When will the multi-decade active era that began in 1995 end?

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Re: When will the multi-decade active era that began in 1995 end?

#501 Postby Category5Kaiju » Tue Apr 12, 2022 8:49 am

NotSparta wrote:
Shell Mound wrote:Top reasons why the +AMO has likely ended post 2010:

  • There have been only two hyperactive seasons (2017, 2020) over the past decade, compared to seven (1995, 1996, 1998, 1999, 2003, 2004, 2005) over a comparable decade
  • Average precipitation over the MDR and Caribbean during two most recent hyperactive seasons was far lower than the mean of the seven previous hyperactive years
  • Instability over the MDR and Caribbean during the peak months of ASO has been much lower post 2010 than before
  • The subtropics have been consistently warmer than the tropics during most of the past ten seasons
  • Long-tracked majors in the MDR and Caribbean have become much less frequent than they used to be
  • Seasonal activity is being inflated by short-lived systems in the subtropics that likely went unclassified/undetected prior to advances in detection and changes to the criteria for classification
  • More ACE is being generated in the subtropics instead of the tropics, while overall ACE is still decreasing due to the fact that the tropics are generating fewer long-lived, intense storms
  • While ACE is still averaging somewhat higher than during the previous -AMO, it is still lower than during the unquestionably +AMO period of 1995–2010; given that warmer global SST due to climate change may result in higher overall ACE in modern-day -AMOs than in pre-global-warming -AMOs, this should not be used to claim that the most recent +AMO did not end
  • The changes in the distribution of precipitation and ACE, as well as the decrease in long-lived, intense systems in the tropics, correlates well with the end of the +AMO
  • In turn, the end of the +AMO can be attributable to changes in the SST over the far northern North Atlantic that have been brought about by Greenland ice melt and freshwater influx, which in turn is attributable to global warming
Conclusion: while there is still uncertainty, the weight of evidence suggests that the most recent +AMO ended circa 2010 and no later than 2013, and that this +AMO lasted for a shorter period than previous +AMOs due to the background changes brought about by climate change. Because climate change results in warmer absolute SST globally, we could still end up with higher seasonal ACE in a -AMO cycle today than in past -AMO cycles, yet still be in a -AMO rather than a +AMO. It would be misleading to use a single piece of evidence such as the warm Canary Current and active WAM to argue that we are still in a +AMO, at least in my view.


Top reasons why the +AMO has (functionally) likely not ended post 2010:

  • The last below average season was literally 7 years ago
  • In 25 years, the last -AMO had 2 above average seasons (13 below)
  • Since 2011 (11 years), there have been 8 above average seasons (3 below)
  • 2017
  • 2020

Just because the hyperactive seasons don't look "classic" or that we haven't had the same extreme activity that is excessive even for a +AMO doesn't mean it has ended. If we were truly in a -AMO, we would not have seen 2016-21 (and likely 2022). The past 6 years (or even going back to 2010) has had activity far and away above what you'd expect in a -AMO. I understand making this argument in 2014, 2015, 2016, even early 2017. But this argument has become harder and harder to defend with time. Just a fool's errand to argue that we're in a -AMO when we're probably at the precipice of yet another active season (ACE is not significantly affected by short lived storms!). If ACE is this high even in a -AMO due to AGW, we may as well be in a permanent +AMO, because the recent activity is far more consistent with +AMO


Also, let's keep in mind that getting a hyperactive season in the first place is not something you would expect to see every year that passes. In other words, while yes we had back to back hyperactive years like 1995-1996, 1998-1999, 2003-2005, notice how one typically occurs every 2-4 years or so. I don't think we can simply conclude that "oh, we got back to back hyperactive years back then and since 2017 and 2020 are not back to back hyperactive years they are not common anymore." Also, you have to go back 26 years from 1995 to 1969 if you wanted to see another hyperactive year. Like I said, the fact that we are still getting hyperactive seasons imho is way more significant that their timing.
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Re: When will the multi-decade active era that began in 1995 end?

#502 Postby Shell Mound » Tue Apr 12, 2022 11:21 am

Category5Kaiju wrote:
NotSparta wrote:
Shell Mound wrote:Top reasons why the +AMO has likely ended post 2010:

  • There have been only two hyperactive seasons (2017, 2020) over the past decade, compared to seven (1995, 1996, 1998, 1999, 2003, 2004, 2005) over a comparable decade
  • Average precipitation over the MDR and Caribbean during two most recent hyperactive seasons was far lower than the mean of the seven previous hyperactive years
  • Instability over the MDR and Caribbean during the peak months of ASO has been much lower post 2010 than before
  • The subtropics have been consistently warmer than the tropics during most of the past ten seasons
  • Long-tracked majors in the MDR and Caribbean have become much less frequent than they used to be
  • Seasonal activity is being inflated by short-lived systems in the subtropics that likely went unclassified/undetected prior to advances in detection and changes to the criteria for classification
  • More ACE is being generated in the subtropics instead of the tropics, while overall ACE is still decreasing due to the fact that the tropics are generating fewer long-lived, intense storms
  • While ACE is still averaging somewhat higher than during the previous -AMO, it is still lower than during the unquestionably +AMO period of 1995–2010; given that warmer global SST due to climate change may result in higher overall ACE in modern-day -AMOs than in pre-global-warming -AMOs, this should not be used to claim that the most recent +AMO did not end
  • The changes in the distribution of precipitation and ACE, as well as the decrease in long-lived, intense systems in the tropics, correlates well with the end of the +AMO
  • In turn, the end of the +AMO can be attributable to changes in the SST over the far northern North Atlantic that have been brought about by Greenland ice melt and freshwater influx, which in turn is attributable to global warming
Conclusion: while there is still uncertainty, the weight of evidence suggests that the most recent +AMO ended circa 2010 and no later than 2013, and that this +AMO lasted for a shorter period than previous +AMOs due to the background changes brought about by climate change. Because climate change results in warmer absolute SST globally, we could still end up with higher seasonal ACE in a -AMO cycle today than in past -AMO cycles, yet still be in a -AMO rather than a +AMO. It would be misleading to use a single piece of evidence such as the warm Canary Current and active WAM to argue that we are still in a +AMO, at least in my view.


Top reasons why the +AMO has (functionally) likely not ended post 2010:

  • The last below average season was literally 7 years ago
  • In 25 years, the last -AMO had 2 above average seasons (13 below)
  • Since 2011 (11 years), there have been 8 above average seasons (3 below)
  • 2017
  • 2020
Just because the hyperactive seasons don't look "classic" or that we haven't had the same extreme activity that is excessive even for a +AMO doesn't mean it has ended. If we were truly in a -AMO, we would not have seen 2016-21 (and likely 2022). The past 6 years (or even going back to 2010) has had activity far and away above what you'd expect in a -AMO. I understand making this argument in 2014, 2015, 2016, even early 2017. But this argument has become harder and harder to defend with time. Just a fool's errand to argue that we're in a -AMO when we're probably at the precipice of yet another active season (ACE is not significantly affected by short lived storms!). If ACE is this high even in a -AMO due to AGW, we may as well be in a permanent +AMO, because the recent activity is far more consistent with +AMO


Also, let's keep in mind that getting a hyperactive season in the first place is not something you would expect to see every year that passes. In other words, while yes we had back to back hyperactive years like 1995-1996, 1998-1999, 2003-2005, notice how one typically occurs every 2-4 years or so. I don't think we can simply conclude that "oh, we got back to back hyperactive years back then and since 2017 and 2020 are not back to back hyperactive years they are not common anymore." Also, you have to go back 26 years from 1995 to 1969 if you wanted to see another hyperactive year. Like I said, the fact that we are still getting hyperactive seasons imho is way more significant that their timing.

Some responses to the bolded points:

  • ACE during the previous active cycles (especially prior to 1900) was likely sorely underestimated due to sparse data coverage; in fact, a preliminary reanalysis found significantly higher ACE from 1851–98, and even these results are likely too low, given relatively sparser coastal and maritime observations during this era
  • As I mentioned earlier:
    While ACE is still averaging somewhat higher than during the previous -AMO, it is still lower than during the unquestionably +AMO period of 1995–2010; given that warmer global SST due to climate change may result in higher overall ACE in modern-day -AMOs than in pre-global-warming -AMOs, this should not be used to claim that the most recent +AMO did not end

    ±AMOs are relative to one another and to the era in which they occur; the post-2010/-‘13 downturn (relative to 1995–2010/‘12) is of similar magnitude to that which occurred between 1970–94 (relative to the +AMO of 1926–69), even if not in absolute terms—just compare the ratio between average seasonal ACE from 1995–2010/‘12 and from the post-2010/‘12 period; you will notice a comparable decrease in the mean to that of 1970–94 (relative to 1926–69)
  • Storms as late as the 1980s, especially smaller systems, seem to have been underestimated by ±25 kt or more while at sea: for example, based on satellite imagery, Frances (1980) seems to have been a T6.5 (~125 kt) around 15Z on 8 Sept 1980 (best track has 100 kt during this timeframe)—such differences per storm could significantly bolster seasonal ACE during the 1980s and earlier
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Re: When will the multi-decade active era that began in 1995 end?

#503 Postby AlphaToOmega » Tue Apr 12, 2022 2:06 pm

Shell Mound wrote:
Category5Kaiju wrote:
NotSparta wrote:
Top reasons why the +AMO has (functionally) likely not ended post 2010:

  • The last below average season was literally 7 years ago
  • In 25 years, the last -AMO had 2 above average seasons (13 below)
  • Since 2011 (11 years), there have been 8 above average seasons (3 below)
  • 2017
  • 2020
Just because the hyperactive seasons don't look "classic" or that we haven't had the same extreme activity that is excessive even for a +AMO doesn't mean it has ended. If we were truly in a -AMO, we would not have seen 2016-21 (and likely 2022). The past 6 years (or even going back to 2010) has had activity far and away above what you'd expect in a -AMO. I understand making this argument in 2014, 2015, 2016, even early 2017. But this argument has become harder and harder to defend with time. Just a fool's errand to argue that we're in a -AMO when we're probably at the precipice of yet another active season (ACE is not significantly affected by short lived storms!). If ACE is this high even in a -AMO due to AGW, we may as well be in a permanent +AMO, because the recent activity is far more consistent with +AMO


Also, let's keep in mind that getting a hyperactive season in the first place is not something you would expect to see every year that passes. In other words, while yes we had back to back hyperactive years like 1995-1996, 1998-1999, 2003-2005, notice how one typically occurs every 2-4 years or so. I don't think we can simply conclude that "oh, we got back to back hyperactive years back then and since 2017 and 2020 are not back to back hyperactive years they are not common anymore." Also, you have to go back 26 years from 1995 to 1969 if you wanted to see another hyperactive year. Like I said, the fact that we are still getting hyperactive seasons imho is way more significant that their timing.

Some responses to the bolded points:

  • ACE during the previous active cycles (especially prior to 1900) was likely sorely underestimated due to sparse data coverage; in fact, a preliminary reanalysis found significantly higher ACE from 1851–98, and even these results are likely too low, given relatively sparser coastal and maritime observations during this era
  • As I mentioned earlier:
    While ACE is still averaging somewhat higher than during the previous -AMO, it is still lower than during the unquestionably +AMO period of 1995–2010; given that warmer global SST due to climate change may result in higher overall ACE in modern-day -AMOs than in pre-global-warming -AMOs, this should not be used to claim that the most recent +AMO did not end

    ±AMOs are relative to one another and to the era in which they occur; the post-2010/-‘13 downturn (relative to 1995–2010/‘12) is of similar magnitude to that which occurred between 1970–94 (relative to the +AMO of 1926–69), even if not in absolute terms—just compare the ratio between average seasonal ACE from 1995–2010/‘12 and from the post-2010/‘12 period; you will notice a comparable decrease in the mean to that of 1970–94 (relative to 1926–69)
  • Storms as late as the 1980s, especially smaller systems, seem to have been underestimated by ±25 kt or more while at sea: for example, based on satellite imagery, Frances (1980) seems to have been a T6.5 (~125 kt) around 15Z on 8 Sept 1980 (best track has 100 kt during this timeframe)—such differences per storm could significantly bolster seasonal ACE during the 1980s and earlier


There can be hyperactive seasons in +AMO and -AMO eras; while there has not been a recorded hyperactive season during the last -AMO era, that does not mean it is impossible. To determine whether or not the AMO is positive, negative, or hybrid, we can look at the data:

2019 -0.032 0.063 0.104 0.106 0.071 0.156 0.335 0.321 0.228 0.141 0.093 0.147
2020 0.079 0.339 0.351 0.352 0.249 0.255 0.346 0.431 0.302 0.295 0.118 0.168
2021 0.132 0.144 0.118 0.060 0.077 0.144 0.215 0.250 0.408 0.481 0.451 0.258
2022 0.182 0.139 0.014


The March data for the AMO has come in, and the AMO is still positive and has been since February 2019.

Source: https://psl.noaa.gov/data/correlation/amon.us.long.data
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Re: When will the multi-decade active era that began in 1995 end?

#504 Postby Blown Away » Fri Apr 15, 2022 7:14 am

We are in year 27 of the current warm phase AMO, so based on the very small data set of @150 years we should be moving to cool phase soon. Anybody have links to info on the suggested climate change and increased global temperatures and it's affects on the AMO?
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Re: When will the multi-decade active era that began in 1995 end?

#505 Postby Hypercane_Kyle » Sat Apr 16, 2022 6:43 pm

IMHO, I think the active era that was identified as starting in 1995 ended in 2008 and a new one picked up again in 2016.

There was definitely something "off" about the Atlantic from 2009-2015, in part due to several El Nino events.
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Re: When will the multi-decade active era that began in 1995 end?

#506 Postby Category5Kaiju » Sun Apr 17, 2022 8:24 am

Hypercane_Kyle wrote:IMHO, I think the active era that was identified as starting in 1995 ended in 2008 and a new one picked up again in 2016.

There was definitely something "off" about the Atlantic from 2009-2015, in part due to several El Nino events.


To be fair, I sometimes feel that some people categorize +AMO and -AMO as a black and white sort of thing with regards to activity, but what if there are subtle variations of each kind that can tend to favor inactive or active seasons? In other words, not all +AMO or -AMO periods are identical as there are a myriad of more factors that they are associated with, each being able to lead to a different outcome in terms of overall season activity?
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Re: When will the multi-decade active era that began in 1995 end?

#507 Postby Blown Away » Fri May 06, 2022 7:05 am

https://www.aoml.noaa.gov/phod/amo_faq.php#faq_2

SST/global temperatures are increasing in the background while we are in a warm AMO phase and I don't think there is enough data to know how that will effect AMO when it moves into a cool phase again. Probably in 50 years we will know. :D
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Re: When will the multi-decade active era that began in 1995 end?

#508 Postby tolakram » Thu May 12, 2022 9:59 am

 https://twitter.com/NOAAResearch/status/1524751498248343552




Link to article: https://www.climate.gov/news-features/blogs/beyond-data/can-we-detect-change-atlantic-hurricanes-today-due-human-caused

Take-Aways

Atlantic hurricanes display distinct busy and quiet periods: Busy hurricane decades occurred in the late 19th century, mid-20th century, and from the mid-1990s onward, but quieter decades in the early 20th century and in the 1970s to early-1990s.

These multi-decadal variations in Atlantic tropical storms and hurricanes have been linked to a phenomenon called the Atlantic Multidecadal Variability, which may be primarily natural internal variability or aerosol-driven.

A detectable greenhouse gas-induced influence on observed Atlantic tropical storm and hurricane behavior to date is difficult to identify because of the 50-80 year variability in hurricane activity.

The bottom-line answer to the question in the title is: No, we cannot confidently detect a trend today in observed Atlantic hurricane activity due to man-made (greenhouse gas-driven) climate change. Some human influence may be present though still below the threshold for confident detection.
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Re: When will the multi-decade active era that began in 1995 end?

#509 Postby AlphaToOmega » Thu May 12, 2022 2:23 pm

'The +AMO still marches on with this new data. The April 2022 AMO data has been released, and for the 39th month in a row, the AMO remains positive.

2019 -0.032 0.063 0.104 0.106 0.070 0.156 0.335 0.321 0.228 0.141 0.093 0.147
2020 0.078 0.339 0.351 0.352 0.249 0.255 0.346 0.431 0.302 0.294 0.118 0.168
2021 0.132 0.144 0.118 0.060 0.077 0.144 0.215 0.250 0.407 0.480 0.451 0.258
2022 0.182 0.139 0.014 0.116 -99.990 -99.990 -99.990 -99.990 -99.990 -99.990 -99.990 -99.990
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Re: When will the multi-decade active era that began in 1995 end?

#510 Postby jconsor » Fri Sep 30, 2022 1:45 am

Alex, I agree wholeheartedly with what you wrote below re: clear signs that the +AMO era has not yet ended. I would add that the frequency of rapid intensification since 2017 has been nothing short of spectacular, and unfortutately a disproportionate number of these RI events happened in the 24 hours prior to US landfall. I haven't seen stats, but I believe the frequency of RI overall in the basin in the past six years outpaces any other six year period since the active era began in 1995, though the 1995-2000 period may have come close.

IMHO There is a pressing need for research to address the causes of this sudden increase in RI events near the US coast and the reasons behind cycles of RI frequency in general, as I mention in the tweet thread below.

 https://twitter.com/yconsor/status/1575735642440728577




 https://twitter.com/yconsor/status/1575736493145960448




NotSparta wrote:Top reasons why the +AMO has (functionally) likely not ended post 2010:

  • The last below average season was literally 7 years ago
  • In 25 years, the last -AMO had 2 above average seasons (13 below)
  • Since 2011 (11 years), there have been 8 above average seasons (3 below)
  • 2017
  • 2020

Just because the hyperactive seasons don't look "classic" or that we haven't had the same extreme activity that is excessive even for a +AMO doesn't mean it has ended. If we were truly in a -AMO, we would not have seen 2016-21 (and likely 2022). The past 6 years (or even going back to 2010) has had activity far and away above what you'd expect in a -AMO. I understand making this argument in 2014, 2015, 2016, even early 2017. But this argument has become harder and harder to defend with time. Just a fool's errand to argue that we're in a -AMO when we're probably at the precipice of yet another active season (ACE is not significantly affected by short lived storms!). If ACE is this high even in a -AMO due to AGW, we may as well be in a permanent +AMO, because the recent activity is far more consistent with +AMO
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Re: When will the multi-decade active era that began in 1995 end?

#511 Postby weeniepatrol » Fri Sep 30, 2022 1:54 am

jconsor wrote:Alex, I agree wholeheartedly with what you wrote below re: clear signs that the +AMO era has not yet ended. I would add that the frequency of rapid intensification since 2017 has been nothing short of spectacular, and unfortutately a disproportionate number of these RI events happened in the 24 hours prior to US landfall. I haven't seen stats, but I believe the frequency of RI overall in the basin in the past six years outpaces any other six year period since the active era began in 1995, though the 1995-2000 period may have come close.

IMHO There is a pressing need for research to address the causes of this sudden increase in RI events near the US coast and the reasons behind cycles of RI frequency in general, as I mention in the tweet thread below.

https://twitter.com/yconsor/status/1575735642440728577

https://twitter.com/yconsor/status/1575736493145960448

NotSparta wrote:Top reasons why the +AMO has (functionally) likely not ended post 2010:

  • The last below average season was literally 7 years ago
  • In 25 years, the last -AMO had 2 above average seasons (13 below)
  • Since 2011 (11 years), there have been 8 above average seasons (3 below)
  • 2017
  • 2020

Just because the hyperactive seasons don't look "classic" or that we haven't had the same extreme activity that is excessive even for a +AMO doesn't mean it has ended. If we were truly in a -AMO, we would not have seen 2016-21 (and likely 2022). The past 6 years (or even going back to 2010) has had activity far and away above what you'd expect in a -AMO. I understand making this argument in 2014, 2015, 2016, even early 2017. But this argument has become harder and harder to defend with time. Just a fool's errand to argue that we're in a -AMO when we're probably at the precipice of yet another active season (ACE is not significantly affected by short lived storms!). If ACE is this high even in a -AMO due to AGW, we may as well be in a permanent +AMO, because the recent activity is far more consistent with +AMO


Well said. Unfortunately there are no signs that we are not in the thick of it, still. I posted earlier this season about the robust salinity departures observed throughout the Atlantic basin.. consistent with the positive phase.
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Re: When will the multi-decade active era that began in 1995 end?

#512 Postby jconsor » Fri Sep 30, 2022 2:12 am

Alex, I agree wholeheartedly with what you wrote below re: clear signs that the +AMO era has not yet ended. I would add that the frequency of rapid intensification since 2017 has been nothing short of spectacular, and unfortutately a disproportionate number of these RI events happened in the 24 hours prior to US landfall. I haven't seen stats, but I believe the frequency of RI overall in the basin in the past six years outpaces any other six year period since the active era began in 1995, though the 1995-2000 period may have come close.

IMHO There is a pressing need for research to address the causes of this sudden increase in RI events near the US coast and the reasons behind cycles of RI frequency in general, as I mention in the tweet thread below.

 https://twitter.com/yconsor/status/1575735642440728577




 https://twitter.com/yconsor/status/1575736493145960448




NotSparta wrote:Top reasons why the +AMO has (functionally) likely not ended post 2010:

  • The last below average season was literally 7 years ago
  • In 25 years, the last -AMO had 2 above average seasons (13 below)
  • Since 2011 (11 years), there have been 8 above average seasons (3 below)
  • 2017
  • 2020

Just because the hyperactive seasons don't look "classic" or that we haven't had the same extreme activity that is excessive even for a +AMO doesn't mean it has ended. If we were truly in a -AMO, we would not have seen 2016-21 (and likely 2022). The past 6 years (or even going back to 2010) has had activity far and away above what you'd expect in a -AMO. I understand making this argument in 2014, 2015, 2016, even early 2017. But this argument has become harder and harder to defend with time. Just a fool's errand to argue that we're in a -AMO when we're probably at the precipice of yet another active season (ACE is not significantly affected by short lived storms!). If ACE is this high even in a -AMO due to AGW, we may as well be in a permanent +AMO, because the recent activity is far more consistent with +AMO
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Re: When will the multi-decade active era that began in 1995 end?

#513 Postby NotSparta » Fri Sep 30, 2022 7:11 am

Sure is a good thing this thread didn't get dug up a few weeks ago
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Re: When will the multi-decade active era that began in 1995 end?

#514 Postby Category5Kaiju » Fri Sep 30, 2022 8:13 am

NotSparta wrote:Sure is a good thing this thread didn't get dug up a few weeks ago


It would have been an absolute peak season cancel bust-casting :lol:
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