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

[Category5Kaiju]

Wild hypothesis: The amount of season cancel posts correlates with current activity, not potential activity.

There was a brief lull in season cancelling yesterday when 95L and 97L looked impressive for invests. Then they returned immediately today when they became naked swirls.

On a more serious note, this has been well-modeled in advance. We know a suppressed phase was bound to happen in mid-September, and we also know they will become more favorable in one or two weeks. I would reserve all 2013 calls until at least end of October.

To be fair, 2013 should in no way serve as any comparison with this season given we have already had 6 hurricanes, 3 major hurricanes, and more NSs (and counting) with twice the ACE than that season ever had. I am honestly unsure about where this general idea of 2013 is suddenly coming from if you ask me.

There's a world of difference between comparing 2013 as a season, and comparing the conditions that led to it (a decrease in the thermohaline circulation), which itself can lead to a sudden decrease in favorability.

The THC IS getting weaker with time, so this definitely something to question when we end up with such massively unfavorable conditions all of a sudden.

Eh, I suppose, but I personally I am going to wait until later this month and October and see. I think this is simply due to the unfavorable MJO phase, because the simple fact is we are still getting storms, and have already been getting major hurricanes in late August. I just think the MJO phase's timing was a bit awry, which is why we are not seeing major activity during what is usually the peak season. From the way I see it, a THC collapse would cause even more unfavorable conditions than what we are seeing now, with waves simply drying up as they exit Africa (tropical cyclone genesis itself being a major problem) as we saw in 2013 as an example. GEFS and GEPS are still hinting at a late September and early October burst in activity, so personally I am not sure if this is necessarily due to a THC collapse. I think more evidence in the near future will be needed for us to make such sort of judgement.

*btw, just now Rose has officially been designated to have formed by the NHC on its map. And not to mention we now have an AOI that has a 40% chance within the next 5 days as well as an Odette that could reform as a zombie storm. Interpret this situation as you will, but personally, I find it a bit hard to believe that a THC collapse is to blame, I really think it's just a suppressive MJO phase that is the culprit.

[Category5Kaiju]

Wild hypothesis: The amount of season cancel posts correlates with current activity, not potential activity.

There was a brief lull in season cancelling yesterday when 95L and 97L looked impressive for invests. Then they returned immediately today when they became naked swirls.

On a more serious note, this has been well-modeled in advance. We know a suppressed phase was bound to happen in mid-September, and we also know they will become more favorable in one or two weeks. I would reserve all 2013 calls until at least end of October.

To be fair, 2013 should in no way serve as any comparison with this season given we have already had 6 hurricanes, 3 major hurricanes, and more NSs (and counting) with twice the ACE than that season ever had. I am honestly unsure about where this general idea of 2013 is suddenly coming from if you ask me.

There's a world of difference between comparing 2013 as a season, and questioning if the conditions that led to it (a decrease in the thermohaline circulation) might be occurring, since there aren't exactly a lot of seasons where this occurred that would offer clearer answers for comparison.

Something is clearly going on in the background that's leading to September (and practically the entire open Atlantic in general) substantially underperforming and I don't see why people need take issue with considering all possible factors.

It's also worth noting that the CFS has both gradually backed off of storm activity for October (aside from a continuation of weaker MDR storms) as well as Caribbean rainfall.

What does the cfs say about activity in the WPAC and EPAC?

[AlphaToOmega]

Wild hypothesis: The amount of season cancel posts correlates with current activity, not potential activity.

There was a brief lull in season cancelling yesterday when 95L and 97L looked impressive for invests. Then they returned immediately today when they became naked swirls.

On a more serious note, this has been well-modeled in advance. We know a suppressed phase was bound to happen in mid-September, and we also know they will become more favorable in one or two weeks. I would reserve all 2013 calls until at least end of October.

To be fair, 2013 should in no way serve as any comparison with this season given we have already had 6 hurricanes, 3 major hurricanes, and more NSs (and counting) with twice the ACE than that season ever had. I am honestly unsure about where this general idea of 2013 is suddenly coming from if you ask me.

There's a world of difference between comparing 2013 as a season, and questioning if the conditions that led to it (a decrease in the thermohaline circulation) might be occurring, since there aren't exactly a lot of seasons where this occurred that would offer clearer answers for comparison.

Something is clearly going on in the background that's leading to September (and practically the entire open Atlantic in general) substantially underperforming and I don't see why people need take issue with considering all possible factors.

It's also worth noting that the CFS has both gradually backed off of storm activity for October (aside from a continuation of weaker MDR storms) as well as Caribbean rainfall.

I remember looking at the CFS on weatheronline.co.uk during mid-August, and it showed almost nothing during September. Six storms formed, with two of them being hurricanes. This is to be expected; model runs thousands of hours out are not very reliable.

[Category5Kaiju]

 https://twitter.com/BMcNoldy/status/1439690655777787905




Whatever happens going forward, just keep this impressive statistic in mind; 2021 is doing something that very few seasons have managed to do.

[Category5Kaiju]

Also, I would like to show this as an additional comparison:

2007's sst profile on September 20:


2013's sst profile on September 19:


2021's sst profile on September 18:


I honestly feel safe to say that unlike 2007 or 2013 that thermodynamics is clearly not going to be an issue whatsoever going forward into the near future.

[Hammy]

Interesting how much closer 2007 looks to 2013 than it does this year. Could there have been a slowing of the circulation, but happening late enough to allow a burst of intense Caribbean activity with Dean and Felix first? (2013's issues began in spring, and led to the unfavorable weather arriving in July). 2007 has long been a curiosity and I feel there was more going on in the background than we know.

I remember looking at the CFS on weatheronline.co.uk during mid-August, and it showed almost nothing during September. Six storms formed, with two of them being hurricanes. This is to be expected; model runs thousands of hours out are not very reliable.

It's generally not going to be accurate as far as exact storm count (especially being that far out) but it was correct in showing largely weaker storms. It's worth noting when checking to assume any low to be a tropical storm as the resolution is very low--there have been active major hurricanes that were showing up as large 996mb lows.

What does the cfs say about activity in the WPAC and EPAC?

A zoom of Mexico shows late September to mid-October being fairly active in the EPAC, with what are likely a few hurricanes given the model's resolution. WPAC seems to also show some storms developing and generally lowered pressures, but the resolution is not enough to tell whether these will be weaker monsoonal systems, or stronger ones.

It's showing nothing other than a few strong fronts in the Gulf or Caribbean through early November after which the maps aren't loading.

[AlphaToOmega]

I remember looking at the CFS on weatheronline.co.uk during mid-August, and it showed almost nothing during September. Six storms formed, with two of them being hurricanes. This is to be expected; model runs thousands of hours out are not very reliable.

It's generally not going to be accurate as far as exact storm count (especially being that far out) but it was correct in showing largely weaker storms. It's worth noting when checking to assume any low to be a tropical storm as the resolution is very low--there have been active major hurricanes that were showing up as large 996mb lows.

What does the cfs say about activity in the WPAC and EPAC?

A zoom of Mexico shows late September to mid-October being fairly active in the EPAC, with what are likely a few hurricanes given the model's resolution. WPAC seems to also show some storms developing and generally lowered pressures, but the resolution is not enough to tell whether these will be weaker monsoonal systems, or stronger ones.

It's showing nothing other than a few strong fronts in the Gulf or Caribbean through early November after which the maps aren't loading.

I forgot to mention that it is also the CFS, which is known to be biased towards -VP in the Maritime Continent and towards +VP in Africa.

[Hammy]

I remember looking at the CFS on weatheronline.co.uk during mid-August, and it showed almost nothing during September. Six storms formed, with two of them being hurricanes. This is to be expected; model runs thousands of hours out are not very reliable.

It's generally not going to be accurate as far as exact storm count (especially being that far out) but it was correct in showing largely weaker storms. It's worth noting when checking to assume any low to be a tropical storm as the resolution is very low--there have been active major hurricanes that were showing up as large 996mb lows.

What does the cfs say about activity in the WPAC and EPAC?

A zoom of Mexico shows late September to mid-October being fairly active in the EPAC, with what are likely a few hurricanes given the model's resolution. WPAC seems to also show some storms developing and generally lowered pressures, but the resolution is not enough to tell whether these will be weaker monsoonal systems, or stronger ones.

It's showing nothing other than a few strong fronts in the Gulf or Caribbean through early November after which the maps aren't loading.

I forgot to mention that it is also the CFS, which is known to be biased towards -VP in the Maritime Continent and towards +VP in Africa.

Can you explain this a bit? The VP anomalies are still very new to me as far as how much I know so that would further aide in interpreting the model biases.

[AlphaToOmega]

It's generally not going to be accurate as far as exact storm count (especially being that far out) but it was correct in showing largely weaker storms. It's worth noting when checking to assume any low to be a tropical storm as the resolution is very low--there have been active major hurricanes that were showing up as large 996mb lows.



A zoom of Mexico shows late September to mid-October being fairly active in the EPAC, with what are likely a few hurricanes given the model's resolution. WPAC seems to also show some storms developing and generally lowered pressures, but the resolution is not enough to tell whether these will be weaker monsoonal systems, or stronger ones.

It's showing nothing other than a few strong fronts in the Gulf or Caribbean through early November after which the maps aren't loading.

I forgot to mention that it is also the CFS, which is known to be biased towards -VP in the Maritime Continent and towards +VP in Africa.

Can you explain this a bit? The VP anomalies are still very new to me as far as how much I know so that would further aide in interpreting the model biases.

VP anomalies indicate rising air. Negative VP anomalies indicate diverging, rising air; positive VP anomalies indicate converging, sinking air. Negative VP anomalies in Africa and the Indian Ocean are conducive for active Atlantic hurricane seasons; positive VP anomalies in Africa and the Indian Ocean are conducive for inactive Atlantic hurricane seasons. This works on a month-by-month basis as well; months with negative VP anomalies in Africa and the Indian Ocean are more favorable than months with positive VP anomalies in Africa and the Indian Ocean.

[LarryWx]

The latest storm on record back to 1851 to have genesis east of 55W in the MDR and to later hit the CONUS is September 25th: storm #9 of 1893

https://www.nhc.noaa.gov/data/tracks/tracks-at-1893.png

Next latest E of 55W geneses were both on 9/21: Inez of 1966 and Lili of 2002. Then Gloria 9/16/1985 and Georges of 9/15/1998.

After 9/25, all geneses on record back to 1851 that later hit the CONUS were W of 55 W. So, when looking at model consensus with the lack of CV threats on them now, climo now says that the CONUS will very likely be safe from any genesis E of 55 W the rest of this season. So, potential remaining threatening genesis locations are mainly just E of or near the LAs, the Caribbean (mainly W half), the GOM, and the SW Atlantic north of the GAs to off the east coast.

[jconsor]

Nice post! There were a lot more October landfalls along the US East Coast from SC northward to New England from the late 1600s to the early 1800s than since 1850.
I was able to find at least two that hit the East Coast in Oct and probably originated east of 55W, based on historical accounts:

The 1804 "Snow hurricane" that caused severe damage from NJ to New England on Oct 9. Chenoweth who did a reanalysis of 1700-1850 cites this storm as having tracked north of Puerto Rico.
https://en.wikipedia.org/wiki/1804_New_ ... _hurricane

Further details on damage in the northeast US: https://myweb.fsu.edu/jelsner/temp/HHIT ... 4/1804.htm

1706 tropical storm that tracked from Barbados to NY, with damage from wind and rain reported in NY/CT on Oct 15.
https://en.wikipedia.org/wiki/List_of_A ... th_century

Chenoweth paper: https://www.aoml.noaa.gov/hrd/hurdat/Chenoweth/chenoweth06.pdf

BTW and for entertainment purposes only, the 12z CFS is fixin' to break the record you mentioned. It shows a TS forming on Sep 27 just west of the CV islands and tracking west to a position just NE of the Leeward Islands Oct 2-3, then rounding an anomalously strong W Atl ridge before hitting eastern New England on Oct 7.

The latest storm on record back to 1851 to have genesis east of 55W in the MDR and to later hit the CONUS is September 25th: storm #9 of 1893

https://www.nhc.noaa.gov/data/tracks/tracks-at-1893.png

Next latest E of 55W geneses were both on 9/21: Inez of 1966 and Lili of 2002. Then Gloria 9/16/1985 and Georges of 9/15/1998.

After 9/25, all geneses on record back to 1851 that later hit the CONUS were W of 55 W. So, when looking at model consensus with the lack of CV threats on them now, climo now says that the CONUS will very likely be safe from any genesis E of 55 W the rest of this season. So, potential remaining threatening genesis locations are mainly just E of or near the LAs, the Caribbean (mainly W half), the GOM, and the SW Atlantic north of the GAs to off the east coast.

[aspen]

With Peter and Rose currently active and Sam likely to form in the next 4-7 days, we’ll probably finish with 20-24 named storms.

Yeah this’ll be another serious quantity-over-quality season, and this September has been underwhelming in the quality department, but it’s crazy that we might exhaust the name list for the second year in a row.

[AlphaToOmega]

Important thing to note: many Septembers, even in active seasons, were quantity-above-quality. September 2016 and September 2020 were all quantity-above-quality. In both cases, October and November featured quality storms. 2016, 2020, and 2021 featured/are featuring strong WAM; all are La Nina seasons; all featured/are featuring quantity-above-quality Septembers. This shows you that a lot can change in the last few months of hurricane seasons.

PS: In terms of timing, 2021 is so far quite close to 2016: one May storm, active June, July lull, active August, and quantity-over-quality September (aside from Matthew). The difference is that 2021 is so far way ahead of 2016 in every metric.

[Hammy]

Important thing to note: many Septembers, even in active seasons, were quantity-above-quality. September 2016 and September 2020 were all quantity-above-quality. In both cases, October and November featured quality storms. 2016, 2020, and 2021 featured/are featuring strong WAM; all are La Nina seasons; all featured/are featuring quantity-above-quality seasons. This shows you that a lot can change in the last few months of hurricane seasons.

PS: In terms of timing, 2021 is so far quite close to 2016: one May storm, active June, July lull, active August, and quantity-over-quality September (aside from Matthew). The difference is that 2021 is so far way ahead of 2016 in every metric.

I disagree on 2020 being quantity over quality given we had quite a few hurricanes, and some stronger ones--including three Cat 2+ hurricanes active at once (and I'm certain Paulette was stronger than the official intensity, though I don't actually have anything to back that up)--10/4/1 with two long trackers (one a major) and a near-major landfall is a respectable showing--it seemed less because everything developed, including things that wouldn't have in any other year, leading to additional weaker storms.

2016 was a strangely uneven year. Hurricane in January, burst of May/June activity, August having only one hurricane on each end (and then Hermine at the start of September), no real long trackers (and the only major during the peak timeframe struggling until it reached the subtropics), and then back to back to back major hurricanes in October/November, and I'm still to this day not sure what was going on that year as all indications were for a more favorable bulk of the season.

[storminabox]

With Peter and Rose currently active and Sam likely to form in the next 4-7 days, we’ll probably finish with 20-24 named storms.

Yeah this’ll be another serious quantity-over-quality season, and this September has been underwhelming in the quality department, but it’s crazy that we might exhaust the name list for the second year in a row.

Ya know I'd almost prefer to say no storms than the constant stream of slop we've seen this month (aside from Nicholas, and Larry). Just skews the seasons statistics and make it look more impressive than it actually is. Though I will say portions of this season have been incredibly notable (Ida), however this September has been quite underwhelming in the MDR. The general favorability of the western part of the basin does have me concerned for what October could bring. This season is reminding me of 2016/2020 so far.

[Category5Kaiju]

Important thing to note: many Septembers, even in active seasons, were quantity-above-quality. September 2016 and September 2020 were all quantity-above-quality. In both cases, October and November featured quality storms. 2016, 2020, and 2021 featured/are featuring strong WAM; all are La Nina seasons; all featured/are featuring quantity-above-quality seasons. This shows you that a lot can change in the last few months of hurricane seasons.

PS: In terms of timing, 2021 is so far quite close to 2016: one May storm, active June, July lull, active August, and quantity-over-quality September (aside from Matthew). The difference is that 2021 is so far way ahead of 2016 in every metric.

I disagree on 2020 being quantity over quality given we had quite a few hurricanes, and some stronger ones--including three Cat 2+ hurricanes active at once (and I'm certain Paulette was stronger than the official intensity, though I don't actually have anything to back that up)--10/4/1 with two long trackers (one a major) and a near-major landfall is a respectable showing--it seemed less because everything developed, including things that wouldn't have in any other year, leading to additional weaker storms.

2016 was a strangely uneven year. Hurricane in January, burst of May/June activity, August having only one hurricane on each end (and then Hermine at the start of September), no real long trackers (and the only major during the peak timeframe struggling until it reached the subtropics), and then back to back to back major hurricanes in October/November, and I'm still to this day not sure what was going on that year as all indications were for a more favorable bulk of the season.

I will say that 2016 was the year right after a super El Nino, so during the Atlantic's peak season the EPAC and WPAC were still very active (both basins ended up being above average too) thanks to the lingering effects of the El Nino. Not surprising, although that could explain parts of why that year September was so inactive in the Atlantic (I'm pretty confident that the WAM that year was nowhere near as strong as 2020 or this year however).

[LarryWx]

Nice post! There were a lot more October landfalls along the US East Coast from SC northward to New England from the late 1600s to the early 1800s than since 1850.
I was able to find at least two that hit the East Coast in Oct and probably originated east of 55W, based on historical accounts:

The 1804 "Snow hurricane" that caused severe damage from NJ to New England on Oct 9. Chenoweth who did a reanalysis of 1700-1850 cites this storm as having tracked north of Puerto Rico.
https://en.wikipedia.org/wiki/1804_New_ ... _hurricane

Further details on damage in the northeast US: https://myweb.fsu.edu/jelsner/temp/HHIT ... 4/1804.htm

1706 tropical storm that tracked from Barbados to NY, with damage from wind and rain reported in NY/CT on Oct 15.
https://en.wikipedia.org/wiki/List_of_A ... th_century

Chenoweth paper: https://www.aoml.noaa.gov/hrd/hurdat/Chenoweth/chenoweth06.pdf

BTW and for entertainment purposes only, the 12z CFS is fixin' to break the record you mentioned. It shows a TS forming on Sep 27 just west of the CV islands and tracking west to a position just NE of the Leeward Islands Oct 2-3, then rounding an anomalously strong W Atl ridge before hitting eastern New England on Oct 7.

The latest storm on record back to 1851 to have genesis east of 55W in the MDR and to later hit the CONUS is September 25th: storm #9 of 1893

https://www.nhc.noaa.gov/data/tracks/tracks-at-1893.png

Next latest E of 55W geneses were both on 9/21: Inez of 1966 and Lili of 2002. Then Gloria 9/16/1985 and Georges of 9/15/1998.

After 9/25, all geneses on record back to 1851 that later hit the CONUS were W of 55 W. So, when looking at model consensus with the lack of CV threats on them now, climo now says that the CONUS will very likely be safe from any genesis E of 55 W the rest of this season. So, potential remaining threatening genesis locations are mainly just E of or near the LAs, the Caribbean (mainly W half), the GOM, and the SW Atlantic north of the GAs to off the east coast.

Thanks, Yaakov. Interesting about the two you noted!

1) 1804: As it says, Dominique and Guadeloupe as well as N of PR on 10/4. So, it appears to have been moving on a NW trajectory from 61-62W. What nobody knows is whether or not it had its genesis E of 55W. It is certainly conceivable that it formed between 55 W and 62 W as I found 6 others that did just that in the records within the MDR after 9/25 during 1873-2016 (see below). That areas seems to have been a sweet spot of sorts for geneses during late Sep/early Oct.

2) 1706: Barbados to New England. Barbados is 59-60W. Again, nobody knows how far E of Barbados it formed. Could it have formed within the sweet spot west of 55 W? Quite possible.

Here are the furthest E geneses on record after 9/25 within the MDR ***that later hit the CONUS***
1) 56W: #6 of 1879 genesis 10/9
2) 58W: Hazel of 1954 genesis 10/5
3) 60W: #13 of 1887 genesis 10/9
4) 60W: Matthew of 2016 genesis 9/28
5) 62W: #5 of 1897 genesis 10/9
6) 62W: #5 of 1873 genesis 9/26

Another to mention within MDR that hit the CONUS:
58W: #7 of 1898 genesis right on 9/25

North of MDR that hit the CONUS:
1) 61W: #7 of 1935 genesis 10/30
2) 63W: #5 of 1941 genesis 10/3
3) 64W: #7 of 1923 genesis 10/15
---------------------------------------------------------------------------
Edit: Here's another way to look at this that you may find interesting:

From 1851-2020, there were 43 T.S.+'s that were first declared a T.D.+ east of 55W within the MDR 9/26+. NONE of these later hit the CONUS.

***Corrected to add that those in the lists hit the CONUS.

[Deshaunrob17]

Important thing to note: many Septembers, even in active seasons, were quantity-above-quality. September 2016 and September 2020 were all quantity-above-quality. In both cases, October and November featured quality storms. 2016, 2020, and 2021 featured/are featuring strong WAM; all are La Nina seasons; all featured/are featuring quantity-above-quality seasons. This shows you that a lot can change in the last few months of hurricane seasons.

PS: In terms of timing, 2021 is so far quite close to 2016: one May storm, active June, July lull, active August, and quantity-over-quality September (aside from Matthew). The difference is that 2021 is so far way ahead of 2016 in every metric.

I disagree on 2020 being quantity over quality given we had quite a few hurricanes, and some stronger ones--including three Cat 2+ hurricanes active at once (and I'm certain Paulette was stronger than the official intensity, though I don't actually have anything to back that up)--10/4/1 with two long trackers (one a major) and a near-major landfall is a respectable showing--it seemed less because everything developed, including things that wouldn't have in any other year, leading to additional weaker storms.

2016 was a strangely uneven year. Hurricane in January, burst of May/June activity, August having only one hurricane on each end (and then Hermine at the start of September), no real long trackers (and the only major during the peak timeframe struggling until it reached the subtropics), and then back to back to back major hurricanes in October/November, and I'm still to this day not sure what was going on that year as all indications were for a more favorable bulk of the season.

I guess what defines a season with quality is having several long-tracked hurricanes... 2020 only had Teddy as a long track hurricane. Paulette was a long tracked storm

[Teban54]

Important thing to note: many Septembers, even in active seasons, were quantity-above-quality. September 2016 and September 2020 were all quantity-above-quality. In both cases, October and November featured quality storms. 2016, 2020, and 2021 featured/are featuring strong WAM; all are La Nina seasons; all featured/are featuring quantity-above-quality seasons. This shows you that a lot can change in the last few months of hurricane seasons.

PS: In terms of timing, 2021 is so far quite close to 2016: one May storm, active June, July lull, active August, and quantity-over-quality September (aside from Matthew). The difference is that 2021 is so far way ahead of 2016 in every metric.

I disagree on 2020 being quantity over quality given we had quite a few hurricanes, and some stronger ones--including three Cat 2+ hurricanes active at once (and I'm certain Paulette was stronger than the official intensity, though I don't actually have anything to back that up)--10/4/1 with two long trackers (one a major) and a near-major landfall is a respectable showing--it seemed less because everything developed, including things that wouldn't have in any other year, leading to additional weaker storms.

2016 was a strangely uneven year. Hurricane in January, burst of May/June activity, August having only one hurricane on each end (and then Hermine at the start of September), no real long trackers (and the only major during the peak timeframe struggling until it reached the subtropics), and then back to back to back major hurricanes in October/November, and I'm still to this day not sure what was going on that year as all indications were for a more favorable bulk of the season.

I guess what defines a season with quality is having several long-tracked hurricanes... 2020 only had Teddy as a long track hurricane. Paulette was a long tracked storm

2005 also didn't have that many hurricanes with long tracks. Emily perhaps, and it's only limited to the Caribbean and Gulf.

[AxaltaRacing24]

Crazy how years like 2005, 2020, and this season have unfavorable MDR's and look unfavorable as a whole, produce the highest numbers in quality and quantity. Even though this season "feels" like a struggle, one more MJO push will likely boost us to 5-6 majors and 10 hurricanes. 20+ storms looks likely too.

Even if 2021's numbers end up higher than 2017's, it wouldn't "feel" that way at all. Especially considering the fact that 2020 was last year.