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

[LarryWx]

Accuweather is going all in September

https://youtu.be/ywHWLaf5o9Q?si=WTv5KQbY1nvd73yR

In this Bernie Rayno says due to the ITCZ being down at 10N, the MDR waves are currently having difficulty developing. He said that normally the ITCZ is up at 15N at this time of year. He implied it will later go up to 15N and then allow AEWs to develop again.

This sounds like the reverse of what I’m reading here. Here I’m reading that waves are coming off Africa so far N (20N) that they’re too dry to develop due to having traveled over desert.

So these two things sound contradictory/inconsistent: ITCZ S of normal (10N) and AEWs N of normal (20N). Are both of these true? If so, how/why?

So, Danny Morris refers to the “northern displaced ITCZ” in here:
https://x.com/dmorris9661/status/182709 ... _&ref_url=

And Bernie Rayno at 2:55-3:10 of this says ITCZ is 5 degrees S of normal (10N instead of 15N):
https://m.youtube.com/watch?v=ywHWLaf5o9Q

So, what’s the truth?

I included the current ITCZ tracker from the CPC to help bring clarity here below...

https://www.cpc.ncep.noaa.gov/products/international/itf/itcz.jpg

Danny Morris has it correct, while accuweather goofed here. The ITCZ is and has been anomalously far north for the last few weeks. Because of this, tropical waves are tracking across Africa further north. The result of tropical waves tracking further north is that they tend to pick up more dust and dry air that stabilizes the atmosphere and are sending it out over the Atlantic ahead and behind them. This is why tropical cyclone formation has been a hard feat to achieve out over the Atlantic as of late and may very well continue to be an issue through peak season unless we see the ITCZ shift southward and ridging over Europe (which is also helping pump dry air out over the Atlantic) collapses.

Thanks very much for your reply. Are you saying that when Bernie Rayno pointed to the “white and blue” as the ITCZ that he was totally wrong? Did you see that part of the video? How can he, a pro met. for several decades be so wrong on something basic like that?

[WiscoWx02]

In this Bernie Rayno says due to the ITCZ being down at 10N, the MDR waves are currently having difficulty developing. He said that normally the ITCZ is up at 15N at this time of year. He implied it will later go up to 15N and then allow AEWs to develop again.

This sounds like the reverse of what I’m reading here. Here I’m reading that waves are coming off Africa so far N (20N) that they’re too dry to develop due to having traveled over desert.

So these two things sound contradictory/inconsistent: ITCZ S of normal (10N) and AEWs N of normal (20N). Are both of these true? If so, how/why?

So, Danny Morris refers to the “northern displaced ITCZ” in here:
https://x.com/dmorris9661/status/182709 ... _&ref_url=

And Bernie Rayno at 2:55-3:10 of this says ITCZ is 5 degrees S of normal (10N instead of 15N):
https://m.youtube.com/watch?v=ywHWLaf5o9Q

So, what’s the truth?

I included the current ITCZ tracker from the CPC to help bring clarity here below...

https://www.cpc.ncep.noaa.gov/products/international/itf/itcz.jpg

Danny Morris has it correct, while accuweather goofed here. The ITCZ is and has been anomalously far north for the last few weeks. Because of this, tropical waves are tracking across Africa further north. The result of tropical waves tracking further north is that they tend to pick up more dust and dry air that stabilizes the atmosphere and are sending it out over the Atlantic ahead and behind them. This is why tropical cyclone formation has been a hard feat to achieve out over the Atlantic as of late and may very well continue to be an issue through peak season unless we see the ITCZ shift southward and ridging over Europe (which is also helping pump dry air out over the Atlantic) collapses.

Thanks very much for your reply. Are you saying that when Bernie Rayno pointed to the “white and blue” as the ITCZ that he was totally wrong? Did you see that part of the video? How can he, a pro met. for several decades be so wrong on something basic like that?

I did indeed...we all make mistakes as meteorologists, be it terminology, pointing at the wrong thing...it happens I certainly wouldn't judge him too heavily for that.

[skyline385]

Keeping in mind that it's just a single person's opinion, which may be wrong (as being discussed concurrently in the models thread):

 https://x.com/dmorris9661/status/1827080052951138663

Few days ago he was blaming wavebreaking for it and was completely wrong there as well, I wouldn't put too much faith into his opinions. He is just another casual wx enthusiast on twitter who has been wrong many times before. If Philip K. thinks the active season will resume (which they specifically noted in their biweekly forecast) then it will.

[LarryWx]

I included the current ITCZ tracker from the CPC to help bring clarity here below...

https://www.cpc.ncep.noaa.gov/products/international/itf/itcz.jpg

Danny Morris has it correct, while accuweather goofed here. The ITCZ is and has been anomalously far north for the last few weeks. Because of this, tropical waves are tracking across Africa further north. The result of tropical waves tracking further north is that they tend to pick up more dust and dry air that stabilizes the atmosphere and are sending it out over the Atlantic ahead and behind them. This is why tropical cyclone formation has been a hard feat to achieve out over the Atlantic as of late and may very well continue to be an issue through peak season unless we see the ITCZ shift southward and ridging over Europe (which is also helping pump dry air out over the Atlantic) collapses.

Thanks very much for your reply. Are you saying that when Bernie Rayno pointed to the “white and blue” as the ITCZ that he was totally wrong? Did you see that part of the video? How can he, a pro met. for several decades be so wrong on something basic like that?

I did indeed...we all make mistakes as meteorologists, be it terminology, pointing at the wrong thing...it happens I certainly wouldn't judge him too heavily for that.

Fair enough. I’ll let it slide.
I looked at the ITCZ map. I see that it is 2-3 degrees N of normal over E half of Africa but then it is right at normal over the W half. Is that enough N to make a big difference in how dry the AEWs are? And with it at its normal position over the W half of Africa, why would AEWs be coming off Africa N of normal position?

[WiscoWx02]

Thanks very much for your reply. Are you saying that when Bernie Rayno pointed to the “white and blue” as the ITCZ that he was totally wrong? Did you see that part of the video? How can he, a pro met. for several decades be so wrong on something basic like that?

I did indeed...we all make mistakes as meteorologists, be it terminology, pointing at the wrong thing...it happens I certainly wouldn't judge him too heavily for that.

Fair enough. I’ll let it slide.
I looked at the ITCZ map. I see that it is 2-3 degrees N of normal over E half of Africa but then it is right at normal over the W half. Is that enough N to make a big difference in how dry the AEWs are? And with it at its normal position over the W half of Africa, why would AEWs be coming off Africa N of normal position?

If I remember correctly, the source region for a majority of Saharan Dust is this little basin in Sudan or Chad...where the ITCZ has been further than north as of late. I can't remember for the life of me what the basin/depression is called but I remember discussion of it either on here or Twitter a couple of years ago. One would surmise that a further north displaced ITCZ would bring stronger easterly winds to the basin, stirring up more dust which can then hitch a ride with the screaming AEJ. I won't pretend I know that as 100% fact, but that is my thought process behind it. Again though, this isn't the only reason dry air has been flooding the Atlantic basin and killing off most of the tropical waves that have attempted to exit Africa...ridging over Europe plays a major part in that too...if you look at 700-300mb relative humidity model runs, dry air coming down from the north in the eastern Atlantic is a big killer as well. This is because you have blocking over Europe that doesn't allow things to progress, so you are stuck with the same atmosphere pattern that is pushing dry air into the deep tropics from the north for weeks at a time...that high needs to break down and allow things to move along from my understanding for things to really get going again.

[Teban54]

The issue I have with the Europe ridging theory is: This can't be the only year with ridges over Europe. Why was it apparently never a problem until now? Were there other years with a similar pattern in August, and how did those years turn out?

Plus, I have an extremely hard time believing this single factor can kill off activity in the entire basin. (For example, some people are saying that because models expect the ridging to still be in place in early September even though other possible detrimental factors will fade away, that they don't expect the tropical Atlantic to wake up similar to 2022.) There are countless other years in which a single negative factor did nothing to stop an active season, and on the flip side of the coin, people love to say that a single positive factor (or even a combination of them) aren't enough to guarantee an active one.

Just throwing the question out there. I may try to answer that myself to some extent, but may not be able to.

[weeniepatrol]

The issue I have with the Europe ridging theory is: This can't be the only year with ridges over Europe. Why was it apparently never a problem until now? Were there other years with a similar pattern in August, and how did those years turn out?

Plus, I have an extremely hard time believing this single factor can kill off activity in the entire basin. (For example, some people are saying that because models expect the ridging to still be in place in early September even though other possible detrimental factors will fade away, that they don't expect the tropical Atlantic to wake up similar to 2022.) There are countless other years in which a single negative factor did nothing to stop an active season, and on the flip side of the coin, people love to say that a single positive factor (or even a combination of them) aren't enough to guarantee an active one.

Just throwing the question out there. I may try to answer that myself to some extent, but may not be able to.

[Hammy]

Pivotal Weather (which has 12z CFS runs) has at least five storms showing up in the western basin (including two in the Gulf) through September 20, including one brushing the Caribbean on September 3 (it's been very consistent doing this or recurving around this time) which would be the system that's likely to form between Aug 28-31

It's been showing this almost every single run now for the last 2-3 weeks

[Teban54]

FWIW, Euro weeklies still show a very wet tropical Atlantic in September. Unclear if these are the same runs that showed below-average ACE that Larry had been quoting earlier.

 https://x.com/WXTriad/status/1827208569353097291

[LarryWx]

FWIW, Euro weeklies still show a very wet tropical Atlantic in September. Unclear if these are the same runs that showed below-average ACE that Larry had been quoting earlier.

 https://x.com/WXTriad/status/1827208569353097291

Yes, it is the same run that I last posted although this goes a week later and is a WxBell version vs direct ECMWF source. Regardless, this map of rainfall anoms jibes pretty well with the wet ECMWF rainfall anoms 9/2-23. 9/23-30 is not as wet. Also, they’re not as wet in the W GOM as this WxBell map. Of course, wet anoms don’t necessarily mean “big hurr season” as this tweet said.

Yesterday JB showed the BN ACE of yesterday’s Euro Weeklies and said he was going to have to reduce the high level of impact he’s had in his forecasts although he’s implying he’ll still have pretty active. He sounded frustrated.

[Category5Kaiju]

The issue I have with the Europe ridging theory is: This can't be the only year with ridges over Europe. Why was it apparently never a problem until now? Were there other years with a similar pattern in August, and how did those years turn out?

Plus, I have an extremely hard time believing this single factor can kill off activity in the entire basin. (For example, some people are saying that because models expect the ridging to still be in place in early September even though other possible detrimental factors will fade away, that they don't expect the tropical Atlantic to wake up similar to 2022.) There are countless other years in which a single negative factor did nothing to stop an active season, and on the flip side of the coin, people love to say that a single positive factor (or even a combination of them) aren't enough to guarantee an active one.

Just throwing the question out there. I may try to answer that myself to some extent, but may not be able to.

This is the reason why unless I see evidence otherwise, I’m going to hedge this on intraseasonal variability rather than some weird X factor that we’ve never seen yet that ultimately decided to show its power for some reason this year. I sincerely think the former is much more likely than the latter

[LarryWx]

The progged Euro Weeklies ACE mean for 8/26-9/22 is 30. This is significantly below the 1991-2020 avg of 58. Over 75% of this deficit is due to weeks 1-2. The point is that despite wet Euro Weekly maps, they at the same time have much BN ACE. Wet anoms don’t necessarily mean active tropics.

JB yesterday showed these low ACE maps and said while laughing: “My numbers are just… they’re shot….I’m talking about the impact…This is just wild stuff. 50% of the normal ACE at the height of the season. Holy smokes. Now do I believe it? No, not really. But maybe it’s going to happen. There’s still going to be a lot of high impact forecasted but the numbers gotta come down”

[WeatherBoy2000]

Something strange is going on. Maybe whatever it is sorts itself out relatively quickly and models are just struggling, or this could be a long term issue. Tbh I think we'll reach hyperactivity due to what has already been accumulated, but it could be more in the realm of a 2010 minimally hyperactive season than a super one like 2005 and 2017. 2010 interestingly had record warm ssts for the time, and many agencies were putting out overly bullish forecasts due to it. It's clear that other things have to align right for a 200+ ace season than just record warm ssts and -enso.

[tolakram]

Something strange is going on. Maybe whatever it is sorts itself out relatively quickly and models are just struggling, or this could be a long term issue. Tbh I think we'll reach hyperactivity due to what has already been accumulated, but it could be more in the realm of a 2010 minimally hyperactive season than a super one like 2005 and 2017. 2010 interestingly had record warm ssts for the time, and many agencies were putting out overly bullish forecasts due to it. It's clear that other things have to align right for a 200+ ace season than just record warm ssts and -enso.

I'm going to disagree, I don't think anything strange is going on. Dare I say we've kind of gamified hurricane seasons, and they're more complex than that, much more complex than simple numbers. This year still has the potential to produce devastating storms if conditions line up correctly. This is why it's dangerous to predict extreme seasons with a number count that can pass or fail. Again, in my opinion.

I think IF this season fails to produce the extreme numbers we might see a move away from the storm counting and on to something else. I'd hate to see any forecasters suffer just because some number was incorrect. Heading into La Nina with record warm ocean temperatures should lead to a very bad season.

[cycloneye]

The Saharan desert is moist that means less SAL.

 https://x.com/cyclonicwx/status/1827356214335856894

[canes04]

Can someone ring the dam bell again!!

[chaser1]

Can someone ring the dam bell again!!

Sure thing, on September 2nd

[Hammy]

CFS continuing to show things taking off in about a week, looks like its zeroing in on August 31 (the same system the AIRS Euro is showing) with four additional storms by September 20

After this point, it shows a lull, and then an MDR outbreak in early October along with some Caribbean activity, so it seems to be adjusting for the monsoon trough slipping back southward more slowly than expected, so we might see a delayed peak and backloaded season similar to 2001

[MarioProtVI]

CFS continuing to show things taking off in about a week, looks like its zeroing in on August 31 (the same system the AIRS Euro is showing) with four additional storms by September 20

After this point, it shows a lull, and then an MDR outbreak in early October along with some Caribbean activity, so it seems to be adjusting for the monsoon trough slipping back southward more slowly than expected, so we might see a delayed peak and backloaded season similar to 2001

I’m having a bit of a hard time believing only 5 storms will form in September. Could see a bit more, perhaps 6 or 7, especially since CFS might not be catching some weaker short-lived storms that can easily fly under the radar at its current res.

[aspen]

CFS continuing to show things taking off in about a week, looks like its zeroing in on August 31 (the same system the AIRS Euro is showing) with four additional storms by September 20

After this point, it shows a lull, and then an MDR outbreak in early October along with some Caribbean activity, so it seems to be adjusting for the monsoon trough slipping back southward more slowly than expected, so we might see a delayed peak and backloaded season similar to 2001

I’m having a bit of a hard time believing only 5 storms will form in September. Could see a bit more, perhaps 6 or 7, especially since CFS might not be catching some weaker short-lived storms that can easily fly under the radar at its current res.

Alternatively, it could be a 2017-lite September where we don’t get as many NS as some other active years, but all or most of the are quality storms. So far this season hasn’t had a single shortie outside of Chris, and that was still a wave-genesis system in the tropics. I think it’s very probable we only get 5 this September, but I won’t say 6-7+ is impossible.