2021 Indicators: SST's / SAL / MSLP / Shear / Steering / Instability / Sat Images

[cycloneye]

Reanalyses are a poor dataset to use for SST. It's best to use a dataset that is designed for ocean temperatures.

NOAA OI SST maps show that of the five years I mentioned that had Atlantic Niños and a flip from -AMM to +AMM by peak season, two (2008 and 2019) had July MDR SSTs that were slightly warmer than 2021 to date, and three (1996, 1999 and 2003) were cooler. Note that I use a broad definition of the MDR (10 to 20N and 20W to 90W).

https://i.ibb.co/hfp645Z/oisst-anom-14d-tropatl-2021071300.png
https://i.ibb.co/MgH9Gz0/oisst-anom-28d-tropatl-2019073000.png
https://i.ibb.co/YkvCkkY/oisst-anom-28d-tropatl-2008073000.png
https://i.ibb.co/56KtkCj/oisst-anom-28d-tropatl-2003073000.png
https://i.ibb.co/P5TTM9t/oisst-anom-28d-tropatl-1999073000.png
https://i.ibb.co/8jYhz2c/oisst-anom-28d-tropatl-1996073000.png

The main problem, then, is that July 2021 to date seems to be much cooler in the MDR and have more of a -AMM/-AMO than any of the years that you mentioned.

https://i.ibb.co/FBsRY5j/Ska-rmavbild-2021-07-15-kl-13-43-25.png
https://i.ibb.co/w4rVwLG/Ska-rmavbild-2021-07-15-kl-13-42-30.png

Clearly, 2021 has more of a hurdle to overcome in the AMM/AMO department than any of the other years to date. The -IOD/-ENSO could help somewhat, however.

Thank you for clarifying. Of the five years mentioned, the three that featured a cooler MDR to date ultimately yielded intense long-trackers such as Bertha, Edouard, Fran, Hortense, and Isidore (1996); Cindy, Floyd, and Gert (1999); and Fabian, Isabel, and Kate (2003). In particular, Edouard, Floyd, Gert, Fabian, and Isabel were all at least ≥ 125 kt at their respective peak intensities, and either Edouard or Floyd or both may have briefly attained Cat-5 status. Storms such as these belong to the same class as other intense CV long-trackers like Ivan (2004), Igor (2010), and Irma (2017)—several of which have been notorious “I” storms. Interestingly, the years that featured a cooler MDR than 2021 to date ended up with more intense activity in the MDR than did the two years that were slightly warmer. Additionally, the years that were cooler than 2021 to date ended up with more seasonal ACE (in the range of 166 to 177) than the years that were warmer. Given that 2021 will likely feature -IOD/-ENSO during ASO, the likelihood of a suppressed EPAC should further act to enhance the MDR for long-trackers. We could easily see multiple long-tracking majors in the MDR during ASO, in light of the years mentioned above. An enhanced MDR + projected steering currents favouring peninsular FL and the western Gulf → potentially significant trouble for portions of the CONUS and the southwestern Caribbean. If one takes into account “unofficial” indicators such as this—that happen to reinforce the “official” ones mentioned in this thread—then we could see multiple Cat-4+ threats to portions of the CONUS and Caribbean during ASO. A blend of 1943, 1945, 1949, 1961, 1996, 1999, and 2003 yields some rather unpleasant outcomes, as the following illustration of Category-2+ cyclones from those seasons suggests:

https://i.ibb.co/7JTKBFk/Ska-rmavbild-2021-07-16-kl-17-54-24.png

Note that the favoured regions of impact are the western Gulf Coast (principally TX), the SW Caribbean, southern peninsular FL, and eastern NC.

Also the NE Caribbean.

[SFLcane]

Oh oh I am starting to see something resembling a +AMO trend over the last couple weeks.

https://i.postimg.cc/Z5YRS0kh/1626-BBEF-177-E-41-B1-8-D88-EBE9-DD6568-C3.jpg

Hi Adrian. What are those signs that you are seeing?

Seeing signs of a +AMO sst configuration which will certainly favor a potentially hyperactive year. It’s still cool off the NW Coast of Africa - if we go true +AMO you'd see that change but it’s slowly getting there. Something to surely keep an eye on

[Shell Mound]

Reanalyses are a poor dataset to use for SST. It's best to use a dataset that is designed for ocean temperatures.

NOAA OI SST maps show that of the five years I mentioned that had Atlantic Niños and a flip from -AMM to +AMM by peak season, two (2008 and 2019) had July MDR SSTs that were slightly warmer than 2021 to date, and three (1996, 1999 and 2003) were cooler. Note that I use a broad definition of the MDR (10 to 20N and 20W to 90W).

https://i.ibb.co/hfp645Z/oisst-anom-14d-tropatl-2021071300.png
https://i.ibb.co/MgH9Gz0/oisst-anom-28d-tropatl-2019073000.png
https://i.ibb.co/YkvCkkY/oisst-anom-28d-tropatl-2008073000.png
https://i.ibb.co/56KtkCj/oisst-anom-28d-tropatl-2003073000.png
https://i.ibb.co/P5TTM9t/oisst-anom-28d-tropatl-1999073000.png
https://i.ibb.co/8jYhz2c/oisst-anom-28d-tropatl-1996073000.png

Thank you for clarifying. Of the five years mentioned, the three that featured a cooler MDR to date ultimately yielded intense long-trackers such as Bertha, Edouard, Fran, Hortense, and Isidore (1996); Cindy, Floyd, and Gert (1999); and Fabian, Isabel, and Kate (2003). In particular, Edouard, Floyd, Gert, Fabian, and Isabel were all at least ≥ 125 kt at their respective peak intensities, and either Edouard or Floyd or both may have briefly attained Cat-5 status. Storms such as these belong to the same class as other intense CV long-trackers like Ivan (2004), Igor (2010), and Irma (2017)—several of which have been notorious “I” storms. Interestingly, the years that featured a cooler MDR than 2021 to date ended up with more intense activity in the MDR than did the two years that were slightly warmer. Additionally, the years that were cooler than 2021 to date ended up with more seasonal ACE (in the range of 166 to 177) than the years that were warmer. Given that 2021 will likely feature -IOD/-ENSO during ASO, the likelihood of a suppressed EPAC should further act to enhance the MDR for long-trackers. We could easily see multiple long-tracking majors in the MDR during ASO, in light of the years mentioned above. An enhanced MDR + projected steering currents favouring peninsular FL and the western Gulf → potentially significant trouble for portions of the CONUS and the southwestern Caribbean. If one takes into account “unofficial” indicators such as this—that happen to reinforce the “official” ones mentioned in this thread—then we could see multiple Cat-4+ threats to portions of the CONUS and Caribbean during ASO. A blend of 1943, 1945, 1949, 1961, 1996, 1999, and 2003 yields some rather unpleasant outcomes, as the following illustration of Category-2+ cyclones from those seasons suggests:

https://i.ibb.co/7JTKBFk/Ska-rmavbild-2021-07-16-kl-17-54-24.png

Note that the favoured regions of impact are the western Gulf Coast (principally TX), the SW Caribbean, southern peninsular FL, and eastern NC.

Also the NE Caribbean.

I was mainly referring to Cat-2+ impacts. TX, S FL, the SW Caribbean, and NC received most of them, but the NE Caribbean did incur Lenny (1999).

[AutoPenalti]

Well looks like the EPAC is having fun with their first major of the season but that ultimately means shear in the Caribbean.

[tolakram]

Thank you for clarifying. Of the five years mentioned, the three that featured a cooler MDR to date ultimately yielded intense long-trackers such as Bertha, Edouard, Fran, Hortense, and Isidore (1996); Cindy, Floyd, and Gert (1999); and Fabian, Isabel, and Kate (2003). In particular, Edouard, Floyd, Gert, Fabian, and Isabel were all at least ≥ 125 kt at their respective peak intensities, and either Edouard or Floyd or both may have briefly attained Cat-5 status. Storms such as these belong to the same class as other intense CV long-trackers like Ivan (2004), Igor (2010), and Irma (2017)—several of which have been notorious “I” storms. Interestingly, the years that featured a cooler MDR than 2021 to date ended up with more intense activity in the MDR than did the two years that were slightly warmer. Additionally, the years that were cooler than 2021 to date ended up with more seasonal ACE (in the range of 166 to 177) than the years that were warmer. Given that 2021 will likely feature -IOD/-ENSO during ASO, the likelihood of a suppressed EPAC should further act to enhance the MDR for long-trackers. We could easily see multiple long-tracking majors in the MDR during ASO, in light of the years mentioned above. An enhanced MDR + projected steering currents favouring peninsular FL and the western Gulf → potentially significant trouble for portions of the CONUS and the southwestern Caribbean. If one takes into account “unofficial” indicators such as this—that happen to reinforce the “official” ones mentioned in this thread—then we could see multiple Cat-4+ threats to portions of the CONUS and Caribbean during ASO. A blend of 1943, 1945, 1949, 1961, 1996, 1999, and 2003 yields some rather unpleasant outcomes, as the following illustration of Category-2+ cyclones from those seasons suggests:

https://i.ibb.co/7JTKBFk/Ska-rmavbild-2021-07-16-kl-17-54-24.png

Note that the favoured regions of impact are the western Gulf Coast (principally TX), the SW Caribbean, southern peninsular FL, and eastern NC.

This is not a knock on you, but eventually I think it becomes obvious it's extremely hard to predict any definitive outcomes season to season.

We can come up with a background state (some of the time), and say that this background state is more or less favorable for storm formation, or more or less likely for strong ridges, but to target most likely areas for landfall or the strength of individual storms? I'm not on board. I fully admit I could be wrong, but for the most part it's going to depend on where the storm is and when based on the pattern at that exact moment.

Southern Florida is 140 miles wide. A storm stuck under a ridge heading west might hit Florida, or it might go south like Ike, or be driven into Cuba and end up on the west coast or in the gulf. I guess one could say that the seasonal pattern favored more robust ridging and more often, but what actual percentage risk change are we looking at?

I think it's an extremely small change, but probably not 0.

[aspen]

Well looks like the EPAC is having fun with their first major of the season but that ultimately means shear in the Caribbean.

There’s nothing in the Caribbean to be impacted by shear, and by the time the suppressive CCKW leaves, Felicia will either be dead or way too far away to have any impact on the Caribbean. Guillermo will probably be too weak for any impacts.

[NDG]

Had some dust fall down with the rain the last couple of days as seen on our cars today, but nothing like when I was in Mallorca Spain late last month.
A low pressure over the mainlad of Spain drew in some moisture along with Saharan dust. It was a muddy mess everywhere after it rained.

[AnnularCane]

Well looks like the EPAC is having fun with their first major of the season but that ultimately means shear in the Caribbean.

There’s nothing in the Caribbean to be impacted by shear, and by the time the suppressive CCKW leaves, Felicia will either be dead or way too far away to have any impact on the Caribbean. Guillermo will probably be too weak for any impacts.

Felicia seems pretty far away already. How close do they have to be to affect the Caribbean?

[aspen]

Well looks like the EPAC is having fun with their first major of the season but that ultimately means shear in the Caribbean.

There’s nothing in the Caribbean to be impacted by shear, and by the time the suppressive CCKW leaves, Felicia will either be dead or way too far away to have any impact on the Caribbean. Guillermo will probably be too weak for any impacts.

Felicia seems pretty far away already. How close do they have to be to affect the Caribbean?

A hurricane or major near the Mexican coast like last year’s Genevieve will definitely produce shear over the Caribbean. However, I’m not sure how far west past 100W a storm can be and still cause impacts.

[Category5Kaiju]

There’s nothing in the Caribbean to be impacted by shear, and by the time the suppressive CCKW leaves, Felicia will either be dead or way too far away to have any impact on the Caribbean. Guillermo will probably be too weak for any impacts.

Felicia seems pretty far away already. How close do they have to be to affect the Caribbean?

A hurricane or major near the Mexican coast like last year’s Genevieve will definitely produce shear over the Caribbean. However, I’m not sure how far west past 100W a storm can be and still cause impacts.

Not to mention Felicia is extremely small in size, so I would have to imagine that hypothetically speaking if you were to put a Felicia right next to Mexico then it would not impart much Caribbean shear as opposed to a much larger and stronger system like Genevieve, Odile, or Patricia per se.

[wxman57]

According to the Klotzbach-Gray method of calculating AMO, last month was at -1.17C, which is the coolest reading since June of 2015 with -2.37C. During 3 of the past 4 hurricane seasons, the AMO switched to warm cycle at peak season.

https://tropical.colostate.edu/archive.html#amo

[SFLcane]

You see we’re i am going with this?

[SFLcane]

Guess what? More warming is coming.

[AlphaToOmega]

I know that CDAS has a massive cool bias in the MDR, but is NOAA Coral Reef or OISST more accurate for the MDR?

[SFLcane]

I know that CDAS has a massive cool bias in the MDR, but is NOAA Coral Reef or OISST more accurate for the MDR?

Hmm I’d use cyclone wx site. OISST more accurate in my opinion. Either way +AM0 should be here soon and more continued warming in the Mdr

[AutoPenalti]

You are right, I didn't realize Felicia was too small to create shear from the outflow.

[Category5Kaiju]

Yeah the warming MDR forecast does make sense; in fact, I would honestly be more confused if we were to see this Atlantic season have a cooler than average MDR persist into the peak season while the EPAC experiences its cooling as well. At least in the +AMO period, I would think that the warming trend in both basins is usually alternate, like when the EPAC is in Nino this somewhat increases the chances that the Atlantic can be cooler than usual while vice versa?

[AlphaToOmega]

Yeah the warming MDR forecast does make sense; in fact, I would honestly be more confused if we were to see this Atlantic season have a cooler than average MDR persist into the peak season while the EPAC experiences its cooling as well. At least in the +AMO period, I would think that the warming trend in both basins is usually alternate, like when the EPAC is in Nino this somewhat increases the chances that the Atlantic can be cooler than usual while vice versa?

That is not really the case. Compare 2007 (a strong La Nina year during +AMO) with 2015 (a strong El Nino year during +AMO). 2007 really tried its hardest to look like a -AMO year during a +AMO phase.

2007 ASO SST anomalies:


2015 ASO SST anomalies:

[Category5Kaiju]

Yeah the warming MDR forecast does make sense; in fact, I would honestly be more confused if we were to see this Atlantic season have a cooler than average MDR persist into the peak season while the EPAC experiences its cooling as well. At least in the +AMO period, I would think that the warming trend in both basins is usually alternate, like when the EPAC is in Nino this somewhat increases the chances that the Atlantic can be cooler than usual while vice versa?

That is not really the case. Compare 2007 (a strong La Nina year during +AMO) with 2015 (a strong El Nino year during +AMO). 2007 really tried its hardest to look like a -AMO year during a +AMO phase.

2007 ASO SST anomalies:
https://i.postimg.cc/d1yPBx22/FFTERKm7-It.png

2015 ASO SST anomalies:
https://i.postimg.cc/yxyGp4kZ/fq7y-AKN9ah.png

Huh ok that’s interesting. Still seems interesting to note that 2007 went on to become a 2 Cat 5 year with a favorable Caribbean. 2015 was shut down due to the Super El Niño anyways

[AlphaToOmega]

The posts in this forum are NOT official forecasts and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the NHC and NWS.

This can be quite confusing to follow, which is why I am writing a short-but-sweet summary for everything that people are discussing at the moment.

The Main Development Region

For the past couple of years, the sea surface temperature patterns in the Atlantic have been quite supportive of tropical development. As of now, the Atlantic sea surface temperature pattern does not seem very favorable for tropical development; the Main Development Region is near-average in a month that is usually not conducive for tropical development. Recently sea surface temperature anomalies in the Main Development Region have been decreasing.



However, this is likely intra-seasonal variation; suppressive Madden-Julian Oscillation phases and suppressive Kelvin Waves can create sinking air over the Main Development Region, leading to cooler sea surface temperatures. There is extensive climate model support to suggest the Main Development Region will have above-average sea surface temperatures come the peak of hurricane season. A warmer-than-average Main Development Region typically means an above-average Atlantic hurricane season.




The Caribbean Sea

In recent times, most Category V hurricanes have attained such intensity in the Caribbean Sea. From 2005 to 2019, Hurricanes Emily, Wilma, Dean, Felix, Matthew (disputed), and Maria attained Category V intensity in the Caribbean Sea. The 2020 Atlantic Hurricane Season featured Hurricanes Eta and Iota, two major hurricanes that causes billions of dollars in damage in Central America. In November 2020, the sea surface temperature anomalies in the Caribbean were uniformly positive.



With Hurricane Elsa (2021) being the third recorded Caribbean hurricane in early July along with the Trinidad Hurricane of 1933 and Hurricane Dennis (2005), this makes it likely that 2021 ends up as much of a Caribbean season as 1933 and 2005. The 1933 Atlantic Hurricane Season featured the Great Tampico Hurricane in September and the Cuba-Bahamas Hurricane in October. The 2005 Atlantic Hurricane Season had Hurricanes Dennis, Emily, Wilma, and Beta. Moreover, the models generally show above-average sea surface temperatures in the Caribbean during the late season.




The West African Monsoon

Ever since the 1990s, there has been a large mass rising air over Africa. This phenomenon, known as the West African Monsoon, creates tropical waves that can either develop in the Atlantic or the Pacific. This year, the West African Monsoon has been enhanced by the Atlantic Equatorial Mode, positive sea surface temperature anomalies in the Gulf of Guinea; the warm sea surface temperatures create rising air over West Africa. The West African Monsoon is currently stronger this year than it was last year.




Models expect the West African Monsoon to continue like it has since the 1990s. Moreover, the very strong Atlantic Equatorial Mode should cause the Intertropical Convergence Zone to be farther south than usual, causing tropical waves to develop in much warmer-than-average waters; this will likely allow for more tropical waves to develop into tropical storms and potentially hurricanes. Tropical waves are already developing farther south than usual. For instance, Hurricane Elsa (2021) formed at a latitude of 9.4 degrees North.

AL, 05, 2021063018, , BEST, 0, 94N, 428W, 30, 1008, LO, 0, , 0, 0, 0, 0, 1012, 140, 70, 40, 0, L, 0, , 0, 0, INVEST, M, 0, , 0, 0, 0, 0, genesis-num, 010, TRANSITIONED, alA72021 to al052021,

The Equatorial Pacific

The Equatorial Pacific dictates so much of the weather on Earth. As of now, sea surface temperature anomalies in Niño 3.4 region of the Equatorial Pacific are neutral, which is expected for July. However, the Southern Oscillation Index has been in the positive since late June, which is indicative of strong easterly trade winds in the Pacific. The daily Southern Oscillation index contribution for 2021-07-16 is 33.05.



Climate models also support a transition to La Niña conditions by August-September-October. NOAA issued a La Niña watch. La Niña conditions are also expected to create sinking air over the East Pacific, further hindering activity in the East Pacific basin. El Niños create vertical wind shear over the Atlantic, so the lack of an El Niño will decrease wind shear in the Main Development Region and the Caribbean Sea. None of the CFSv2 ensemble members suggest El Niño conditions by peak hurricane season.



Ridging

Ridges steer storms in certain directions; storms typically go around them. The 2004 Atlantic Hurricane Season had a strong ridge in Southeast Canada, which steered storms towards the mainland United States. The season featured Hurricanes Charley and Ivan. The 2012 Atlantic Hurricane Season also had a strong ridge in Southeast Canada. The season featured Hurricane Sandy, which impacted New York and New Jersey as an extratropical cyclone.




Climate models forecast a strong ridge in Southeast Canada during peak hurricane season. This will likely steer storms towards the mainland United States and prevent them from curving out to sea. The consequences of this should be obvious.




Conclusion (most important section to read)

The conditions for a hyperactive hurricane season are present: a strong West African Monsoon, expected above-average sea surface temperatures in the Main Development Region and the Caribbean Sea, expected La Niña, and a southward Intertropical Convergence Zone. The current negative sea surface temperature anomalies in the Main Development region and caused by a suppressive Madden-Julian Oscillation and a suppressive Kelvin Wave, both of which are intra-seasonal patterns; once they subside, the Main Development Region will be ripe for tropical development. Sea surface temperature anomalies are neutral in the Niño 3.4 region because it is July, but based on the Southern Oscillation Index, La Niña conditions are expected for the peak of hurricane season. The strong West African Monsoon will create many robust tropical waves, and a southward Intertropical Convergence Zone will give the waves warm enough waters in which to develop and intensity. Because of the strong ridge in Southeast Canada and because of favorable conditions for tropical cyclogenesis, people who live in hurricane-prone areas should be very prepared for any impacts.