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

[TheStormExpert]

:uarrow:

Just LOOK at the difference between the start of the season and now. Nearly a 180 flip

Another reason why pre-seasonal forecasts are no good. Almost everyone was harping on that the cooler SST's and the way it was configured would kill this season.

[StruThiO]

doesn't look like a -AMO year to me

[Shell Mound]

Well, there have only been *four* major hurricanes over the MDR since 2011: DANNY ('15), IRMA/MARIA ('17), and now LORENZO ('19). Aside from 2017, we haven't seen many hyperactive seasons recently, ACE-wise. Given that +AMO years typically feature at least one major hurricane in the MDR, I would say that overall numbers can be highly misleading, especially given the high ratio of subtropical development in recent years. Therefore, several consecutive seasons with above-average numbers of total named storms need not be associated with an +AMO cycle. Plus, climate change is likely to promote greater development over the subtropics, given warming SSTs over the North Atlantic, plus typical -AMO signatures. Based on the relative absence of major hurricanes over the MDR since 2011, I would say that the +AMO cycle has likely concluded earlier than in the past.

[StruThiO]

Oh no there's still -AMOposting lolll

My honest opinion? We may be going through a relative cold period (in terms of SST anomalies during winter, last year during summer etc) inside of the broader +AMO era. I believe the last +AMO cycle had that sort of set up?

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[plasticup]

We may be going through a relative cold period (in terms of SST anomalies during winter, last year during summer etc)[/div]

This is demonstrably untrue, as the mean North Atlantic sea surface temperature in the last decade has been higher than any other on records

[Shell Mound]

We may be going through a relative cold period (in terms of SST anomalies during winter, last year during summer etc)[/div]

This is demonstrably untrue, as the mean North Atlantic sea surface temperature in the last decade has been higher than any other on records

https://bobtisdale.files.wordpress.com/2013/09/figure-2-31.png?resize=640%2C426

I think StruThiO meant to imply that Atlantic SSTs have been on a relative downward incline since 2011, as your graphic seems to indicate (especially since '13).

[plasticup]

We may be going through a relative cold period (in terms of SST anomalies during winter, last year during summer etc)[/div]

This is demonstrably untrue, as the mean North Atlantic sea surface temperature in the last decade has been higher than any other on records

https://bobtisdale.files.wordpress.com/2013/09/figure-2-31.png?resize=640%2C426

I think StruThiO meant to imply that Atlantic SSTs have been on a relative downward incline since 2011, as your graphic seems to indicate (especially since '13).

Relative decline does not imply a relative cold period. Compared to any other period, this is the warmest SST in human history. Over the course of the decade an overly-fit line may have a slight downward trend, but it is still objectively a really hot period.

I don't mean to sound pedantic. The difference between these two statements is enormous.

[StruThiO]

Problem is our record warmth has been in the subtropics. Actual anomalous warmth has been tougher to find in the far north Atlantic near Greenland and in the deep tropics (both of where it is much more associated with +AMO) except for summer/fall and 2017.

That's why CSU's AMO index has been very low, imo it is too low but still shows how we havent been in a classical +AMO

https://tropical.colostate.edu/colorado ... rsity-amo/

How much is global warming influencing the sst pattern vs the AMO?

[CyclonicFury]

Regardless of the state of the AMO, it's significant that the Atlantic is well on its way to a fourth consecutive season of meeting NOAA's above average criteria when it did not manage to do it ONCE from 1970-94. This has never happened on record before.

If we really were in an inactive era, we'd frequently see seasons with only ~1 major hurricane or so. That was commonplace in the 1970s to early 1990s. Aside from 2013, every season this decade has had at least 2 major hurricanes. 3 of the last 4 have had at least 3, and only once between 1970 and 1994 did the Atlantic have 3 or more major hurricanes. It's not like the Atlantic's activity has been substantially inflated by weak storms that would not have been named in the past - ACE has been above average four years in a row.

[StruThiO]

 https://twitter.com/EricBlake12/status/1178404125211594754

[Hammy]

Regardless of the state of the AMO, it's significant that the Atlantic is well on its way to a fourth consecutive season of meeting NOAA's above average criteria when it did not manage to do it ONCE from 1970-94. This has never happened on record before.

If we really were in an inactive era, we'd frequently see seasons with only ~1 major hurricane or so. That was commonplace in the 1970s to early 1990s. Aside from 2013, every season this decade has had at least 2 major hurricanes. 3 of the last 4 have had at least 3, and only once between 1970 and 1994 did the Atlantic have 3 or more major hurricanes. It's not like the Atlantic's activity has been substantially inflated by weak storms that would not have been named in the past - ACE has been above average four years in a row.

I'll add to this--1997 and 2013 were actually the only two seasons that failed to have at least two majors since the start of the active period--and both of those featured extreme amounts of basin-wide shear (and in 2013's case some abnormalities beyond the usual cycles and indicators).

[Shell Mound]

Well, there have only been *four* major hurricanes over the MDR since 2011: DANNY ('15), IRMA/MARIA ('17), and now LORENZO ('19). Aside from 2017, we haven't seen many hyperactive seasons recently, ACE-wise. Given that +AMO years typically feature at least one major hurricane in the MDR, I would say that overall numbers can be highly misleading, especially given the high ratio of subtropical development in recent years. Therefore, several consecutive seasons with above-average numbers of total named storms need not be associated with an +AMO cycle. Plus, climate change is likely to promote greater development over the subtropics, given warming SSTs over the North Atlantic, plus typical -AMO signatures. Based on the relative absence of major hurricanes over the MDR since 2011, I would say that the +AMO cycle has likely concluded earlier than in the past.

To add to this, I would wish to inquire: Has anyone composed a graph by which to compare the trend in ACE index, by gridded latitudinal/longitudinal boxes, since 2012? Such a graph could illustrate how the mean location of ACE generation, especially by major hurricanes, has migrated from the MDR and Caribbean to the subtropics, based on a comparison between ACE generated over respective time frames before (1995–2012) vs. after 2012 (2013–present)—that is, ACE generation per TC after minus before 2012. I think such a graph would better illustrate how the AMO index has likely gone negative since 2012, based solely on the shift in mean ACE generation (which is heavily weighted toward major-hurricane days) from the MDR/Caribbean to the subtropics.

[gigabite]

Well, there have only been *four* major hurricanes over the MDR since 2011: DANNY ('15), IRMA/MARIA ('17), and now LORENZO ('19). Aside from 2017, we haven't seen many hyperactive seasons recently, ACE-wise. Given that +AMO years typically feature at least one major hurricane in the MDR, I would say that overall numbers can be highly misleading, especially given the high ratio of subtropical development in recent years. Therefore, several consecutive seasons with above-average numbers of total named storms need not be associated with an +AMO cycle. Plus, climate change is likely to promote greater development over the subtropics, given warming SSTs over the North Atlantic, plus typical -AMO signatures. Based on the relative absence of major hurricanes over the MDR since 2011, I would say that the +AMO cycle has likely concluded earlier than in the past.

To add to this, I would wish to inquire: Has anyone composed a graph by which to compare the trend in ACE index, by gridded latitudinal/longitudinal boxes, since 2012? Such a graph could illustrate how the mean location of ACE generation, especially by major hurricanes, has migrated from the MDR and Caribbean to the subtropics, based on a comparison between ACE generated over respective time frames before (1995–2012) vs. after 2012 (2013–present)—that is, ACE generation per TC after minus before 2012. I think such a graph would better illustrate how the AMO index has likely gone negative since 2012, based solely on the shift in mean ACE generation (which is heavily weighted toward major-hurricane days) from the MDR/Caribbean to the subtropics.

My take on your suggestion is this. I have a statistically significant database that goes back to 1944 that describes the latitude and longitude of the Mid Summer New Moon. I compared that to the wikipedia list of ACE numbers. There was a 20 percent correlation between the longitude and the ACE. The graph demonstrates a chance that when the Mid Summer New Moon is in the Western Pacific Ocean a better than average Atlantic ACE can be expected. That makes sense. The water there is very warm which adds sublimation to evaporation into the atmospheric tide. This year it looks like a 95 percent chance for a normal season. That being said, most data before 2005 is obsolete because of a dramatic improvement in detection capability, so realistically hindcasting using pre-upgrade data requires extra thought. This is raw graphical deduction not a model.

[TheStormExpert]

With the current -AMO look the Atlantic has suddenly taken on again it makes you wonder but let’s see how things evolve as we head into the meat off the season in August, September, and October.

[gigabite]

The ACE by Year Graph. Describes a global cooling event that took place between 1970 and 1994.

Looks like some kind of orbital alignment.
1. Load in the dates: 1970-01-01 0:00:00 and 1970-01-01 0:00:00
2. Watch how the colored orbital semicircles line up.

Solar System Live
https://www.fourmilab.ch/cgi-bin/Solar

tag; Mayan Cooling, ace, ACE, Hurricane, newMoon, Path,

[TheAustinMan]

To add to this, I would wish to inquire: Has anyone composed a graph by which to compare the trend in ACE index, by gridded latitudinal/longitudinal boxes, since 2012? Such a graph could illustrate how the mean location of ACE generation, especially by major hurricanes, has migrated from the MDR and Caribbean to the subtropics, based on a comparison between ACE generated over respective time frames before (1995–2012) vs. after 2012 (2013–present)—that is, ACE generation per TC after minus before 2012. I think such a graph would better illustrate how the AMO index has likely gone negative since 2012, based solely on the shift in mean ACE generation (which is heavily weighted toward major-hurricane days) from the MDR/Caribbean to the subtropics.

Thought this was an interesting idea, so here's a map of the change in annual ACE in 5x5 degree gridboxes between the 2013-2019 period and the 1995-2012 period, and a few other comparisons to the 1970-1994 -AMO period. I would caution looking too deeply into this as the recent 7-season period is quite short, but it does highlight the relative quiet of the western Caribbean in the past decade. Some of the changes on the fringes of the basin may be related to increased usage and coverage of satellites, but the effect is probably not very considerable as I don't think major hurricanes, which contribute most to ACE, would be missed (a 100kt major hurricane instantaneously generates 8x more ACE than a 35kt tropical storm).

A relevant paper was published in the Monthly Weather Review in 1998, "The 1995 and 1996 North Atlantic Hurricane Seasons: A Return of the Tropical-Only Hurricane ", noting the uptick in tropically-based activity in what we now understand to have been the start of an +AMO period.

214KB. Source: Generated myself in QGIS using HURDAT data


For comparison's sake here's the -AMO 1970-1994 period minus the 1995-2012 period:
215KB


And finally, 2013-2019 compared to the -AMO 1970-1994 period:
156KB

[Steve H.]

To the topic question posed, uh a resounding NO. The 1997 season featured a terrifically strong El Nino as I remember. And I believe a very busy EPAC season including a picturesque Linda I think. But the end of multi-decade hurricane run? No. Things are a lot different nowadays and the positive feedback in the warmth will take time to settle out. May not occur in my lifetime if at all IMO. But I'm being lazy and am ready for a nap .

[gigabite]

1. map of the change in annual ACE in 5x5 degree gridboxes
2. usage and coverage of satellites, but the effect is probably not very considerable

A relevant paper was published in the Monthly Weather Review in 1998, "The 1995 and 1996 North Atlantic Hurricane Seasons: A Return of the Tropical-Only Hurricane ", noting the uptick in tropically-based activity in what we now understand to have been the start of an +AMO

Nice work:
1. Is the ACE simply at the tropical storm to hurricane point per hurricane or along the entire track?
2. Understood, generalizations are okay
3. Thanks for the HURDAT source
4. Can you post a Dropbox link to your shapefile?

[TheAustinMan]

Nice work:
1. Is the ACE simply at the tropical storm to hurricane point per hurricane or along the entire track?
2. Understood, generalizations are okay
3. Thanks for the HURDAT source
4. Can you post a Dropbox link to your shapefile?

On those maps, ACE was recorded at every point along the storm's track. Here is a simple shapefile with points for all storms and the ACE generated at that point on Dropbox.

[gigabite]

Nice work:
1. Is the ACE simply at the tropical storm to hurricane point per hurricane or along the entire track?
2. Understood, generalizations are okay
3. Thanks for the HURDAT source
4. Can you post a Dropbox link to your shapefile?

On those maps, ACE was recorded at every point along the storm's track. ***DELETED TEXT***

Thanks that was lotsa worka