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

[Category5Kaiju]

Aside from tropical meterology and biology, one field of science that I am also a fan of is paleontology, and given that, I am very much aware that the Permian/Triassic mass extinction is known colloquially as the "Great Dying." Seems like with tropical cyclones after September in 2021 worldwide, there was also a sort of "Great Dying" that occurred as well .

[dexterlabio]

Nyatoh says hi.

[ElectricStorm]

Welp. That's gonna do it for the 2021 Atlantic season. Another active and destructive year in the books, despite the late season shutdown. Definitely had some insane storms though. Now we wait to see what 2022 will bring. I'm personally hoping for a less active Atlantic, and a more active Pacific. The Atlantic needs a break after the last 6 years...

[Hammy]

This was perhaps the most disappointing third act of any hurricane season since 2006.

[Teban54]

Was the late-season shutdown (both in Atlantic and worldwide) expected beforehand, or in other words, were there signs that in hindsight could have predicted an inactive late season with certainty? Or was it a surprise to everyone except the bears?

[hurricanes1234]

Was the late-season shutdown (both in Atlantic and worldwide) expected beforehand, or in other words, were there signs that in hindsight could have predicted an inactive late season with certainty? Or was it a surprise to everyone except the bears?

I think it came as a complete surprise to nearly everyone (and to some extent, even those who were bearish) because I remember down to late September, there was talk of the Atlantic producing lots of storms in October and November when the MJO was supposed to be more favourable. But it kept being pushed back on the models until eventually it just got too late in the year for anything substantial, which was a universal shocker in a La Niña year that was supposed to be favourable. Even the bears probably didn't expect that only one weak swirl would form after Sam. Although to be fair, I do remember a couple meteorologists tweeting in early October that the season might end after Sam but at the time it seemed like a crazy idea.

All in all, IMO it was a fairly active year but given all the lulls, storms which struggled and the ridiculously early shutdown, in a sense it feels like it never really had the chance to take off (minus a few individual storms which broke the trend of everything struggling). I'm kinda glad we never got to the auxiliary list because I feel like this season probably wasn't deserving of that rare feat which only exceptional years such as 2005 and 2020 achieved. With 21 named storms, 7 hurricanes and 4 major hurricanes, I'd say it was slightly above-average overall but with a high number of borderline (yet completely valid) storms that helped inflate the numbers somewhat. The ACE finished close to the hyperactive threshold but much of that was from Sam and we probably wouldn't have crossed 100 otherwise.

This was perhaps the most disappointing third act of any hurricane season since 2006.

I wouldn't even call it an act because no actors came on stage and all the theatre lights were off.

[Shell Mound]

According to CSU, the AMO average for August–September 2021 was the most positive value on record for this bimonthly period since 2013. Nevertheless, as CSU’s annual verification mentioned, despite the +AMO, -ENSO, and westward-bound steering currents, bouts of strong vertical wind shear, especially during October, kept seasonal ACE at a lower level than might otherwise have been expected, while reducing the potential impacts somewhat as well. Given the relative dearth of quality—apart from Ida, Sam, and perhaps Larry—vs. quantity, I still think that this season was underwhelming from a statistical and climatological standpoint, in light of the background state. One would have expected more hurricane and major-hurricane days than actually occurred, for instance.

[aspen]

According to CSU, the AMO average for August–September 2021 was the most positive value on record for this bimonthly period since 2013. Nevertheless, as CSU’s annual verification mentioned, despite the +AMO, -ENSO, and westward-bound steering currents, bouts of strong vertical wind shear, especially during October, kept seasonal ACE at a lower level than might otherwise have been expected, while reducing the potential impacts somewhat as well. Given the relative dearth of quality—apart from Ida, Sam, and perhaps Larry—vs. quantity, I still think that this season was underwhelming from a statistical and climatological standpoint, in light of the background state. One would have expected more hurricane and major-hurricane days than actually occurred, for instance.

It was a weird mix of quality and quantity. Remember, Sam was one of the top ten biggest ACE makers of the satellite era, joining the 50+ ACE club and just edging out Luis for the #7 spot. Larry was also over 30 ACE, making 2021 the first season with multiple >30 ACE systems since 2017 or 2019* — and both storms occurred in a month with only one other hurricane and so many weak, short-lived slop storms.

*I forget what Lorenzo’s ACE total was

[aspen]

The global MH drought between Sam’s final peak and Nyatoh’s RI was 60 or 61 days; it depends on whether or not Sam became a Cat 3 again on October 4th. How does this compare to other global MH droughts? Based on Phil’s tweets, this might be the longest in the satellite era.

[Category5Kaiju]

What a thread guys, before this thread gets locked just wanted to say that it was very fun interacting with all of you guys on this 2021 indicators thread. Plus, it looks like with 4250 posts as of writing this now we've officially created the longest sst indicators thread of any year so far! Let's see if 2022's thread becomes longer, can't wait to see all the interesting thoughts that appear on the 2022 thread!

[cycloneye]

These indicator threads are never locked so if anyone has comments about the 2021 indicators, you can post them.

Category5Kaiju, it depends on how things pan out that a indicators thread has more or less pages.

[Category5Kaiju]

These indicator threads are never locked so if anyone has comments about the 2021 indicators, you can post them.

Category5Kaiju, it depends on how things pan out that a indicators thread has more or less pages.

Oh ok that's good to know (I noticed how the 2020 sst thread was locked so I wasn't sure if locking the sst indicators thread after a given year passes was routine on this site). Anyhow, looking forward to 2022! Hopefully it's a calmer year than the past 6 brutal seasons, but only time will tell of course.

[AlphaToOmega]

What I think might be occurring is that 2021 was such an MDR-focused season that it could not "adjust" to the climatology of the late season: one that is heavily focused in the Western Atlantic. Other MDR-heavy seasons, such as 2004 and 2017, despite being La Niña/El Niño Modoki seasons, had very lackluster late seasons, probably because they were so MDR-heavy. Something else that might be occurring (correlated to the fact about the reliance on the MDR) is that the low-latitude ITCZ "shoved" tropical waves into the East Pacific during the later part of the season. Seasons with low-latitude ITCZs such as 2004 and 2007, despite being La Niña/El Niño Modoki seasons, had very lackluster late seasons, probably because of their low-latitude ITCZs.

With this post, I am officially signing off for 2021...