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

[Hammy]

I originally quoted this in the model runs discussion but it seems more relevent here since it's an indicator:

Yep, switch flip is almost here. Ensembles continue to slowly uptick every run.

https://i.imgur.com/qFjkZ5X.png

Even though development seems limited for now, this is the most noteworthy change in the runs: the wave tracks are starting to show up further south--no longer seemingly diving southwest (accompanied by dry air) but actually STARTING further south. That's a trend to watch, and I imagine those 20N tracks will start disappearing gradually as the end of the month nears

[Hammy]

I've looked into the African InterTropical Front (ITF) position since 1990, and the mean eastern extent is significantly farther north compared to climatology for the first 10 days of August. The average mean position is currently at 19.95N, with the only year surpassing this being 2023 (20.45). List of years where the eastern extent was this far north:

[Full post here]

I have wondered even then if there's something to this even then, there seems to (especially with more sample sizes) be a correlation between early MDR formation and the ITCZ being much farther north than normal--and the end result of this also leading to a significant lull or absence of activity until the end of August followed by more significant activity

[Full post here]

Inspired by the two posts above, I made a scatter plot of ACE vs. the ITCZ positions of whichever years I can find. I'm sure someone else can do the analysis in a much more rigorous and complete fashion than I have, since I was manually scraping the data from Wayback Machine. (Historical data is available if you reach out to them, but I didn't. This might also be why my data is slightly different from USTropics's, particularly for 2020, if they recalibrated the data later.)

For August 1-10 positions: (I didn't move the data labels manually, so they always refer to the dot below the label. 2024 is at the bottom with 0 ACE just for easy reference.)

https://i.imgur.com/55KyysH.png

I only glanced at the data, but my impression is that there doesn't seem to be a clear correlation, if at all. The years with an August lull that Hammy mentioned seemed to be all over the place in both the western and eastern extents, with some of them (1996, 2000) even having the southernmost ITCZ. Not all years with the ITCZ displaced to the north had the issue of waves coming off too far north or a lack of MDR activity, either.

I also plotted September 1-10, and there doesn't seem to be much of a correlation either:

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

That's actually interesting, and surprising honestly, but a secondary pondering is, if the maximum latitude of the monsoon trough pushes north, this could be having a splitting effect and creating two peaks, pushing the main peak a bit later (and contributing to seasonal backloading) while making June/early July gradually more favorable for MDR development, while limiting the activity that would otherwise occur between

[skyline385]

I originally quoted this in the model runs discussion but it seems more relevent here since it's an indicator:

Yep, switch flip is almost here. Ensembles continue to slowly uptick every run.

https://i.imgur.com/qFjkZ5X.png

Even though development seems limited for now, this is the most noteworthy change in the runs: the wave tracks are starting to show up further south--no longer seemingly diving southwest (accompanied by dry air) but actually STARTING further south. That's a trend to watch, and I imagine those 20N tracks will start disappearing gradually as the end of the month nears

https://i.imgur.com/BcTE4bd.png

To being with, I would definitely not call the development as limited. This is pretty much how every long range signal begins, you arent going to see every member light up to a major on a long range ensemble signal before the wave is even offshore. And this is especially true near the Aug 20th date where the quickly changing conditions in the basin are not captured by the models until they get into the initialization data. There are more than 50% members developing in the 0z run ranging from a TS to a major which is a significant number and this will only increase as we get near the switch flip.

Secondly, the members you marked are starting from the same location over Africa as the members which got launched north, the latter ones just have a different trajectory when coming offshore moving in a WSW direction as seen in the plot below. The ITCZ is still at season peak and will slowly start moving south but its not going to be suddenly in a single model run. As for the members forming southwards off the coast of Africa, there will always be some members like that in an ensemble run which are further south than the rest. I have also attached a model run from 4 days and you can see some members forming south again here.

Latest EPS:


Older EPS:

[Hammy]

I originally quoted this in the model runs discussion but it seems more relevent here since it's an indicator:
Secondly, the members you marked are starting from the same location over Africa as the members which got launched north, the latter ones just have a different trajectory when coming offshore moving in a WSW direction as seen in the plot below. The ITCZ is still at season peak and will slowly start moving south but its not going to be suddenly in a single model run. As for the members forming southwards off the coast of Africa, there will always be some members like that in an ensemble run which are further south than the rest. I have also attached a model run from 4 days and you can see some members forming south again here.

That was largely the point (I'm sleep deprived so I'm probably flubbing my wording today) that this is a trend to watch, there are more wave tracks further south (and more closer to 10M), and we're going to likely see this trend continue over the next week or so. But it's definitely a change from what we've been seeing in recent weeks' ensembles.

My point about the activity being limited was to point out that it being relatively limited at this time is not an inactive signal, and that the lower-latitude MDR trend was increasing, since there are a few posters here who are claiming everything is a season cancel post.

[Category5Kaiju]

It would be something if we somehow get an Irma or Ivan-like storm in September, and our ACE absolutely jumps through the roof. If there was any season that could produce such a kind of high-ACE system, I'm willing to place my bets on this year.

[cycloneye]

Great post here at X from Craig Setzer.

 https://x.com/CraigSetzer/status/1825498938276753748

[toad strangler]

Michael Lowry ....

"We’ve already seen 42% of tropical activity during an average year but historically 86% of tropical activity happens after August 19th so we’re running well ahead of schedule in 2024. In fact, the season has been so unusually busy that even average tropical activity from here through the rest of the season would produce a hyperactive hurricane season overall.

We’ll hope the season underperforms expectations, but nothing yet suggests it will.

[psyclone]

Happy bell ring eve everyone. Things are pretty quiet in what is expected to be a bang up season so the angst in the weather geek world is understandable (patience is not our strong suit). We're probably going to be delayed a bit but likely not denied. There's just too much going for the Atlantic basin. Most likely over the next 7 days or so the models will awaken and things will start to happen. In addition to looking way out east...keep an eye on things close to home. We have rocket fuel shelf waters bathing out shores and things can happen fast. In the meantime..enjoy the silence. Not having to worry about a monster storm is a luxury we may be longing for in a few weeks

[Steve]

Most of the MJO models have it going through Phases 4 into 5. 5 isn't indicative of storms being close to the USA. Many of the globals want to take it around through 6 and 7 as well which would put us to roughly September 14 in phases that aren't western Atlantic phases. Bias-corrected Australian goes briefly into 5 before going through the circle and heading back toward 2 or 3. That's a month out, so expect the outputs to be different by the end of the week. No real indication of any systems anytime soon in our part of the world but Phase 4 does have incidences of Texas landfalls. I don't really see a setup for a pattern system as there is general troughing in the eastern US through 3 days, but a piece does split back across the north Gulf. So I guess it's possible that there could be something early next week. This is a link to GFS @ 500mb valid for 1am CDT on Friday. You can see the piece of trough getting left back across FL/GA/AL.

https://www.tropicaltidbits.com/analysi ... 1906&fh=96

[skyline385]

Missed this tweet few days ago which confirmed the active SAL season which peaking in July combined with the high latitude ITCZ kept July slightly quieter (relatively speaking) than many expected. It's on the decline now and models show no more outbreaks even in long range so expecting peak to pop off as always.

 https://x.com/MichaelRLowry/status/1823916232145330646

[Teban54]

 https://x.com/BMcNoldy/status/1825524282421883214

[MEANINGLESS_NUMBERS]

Michael Lowry ....

"We’ve already seen 42% of tropical activity during an average year but historically 86% of tropical activity happens after August 19th so we’re running well ahead of schedule in 2024. In fact, the season has been so unusually busy that even average tropical activity from here through the rest of the season would produce a hyperactive hurricane season overall.

We’ll hope the season underperforms expectations, but nothing yet suggests it will.

https://i.ibb.co/j56RLyy/Capture1.png

So you’re saying I need to pack away my Season Canceled sign? I take his point about most of the season being ahead of us, but I am going to disagree about this season underperforming relative to expectations. The preseason forecasts were for the worst season ever.

[LarryWx]

If the GFS/Euro end up verifying well, there could be as many as 4 straight Tahiti SLPs of 1019+ during Aug 19-22. I’d be very surprised if there isn’t at least one. Keep in mind that higher Tahiti pressure is favored during developing La Niña. There hasn’t been even a single day of 1019+ since 2010!


Tahiti SLP 1019+ since 1991:

1019.55: 1994 (Aug)

1019.1, 1019.44: 1996 (June)

1019.3: 1998 (Aug)

1019.28: 1999 (Aug)

1019.24: 2010 (July)

1019.44, 1019.61, 1019.78, 1019.59, 1019.14: 2010 (Sep)

1019.05: 2010 (Sep)



-So, there have been only 13 days of Tahiti SLP of 1019+ over the last 33 years with the record high being 1019.78 (Sep of 2010).

- This shows there’s been only one time when there were more than two days in a row of that (Sep of 2010). That was during the longest streak on record, 5 days.

- This shows that all were during June-Sep with a mean date of Aug. That makes sense because that’s during their winter, when sfc cold high pressures are at their highest SLP of the year.

- There is a decent correlation between high Tahiti SLP periods and an active Atlantic tropics mainly 1-3 weeks afterward. That jibes well with the idea of an active Atlantic sometime between very late this month and mid Sep.

[Stratton23]

LarryWx whats tahiti? Ive never heard of that and why does it correlate with a busy atlantic?

[LarryWx]

LarryWx whats tahiti? Ive never heard of that and why does it correlate with a busy atlantic?

I mean the island of Tahiti in the Pacific. Their pressure and Darwin, Australia’s, SLPs are used to calculate the daily SOI. An approaching La Niña like what were in now favors above avg Atlantic tropical activity. An oncoming La Niña also favors a +SOI. A higher Tahiti SLP correlates to a +SOI. So, putting all of this together SSTs, it isn’t surprising that a period of high Tahiti SLP correlates somewhat to an active Atlantic 1-3 weeks later.

[Steve]

Michael Lowry ....

"We’ve already seen 42% of tropical activity during an average year but historically 86% of tropical activity happens after August 19th so we’re running well ahead of schedule in 2024. In fact, the season has been so unusually busy that even average tropical activity from here through the rest of the season would produce a hyperactive hurricane season overall.

We’ll hope the season underperforms expectations, but nothing yet suggests it will.

https://i.ibb.co/j56RLyy/Capture1.png

So you’re saying I need to pack away my Season Canceled sign? I take his point about most of the season being ahead of us, but I am going to disagree about this season underperforming relative to expectations. The preseason forecasts were for the worst season ever.

I watched some of the Saturday summary on weatherbell at least what was related to tropical which is the first 8 or so minutes when Joe comes on. At 2:36 (minutes) into the video, he shows his early December forecast which was for 25-30 named storms, 13-17 hurricanes, 5-9 majors and total ACE of 200-240. He backtracked a little off of that and said he wasn't changing ACE at all. He was taking his total named storms down to 20-25 because there haven't been any quick spinup, lowgrade TS's named and he said he always hedges toward 5. He said he might drop hurricanes and majors by 1 but wasn't touching his ACE forecast because we're only 1/8th of the way through the meat of the season (he's talking about activity not time).

So it can still be the worst if we get by multiple majors and regular even though he's probably going to reduce his numbers. He's got 10-14 US Named storm impacts, 5-8 of those hurricane impacts and 3-5 major impacts.

If he's close on those predictions, it could be the worst season ever for the US. There's just so many different ways we could say x year is the worst - most named storms ever, highest ACE ever, most hurricanes, most hurricane US landfalls, highest season damage total (adjusted). We bout to find out.

[WiscoWx02]

Michael Lowry ....

"We’ve already seen 42% of tropical activity during an average year but historically 86% of tropical activity happens after August 19th so we’re running well ahead of schedule in 2024. In fact, the season has been so unusually busy that even average tropical activity from here through the rest of the season would produce a hyperactive hurricane season overall.

We’ll hope the season underperforms expectations, but nothing yet suggests it will.

https://i.ibb.co/j56RLyy/Capture1.png

So you’re saying I need to pack away my Season Canceled sign? I take his point about most of the season being ahead of us, but I am going to disagree about this season underperforming relative to expectations. The preseason forecasts were for the worst season ever.

I watched some of the Saturday summary on weatherbell at least what was related to tropical which is the first 8 or so minutes when Joe comes on. At 2:36 (minutes) into the video, he shows his early December forecast which was for 25-30 named storms, 13-17 hurricanes, 5-9 majors and total ACE of 200-240. He backtracked a little off of that and said he wasn't changing ACE at all. He was taking his total named storms down to 20-25 because there haven't been any quick spinup, lowgrade TS's named and he said he always hedges toward 5. He said he might drop hurricanes and majors by 1 but wasn't touching his ACE forecast because we're only 1/8th of the way through the meat of the season (he's talking about activity not time).

So it can still be the worst if we get by multiple majors and regular even though he's probably going to reduce his numbers. He's got 10-14 US Named storm impacts, 5-8 of those hurricane impacts and 3-5 major impacts.

If he's close on those predictions, it could be the worst season ever for the US. There's just so many different ways we could say x year is the worst - most named storms ever, highest ACE ever, most hurricanes, most hurricane US landfalls, highest season damage total (adjusted). We bout to find out.

I personally see a fish platter this season and that is about it at this point. Especially with the new semi-permanent low along and off the east coast. Those only become more common as we head into September, and if we are already seeing them this much in August it'll probably be there most of September as well imo and perhaps into October, which would probably shut down the Caribbean Sea since the trough would cause the subtropical jet to come crashing down from the north over the Gulf(imparting shear into the Caribbean Sea) as opposed to it being more east to west oriented over the southern US allowing persistent anticyclonic flow aloft over the Caribbean, which is what we saw a lot of in 2020 and it certainly aided in all the Caribbean mayhem we saw that year. Just my two cents in the matter, not saying it's right of course.

[Category5Kaiju]

We’re at 54 ACE. The average for the Atlantic by now is 18. We also had a record breaking, Cape Verde-born Category 5 hurricane in early July.

That’s all I’m going to say for now.

[WiscoWx02]

Hmmm....makes you wonder doesn't it? Of course we have Ernesto but if we didn't, talk about being tropically depressed!

[psyclone]

We’re at 54 ACE. The average for the Atlantic by now is 18. We also had a record breaking, Cape Verde-born Category 5 hurricane in early July.

That’s all I’m going to say for now.

I think the issue at this point becomes a question of
What have you done for me lately? As impressive as Beryl was it's fading into the rear view mirror and what's front and center now is a relative dearth of activity when we're entitled to plenty. The questions aren't absent merit. I remain a bull on the season but open to the idea of a downside surprise...which would still likely yield above normal activity.