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

[CyclonicFury]

I split every September from 1997 to 2020 into three categories: above-average, average, and below-average. An above-average September features seven or more storms. An average September features four to six storms. A below-average September features three or fewer storms.

Above-average September:
https://i.postimg.cc/PJZHfjnx/Rj7-B2kvd7j.png

Average September:
https://i.postimg.cc/sfZs4pGr/Do-X64-Ub-Xc2.png

Below-average September:
https://i.postimg.cc/sDdy6v5Z/KM5-C8-Ar-X20.png

There is one key difference between the above-average Septembers, the average Septembers, and the below-average Septembers: the VP anomalies in the Indian Ocean. For above-average Septembers, VP anomalies in the Indian Ocean are consistently negative. For average Septembers, VP anomalies in the Indian Ocean are negative in some parts and positive in other parts. For below-average Septembers, VP anomalies in the Indian Ocean are consistently positive. What will September 2021 likely feature?

https://i.postimg.cc/prjmvSZB/cansips-chi200-global-1.png
https://i.postimg.cc/FFkd0f4J/cfs-mon-01-chi200-global-1.png
https://i.postimg.cc/JzHN1YGF/Y202108-D0900-gl0.png

This matches with an above-average September (seven or more storms) signature. The CanSIPS, CFSv2, and JMA would all have to bust in a major way for September 2021 to have fewer than seven storms.

The thing is, there aren't many model signals for storms to form in the near future. 91L only has a 30% chance of development. After that, the GEFS and EPS aren't really showing that much activity other than a potential MDR storm or two after Day 10. It seems unlikely IMO that we'll see 6 storms after September 10, but it can't be ruled out. There's more to how active a month is than velocity potential. I do think we'll see a few more storms (and potentially hurricanes) form this month, but I just don't see TC spam like 2020. There's a reason the Atlantic has only had 10 named storms in September once, despite having a similar VP pattern to 2020 in many years.

[AlphaToOmega]

I split every September from 1997 to 2020 into three categories: above-average, average, and below-average. An above-average September features seven or more storms. An average September features four to six storms. A below-average September features three or fewer storms.

Above-average September:
https://i.postimg.cc/PJZHfjnx/Rj7-B2kvd7j.png

Average September:
https://i.postimg.cc/sfZs4pGr/Do-X64-Ub-Xc2.png

Below-average September:
https://i.postimg.cc/sDdy6v5Z/KM5-C8-Ar-X20.png

There is one key difference between the above-average Septembers, the average Septembers, and the below-average Septembers: the VP anomalies in the Indian Ocean. For above-average Septembers, VP anomalies in the Indian Ocean are consistently negative. For average Septembers, VP anomalies in the Indian Ocean are negative in some parts and positive in other parts. For below-average Septembers, VP anomalies in the Indian Ocean are consistently positive. What will September 2021 likely feature?

https://i.postimg.cc/prjmvSZB/cansips-chi200-global-1.png
https://i.postimg.cc/FFkd0f4J/cfs-mon-01-chi200-global-1.png
https://i.postimg.cc/JzHN1YGF/Y202108-D0900-gl0.png

This matches with an above-average September (seven or more storms) signature. The CanSIPS, CFSv2, and JMA would all have to bust in a major way for September 2021 to have fewer than seven storms.

The thing is, there aren't many model signals for storms to form in the near future. 91L only has a 30% chance of development. After that, the GEFS and EPS aren't really showing that much activity other than a potential MDR storm or two after Day 10. It seems unlikely IMO that we'll see 6 storms after September 10, but it can't be ruled out. There's more to how active a month is than velocity potential. I do think we'll see a few more storms (and potentially hurricanes) form this month, but I just don't see TC spam like 2020. There's a reason the Atlantic has only had 10 named storms in September once, despite having a similar VP pattern to 2020 in many years.

There is still an entire month left. A lot can change in a few weeks, never mind a month. Invest 91L could develop once it moves into the Gulf Stream, a tropical wave could develop in the MDR, and another storm could form in the Western Atlantic after Invest 91L. GEFS ensemble members all show this happening within the September 10 to September 15 timeframe. Should all of those develop, that would bring us to four storms for September. Moreover, the only Septembers since 2000 with a similar pattern VP to September 2020 and 2007, 2010, and 2020. They each had at least eight storms.

[aspen]

To be fair, this September was always gonna look “inactive” coming off of last year. There’s no way the following season could also rival 2020’s 10 named storms in September. However, I will be surprised if we don’t see 4-6 total NS (including Larry) and at least another hurricane and major this month. One of those 7-10 day range waves could have potential when the weak Kelvin Wave passes through.

[AlphaToOmega]

To be fair, this September was always gonna look “inactive” coming off of last year. There’s no way the following season could also rival 2020’s 10 named storms in September. However, I will be surprised if we don’t see 4-6 total NS (including Larry) and at least another hurricane and major this month. One of those 7-10 day range waves could have potential when the weak Kelvin Wave passes through.

Are you sure about that? The VP forecasts for September 2021 look awfully similar to the maps of the Septembers of 2020 (ten storms formed), 2010 (eight storms formed), and 2007 (eight storms formed). Similar levels of activity in September 2020 has been achieved before, so September 2020 was not a once-in-a-lifetime event.

[aspen]

To be fair, this September was always gonna look “inactive” coming off of last year. There’s no way the following season could also rival 2020’s 10 named storms in September. However, I will be surprised if we don’t see 4-6 total NS (including Larry) and at least another hurricane and major this month. One of those 7-10 day range waves could have potential when the weak Kelvin Wave passes through.

Are you sure about that? The VP forecasts for September 2021 look awfully similar to the maps of the Septembers of 2020 (ten storms formed), 2010 (eight storms formed), and 2007 (eight storms formed). Similar levels of activity in September 2020 has been achieved before, so September 2020 was not a once-in-a-lifetime event.

If we go until mid September without another storm, then 7-10 NS is definitely off the table unless the second half of the month is absurdly active. 4-6 NS (3-5 without Larry) seems more reasonable, and like 1995 or 2004, they could be higher ACE long-trackers — the polar opposite of 2020’s quantity-over-quality September. Even just one more long-tracking MDR major like Larry, on top of a few shorter lived storms and hurricanes, could put September 2021’s ACE at or higher than that of September 2020.

[AlphaToOmega]

To be fair, this September was always gonna look “inactive” coming off of last year. There’s no way the following season could also rival 2020’s 10 named storms in September. However, I will be surprised if we don’t see 4-6 total NS (including Larry) and at least another hurricane and major this month. One of those 7-10 day range waves could have potential when the weak Kelvin Wave passes through.

Are you sure about that? The VP forecasts for September 2021 look awfully similar to the maps of the Septembers of 2020 (ten storms formed), 2010 (eight storms formed), and 2007 (eight storms formed). Similar levels of activity in September 2020 has been achieved before, so September 2020 was not a once-in-a-lifetime event.

If we go until mid September without another storm, then 7-10 NS is definitely off the table unless the second half of the month is absurdly active. 4-6 NS (3-5 without Larry) seems more reasonable, and like 1995 or 2004, they could be higher ACE long-trackers — the polar opposite of 2020’s quantity-over-quality September. Even just one more long-tracking MDR major like Larry, on top of a few shorter lived storms and hurricanes, could put September 2021’s ACE at or higher than that of September 2020.

September 2019 featured a lull of activity in the beginning of the month. Seven storms formed. September 2020 featured a lull of activity in the end of the month. Ten storms formed. A lull of activity does not mean an inactive month. Of course, if the lull of activity lasts for longer than ~10 days, that could be significant; but August 2021 showed that multiple storms can form within a period of ~2 weeks.

One more thing as food for thought: 2021 is not experiencing any of the issues or blessings (depending on how you look at them) that 2007, 2010, or 2020 featured. September 2007 featured below-average SSTs throughout much of the MDR. September 2010 featured large amounts of dry air. September 2020 featured many TUTTs. I am not expecting September 2021 to exceed September 2020 in terms of storm count; but there is a chance it could if and only if it does not experience below-average SSTs, does not experience large amounts of dry air, does not experience TUTTs, and experiences the VP anomaly patterns forecasted by the JMA, CanSIPS, and CFSv2.

[Spacecoast]

....does not experience large amounts of dry air, ...

Not sure if this qualifies as large amounts, (or if it's in the right location(s)), but there seems to be bit of dry air lurking end of run around Morroco.

[AlphaToOmega]

I am curious: what climate models are people using to come to the conclusion that September will be dead? There is no indication that September will be anything less than crazy.

[GeneratorPower]

I am curious: what climate models are people using to come to the conclusion that September will be dead? There is no indication that September will be anything less than crazy.

Nobody would use a climate model for a current-month forecast. They are referencing GFS and ECMWF showing little to worry about through end of forecast.

[IcyTundra]

To be quite honest I don't trust the GFS and ECMWF. There could be a bit of lull like the GFS and Euro are showing but I doubt it will be as long as the GFS and Euro are indicating.

[AxaltaRacing24]

To be quite honest I don't trust the GFS and ECMWF. There could be a bit of lull like the GFS and Euro are showing but I doubt it will be as long as the GFS and Euro are indicating.

Almost never is

[SFLcane]

There’s definitely a long range inhibiting factor across the Atlantic not much to speak off in terms of development even at climo peak season.

[aspen]

There’s definitely a long range inhibiting factor across the Atlantic not much to speak off in terms of development even at climo peak season.

The question is: why? 2018 and 2019 seemingly didn’t have it, even though both were warm neutral/weak Niño years. 2021 is a developing Nina year like 2020 with an inactive Pacific and a favorable VP setup, although not the greatest MJO phase.

[AlphaToOmega]

There’s definitely a long range inhibiting factor across the Atlantic not much to speak off in terms of development even at climo peak season.

The question is: why? 2018 and 2019 seemingly didn’t have it, even though both were warm neutral/weak Niño years.

That is the thing: there is none! The VP anomalies are and will be favorable for Atlantic tropical activity. I am saying it again: you cannot fight the climatological peak of hurricane season! The VP maps speak for themselves!

[SFLcane]

There’s definitely a long range inhibiting factor across the Atlantic not much to speak off in terms of development even at climo peak season.

The question is: why? 2018 and 2019 seemingly didn’t have it, even though both were warm neutral/weak Niño years.

That is the thing: there is none! The VP anomalies are and will be favorable for Atlantic tropical activity. I am saying it again: you cannot fight the climatological peak of hurricane season! The VP maps speak for themselves!

VP as you know is not every thing I think there could be other negative factors at play here.

[Category5Kaiju]

There’s definitely a long range inhibiting factor across the Atlantic not much to speak off in terms of development even at climo peak season.

The question is: why? 2018 and 2019 seemingly didn’t have it, even though both were warm neutral/weak Niño years. 2021 is a developing Nina year like 2020 with an inactive Pacific and a favorable VP setup, although not the greatest MJO phase.

Yeah, whatever “inhibiting factor” that is sure seems very brazen to try to challenge the power and influence of climatology, as it looks like the WPAC and EPAC will be relatively quiet for the foreseeable future. For the Atlantic to be quiet as well makes very little logical and practical sense (again, when was the last time all three basins were quiet in September? 1977?)

[AlphaToOmega]

Let me repeat it again: just because we do not see activity in the next few days DOES NOT mean September will be dead. As shown a few weeks ago, lots of storms can form within a very short amount of time (~2 weeks). I expect a couple storms (2-3) to form before September 15, but I think September 15-30 will see 5-8 storms. No matter how you slice it, you cannot fight against the climatological peak of hurricane season. Therefore, I still think September as a whole will be very active, just like in 2007, 2010, 2018, 2019, and 2020.

[Category5Kaiju]

Let me repeat it again: just because we do not see activity in the next few days DOES NOT mean September will be dead. As shown a few weeks ago, lots of storms can form within a very short amount of time (~2 weeks). I expect a couple storms (2-3) to form before September 15, but I think September 15-30 will see 5-8 storms. No matter how you slice it, you cannot fight against the climatological peak of hurricane season. Therefore, I still think September as a whole will be very active, just like in 2007, 2010, 2018, 2019, and 2020.

Hmm, not sure if I totally agree that it would be possible to see at most 11 NSs this month alone, but I do think 7 NSs is a reasonable maximum to how many storms we could see this month. And yes, I agree that I feel some are really underestimating what will happen this month just because the models show little; I just cannot think of why a 12/5/3 season would suddenly slow down in what should be the most climo favorable month. Whatever inhibiting factor SFLcane is saying, I just cannot think of one that makes practical sense and is something we have seen in a recent past year. Poseidon getting tired and wanting to shut down the ocean?

[tolakram]

Let me repeat it again: just because we do not see activity in the next few days DOES NOT mean September will be dead. As shown a few weeks ago, lots of storms can form within a very short amount of time (~2 weeks). I expect a couple storms (2-3) to form before September 15, but I think September 15-30 will see 5-8 storms. No matter how you slice it, you cannot fight against the climatological peak of hurricane season. Therefore, I still think September as a whole will be very active, just like in 2007, 2010, 2018, 2019, and 2020.

Don't be argumentative, we know what you think, you reply to every post indicating there appears to be something missing. Have a conversation. We are in peak season with a major hurricane in the Atlantic and models showing very little. What they did show they backed off on. Face it, every prognostication up to this point has been wrong. No strong hurricanes, no large hurricanes, season will be super busy! 5 to 8 storms in a 15 day period would be quite insane, and if you step back a second you will have to admit nearly impossible. Not every season is going to be mega hyper active, regardless of the indicators. There are multiple pieces of the puzzle we do not understand. What makes a season more or less active than we think it will be is what makes hurricanes seasons interesting, IMO. It will do what it will do, regardless.

[SFLcane]

Let me repeat it again: just because we do not see activity in the next few days DOES NOT mean September will be dead. As shown a few weeks ago, lots of storms can form within a very short amount of time (~2 weeks). I expect a couple storms (2-3) to form before September 15, but I think September 15-30 will see 5-8 storms. No matter how you slice it, you cannot fight against the climatological peak of hurricane season. Therefore, I still think September as a whole will be very active, just like in 2007, 2010, 2018, 2019, and 2020.

Hmm, not sure if I totally agree that it would be possible to see at most 11 NSs this month alone, but I do think 7 NSs is a reasonable maximum to how many storms we could see this month. And yes, I agree that I feel some are really underestimating what will happen this month just because the models show little; I just cannot think of why a 12/5/3 season would suddenly slow down in what should be the most climo favorable month. Whatever inhibiting factor SFLcane is saying, I just cannot think of one that makes practical sense and is something we have seen in a recent past year. Poseidon getting tired and wanting to shut down the ocean?

Well see what happens once the kelvin wave moves over mid month.