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

[LarryWx]

My biggest hope is that any well above normal season in activity is like 2010, when the CONUS got off largely unscathed. The fact that 2010 is an analog for at least a couple of the main forecasters is giving me at least some hope.

As far as I can tell, 2010 is an analog by virtue of its ENSO evolution and extremely warm Tropical Atlantic configuration, not because of potential storm track or the other elements that govern the latter.

I fully realize that. Indeed, 2010 isn’t listed as an analog based on tracks. But it is still an ENSO/warm tropical Atlantic analog listed by at least two well-known forecasters that ended up very active but with little impact on the lower 48. So, based especially on 2010, here’s to hoping for a break since getting a break wouldn’t be far-fetched. Track tendencies are difficult to forecast as they vary so much. I’m not actually predicting another 2010 but rather am hoping for it. If I were to now predict a 2010 like season among the other analogs, that would be a wishcast unless I had other data/info to go on. But rather than a wishcast it is simply a wish.

[cycloneye]

The C35 model on precipitation for JAS.

July:



August:



September:

[Hurricane2022]

The C35 model on precipitation for JAS.

July:

https://i.imgur.com/uB5cYH3.png

August:

https://i.imgur.com/k63qpn7.png

September:

https://i.imgur.com/bJeDZq8.png

Looks like that we're going to see an considerably active July this year.

[MetroMike]

The C35 model on precipitation for JAS.

July:

https://i.imgur.com/uB5cYH3.png

August:

https://i.imgur.com/k63qpn7.png

September:

https://i.imgur.com/bJeDZq8.png

Why are there holes in the middle of green in central Florida? Don't need another drought this summer. I know its long range but hope it's not the trend.

[cycloneye]

Very favorable set up from C3S.

 https://twitter.com/cyclonicwx/status/1778210851012685896




 https://twitter.com/cyclonicwx/status/1778210854141354363

[Teban54]

In addition to the ridiculousness of +AMO persisting throughout the winter, from a quick eyeballing, this also seems to suggest anomalous warmth being transferred from the Canary Current down to the MDR proper. IIRC, this may actually be the main mechanism for why a warm Canary Current early in the year correlates with activity - by supplying warm water to the MDR (correct me if I'm wrong). 
 https://twitter.com/daniloevan11/status/1778046284609298812

[Ntxw]

In addition to the ridiculousness of +AMO persisting throughout the winter, from a quick eyeballing, this also seems to suggest anomalous warmth being transferred from the Canary Current down to the MDR proper. IIRC, this may actually be the main mechanism for why a warm Canary Current early in the year correlates with activity - by supplying warm water to the MDR (correct me if I'm wrong). 
https://twitter.com/daniloevan11/status/1778046284609298812

I'm not sure that is how it works. Anomalies is not actual SSTs, it doesn't carry an anomaly. That's just the difference compared to climo averages. Canary current is a N to S current which the northern SSTs is always cooler in terms of true temperatures in this region. It's the antithesis to the Gulf stream in the west Atlantic.

With that noted a weaker current would transport less colder waters S thus keeping anomalies warmer to the S.

[USTropics]

In addition to the ridiculousness of +AMO persisting throughout the winter, from a quick eyeballing, this also seems to suggest anomalous warmth being transferred from the Canary Current down to the MDR proper. IIRC, this may actually be the main mechanism for why a warm Canary Current early in the year correlates with activity - by supplying warm water to the MDR (correct me if I'm wrong). 
https://twitter.com/daniloevan11/status/1778046284609298812

The Canary Current is actually a cold water current (as are most currents along the western coastlines of continents). Its stable air mass is associated with the arid/desert conditions of the Western Saharan along the west coast of Africa. What we can infer from the anomalous warmth of the Canary Current, since it's largely a wind driven current, is that winds have been anomalously low for most of January - April. The correlation here is:

Reduced winds → reduced upwelling → reduced transport of cold water to the MDR.

You can see some of this upwelling has occurred in the plots below:

[cycloneye]

Speaking about the Alberto Poll.

 https://twitter.com/BigJoeBastardi/status/1778460643349135670

[zzzh]

 https://twitter.com/WorldClimateSvc/status/1778516777800192420



Positive NAO during summer.

[DorkyMcDorkface]

https://twitter.com/WorldClimateSvc/status/1778516777800192420
Positive NAO during summer.

Steering implications aside, if we get a +NAO to persist throughout the summer, I'm curious to see if/how much the WAM mitigates any sort of potential cooling effect that may come with it. WAM will likely be particularly strong this year given the +IOD the seasonal models are now showing in tandem with La Niña which should in theory really reinforce the ASW. I suppose that's a potential fail mode in itself, if it gets supercharged a la 2020 and we see lumbering Isaias-sized waves that take an eternity to develop.

[zzzh]

https://twitter.com/WorldClimateSvc/status/1778516777800192420
Positive NAO during summer.

Steering implications aside, if we get a +NAO to persist throughout the summer, I'm curious to see if/how much the WAM mitigates any sort of potential cooling effect that may come with it. WAM will likely be particularly strong this year given the +IOD the seasonal models are now showing in tandem with La Niña which should in theory really reinforce the ASW. I suppose that's a potential fail mode in itself, if it gets supercharged a la 2020 and we see lumbering Isaias-sized waves that take an eternity to develop.

NAO during the summer usually result in stronger trades over the subtropics (near 40N), it has little correlation with trades in the deep tropics. I do agree with you that we are likely going to see a supercharged WAM and sloppy waves this year (again). I wouldn't be surprised if July to first half of August is less active than expected.

[zzzh]

Just for fun:

You know it's that time of the year when GEFS 840h spins up a major hurricane in the W. Caribbean

[Hurricane2022]

Just for fun:
https://i.imgur.com/Hrih1wc.png
You know it's that time of the year when GEFS 840h spins up a major hurricane in the W. Caribbean

Ah yes... The usual early-season phantom that GFS likes to do almost every single year. So far in Apr 11 2024, everything (except almost everything) is right on track. We still have just ~50 days until the official start of the season.

[AnnularCane]

Seems a little early even for phantoms though.

[chaser1]

https://twitter.com/WorldClimateSvc/status/1778516777800192420
Positive NAO during summer.

Screaming zonal flow north of 60N?? I find that particularly interesting if that verifies. That suggests to me particularly stout mid level ridging across the tropics and sub-tropics. Perhaps a bit of overextrapolation on my part but I think this would imply a pretty progressive pattern; A pattern less apt to have lazy stagnant troughs or large cut-off lows patrolling the Central and W. Atlantic for weeks on end.
Other then the possibility of occasional fits of easterly shear issues I interpret such a set up to generally support enhanced Westward motion storm tracks.

[Teban54]

https://twitter.com/WorldClimateSvc/status/1778516777800192420
Positive NAO during summer.

Steering implications aside, if we get a +NAO to persist throughout the summer, I'm curious to see if/how much the WAM mitigates any sort of potential cooling effect that may come with it. WAM will likely be particularly strong this year given the +IOD the seasonal models are now showing in tandem with La Niña which should in theory really reinforce the ASW. I suppose that's a potential fail mode in itself, if it gets supercharged a la 2020 and we see lumbering Isaias-sized waves that take an eternity to develop.

https://i.imgur.com/ptAgVPk.png
NAO during the summer usually result in stronger trades over the subtropics (near 40N), it has little correlation with trades in the deep tropics. I do agree with you that we are likely going to see a supercharged WAM and sloppy waves this year (again). I wouldn't be surprised if July to first half of August is less active than expected.

If I'm understanding this right, the summer +NAO seems like the worst-case scenario. Stronger ridging that steers storms further west, and the cooling effect is too far north to wipe out the MDR warmth (if not even enhancing the +AMO), plus there's not enough time to reverse the warm anomalies.

[chaser1]

Steering implications aside, if we get a +NAO to persist throughout the summer, I'm curious to see if/how much the WAM mitigates any sort of potential cooling effect that may come with it. WAM will likely be particularly strong this year given the +IOD the seasonal models are now showing in tandem with La Niña which should in theory really reinforce the ASW. I suppose that's a potential fail mode in itself, if it gets supercharged a la 2020 and we see lumbering Isaias-sized waves that take an eternity to develop.

https://i.imgur.com/ptAgVPk.png
NAO during the summer usually result in stronger trades over the subtropics (near 40N), it has little correlation with trades in the deep tropics. I do agree with you that we are likely going to see a supercharged WAM and sloppy waves this year (again). I wouldn't be surprised if July to first half of August is less active than expected.

If I'm understanding this right, the summer +NAO seems like the worst-case scenario. Stronger ridging that steers storms further west, and the cooling effect is too far north to wipe out the MDR warmth (if not even enhancing the +AMO), plus there's not enough time to reverse the warm anomalies.

One potential fly in the ointment as a result of strong W Hemispheric ridging (i.e. Bermuda High) could be an enhancement of dryer air subsidence that would temper convection and also limit higher end intensity. I think low to mid-level RH values throughout the subtropics (and deeper tropics) are worth monitoring as we march closer to June 1st. I think lower SLP throughout the MDR which tend to go hand in hand with La Nina would potentially counter lower average mid-level humidity issues, especially if storm tracks remained low latitude. Then again, I also think that fortuitous conditions for development as a result of LaNina might not be particularly realized until later in the season depending of course on how quickly the ENSO transition from Nino to Nina occurs. One thing I'm curious about and have never really taken the time to look into, is to what degree does the upper (200-400mb) level environment play a role in broad basin RH "capping" or for that matter disbursement of SAL (or subsidence as a whole)?

[LarryWx]

Steering implications aside, if we get a +NAO to persist throughout the summer, I'm curious to see if/how much the WAM mitigates any sort of potential cooling effect that may come with it. WAM will likely be particularly strong this year given the +IOD the seasonal models are now showing in tandem with La Niña which should in theory really reinforce the ASW. I suppose that's a potential fail mode in itself, if it gets supercharged a la 2020 and we see lumbering Isaias-sized waves that take an eternity to develop.

https://i.imgur.com/ptAgVPk.png
NAO during the summer usually result in stronger trades over the subtropics (near 40N), it has little correlation with trades in the deep tropics. I do agree with you that we are likely going to see a supercharged WAM and sloppy waves this year (again). I wouldn't be surprised if July to first half of August is less active than expected.

If I'm understanding this right, the summer +NAO seems like the worst-case scenario. Stronger ridging that steers storms further west, and the cooling effect is too far north to wipe out the MDR warmth (if not even enhancing the +AMO), plus there's not enough time to reverse the warm anomalies.

JJA averaged NAO (assuming neutral being +0.24 to -0.24)

2010+: 9 -NAO, 2 neut, 3 +NAO
2000s: 4 -NAO, 5 neut, 1 +NAO
1990s: 2 -NAO, 4 neut, 4 +NAO
1980s: 2 -NAO, 7 neut, 1 +NAO
1970s: 2 -NAO, 2 neut, 6 +NAO
1960s: 4 -NAO, 2 neut, 4 +NAO
1950s: 6 -NAO, 1 neut, 3 +NAO

Sum: 25 -NAO, 23 neut, 22 +NAO

- So, summer +NAO frequency only 4 (1 in 6) since 2000
- Since 2000: only 2002 (Nino), 2013 (cold neutral), 2018 (warm neutral), and 2022 (Niña) were +NAO. No pattern.
- 3 of those 4 +NAO summers since 2000 had +NAO in June. The other had a neutral June. So, June should give some hint for summer +NAO chances.
- 5 of 24 Junes since 2000 had +NAO. Out of those 5, 3 had a +NAO for summer and 2 had a neutral summer NAO
- Of the 22 +NAO summers, only 1 (1955) had a -NAO June.


NAO monthlies: https://www.cpc.ncep.noaa.gov/products/ ... scii.table

[Teban54]

PMM and its impact on late-season activity. Note the tweet made a typo and meant PMM is currently slightly negative.
 https://twitter.com/yconsor/status/1778342978576060718