeks considering this, but the truth remains that there is massive untapped potential in the deep tropics.

The North Atlantic as a whole now has a +0.31C anomaly wrt 1991-2020 climatology which is far removed from the record years 2024 (+0.80C) and 2023 (+1.22C). But this is mainly due to the cooler subtropics and near-polar regions. The MDR is the third-warmest on record (of course behind 2023, 2024) with an anomaly of +0.70C and is at a similar level as 2010, 2017 & 2020 this time of year. The Gulf is even warmer than 2024 with an average anomaly of +0.93C (only behind 2023 which had +1.32C this time of year). Other years I remember the argument that a lot of heat build-up in the subtropics prevented deep tropics TCs. But now the deep tropics are on fire SST-wise and it's been all crickets the last few weeks. Maybe the rest of the season will change that.

September
https://i.imgur.com/Im1pZV8.png

July
https://i.imgur.com/4ZwA88R.png

I wonder if the relatively cool Canary Current/North Atlantic might have something to do with the suppressed activity. Although the MDR/Caribbean are warm, the ssts further north are not that of a favorable +amo configuration for TC activity.

Here's an example of a classic +amo pattern:

https://cyclonicfury.com/wp-content/uploads/2017/06/AMO2010-300x182.png

Ssts south of Greenland and in the Eastern Atlantic are warm as well, along a cool western subtropics. We're seeing the opposite of this right now north of the tropical Atlantic.

The more notable mdr years of the +amo era tended to have a configuration that looked like this:

https://i.imgur.com/Ua4oOqC.png

The Canary current was anomalously warm at the end of August / early September: see my post back then.

[LarryWx]

The chance of total season ACE exceeding 100 continues to decline.

For reference, the 1991-2020 average from now to the end is 51:

-22 rest of Sept

-22 during Oct

-6 during Nov

-1 during Dec

So, to reach 100, 2025 would need to be ~10 above the 1991-2020 avg, a tall but not near impossible order. It being a weak La Nina and recent seasons being pretty heavily backloaded help those chances to an extent. What Gabrielle does or doesn’t do will be a pretty significant part of the mix.

[chaser1]

This year feels very 1992. One powerful hurricane (Andrew vs Erin), and primarily weak/low numbers of storms. The biggest deviation was the early strength of the W Atlantic ridge for a short period in August forcing Andrew westward into S. Florida. Beyond that, perhaps a more conservative standard for tropical cyclone designation & upgrade during the Neil Frank & Bob Sheet days.

After mid September 1992, no further threat to the Caribbean or U.S. occured. Will overall conditions result in the same quiet end of season? I think so. Of course, nothing is a given.

[LarryWx]

As of September 16th, total ACE in the Atlantic this season remains at 38.98 units. Of all Atlantic hurricane seasons since 1950 to feature below 40 units of ACE to date, only 1 single season has ever come back to produce a seasonal total of more than 100.

Historically, it is very difficult for late-season to make up for such prolonged inactivity during the peak-season in the Atlantic.


https://x.com/FerragamoWx/status/1968043029274796146?

[chaser1]

August 24 - September 24 2025 (6 more days)
- Highest sustained winds of any Atlantic tropical cyclone in the basin: 50 mph.
- Number of named storms: 1
- Number of hurricanes: 0

Looking at Gale-briella right now, I'd give those numbers a 50/50 shot of verifying

[REDHurricane]

If this season actually does end up with less than 100 ACE, then my money is on the record-shattering warm SST anomalies throughout the whole north Pacific as the confounding factor in this ostensibly ideal background state for Atlantic tropical cyclone development. I honestly don't know a whole lot about how the various global climate teleconnections work, but I'd be surprised if half of the Pacific Ocean boiling didn't cause some sort of weird chain effect down the line and somehow disrupt what history strongly suggests should be a favorable setup for a very busy hurricane season.

I mean, literally the entire north Pacific past approximately 25ºN is at least 2 degrees Celsius above average, with a huge chunk of that sitting at 3-4 degrees (or more) above average (!) -- nothing like this has ever been seen before:

[chaser1]

If this season actually does end up with less than 100 ACE, then my money is on the record-shattering warm SST anomalies throughout the whole north Pacific as the confounding factor in this ostensibly ideal background state for Atlantic tropical cyclone development. I honestly don't know a whole lot about how the various global climate teleconnections work, but I'd be surprised if half of the Pacific Ocean boiling didn't cause some sort of weird chain effect down the line and somehow disrupt what history strongly suggests should be a favorable setup for a very busy hurricane season.

I mean, literally the entire north Pacific past approximately 25ºN is at least 2 degrees Celsius above average, with a huge chunk of that sitting at 3-4 degrees (or more) above average (!) -- nothing like this has ever been seen before:

https://i.ibb.co/RkMFz1Bg/ct5km-ssta-v3-1-global-current.png

I think you make an interesting point. And if not the crazy flip-flop of cool Pacific equatorial SST's and VERY warm Pacific higher latitude SST's.... then what? I would be curious to know more about 2025's Northern Hemisphere atmospheric moisture gradients. Dry air seemed to play a significant factor on the Atlantic side but I'd be hard pressed to even guess what teleconnections might extraordinarily impact those conditions.

One correlation that I did find rather interesting is regarding those years that exhibit extremely low Total Season ACE exclusively for the GOM & Caribbean. In the 35 years going back to 1995, there seemed to be a clear link for those years having extreme low (GOM & Caribbean) ACE, to also equate to some of the most underactive Atlantic seasons during that same period. One recurring theme for those years was a weak and perhaps more northerly positioning of the Azores/Bermuda high. The other recurring theme during these same years was some type of backround factor which also seemed to mitigate nearly anything from developing in the Caribbean or the GOM during those same years. That's got to be more than just coincidence, and not entirely a result of "all" tropical waves entering the E. Atlantic further north and/or quickly recurving. Some type of unfavorable conditions had to be at play to also cap early & late season W. Caribbean ITCZ purtibations or Central America originating Gyre's from lifting north and developing? Oddly, there doesn't seem to be any kind of reverse correlation between weak West Atlantic mid (or deep) level ridging, and lower Sea Level (surface) Pressures through parts of the Caribbean or GOM during these years as one would think.

[Hammy]

I don't know what visible indicators there are to tell whether this has happened or not, but I wonder if something similar to 2013 (albeit later since we did have Erin) might've happened given basin-wide shear and intense troughing was a characteristic for that year--or if Erin's sheer size could have itself disrupted the ocean circulation in some way

[WeatherBoy2000]

I don't know what visible indicators there are to tell whether this has happened or not, but I wonder if something similar to 2013 (albeit later since we did have Erin) might've happened given basin-wide shear and intense troughing was a characteristic for that year--or if Erin's sheer size could have itself disrupted the ocean circulation in some way

I don't think Erin's the cause of what we're seeing now as the basin's largely been in an unfavorable state since the beginning of the season. Imo Erin was the equivalent to Andrew in 1992, an anomaly that found a small gap of favorability in an otherwise hostile basin.