2020 Indicators: SST's / SAL / MSLP / Steering / Shear / Instability / Sat Images

[TheStormExpert]

The MDR has recently cooled down significantly, despite a near-neutral NAO. The expansion of the Hadley cells due to climate change may mean that even a neutral or negative NAO may yield relatively stronger easterlies over the MDR than in the past, particularly during the height of late summer or early fall, as wavelengths also lengthen seasonally. So, contrary to popular expectations, the MDR may not warm substantially or even cool down quite a bit between now and the peak of the Atlantic hurricane season, depending in part on the state of the NAO. We do know that climate change tends to promote greater stability over the MDR, due in part to the expansion of the Hadley cells, but also related to the warming of the subtropical as well as the tropical North Atlantic, given that the subtropics tend to warm up even faster than the tropics, at least in the Atlantic basin. Overall, the NAO and climate change, along with the absence of La Niña by ASO, may serve to temper not just overall numbers in 2020, but also ACE and the risk of landfalls, given a weaker -PDO signature during neutral ENSO vs. La Niña.

This is exactly why I’ve been saying the Spring Barrier could change things. Hopefully it continues to cool and we have a quiet Atlantic Hurricane Season.

[Steve]

They updated the 50km SSTA map to a 5k SSTA map in March. Looks pretty warm (anomalously anyway) in the MDR even if maybe there has been some cooling (since I trust Shell Mound).
https://www.ospo.noaa.gov/data/cb/ssta/ ... urrent.png

[SFLcane]

The MDR has recently cooled down significantly, despite a near-neutral NAO. The expansion of the Hadley cells due to climate change may mean that even a neutral or negative NAO may yield relatively stronger easterlies over the MDR than in the past, particularly during the height of late summer or early fall, as wavelengths also lengthen seasonally. So, contrary to popular expectations, the MDR may not warm substantially or even cool down quite a bit between now and the peak of the Atlantic hurricane season, depending in part on the state of the NAO. We do know that climate change tends to promote greater stability over the MDR, due in part to the expansion of the Hadley cells, but also related to the warming of the subtropical as well as the tropical North Atlantic, given that the subtropics tend to warm up even faster than the tropics, at least in the Atlantic basin. Overall, the NAO and climate change, along with the absence of La Niña by ASO, may serve to temper not just overall numbers in 2020, but also ACE and the risk of landfalls, given a weaker -PDO signature during neutral ENSO vs. La Niña.

This is exactly why I’ve been saying the Spring Barrier could change things. Hopefully it continues to cool and we have a quiet Atlantic Hurricane Season.

Spring Barrier refers to enso and enso is definitely cooling.

[WeatherEmperor]

They updated the 50km SSTA map to a 5k SSTA map in March. Looks pretty warm (anomalously anyway) in the MDR even if maybe there has been some cooling (since I trust Shell Mound).
https://www.ospo.noaa.gov/data/cb/ssta/ ... urrent.png

Does the change in resolution from 50km to 5km improve SST readings? How does the resolution work for SST's?


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[TheStormExpert]

The MDR has recently cooled down significantly, despite a near-neutral NAO. The expansion of the Hadley cells due to climate change may mean that even a neutral or negative NAO may yield relatively stronger easterlies over the MDR than in the past, particularly during the height of late summer or early fall, as wavelengths also lengthen seasonally. So, contrary to popular expectations, the MDR may not warm substantially or even cool down quite a bit between now and the peak of the Atlantic hurricane season, depending in part on the state of the NAO. We do know that climate change tends to promote greater stability over the MDR, due in part to the expansion of the Hadley cells, but also related to the warming of the subtropical as well as the tropical North Atlantic, given that the subtropics tend to warm up even faster than the tropics, at least in the Atlantic basin. Overall, the NAO and climate change, along with the absence of La Niña by ASO, may serve to temper not just overall numbers in 2020, but also ACE and the risk of landfalls, given a weaker -PDO signature during neutral ENSO vs. La Niña.

This is exactly why I’ve been saying the Spring Barrier could change things. Hopefully it continues to cool and we have a quiet Atlantic Hurricane Season.

Spring Barrier refers to enso and enso is definitely cooling.

Regardless of the ENSO cooling, so is the Tropical Atlantic just take a look on Tropical Tidbits. Doesn’t really scream a super active season if trends continue for awhile.

[aspen]

This is exactly why I’ve been saying the Spring Barrier could change things. Hopefully it continues to cool and we have a quiet Atlantic Hurricane Season.

Spring Barrier refers to enso and enso is definitely cooling.

Regardless of the ENSO cooling, so is the Tropical Atlantic just take a look on Tropical Tidbits. Doesn’t really scream a super active season if trends continue for awhile.

Yep, I see a general cooling trend in the Caribbean, Gulf, an MDR. However, so far it’s looking like another temporary fluctuation, and parts of all three areas are still slightly to significantly warmer than average. This will probably only mean anything if the cooling trend continues for at least a week or two.

[ScottNAtlanta]

They updated the 50km SSTA map to a 5k SSTA map in March. Looks pretty warm (anomalously anyway) in the MDR even if maybe there has been some cooling (since I trust Shell Mound).
https://www.ospo.noaa.gov/data/cb/ssta/ ... urrent.png

That image sure looks like a warm AMO is developing

[CyclonicFury]

The MDR has recently cooled down significantly, despite a near-neutral NAO. The expansion of the Hadley cells due to climate change may mean that even a neutral or negative NAO may yield relatively stronger easterlies over the MDR than in the past, particularly during the height of late summer or early fall, as wavelengths also lengthen seasonally. So, contrary to popular expectations, the MDR may not warm substantially or even cool down quite a bit between now and the peak of the Atlantic hurricane season, depending in part on the state of the NAO. We do know that climate change tends to promote greater stability over the MDR, due in part to the expansion of the Hadley cells, but also related to the warming of the subtropical as well as the tropical North Atlantic, given that the subtropics tend to warm up even faster than the tropics, at least in the Atlantic basin. Overall, the NAO and climate change, along with the absence of La Niña by ASO, may serve to temper not just overall numbers in 2020, but also ACE and the risk of landfalls, given a weaker -PDO signature during neutral ENSO vs. La Niña.

The MDR is still warmer than average by most datasets and MDR SSTAs can be quite noisy, so it's best to use a 30 day SSTA average to eliminate short-term fluctuations.

It's also too early to assume La Niña won't be present by ASO, even though the ENSO regions haven't cooled much yet. Finally, as I noted a couple days back, neutral ENSO actually tends to have higher Atlantic ACE than moderate/strong La Niñas.

[TheStormExpert]

Spring Barrier refers to enso and enso is definitely cooling.

Regardless of the ENSO cooling, so is the Tropical Atlantic just take a look on Tropical Tidbits. Doesn’t really scream a super active season if trends continue for awhile.

Yep, I see a general cooling trend in the Caribbean, Gulf, an MDR. However, so far it’s looking like another temporary fluctuation, and parts of all three areas are still slightly to significantly warmer than average. This will probably only mean anything if the cooling trend continues for at least a week or two.

I can understand why the Gulf of Mexico is cooling since there has been an increase in frontal passages in that region since the winter months.

[BYG Jacob]

We really gonna pretend SSTs in April matter, and SSTs won't be warm enough during peak?

[TheStormExpert]

We really gonna pretend SSTs in April matter, and SSTs won't be warm enough during peak?

Of course they’ll be warm enough, it’s just what will the SST configuration look like come August/September/October timeframe? The trend is your friend and it is in this case if it holds for a long enough time.

[TheStormExpert]

Overall the Tropical Atlantic, Gulf of Mexico, and Caribbean SST anomalies are trending downward over the past 2-4 weeks, will it continue? That is the key and hopefully this COULD be a good indicator after all the talk of yet another active Atlantic Hurricane Season.

[aspen]

Overall the Tropical Atlantic, Gulf of Mexico, and Caribbean SST a anomalies are trending downward over the past 2-4 weeks, will it continue? That is the key and hopefully this COULD be a good indicator after all the talk of yet another active Atlantic Hurricane Season.

[url]https://i.ibb.co/hg5V834/0-B792570-3-C11-4-C55-8-E5-C-B88712-CDD643.png [/url]
[url]https://i.ibb.co/7SMVMJM/ED5-A4-A2-D-9-F2-F-4-A36-AB92-0-C4-D4629-CCF2.png [/url]
[url]https://i.ibb.co/37W1t8F/71-B983-FC-6661-4391-A47-C-DB06-C6-F25245.png [/url]
[url]https://i.ibb.co/vC9gjyj/63622-B9-A-E445-41-E6-AD45-A005-A34-F147-E.png [/url]

The cooling in the MDR, Gulf, and Caribbean seems like it could just be a temporary variation; several of those can be seen in all three graphs. However, the East Tropical Atlantic cooling is so significant that it might continue for some time, or be an extreme sudden cold variation.

If all four areas continue to cool throughout May and don’t start to rise again, then it would be safe to say that SSTs might not be above-average by ASO.

[chaser1]

We really gonna pretend SSTs in April matter, and SSTs won't be warm enough during peak?

Correct; SST's will be plenty warm. Furthermore, you could easily have a neutral anomaly SST year while other conditions clearly result in over or under active activity within the basin. I hear where your coming from though....sometimes it does seem that there is just a bit of over-analysis for Nino, SST's, etc. but then again it is nearly May and this is the primary purpose of the forum itself.

[CyclonicFury]

Even if the MDR cools to below normal levels during the peak of season (which I don't think is very likely), an above average season (though probably not hyperactive) would still be very possible if the West African Monsoon (WAM) is strong and ENSO dips to cool neutral or La Niña. 2018 had one of the coldest MDRs on record in May/June and still finished above average.

[TheStormExpert]

Even if the MDR cools to below normal levels during the peak of season (which I don't think is very likely), an above average season (though probably not hyperactive) would still be very possible if the West African Monsoon (WAM) is strong and ENSO dips to cool neutral or La Niña. 2018 had one of the coldest MDRs on record in May/June and still finished above average.

This is all so true but at the same time the MDR is so very fragile that if one component is off it could prevent or at the very least delay tropical development which is also a concern especially as was the case in 2005 with many storms.

[toad strangler]

Lot's of hand wringing over SST's in the MDR recently and it's certainly a viable topic for sure. But the most powerful landfalls in the US didn't care about MDR SST's. At all. They were all Tropical Storms three days out from landfall.

 https://twitter.com/JohnMoralesNBC6/status/1255523047995473923

[CrazyC83]

Also, of the four Cat 5 landfalls:

* 1935 was near normal
* 1969 was well above normal
* 1992 was well below normal
* 2018 was slightly above normal

There's no correlation at all between the strongest storms and their seasons.

[USTropics]

It's typical to see SSTA's decrease between the months of April-July. This process is directly related to the annual propagation of the ITCZ from the equator in winter (DJF) to northern latitudes in the summer (JAS) with an active Western African Monsoon present:


The SST gradient between the Atlantic Cold Tongue (ACT) and waters along and northwest of the Gulf of Guinea creates a strong temperature gradient between ocean and land, and strengthens southerly winds. Stronger southeasterly winds produces upwelling (particularly along the coastline) and elevates the thermocline.


This process enhances the northward migration of rainbands away from the equator onto the West African continent, which interacts with the Sahelian region of Africa and the Western African Monsoon (WAM). An increase in convection that extends off the coastline lowers SSTA profiles as well.


TL;DR Annual seasonal processes of the ITCZ lifting north and an active WAM typically result in decreasing SSTA's in the Eastern Atlantic during the months of April-July.

This study in 2018 covers it in more depth - https://link.springer.com/article/10.1007/s00382-018-4489-4

[Steve]

They updated the 50km SSTA map to a 5k SSTA map in March. Looks pretty warm (anomalously anyway) in the MDR even if maybe there has been some cooling (since I trust Shell Mound).
https://www.ospo.noaa.gov/data/cb/ssta/ ... urrent.png

Does the change in resolution from 50km to 5km improve SST readings? How does the resolution work for SST's?

I would assume so. There isn’t that much out there. They updated the site link at the old link and said the old 50km info was archived. This is about the only thing I can find.

https://www.frontiersin.org/articles/10 ... 00420/full