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

[cycloneye]

 https://x.com/BenNollWeather/status/1829171901022789827

An eastward-propagating convective pulse will leave the Atlantic quite favorable toward hurricane development in the weeks ahead.

Another pulse may reach the Atlantic in late September, potentially enhancing any ongoing activity or helping to spawn new activity.

[WeatherBoy2000]

I'm starting to think something might be off and the seasonal forecasting brain trust industrial complex could take a category 5 credibility hit. That's what makes the weather interesting and fun. Maybe as we get into fall and upper levels cool we can get some instability and some storms. In the meantime...not worrying about a monster storm system is a luxury I definitely did not anticipate. I guess we don't know what we don't know...but there's a lot of missing pieces..

With each passing day it looks like CSU/others are going to take a reputation hit. I can't blame them for predicting the season that they did, everything seemed to be in place for it. I wonder if this will trigger agencies to be more conservative in their predictions going forward.

I think that's a little over the top, but it is a fact that after 2013 CSU lost a major source of funding and had to scramble to replace it. It wasn't all due to the forecast, but a big chunk was. I'm hoping funders understand that hurricane forecasting has a long way to go, and the fact everyone started out wrong is a pretty big deal IMO, it's not just CSU.

This post will look pretty silly though if 3 weeks from now we're staring down 3 storms threatening someone.

Might be more like a week at this rate

[USTropics]

Given all the recent chatter on Atlantic Nino, I thought I would revisit this topic. I originally posted this back in 2021, but have made/added more plots and extend the data back to the 1930s using reanalysis (as well as included recent years).

First, I’ll state the research and designation for Atlantic Nino (or Atlantic equatorial mode) is rather ongoing/recent and still quite fluid. Some recent research describes the Atlantic Nino as having an eastern or central extent, ,having just a cold/neutral/warm mode, or having various modes/signatures based on climatological anomalies (mainly SSTA signature). I still prefer to analyze the Atlantic Nino for four specific modes (i.e., early termination, early onset, late onset, and persistent) and I will describe each mode below and what exactly ‘Atlantic Nino’ is.

The Atlantic equatorial mode is a localized quasiperiodic interannual climate pattern, which is a fancy way of saying it impacts the climate pattern at irregular intervals for the eastern Atlantic (and other regions outlined below). While Atlantic Nino is similar to the ENSO state in the Pacific in that it is primarily modulated by SSTs, it does not have the same global impact on weather patterns/climate circulations. In addition to its shorter geographical extent (see graph below) and climate impacts, the Atlantic Nino events tend to peak in the boreal summer and have short durations, whereas ENSO tends to peak in the winter and can have multi-year events. I’ve also labeled some other regions that we can analyze different statistical parameters for in relation to these four modes:

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Description of Four Modes

Early Onset

• Years: 1945, 1985, 1988, 1998, 2008, 2020
• Climate Impacts: Persistent interhemispheric wind anomalies and their correlation with preceding Pacific El Nino events.
• Atmospheric Conditions: Increased precipitation is typically not observed over the West Africa/sub-Sahel region between September-March, but does exhibit increased precipitation anomalies between the months of May-August. Northeastern South America experiences enhanced precipitation from April-May and from September-November.
• Oceanic Observations: Gradual development of equatorial warm SSTAs starting in January but begin to dissipate as early as March. Eastern Atlantic develops warm SSTAs in MAM. Cooler SSTAs are common in Tropical North Atlantic (TNA) from December-May. Positive SSTAs are confined to the eastern equatorial Atlantic region.
• Mode Observations: Strong Pacific El Nino events during the preceding boreal winter are typical.
• Wind Observations: Persistent interhemispheric wind anomalies from December-May.

Early Termination

• Years: 1944, 1963, 1966, 1974, 1991, 1996, 1999, 2009
• Climate Impacts: Impact on oceanic circulation, coastal upwelling, and regional precipitation patterns, particularly over West Africa and northeastern South America.
• Atmospheric Conditions: Precipitation over the West Africa/sub-Sahel region (5N-15N latitude) persists only through June-November, before shifting south in DJF. Reduced precipitation over northern South America from March - August.
• Oceanic Observations: Rapid and complete termination of Atlantic Nino and warm equatorial Atlantic SSTAs shortly after August. From December-May, SSTAs in the TNA are typically cooler and SSTAs in the tropical South Atlantic (TSA) are typically warmer.
• Mode Observations: -AMM develops in DJF and persists through MAM. Cold SSTAs in the equatorial Pacific along with La Nina conditions are typically exhibited in boreal winter.
• Wind Observations: Positive northeasterly wind anomalies in TNA and positive northwesterly wind anomalies in TSA during MAM.

Late Onset

• Years: 1934, 1949, 1951, 1960, 1968, 1979, 1981, 1993, 2003, 2007, 2018, 2021
• Climate Impacts: Delayed onset of warm equatorial SSTAs, typically starting in May and persisting through boreal summer, affecting rainfall patterns over West Africa and Sahelian regions.
• Atmospheric Conditions: Precipitation over the West Africa/sub-Sahel region persists mainly through June-August. Reduced precipitation over northeastern South America is observed.
• Oceanic Observations: Rapid and sudden onset of warming SSTA in the Atlantic Nino region begins in June and extends into November. From December-May, SSTAs in the tropical North Atlantic (TNA) are typically cooler and SSTAs in the tropical South Atlantic (TSA) are typically warmer.
• Mode Observations: -AMM develops in DJF and persists through MAM. Cold SSTAs in the equatorial Pacific along with La Nina conditions are exhibited in boreal winter.
• Wind Observations: Positive northeasterly wind anomalies in TNA and positive northwesterly wind anomalies in TSA during MAM.

Persistent

• Years: 1973, 1984, 1987, 2010, 2016, 2019, 2023
• Climate Impacts: Sustained warm SSTAs throughout the Atlantic Nino region, influencing precipitation patterns over South America and trade wind anomalies.
• Atmospheric Conditions: Precipitation is enhanced over northeastern South America, with reduced rainfall over northern South America from December-May.
• Oceanic Observations: Strong SSTAs observed in the Atlantic Nino area and warm equatorial Atlantic SSTAs that continue through all four seasons.
• Mode Observations: Strong Pacific El Nino events during the preceding boreal winter are typical.
• Wind Observations: Weak trade wind anomalies in both hemispheres from December-May. Reduced trade wind and AEJ anomalies reduces coastal upwelling over western Africa (reinforcing Atlantic Nino).

For more information, see the research articles I linked above and this very informative breakdown (https://www.aoml.noaa.gov/the-atlantic- ... e-brother/)

In addition, I have plotted storm tracks and density plots (two subsets, all storms and filtered to just hurricanes).

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Anomaly Composites

Sea Surface Temperature (Anomaly)


Precipitation Rate (Surface)


Relative Humidity (700-300mb)


Geopotential Heights (500mb)


Divergence (200mb)


Velocity Potential (200mb)


Zonal Wind (700mb)


Meridional Wind (700mb)

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Storm Tracks and Density Plots for All Storms

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Storm Tracks and Density Plots for Hurricanes

[Teban54]

 https://x.com/KNubez/status/1829309281469907340

[LarryWx]

Today’s Euro Weeklies update: significantly more active than run from 2 days back

9/2-8: 60%/norm 15/ACE =9 (was 6 two days ago)
9/9-15: 80%/norm 16/ACE = 13 (was 8 two days ago)
9/16-22: 80%/norm 13/ACE = 10 (was 9 two days ago)
9/23-29: 150%/norm 10/ACE = 15 (was 12 two days ago)

-So, the 4 week period has risen from two days ago’s 35 (65% of normal) to 47 today (87% of normal).

-It not only has incorporated anticipated increased near term activity, but has also increased week 4

-Since week 4 was first released two runs ago, it has been projected to be the busiest week of the 4 despite it having significantly lower normal ACE.

-Typically, a reversion to the mean is stronger further out in time. So, a forecast for a whopping 150% of normal way out in week 4 is quite a strong signal that late Sept. is liable to be nasty. Very active wouldn’t necessarily mean high land impacts if we’re lucky, however.

[Spacecoast]

Today’s Euro Weeklies update: significantly more active than run from 2 days back

9/2-8: 60%/norm 15/ACE =9 (was 6 two days ago)
9/9-15: 80%/norm 16/ACE = 13 (was 8 two days ago)
9/16-22: 80%/norm 13/ACE = 10 (was 9 two days ago)
9/23-29: 150%/norm 10/ACE = 15 (was 12 two days ago)

-So, the 4 week period has risen from two days ago’s 35 (65% of normal) to 47 today (87% of normal).

-It not only has incorporated anticipated increased near term activity, but has also increased week 4

-Since week 4 was first released two runs ago, it has been projected to be the busiest week of the 4 despite it having significantly lower normal ACE.

-Typically, a reversion to the mean is stronger further out in time. So, a forecast for a whopping 150% of normal way out in week 4 is quite a strong signal that late Sept. is liable to be nasty. Very active wouldn’t necessarily mean high land impacts if we’re lucky, however.

Here is week 4 anomalies...
Appears (to me), that we will finally see some ACE E of 60W...

[weeniepatrol]

Just like that there are members everywhere

[Teban54]

https://i.imgur.com/bGQ7XBl.png

Just like that there are members everywhere

A few caveats to keep in mind, though that doesn't take away your overall point about the active EPS run:

• EPS has 51 members, so they may look more plentiful in absolute numbers than GEFS (or one's expectations looking at a visual like this) even in a hypothetical where the actual proportions of developing members are the same. (In this case, 18z EPS indeed has a higher share of members developing the Central Atlantic AOI than 18z GEFS does.)
• Some of these are just low-pressure centers, which may be disorganized and/or still an open wave, some of which may never develop. This can be seen most clearly in the two eastern waves on this run.
• While I don't have access to individual ensemble members, operational models seem to suggest at most one of the two eastern waves may develop, if at all. Most of the recent runs try to consolidate the two systems in some way, which fails more often than not.

[WiscoWx02]

https://i.imgur.com/bGQ7XBl.png

Just like that there are members everywhere

A few caveats to keep in mind, though that doesn't take away your overall point about the active EPS run:

• EPS has 51 members, so they may look more plentiful in absolute numbers than GEFS (or one's expectations looking at a visual like this) even in a hypothetical where the actual proportions of developing members are the same. (In this case, 18z EPS indeed has a higher share of members developing the Central Atlantic AOI than 18z GEFS does.)
• Some of these are just low-pressure centers, which may be disorganized and/or still an open wave, some of which may never develop. This can be seen most clearly in the two eastern waves on this run.
• While I don't have access to individual ensemble members, operational models seem to suggest at most one of the two eastern waves may develop, if at all. Most of the recent runs try to consolidate the two systems in some way, which fails more often than not.

Agreed…I’ll believe development when I see it. Odds are largely stacked against all of these potential systems and the most likely outcome is no development takes place at all. Imo it could be a few more weeks before we have another name out there…

[chaser1]

Specifically with regard to the present and the active disturbance approaching 50W and this juncture in the season that we find ourselves at really is a head scratcher. I mean this far west, we're no longer talking about any influence of some W. African monsoonal flow. A more focused look at this particular region does suggest that there is still a fairly clear dry 300mb-700mb line of delineation right at about 15N however. Moisture south of that point clearly should not be an issue though. Surface pressures are not particularly low but are definitely not a mitigating factor either. 200mb - 850mb wind shear? Meh...... Certainly, could be a little more conducive but nothing that a robust vorticity shouldn't be able to overcome. Of course, we really don't quite have a clear point of robust vorticity (or COC). Overall though, 200mb winds don't seem to be any kind of mitigating factor as the disturbance(s) move westward. I still think that some pocket within this ITCZ flare up is going to try and consolidate upon approach to the Lesser Antilles and eventually develop into the basin's next named storm. Model support has been cool at best with the ICON showing inconsistent run to run signs of development. That's not any kind of knock on the models either. For the models to continue to flip flop on this disturbance along with the strained effort for any consolidation to maintain itself just tells me that some environmental conditions are still "off" and climo just has no bearing on overcoming it. Maybe the other big global models will follow suit and join the ICON's 12Z run, and we will in fact begin to see the normal consolidation and development of a disturbance that we are accustomed to see around the end of August. Let's see if this will be "the switch" or real bell that would simply only be about 10 days late.

[toad strangler]

 https://twitter.com/bmcnoldy/status/1829569863322661148

[chaser1]

https://twitter.com/bmcnoldy/status/1829569863322661148?s=46

152% of ACE?? Darn it McNoldy, you sucked me in. Hey Cycloneye? Any chance I can revise my 2024 Poll prediction from 23/15/7 to 35/23/11 ?

[Hammy]

Checked in on the CFS and seems like Sep 10-30 looks to be pretty active, at least five storms (on this particular run) in the MDR

Seems like that wave that seems like all the models are showing getting sucked up into Morocco before it actually exits is the end of the monsoon amplification, most of the models are showing the waves coming off further south after that.

[al78]

Imo it could be a few more weeks before we have another name out there…

You think we could go through the whole of September without a named storm? I don't recall that ever happening in the period of reliable records.

[Category5Kaiju]

Imo it could be a few more weeks before we have another name out there…

You think we could go through the whole of September without a named storm? I don't recall that ever happening in the period of reliable records.

Highly unlikely. There's a reason why September is historically among the busiest, if not the busiest, month of Atlantic hurricane season, even during traditional El Nino seasons. Many early-season impediments are gone by then, and Africa is typically spitting out waves after waves at that point. It's simply a much more physically conducive time of year.

We're also highly likely going to see what looks to be Francine soon.

[gatorcane]

Activity has picked up but you would expect this uptick as we approach the climatological peak of Sept 10th, nothing to indicate hyperactive. The Caribbean-bound system NHC is tracking could be an issue down the road in the Gulf, possibly western Gulf and Texas. For Florida and northern/eastern Gulf, I do continue to have some concerns as we approach late Sept through late October for recurving systems coming out of the Caribbean. SSTs are above normal and the La Niña should provide favorable conditions.

[chaser1]

Imo it could be a few more weeks before we have another name out there…

You think we could go through the whole of September without a named storm? I don't recall that ever happening in the period of reliable records.

I would lay down a sizeable bet against going through all of September without a named storm.

On the other hand, I wonder how often has the following occurred?
Ernesto formed on August 12. Could anyone have imagined the possibility of going 30 days straight from August 12 to Sept 12 without an additional named storm? Mind you, I doubt that will happen but it's not out of the realm of possibility. That alone might prove historically rare. It would be interesting to go through the record books to find those years having such a "prime-time lull" where any named storm formed between Aug 10-15, with the next named storm not developing until 30 or more days later.

[aspen]

I’d say if we reach September 5th with no development expected within the following 2-3 days, then it’s clear that something is wrong with the basin, and another 2022 becomes more likely.

Hard to believe that a year with a 35 ACE July Cat 5 would end up under-performing, but that seems to be where we’re headed. Perhaps Beryl was simply a freak anomaly…which just makes its existence ever more unusual. Perhaps something like 2007: a first year La Niña after a single-year El Niño that produced Cat 5 Caribbean cruisers but not much else of significance and ended up as one of the weakest La Niña hurricane seasons.

[penguinzee]

3 weeks at this time of year, I'm sure is quite rare, 4 weeks would be bonkers!

A thought I had over the last few days-with the global warming that we've seen over the last several decades, and the longer summers (10 days earlier and later MOL) would it be possible that the peak point of Sept.10th may have moved later over the last few years, to maybe Sept.15th-20th? Just spitballing an amateur observation that the last few years had a lot more impactful storms in late August-early September, then again in late September-early October, but not a whole lot around Sept. 10th...

[psyclone]

The lack of activity as in latter August as we sit on September eve is just remarkable. Atlantic basin climo is very peaky and we're in the short window where storms grow out of sidewalk cracks in a season that was expected to be extremely exceptional by the expert and amateur class alike. Even in a normal to somewhat below normal season this level of recent tranquility would be noteworthy...but this year..there are no adjectives. We all expected this season to amaze ..and it is. To me the current sedate sea state is every bit as remarkable as an early July cat 5...perhaps more so. The early July crazy was expected...this...no so much. Cue the Depeche Mode song...enjoy the silence..