2025 Indicators: SST's, MSLP, Shear, SAL, Steering, Instability (Day 16+ Climate Models)

[WeatherBoy2000]

 https://x.com/BigJoeBastardi/status/1959731123304669196

Well that’s ominous. Thanks Hurricane Erin.

I’m not saying I agree or disagree with him, but I’ll put this tweet out here from Derek Ortt as he clearly has the opposite take from Bastardi:

Erin has made things far less favorable over the Atlantic

https://x.com/DerekOrtt/status/1959963275161956575

My take is that the cooling will likely reverse to a significant extent fairly quickly as the cooled subtropical anomalies where Erin traversed warm back up. This is typically what happens and the rewarmings have actually averaged to be quicker in recent years than in the past. So, if so, this cooling will probably be forgotten in a couple of weeks.

I honestly disagree with Derek, I'd argue Erin may've made things more favorable for Atlantic activity. Erin cooled the western subtropics (in a textbook +amo configuration you want a cooler western subtropics) while its large circulation helped warm the Caribbean below by slacking the trades there.

The configuration is pretty optimal now for later season Atlantic activity, with warmth focused in the eastern/tropical Atlantic:





Example of a +amo:

[LarryWx]

Well that’s ominous. Thanks Hurricane Erin.

I’m not saying I agree or disagree with him, but I’ll put this tweet out here from Derek Ortt as he clearly has the opposite take from Bastardi:

Erin has made things far less favorable over the Atlantic

https://x.com/DerekOrtt/status/1959963275161956575

My take is that the cooling will likely reverse to a significant extent fairly quickly as the cooled subtropical anomalies where Erin traversed warm back up. This is typically what happens and the rewarmings have actually averaged to be quicker in recent years than in the past. So, if so, this cooling will probably be forgotten in a couple of weeks.

I honestly disagree with Derek, I'd argue Erin may've made things more favorable for Atlantic activity. Erin cooled the western subtropics (in a textbook +amo configuration you want a cooler western subtropics) while its large circulation helped warm the Caribbean below by slacking the trades there.

The configuration is pretty optimal now for later season Atlantic activity, with warmth focused in the eastern/tropical Atlantic:

https://cyclonicwx.com/data/sst/crw_ssta_graph_mdrtrop.png

https://cyclonicwx.com/data/sst/crw_ssta_global.png

Example of a +amo:

https://i0.wp.com/www.cyclonicfury.com/wp-content/uploads/2017/06/AMO2010.png?resize=300%2C182&ssl=1

WxBoy, Thanks for your reply. I understand the idea of cooling the subtropics relative to the tropics tending to make the tropics, themselves, less stable as Bastardi states in his tweet. But don’t these storm induced coolings typically warm back up to a large extent within a couple of weeks as per especially recent history? By the time this forecasted quiet next couple of weeks has passed, that cooled area may very well be back to warm.

[Woofde]

 https://x.com/BigJoeBastardi/status/1959731123304669196

Well that’s ominous. Thanks Hurricane Erin.

I’m not saying I agree or disagree with him, but I’ll put this tweet out here from Derek Ortt as he clearly has the opposite take from Bastardi:

Erin has made things far less favorable over the Atlantic

https://x.com/DerekOrtt/status/1959963275161956575

My take is that the cooling will likely reverse to a significant extent fairly quickly as the cooled subtropical anomalies where Erin traversed warm back up. This is typically what happens and the rewarmings have actually averaged to be quicker in recent years than in the past. So, if so, this cooling will probably be forgotten in a couple of weeks.

My problem with those tweets is that he uses a SSTs minus Global mean map to say that the MDR is cool. The Global mean is misleading, the Tropical mean is better. GM is being inflated by the extremely anomalous SSTs near Northern Japan. That area is unlikely to compete with the rising motion of the Atlantic.

The MDR is definitely above the long term average in comparison to it's competitor basins.

[cycloneye]

 https://x.com/TylerJStanfield/status/1960017583782146238

[Kingarabian]

Models showing a TC breakout in the EPAC. This would favor some subsidence over the GOM and the Caribbean over this period of time. Of course the EPAC has had a really hard time spawning actual systems of significance. So could be short lived.

[chaser1]

Tyler (above) makes a very good point regarding years having less instability typically producing a lower ratio or outright number of hurricanes. I think the discussion points that Ortt and Bastardi regarding Hurricane Erin are also interesting but I'm going to disagree with both in that I do not believe that any short to mid term cooling off SST's as a result of Erin's track will be consequential one way or another in regards to the 2nd half of the season. My reason for that is because I think that other factors will play a larger role toward overall instability and less then favorable overall conditions throughout much of the basin.

I began taking a closer look at 2022 and 2024 and found a few interesting similarities when comparing this season to those years. The similarities included our anticipated lull soon to begin, the general origin and latitudes, as well as the storm tracks of this year's storms thus far and generally "weaker" T.S.'s (only 1 hurricane thus far). I believe that our "Erin", was 2022's even later dated Cat 4 "Fiona" and was last year's (2024) Cat 5 "Bonnie". Both of those other years were backlogged. Both of those years years also produced an even stronger Cat 5 hurricanes then the two mentioned above.

Having said all that, I believe that 2025 will end closer to a weaker version of 2022 (which was an La Nina year), and significantly less impactful or intense as 2024 given less favorable conditions (other then favorably warm SST's) and certainly less intense SST's then 2024 exhibited. Another key factor that ultimately affects impact and destruction, are some clues that might suggest where future storms might develop and eventually track. I'll toss out my hypothetical 2nd half of the season over the next few days

[Teban54]

Apparently, in addition to Erin sucking up the warmth in western subtropical Atlantic, some cold anomalies off the coast of Portugal are now gone.

CRW:


OISST:

[galaxy401]

[xpost][/xpost]

Still weird that in some of those seasons, they had not just one but two Category 5 storms.

[al78]

The Africa inter-tropical front has shifted north of its climatological position by over a degree latitude over the last week or so, similar to what happened this time last year. I wonder if that is a contributory factor to the apparent lull and low model interest in development over the next week or two.

[DorkyMcDorkface]

Lends further credence to the possibility of a quieter than normal climo peak. I still think the back half of September is when we could see an uptick again (perhaps signficantly so)
 https://x.com/AndyHazelton/status/1960125766852571623

[Teban54]

Lends further credence to the possibility of a quieter than normal climo peak. I still think the back half of September is when we could see an uptick again (perhaps signficantly so)
 https://x.com/AndyHazelton/status/1960125766852571623

Emphasis mine:

This is partially driven by Pacific convection as the MJO moves through.

Intraseasonal variations (i.e. timing) often have a bigger impact on activity than generic seasonal indicators like SSTs, and is under-appreciated IMO.

[al78]

Lends further credence to the possibility of a quieter than normal climo peak. I still think the back half of September is when we could see an uptick again (perhaps signficantly so)
 https://x.com/AndyHazelton/status/1960125766852571623

Emphasis mine:

This is partially driven by Pacific convection as the MJO moves through.

Intraseasonal variations (i.e. timing) often have a bigger impact on activity than generic seasonal indicators like SSTs, and is under-appreciated IMO.

They can do in specific years but over the long term, the generic seasonal indicators work well given they have high prediction skill if you knew them perfectly. I'm not sure about the claim that intra-seasonal factors are unappreciated. Firstly, they are not predictable in advance so little can be said about them in a seasonal forecast. Secondly, TSR does state in their Confidence and Uncertainties section in their documents that intra-seasonal factors can play a part and are not accounted for.

[Teban54]

Lends further credence to the possibility of a quieter than normal climo peak. I still think the back half of September is when we could see an uptick again (perhaps signficantly so)
 https://x.com/AndyHazelton/status/1960125766852571623

Emphasis mine:

This is partially driven by Pacific convection as the MJO moves through.

Intraseasonal variations (i.e. timing) often have a bigger impact on activity than generic seasonal indicators like SSTs, and is under-appreciated IMO.

They can do in specific years but over the long term, the generic seasonal indicators work well given they have high prediction skill if you knew them perfectly. I'm not sure about the claim that intra-seasonal factors are unappreciated. Firstly, they are not predictable in advance so little can be said about them in a seasonal forecast. Secondly, TSR does state in their Confidence and Uncertainties section in their documents that intra-seasonal factors can play a part and are not accounted for.

I agree with all points that you made, but to clarify, my intention was that:

• Most seasons have "up" and "down" periods due to intraseasonal variations like MJO. They're unpredictable, and may in fact coincide with "peak climo periods" in either extremes.
• While seasonal indicators like SST, ENSO and others have high forecast skill several months out, they can't predict such fine-grained factors in advance. This means that at their core, seasonal forecasts are essentially probabilistic statements that account for such uncertainties. But it seems common for the general audience (like weather nerds) to overlook this aspect of uncertainties, in both directions.
• Likewise, when favorable or unfavorable environments appear (e.g. TUTTs), it may not be fully indicative of the background state of the whole season. This nuance is also overlooked quite often.

[chaser1]

https://www.cpc.ncep.noaa.gov/products/international/itf/west.gif
https://www.cpc.ncep.noaa.gov/products/international/itf/east.gif

The Africa inter-tropical front has shifted north of its climatological position by over a degree latitude over the last week or so, similar to what happened this time last year. I wonder if that is a contributory factor to the apparent lull and low model interest in development over the next week or two.

Very interesting and perhaps telling as well. Disturbances associated with tropical waves coming off the W African coast last September didn't exhibit the more typical SW drop in latitude as they entered the E Atlantic. Starting with Gordon on or around September 11, there were a total of 5 named storms that developed in the Eastern Atlantic.. Every single one of them were soon steered toward the Northwest and ultimately recurved. Outside of those, I don't believe that one single named storm formed in or near the MDR east of 60W.

My first immediate thought after looking at that graphic was "well, 1 degree certainly wouldn't seem to impact development all to much". More importantly though, I think that is more indicative of the troughing that extends southward from Europe into W Africa; That dip in the mid (or perhaps mid & upper) levels would then well correlate with disturbances coming off the African coast a bit further north, and especially enhance a nearly immediate WNW to NW motion. Perhaps a disturbance trying to develop at a very southern wave axis point "might" be able to sneak westward into the Central Atlantic? That newly developing cool patch of SST's extending for about 5°south of the CV Islands might allow something like that to occur. Otherwise, we might luck out and watch anything else (post mid September), emerge from the far Eastern Atlanic to end up recurving poleward.