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

[aspen]

So far 2021 is running well above-average in pretty much every measurement — named storms (roughly twice average), named storm days, hurricanes, hurricane days, majors (~3x average), major hurricane days (2x average), and ACE. It would take a July-level slumber in activity to give climo means time to catch up, and despite a rather chill September so far compared to 2017-20 with not the greatest MJO setup, that is still quite unlikely.

Also, I have a feeling that this negative MJO phase could lead to a lot of people being caught off guard later in the month. Big MDR/AEW storms in the second half of September are not impossible; Georges and Maria are two notable examples. Someone else mentioned how this season could be similar to 1998 with two peaks: late August/early September, then a gap before enhanced activity in late September (including Georges).

[tolakram]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

[CyclonicFury]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

It depends on which definition of hyperactivity you use. In terms of named storms, it likely will end up "hyperactive", since we are at 13 already. Currently ACE is at 73.1 compared to the average of 46.2, about 158% of normal. The hyperactive ACE threshold is generally considered to be about 165% of normal, so 2021 definitely hasn't been far off from "hyperactive" so far. 2021 also has 5 hurricanes and 3 major hurricanes so far, significantly above the averages of 2.6 and 1.2 respectively.

I think a hyperactive season, by definition, is still technically possible. It's going to come down to how active the rest of September through November is. I'm pretty sure 2020 had a lower ACE at this time than 2021. Granted I don't expect to see a late season as active as last year, but I wouldn't say a "hyperactive" season by definition is off the table by any means.

[tolakram]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

It depends on which definition of hyperactivity you use. In terms of named storms, it likely will end up "hyperactive", since we are at 13 already. Currently ACE is at 73.1 compared to the average of 46.2, about 158% of normal. The hyperactive ACE threshold is generally considered to be about 165% of normal, so 2021 definitely hasn't been far off from "hyperactive" so far. 2021 also has 5 hurricanes and 3 major hurricanes so far, significantly above the averages of 2.6 and 1.2 respectively.

I think a hyperactive season, by definition, is still technically possible. It's going to come down to how active the rest of September through November is. I'm pretty sure 2020 had a lower ACE at this time than 2021. Granted I don't expect to see a late season as active as last year, but I wouldn't say a "hyperactive" season by definition is off the table by any means.

Storm numbers should not be used to define hyperactivity IMO, there should not be a constraint on naming storms (you see arguments about this every year now). For me, I use the ACE definition only. I have no doubt that a hyperactive ACE is at least possible, but not probable.

[Teban54]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

Not sure if hyperactive ACE is truly off the table yet. As I said yesterday, 1998 (which has a very similar pattern of activity bursts as 2021) had lower ACE on this date than we are now, yet still finished with 182 ACE.

The current hyperactive threshold is 159.6, and we're now at 73.1 with Larry still expected to add 5-6 more. Not impossible if one or two more strong CV storms like Larry form in late September, and then some Caribbean action in October.

[Category5Kaiju]

Eh, while not a 100% guarantee, I think hyperactivity cannot be counted out right now just yet. As we saw as recently as last year, an active October with La Niña forcing could really help boost seasonal ACE, and given we are ahead of 2020 now in terms of ACE with possible activity later this month (which could very well last into late October with recent indications that a moderate La Niña could be in the cards once again), I just cannot see what would significantly prevent this season from living up to its expectations or exceeding them.

[aspen]

Regardless if 2021 hits the hyperactive ACE threshold or not, it looks like it’ll be hyperactive in terms of named storms and majors. Only five more storms will bring us to 18 NS, and we’re already at 3 majors with a Nina-fueled October still ahead.

I’m thinking 2021 will finish off in the 120-150 ACE range, similar to 2016/18/19. It all depends on how nuts the Nina-fueled late season gets, and whether or not the MDR can squeeze out one final long-tracker from one of the waves emerging between September 15-20th.

[Woofde]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

It depends on which definition of hyperactivity you use. In terms of named storms, it likely will end up "hyperactive", since we are at 13 already. Currently ACE is at 73.1 compared to the average of 46.2, about 158% of normal. The hyperactive ACE threshold is generally considered to be about 165% of normal, so 2021 definitely hasn't been far off from "hyperactive" so far. 2021 also has 5 hurricanes and 3 major hurricanes so far, significantly above the averages of 2.6 and 1.2 respectively.

I think a hyperactive season, by definition, is still technically possible. It's going to come down to how active the rest of September through November is. I'm pretty sure 2020 had a lower ACE at this time than 2021. Granted I don't expect to see a late season as active as last year, but I wouldn't say a "hyperactive" season by definition is off the table by any means.

Storm numbers should not be used to define hyperactivity IMO, there should not be a constraint on naming storms (you see arguments about this every year now). For me, I use the ACE definition only. I have no doubt that a hyperactive ACE is at least possible, but not probable.

ACE is far too crude of a metric to use as the sole determinant of hyperactivity. It favors less impactful storms that harmlessly curl away to sea. A strong storm that forms quickly and hits land is a sign of a favorable basin, but ACE gives very little points to these style of storms. This leads to seasons like 2020 where West based landfalling consistency causes it's storms to not produce many ACE points. It barely made it to ACE hyperactive status despite clearly being one of, if not the most favorable background basin states ever seen.

A metric that awarded points for systems that landfall could solve this, but would likely be contentious.

The other main issue with ACE is that it only takes wind into account. There are so many other variables (pressure, storm size, rainfall, wind radii, etc) that clearly also represent how favorable a season is/was but ACE ignores them completely.

Solely using ACE is akin to only using the Saffir-simpson scale to determine how impactful a system will be. It's simple, but often very misleading.

[tolakram]

It depends on which definition of hyperactivity you use. In terms of named storms, it likely will end up "hyperactive", since we are at 13 already. Currently ACE is at 73.1 compared to the average of 46.2, about 158% of normal. The hyperactive ACE threshold is generally considered to be about 165% of normal, so 2021 definitely hasn't been far off from "hyperactive" so far. 2021 also has 5 hurricanes and 3 major hurricanes so far, significantly above the averages of 2.6 and 1.2 respectively.

I think a hyperactive season, by definition, is still technically possible. It's going to come down to how active the rest of September through November is. I'm pretty sure 2020 had a lower ACE at this time than 2021. Granted I don't expect to see a late season as active as last year, but I wouldn't say a "hyperactive" season by definition is off the table by any means.

Storm numbers should not be used to define hyperactivity IMO, there should not be a constraint on naming storms (you see arguments about this every year now). For me, I use the ACE definition only. I have no doubt that a hyperactive ACE is at least possible, but not probable.

ACE is far too crude of a metric to use as the sole determinant of hyperactivity. It favors less impactful storms that harmlessly curl away to sea. A strong storm that forms quickly and hits land is a sign of a favorable basin, but ACE gives very little points to these style of storms. This leads to seasons like 2020 where West based landfalling consistency causes it's storms to not produce many ACE points. It barely made it to ACE hyperactive status despite clearly being one of, if not the most favorable background basin states ever seen.

A metric that awarded points for systems that landfall could solve this, but would likely be contentious.

The other main issue with ACE is that it only takes wind into account. There are so many other variables (pressure, storm size, rainfall, wind radii, etc) that clearly also represent how favorable a season is/was but ACE ignores them completely.

Solely using ACE is akin to only using the Saffir-simpson scale to determine how impactful a system will be. It's simple, but often very misleading.

Yep, I made this argument last year. Until we have a better agreed to metric though ACE is the best we have. Storm numbers will be inflated based on years past because of better observations and the always present subjective requirements. The NHC missions statement does not include the definition of a tropical storm, for example.

I think they're both silly, honestly, since a season with two cat 5's hitting populated areas anywhere is going to be an extremely high impact low ACE or storm count season.

This does not change my prediction that we probably won't hit hyperactive ACE. Even if we have a lot of strong storms I feel like they will be shorter lived and western based.

[Category5Kaiju]

While it did get more than 240 ACE, 2005 is an example of the ACE system clearly favoring storms with high 1-min sustained wind speeds; despite being west-focused with hardly any long track, powerful MDR born storms (even less so than 2020 in a way), 4 West Atlantic Cat 5s almost certainly was enough to push the season's ACE count over the top.

[IcyTundra]

2005 had Dennis and Emily as long tracking systems born in the MDR but those were in July and there were no long trackers for the rest of the season. 2005 was such a odd season and we will probably never see a season like it again.

[AlphaToOmega]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

I am not so convinced hyperactivity is off the table. A La Nina is likely going to make October and November very active. If you are using the definition of >210 ACE, I could see the argument; but hyperactivity is currently defined as >159 ACE. The season so far has produced 66.8 ACE.
EDIT: Your definition of "off the table" is probable, not possible. Could you elaborate as to why hyperactivity is not probable?

[tolakram]

I'm expecting another big burst in activity, but I think at this point hyperactive is off the table, as it should be. One would hope hyperactive seasons are quite rare. This talk of hyperactivity has also diminished, in my opinion, how destructive non hyperactive seasons can be.

I am not so convinced hyperactivity is off the table. A La Nina is likely going to make October and November very active. If you are using the definition of >210 ACE, I could see the argument; but hyperactivity is currently defined as >159 ACE. The season so far has produced 66.8 ACE.
EDIT: Your definition of "off the table" is probable, not possible. Could you elaborate as to why hyperactivity is not probable?

Why is it probable? To me it's insane to ever think an extreme season is probable. Statistically it's never probably, otherwise it wouldn't be an outlier. Most probably is a solidly above average season, IMO anyway. Why is it so important that this season reach a certain metric?

[abajan]

[youtube]https://youtu.be/2HGk426JXQo[/youtube]

[AlphaToOmega]

There are two AoIs in the Atlantic. It is likely that at least one of them develop, for both have significant ensemble support. Climatology is the most powerful force of hurricane seasons. Those VP maps never lie, and they surely forecasted an active September. This is not to mention that after September 15, conditions are expected to be even more favorable in the Atlantic than they currently are. I have a feeling that certain people are going to sell their bears right now. Assume the MDR disturbance becomes Nicholas and the BoC disturbance becomes Odette. The ECENS indicates two more MDR disturbances (Peter and Rose) and a possible Caribbean disturbance (Sam). All of this is before September 20. If the forecasts about a burst of activity during the latter half of September verify, it would mean that we would be on track with 2005 and 2020 in terms of activity.

Or a surprise thermohaline circulation could occur and shut down the Atlantic basin for the rest of the year

[IcyTundra]

We better enjoy these next few days of quiet before the Atlantic goes haywire in the 2nd half of September.

[toad strangler]

We better enjoy these next few days of quiet before the Atlantic goes haywire in the 2nd half of September.

There hasn't been any quiet.

[IcyTundra]

We better enjoy these next few days of quiet before the Atlantic goes haywire in the 2nd half of September.

There hasn't been any quiet.

True I guess in my mind it hasn't been that busy compared to August but we still have gotten a MH in Larry and a quick spinup in Mindy so far in the month of September.

[toad strangler]

We better enjoy these next few days of quiet before the Atlantic goes haywire in the 2nd half of September.

There hasn't been any quiet.

True I guess in my mind it hasn't been that busy compared to August but we still have gotten a MH in Larry and a quick spinup in Mindy so far in the month of September.

....and it's not even the 10th

[tolakram]

Stay on topic please. Avoid posting tweets (post moved to moderation) from anyone, including pro mets, that is meant to do nothing but troll. Thanks.