2024 Indicators: SST's, MSLP, Shear, SAL, Steering, Instability (Day 16+ Climate Models)

[Hammy]

For a few days and then it looks like it will jump back above if the 30/70 pans out as a long tracker.

Models have been backing away hard from development

It’s far more likely they are struggling to resolve the MT breakdown and those that are backing off on development are in fact just stringing the system out way too fast. In fact, the latest 12z EURO still shows a strong system, and the ICON (which correctly nailed Francine FWIW) also still shows a strengthening tropical storm heading west. GFS has a notorious string out bias in cases like these so I’m inclined to ignore the oper and pay more attention to the ensembles which are far more active.

Models are showing much of the basin being completely overrun by shear in the next 72-96 hours. Euro OP is the only model that shows deveopment in any reasonable term (GFS is pushing back to 200+ hours as tends to happen when we get these model storms), even the Euro AI dropped it.



Canadian (as it's the only one to have satellite option out that far) shows this pretty well, just shredded by the TUTT

[sasha_B]

Francine is slop and will probably be lucky to become a hurricane at this point while 92L and 93L probably aren’t going to develop due to shear shutting the MDR down in a few days. Still feeling pretty good about a overall quiet season from here on out

Francine has a minimum central pressure well below that of a typical tropical storm (most Atlantic cyclones below hurricane strength with sub-990hPa lows are either sub-/extra-tropical or were at one point hurricanes, or both), and has been forecast to be a hurricane at landfall on 9 consecutive NHC advisories. Development odds for 93L have been steadily rising and are at 80% as of the NHC's 2pm tropical weather outlook. No one wants tropical storms to form or to have serious human impacts, but your strategy of downplaying any and all potential TC activity & laughing at those who don't do the same doesn't seem to add much to a discussion about a hurricane season that has already been substantially destructive & is still forecast to yield above-average activity - especially not when there's an active cyclone approaching a populated area in the next 24 hours or so, and about which people might be seeking reasonable discourse re:potential intensity.

[Category5Kaiju]

Francine's well on its way toward Category 2 status, the red MDR AOI has a 50/90 chance of developing into a system that looks to be a nice, recurving ACE-generator, and there's also increasing model support for a system meandering off the southeast US coast.

It's hard to bet against September.

[toad strangler]

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

Francine's well on its way toward Category 2 status, the red MDR AOI has a 50/90 chance of developing into a system that looks to be a nice, recurving ACE-generator, and there's also increasing model support for a system meandering off the southeast US coast.

It's hard to bet against September.

All of this began before climo peak. I suspected that the basin wouldn't go bone dry through the peak and now it's not a question. Also, I believe it is worth noting that Francine will be the third landfalling US hurricane this season. Entities such as CSU did call for a well above normal chance for multiple major landfalling hurricanes along the US coastlines and Caribbean in their final full season outlook. Although Beryl is the only major thus far (E Caribbean) I'd say that part is verifying pretty well. Also, earlier in this thread SFLcane showed some signs from the long range GFS that this season nay not go away quietly.

[SFLcane]

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

Francine's well on its way toward Category 2 status, the red MDR AOI has a 50/90 chance of developing into a system that looks to be a nice, recurving ACE-generator, and there's also increasing model support for a system meandering off the southeast US coast.

It's hard to bet against September.

All of this began before climo peak. I suspected that the basin wouldn't go bone dry through the peak and now it's not a question. Also, I believe it is worth noting that Francine will be the third landfalling US hurricane this season. Entities such as CSU did call for a well above normal chance for multiple major landfalling hurricanes along the US coastlines and Caribbean in their final full season outlook. Although Beryl is the only major thus far (E Caribbean) I'd say that part is verifying pretty well. Also, earlier in this thread SFLcane showed some signs from the long range GFS that this season nay not go away quietly.

[Emmett_Brown]

Watching 92L and 94L get stripped to naked swirls today gives real visual evidence of the strength of the easterly shear in the MDR this year. I can't recall easterly shear this strong and persistent before. These disturbances could always develop later (like Francine inevitably did)

[MarioProtVI]

Watching 92L and 94L get stripped to naked swirls today gives real visual evidence of the strength of the easterly shear in the MDR this year. I can't recall easterly shear this strong and persistent before. These disturbances could always develop later (like Francine inevitably did)

And yet 07L developed quickly off Africa.

[Emmett_Brown]

Watching 92L and 94L get stripped to naked swirls today gives real visual evidence of the strength of the easterly shear in the MDR this year. I can't recall easterly shear this strong and persistent before. These disturbances could always develop later (like Francine inevitably did)

And yet 07L developed quickly off Africa.

Good point. I guess it's the nature of the monsoon trough environment, where disturbances move much more slowly, vs the more rapidly moving tumbleweed structure of TD7 which is moving rapidly enough to reduce the relative shear.

[Teban54]

Watching 92L and 94L get stripped to naked swirls today gives real visual evidence of the strength of the easterly shear in the MDR this year. I can't recall easterly shear this strong and persistent before. These disturbances could always develop later (like Francine inevitably did)

CIMSS showed 92L and 94L generally in a low-shear environment, however. Unless 10 kts of easterly shear was somehow so detrimental...

[Emmett_Brown]

Watching 92L and 94L get stripped to naked swirls today gives real visual evidence of the strength of the easterly shear in the MDR this year. I can't recall easterly shear this strong and persistent before. These disturbances could always develop later (like Francine inevitably did)

CIMSS showed 92L and 94L generally in a low-shear environment, however. Unless 10 kts of easterly shear was somehow so detrimental...

https://i.postimg.cc/kGd1c62j/wg8shr.gif

Good point, this map implies the shear isn't bad. If you look at the vis loop of 92L, you can clearly see the mid level center and convection moving faster to the W and decoupling from the low level swirl which is lagging behind. So the shear is there, but the map doesn't show that. Perhaps the shear is relaxing.

[chaser1]

Plus, whatever "goldilocks" conditions which somehow have permitted TD7 to prevail seem rather tenuous per the NHC discussion. It is quite clear that its life expectancy may be quite short as well. I think this says volumes regarding the overall state of the Atlantic. Of course we can merrily pick some arbitrary moon phase, or other climo or historical reach to suggest the tropics will soon be "en fuego". Guess what, that view will likely fade at least by the time the first CONUS Arctic outbreak eventually occurs. No, this season is not dead nor is it cancelled but it is severely limping. I think we are fast approaching the point where most anything that even tries to develop east of 60W will be quickly disregarded as a probable recurve event. None of this detracts from whatever harm and destruction that continues to unfold from Francine or the few Caribbean or GOM systems likely to follow but the fear of a non stop raging season is subsiding day by day.

[Teban54]

Plus, whatever "goldilocks" conditions which somehow have permitted TD7 to prevail seem rather tenuous per the NHC discussion. It is quite clear that its life expectancy may be quite short as well. I think this says volumes regarding the overall state of the Atlantic. Of course we can merrily pick some arbitrary moon phase, or other climo or historical reach to suggest the tropics will soon be "en fuego". Guess what, that view will likely fade at least by the time the first CONUS Arctic outbreak eventually occurs. No, this season is not dead nor is it cancelled but it is severely limping. I think we are fast approaching the point where most anything that even tries to develop east of 60W will be quickly disregarded as a probable recurve event. None of this detracts from whatever harm and destruction that continues to unfold from Francine or the few Caribbean or GOM systems likely to follow but the fear of a non stop raging season is subsiding day by day.

The primary reason for TD 7 to weaken in a few days seems to be a wall of shear/TUTT in the subtropics reaching as far south as 20-30N. This has not been the case in late August, and models have been pretty consistent at showing that it will relax later in the month. CSU is also of the opinion that the increase in shear in early September has to do with the unfavorable MJO phase (which is currently in one of the least active phases for the Atlantic), and more importantly, has nothing to do with the main inhibitors people were discussing earlier (dry air etc).

Bottom line is, even if TD 7 weakens and/or underperforms, it would be for different reasons than earlier waves in the season. You can even say it simply got unlucky with timing.

[Teban54]

Danny Morris posted a theory that strong monsoon trough is detrimental to MDR activity. However, as he pointed out himself later in the post, this goes against the typical understanding from research that stronger monsoon trough usually helps with activity.

 https://x.com/dmorris9661/status/1834045374543057379

[Hammy]

Danny Morris posted a theory that strong monsoon trough is detrimental to MDR activity. However, as he pointed out himself later in the post, this goes against the typical understanding from research that stronger monsoon trough usually helps with activity.

 https://x.com/dmorris9661/status/1834045374543057379

There's probably a happy medium here, where if it's too strong, it can end up having the opposite outcome

[otowntiger]

Plus, whatever "goldilocks" conditions which somehow have permitted TD7 to prevail seem rather tenuous per the NHC discussion. It is quite clear that its life expectancy may be quite short as well. I think this says volumes regarding the overall state of the Atlantic. Of course we can merrily pick some arbitrary moon phase, or other climo or historical reach to suggest the tropics will soon be "en fuego". Guess what, that view will likely fade at least by the time the first CONUS Arctic outbreak eventually occurs. No, this season is not dead nor is it cancelled but it is severely limping. I think we are fast approaching the point where most anything that even tries to develop east of 60W will be quickly disregarded as a probable recurve event. None of this detracts from whatever harm and destruction that continues to unfold from Francine or the few Caribbean or GOM systems likely to follow but the fear of a non stop raging season is subsiding day by day.

Well said. Looking at long range models the conditions in the MDR are consistently hostile and when something does manage to spin up its swept OTS due to a virtually non existent Bermuda high. Again just about the exact opposite of what was forecast early in the season.

[toad strangler]

Plus, whatever "goldilocks" conditions which somehow have permitted TD7 to prevail seem rather tenuous per the NHC discussion. It is quite clear that its life expectancy may be quite short as well. I think this says volumes regarding the overall state of the Atlantic. Of course we can merrily pick some arbitrary moon phase, or other climo or historical reach to suggest the tropics will soon be "en fuego". Guess what, that view will likely fade at least by the time the first CONUS Arctic outbreak eventually occurs. No, this season is not dead nor is it cancelled but it is severely limping. I think we are fast approaching the point where most anything that even tries to develop east of 60W will be quickly disregarded as a probable recurve event. None of this detracts from whatever harm and destruction that continues to unfold from Francine or the few Caribbean or GOM systems likely to follow but the fear of a non stop raging season is subsiding day by day.

Well said. Looking at long range models the conditions in the MDR are consistently hostile and when something does manage to spin up its swept OTS due to a virtually non existent Bermuda high. Again just about the exact opposite of what was forecast early in the season.

This is true, As is multiple (three) US hurricane landfalls and only the 9th time in the last 123 years that has happened by the date of 9/11. So we have one extreme to the other. Can't mention one without the other and be fair on assessment mid season. The landfall threat was predicted pre season and has already pretty much verified. Long range GFS shows signs of activity in late Sept into October. Does that pan out and deflate the bust balloon a bit more? We shall see!

[al78]

Given the very quiet Pacific, little activity on the horizon for the Atlantic over the next few days apart from TD7 which will likely generate minimal amounts of ACE, and the Atlantic basin has now dropped below the 1991-2020 climatology to-date, I'm thinking this year could be close to a record low for tropical cyclone activity across the northern hemisphere this year assuming we only include the satellite era.

[USTropics]

Given the very quiet Pacific, little activity on the horizon for the Atlantic over the next few days apart from TD7 which will likely generate minimal amounts of ACE, and the Atlantic basin has now dropped below the 1991-2020 climatology to-date, I'm thinking this year could be close to a record low for tropical cyclone activity across the northern hemisphere this year assuming we only include the satellite era.

Thanks for continuing to post here, gives us a unique opportunity to pick the brain of one of our better mets/seasonal forecasters . Have you had any time to preliminary look at what type of 'fail mechanics' are disrupting activity in the NH and/or Atlantic? There have been quite a few different reasonings (mostly localized to the Atlantic), like (1) ITF position in the August/September months was anomalously higher in latitude due to displaced northern temp gradient,(2) overactive WAM also displaced north with weak vort maxes in the southern axis, (3) NAO+ being too extreme impacting dry air intrusions through regional atmospheric circulations, (4) destabilization of tropical troposphere with increasing upper tropospheric temps (relative to SSTA+) with decreased lapse rates, or (5) intraseasonal variability that can't be accurately forecasted at monthly lead times. If we're talking a hemispheric slowdown, would we want to look more at (4) and (5)? I know this answer is multifaceted with multiple/compounding issues, but which fail mechanic would you give more weight towards (or any other parameters/fail mechanics you're looking at adding to future seasonal forecasts)?

[Teban54]

From the 5am NHC advisory for TD 7:

In terms of moisture, the environment across the tropical Atlantic
has not been kind to weather systems over the past couple of months.

[al78]

Given the very quiet Pacific, little activity on the horizon for the Atlantic over the next few days apart from TD7 which will likely generate minimal amounts of ACE, and the Atlantic basin has now dropped below the 1991-2020 climatology to-date, I'm thinking this year could be close to a record low for tropical cyclone activity across the northern hemisphere this year assuming we only include the satellite era.

Thanks for continuing to post here, gives us a unique opportunity to pick the brain of one of our better mets/seasonal forecasters . Have you had any time to preliminary look at what type of 'fail mechanics' are disrupting activity in the NH and/or Atlantic? There have been quite a few different reasonings (mostly localized to the Atlantic), like (1) ITF position in the August/September months was anomalously higher in latitude due to displaced northern temp gradient,(2) overactive WAM also displaced north with weak vort maxes in the southern axis, (3) NAO+ being too extreme impacting dry air intrusions through regional atmospheric circulations, (4) destabilization of tropical troposphere with increasing upper tropospheric temps (relative to SSTA+) with decreased lapse rates, or (5) intraseasonal variability that can't be accurately forecasted at monthly lead times. If we're talking a hemispheric slowdown, would we want to look more at (4) and (5)? I know this answer is multifaceted with multiple/compounding issues, but which fail mechanic would you give more weight towards (or any other parameters/fail mechanics you're looking at adding to future seasonal forecasts)?

"Better mets" Thanks, but I'm not sure I qualify. When I read the discussion on individual storms on here it makes me realise how little I know about tropical cyclones beyond the fundamentals, so I view this forum as a good learning tool. I suspect contributors on here who live in regions vulnerable to tropical cyclones will have very good local meteorological knowledge which helps to give a perspective on an ongoing situation that someone living remote from the tropics like me doesn't have.

I haven't gone into detail looking at reasons for the huge under-performance of the Atlantic basin this year beyond following the discussion on here and brief communication with Phil Klotzbach. It is something I would like to spend some time doing, as when there is a forecast failure like this, I feel it is important to understand why, rather than brush it under the intra-seasonal variability carpet. The TSR model uses a statistical linear regression model to give an initial prediction of the seasonal numbers, followed by adjustments based on other factors not included in the regression and/or judgement. An understanding of some of the physical mechanisms in place over-riding a normally highly favourable pre-season setup will help improve judgement in the future.

Since I no longer work for a university and now work for EuroTempest, I cannot spend too much time in office hours looking into this given I am encouraged to prioritise work which is likely to contribute to revenue, but I will use at least some of my out-of-office hours to look into this.