Let's discuss ACE as a metric

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Re: Let's discuss ACE as a metric

#41 Postby tolakram » Fri Sep 10, 2021 5:32 pm

I think I might lean heavier on discounting storm numbers in favor of H and MH. So (0.5 * TD) + (3 * H) + (10 * MH)

Now to plug this into a few seasons ...

1996 - 8/6/3 = 4 + 18 + 30 = 52
2005 - 31/15/7 = 15.5 + 45 +70 = 130.5
2013 - 15/2/0 = 7.5 + 6 = 13.5
2017 - 18/10/6 = 9 + 30 + 60 = 99
2020 - 31/14/7 = 15.5 + 42 + 70 = 127.5
2021 - 13/5/3 = 6.5 + 15 + 30 = 51.5 so far

I'm not happy with this, but I do think leaning heavily on hurricanes and majors and severely discounting tropical storms is a little better. People flooded by Allison would disagree, but I'm not sure landfall should be taken into account.

For all the faults ACE has, it does seem to work in most cases, just because stronger storms rack up the ACE so quickly. Yes, it favors long trackers.
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Re: Let's discuss ACE as a metric

#42 Postby Teban54 » Fri Sep 10, 2021 6:00 pm

Hammy wrote:
AlphaToOmega wrote:ACE is heavily skewed towards Cape Verde storms. A Category V Caribbean storm could produce significantly less ACE than a Category II Cape Verde storm, even though the former is more impactful and more strong. If I had a single metric to discuss the activity of hurricane seasons, it would probably be a weighted average of all the storms, hurricanes, and major hurricanes of a season.


S = storm count
H = hurricane count
M = major hurricane count
A = hurricane activity index

A = (S - H) + 2(H - M) + 4M
In words: all the storms that did not reach hurricane status are given 1 point each; all hurricanes that did not reach major hurricane status are given 2 points each; all major hurricanes are given 4 points each.

Examples:
2020: (30 - 14) + 2(14 - 7) + 4(7) = 58
2019: (18 - 6) + 2(6 - 3) + 4(3) = 30
2018: (15 - 8) + 2(8 - 2) + 4(2) = 27
2017: (17 - 10) + 2(10 - 6) + 4(6) = 39
2016: (15 - 7) + 2(7 - 4) + 4(4) = 30
2015: (11 - 4) + 2(4 - 2) + 4(2) = 19
etc...

The average season: (14 - 7) + 2(7 - 3) + 4(3) = 27
The average season would have a hurricane activity index of 27.


I have a similar (but simpler) metric I use where I add up the S/H/MH numbers, where Sx1, Hx2, and MHx3, with Cat 5 being 4, so to date being at 13/5/3, would give a value of 32 to date. To compare to some other active seasons up to this point:

2005: 15/8/4/2 (51)
2004: 9/6/4/1 (37)
2017: 11/6/3/1 (36)
2020: 17/5/2 (33)
2021 13/5/3 (32)
1995: 12/6/2 (30)
2003: 9/5/2/1 (29)
1996: 8/6/3 (29)
2011: 15/4/2 (29)
2007: 7/2/2/2 (25)
2012: 14/7/1 (24)
2008: 10/5/3 (24)
1999: 6/4/3 (23)
2018: 9/5/1 (22)
2010: 9/3/2 (21)
1989: 8/5/1 (21)
1990: 9/4/1 (20)
2016: 8/4/1 (19)
1998: 6/3/1 (18)
2019: 7/2/1/1 (18)
2001: 6/2/2 (16)
2000: 5/2/1 (12)


Another would be to calculate ACE based purely on peak intensity but not something I've attempted to calculate and compare up to this point.

I do think there's value in taking duration into account - a Cat 4 that briefly reached that intensity for one advisory (e.g. Julia 2010) is less impressive than a Cat 4 that stayed at that intensity for days (e.g. Igor 2010). However, the comparison gets tougher with Cat 4s that hit land at peak intensity (e.g. Laura 2020 and Ida 2021, which would have been solid Cat 4/5 long-trackers if the CONUS was water and not land).

Maybe a combination of peak intensity/category and ACE would be a good compromise, possibly with a bonus or multiplier for landfalling storms. Another more sophisticated way would be to estimate, for landfalling storms, what their intensities might be over land if land interaction wasn't a factor for weakening (e.g. Laura and Ida would be Cat 4s over Louisiana for a while instead of borderline hurricanes), but that is obviously too hard to compute with today's technology.
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Re: Let's discuss ACE as a metric

#43 Postby AlphaToOmega » Fri Sep 10, 2021 6:24 pm

Using my hurricane activity index metric ((S - H) + 2(H - M) + 4M), here are the values for each season since 1967:

2021 so far: 24
2020: 58
2019: 30
2018: 27
2017: 39
2016: 30
2015: 19
2014: 18
2013: 16
2012: 33
2011: 34
2010: 41
2009: 16
2008: 34
2007: 25
2006: 19
2005: 57
2004: 36
2003: 29
2002: 20
2001: 32
2000: 29
1999: 30
1998: 30
1997: 13
1996: 34
1995: 40
1994: 10
1993: 14
1992: 13
1991: 16
1990: 24
1989: 22
1988: 23
1987: 12
1986: 10
1985: 24
1984: 20
1983: 9
1982: 10
1981: 25
1980: 24
1979: 19
1978: 21
1977: 13
1976: 20
1975: 21
1974: 19
1973: 14
1972: 10
1971: 21
1970: 20
1969: 40
1968: 13
1967: 16

Based on this metric, the most active seasons since 1967 are 2020 (58 points); 2005 (57 points); 2010 (41 points); 1995 and 1969 (40 points each); 2017 (39 points); 2004 (36 points); and 2011, 2008, and 1996 (34 points each). For pre-satellite era active seasons, there is 1933 (43 points), 1950 (39 points), 1916 (35 points), and 1887 (34 points).
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Re: Let's discuss ACE as a metric

#44 Postby 1900hurricane » Sat Sep 11, 2021 11:01 am

Regarding trying to find the best overall metric for storm impact and overall season activity, I like Track Integrated Kinetic Energy as a concept, but I feel like the execution of it is slightly lacking. Incorporating the system size is a great way to account for aspects a metric like ACE doesn't account for. A larger storm uses more energy, and also has a larger impact footprint. However, the calculation from Powell's Integrated Kinetic Energy seems to prioritize storm size so much that maximum intensity actually has almost no correlation with the metric. As an example, Claudette this season had a larger peak IKE than Eta did a peak intensity last season, despite the former being more of a nuisance tropical storm while the latter was a high end Category 4 that brought the highest observed storm surge recorded anywhere in the world for at least the last 100 years. That seems a bit dissonant to me, to say the least.

As an alternative, I propose the Tropical Cyclone Power and Tropical Cyclone Kinetic Energy metrics. This is a metric first used by Kerry Emanuel, originally implemented by Storm2K user kala, and tweaked a little by me. Power dissipated by the tropical cyclone's winds are calculated using the best track data, and the overall energy expenditure can then be derived using left Riemann Sums from each best track point. Like IKE & TIKE, TCP & TCKE are computationally intensive (arguably even more so than the former), but they appear to me to give a better picture of both instantaneous storm impact and overall season activity than any other metric available. I have the link to kala's original thread for TCP & TCKE below.

Tropical Cyclone Kinetic Energy (TCKE)
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Re: Let's discuss ACE as a metric

#45 Postby tolakram » Sat Sep 11, 2021 12:51 pm

AlphaToOmega wrote:Using my hurricane activity index metric ((S - H) + 2(H - M) + 4M), here are the values for each season since 1967:

2021 so far: 24
2020: 58
2005: 57


SNIPPED

Based on this metric, the most active seasons since 1967 are 2020 (58 points); 2005 (57 points); 2010 (41 points); 1995 and 1969 (40 points each); 2017 (39 points); 2004 (36 points); and 2011, 2008, and 1996 (34 points each). For pre-satellite era active seasons, there is 1933 (43 points), 1950 (39 points), 1916 (35 points), and 1887 (34 points).



I reject any metric that does not put 2005 clearly in front. 2020 was bad, and I agree it's second, but nothing will ever match 2005, and if a metric shows 2020 ahead of 2005 then it's flawed and needs redone.
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Re: Let's discuss ACE as a metric

#46 Postby kevin » Sat Sep 11, 2021 2:10 pm

Tbh I think ACE is a pretty nice measure of a season's activity, at least in terms of the total energy of storms during the season. I mean it is 10^-4 * SUM(v^2) and energy is also proportional to v^2 so it sounds like a reasonable energy measure. However, it does have its limitations in terms of energy vs. human perception of activity as a recurving MDR storm might catapult ACE while not really lingering in people's memory. Doesn't mean that the ACE metric is wrong (it does what it's supposed to), but it does show that it's far from equivalent to how active a season 'feels' or is to most people. What might be even nicer is to have a volume integral over time, something like this.

Image

If I got my dimensional analysis correct this should calculate the total energy of a storm (if SI units are used) and integrates over the projected area of the storm (dr), the height of the storm (dh) and the time of the storm (dt). It's basically an integrated total energy of the storm. It might not be completely correct (I came up with this earlier today during a brainstorm, so definitely not peer reviewed ;)), but whatever it is it should be proportional to the total energy of a storm. However, calculating this would require one to know the velocity and pressure everywhere in the storm at any time. You think this might be possible with recon flights, but note that you don't just need it at every radial distance. You also need data at every single altitude (velocity, pressure and background pressure). Note that this does assume perfect radial symmetry of the storm so if this is not the case you need another integral dtheta that sweeps around the storm. So implementing this in reality is pretty much (and with pretty much I mean '100% sure') impossible, even though a 3D hurricane simulation should be able to calculate it. Still a nice thought experiment as this should give an estimate the total energy output of a storm in Joule. So you can calculate how many fridges the hurricane could theoretically power :lol:. Now that I think about it, it's actually sounds very similar to TIKE (Track Integrated Kinetic Energy), if you want you can read more about that here: https://www.researchgate.net/publication/258698790_The_Track_Integrated_Kinetic_Energy_of_Atlantic_Tropical_Cyclones since that's also a volume integral over time. I use pressure/velocity based energy while TIKE uses standard kinetic energy, but in principle it should be roughly equivalent. Either way, I can understand why people go to the way way easier to calculate and somewhat equivalent ACE method.

Anyways, another way easier method might be to use ACE (so v^2 with v in knots), but only with peak intensity. I call it Kevin's Activity-index of Tropical Storms, or KATS for short :cheesy:. This may remove the advantage that long trackers have and could be more representative of how active a season feels. Here it is for every year since 2000 (might do the rest later). I did 10^-3*v^2 instead of 10^-4 since these numbers are generally lower than the normal ACE since it only takes one data point per storm. I think this method is fairer than only splitting between tropical storms, hurricanes and major hurricanes since a 100kt cat 3 is still very different from a 160kt cat 5 monster such as Wilma.

2021 = 68 (so far)
2020 = 178
2019 = 101
2018 = 97
2017 = 143
2016 = 85
2015 = 58
2014 = 54
2013 = 42
2012 = 93
2011 = 97
2010 = 138
2009 = 47
2008 = 115
2007 = 85
2006 = 51
2005 = 207
2004 = 123
2003 = 106
2002 = 60
2001 = 97
2000 = 88

By this measure the top 5 most active seasons since 2000 would be:
1. 2005 (207)
2. 2020 (178)
3. 2017 (143)
4. 2010 (138)
5. 2004 (123)
Last edited by kevin on Sat Sep 11, 2021 2:46 pm, edited 1 time in total.
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Re: Let's discuss ACE as a metric

#47 Postby Shell Mound » Sat Sep 11, 2021 2:38 pm

How about a weighted seasonal ACE index that is based on the proportion of long-trackers’ ACE to ACE generated over land?

This index would lend weight toward seasons with the maximum number of intense long-trackers and MH impacts on land.
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Re: Let's discuss ACE as a metric

#48 Postby tolakram » Sat Sep 11, 2021 2:49 pm

I say we start with ACE, which I do think is a decent measurement, but I also agree it has flaws. I am purposely trying to make this as simple as possible, so let's look at the top 3 seasons.

The standout statistic of 1933 was the fact it was pre-satellite.

1933 - 259 - 20/11/6
2005 - 250 - 31/15/7
2020 - 180 - 31/14/7

Without knowing anything about these seasons (and ignoring ACE) one might come to the following conclusions:

2005 and 2020 had a lot of opportunity for storms, and a lot spun up, but in the end 2005 was a little bit stronger because it managed to produce more hurricanes than 2020. 1933, on the other hand, looks pretty tame in comparison, but was still able to produce 11 hurricanes and 6 majors.

Now I believe that with better detection 1933 probably had a storm count more like 2005 and 2020, but back in the day these were simply missed.

So now about that ACE.

It's significant that not only did 2005 have a lot of storms but it also had some very big hurricanes that lasted a significant amount of time. AND 2005 didn't have much of a CV season. That's significant because even though much of the season was west based it was still able to rack up 250 ACE.

1933 had two CV long trackers (only two CV storms were observed in fact) that helped pad the ACE, but unlike 2020 all of it's strong storms were very long lived.

2020 only had 180 ACE, mainly because storms strengthened near landfall, or were otherwise not very long trackers. Why should 2020 not be third in overall strength? Remember, landfall and impacts should not be counted here, this is simply trying to find an objective measure of seasonal strength? I think this is an interesting question because I think we need to recognize that long tracking major hurricanes, those that really pad ACE, ARE significant and do reflect a very favorable background state. As we just witnessed with Larry, it had a very long track but had significant issues maintaining strength. ACE will be lower than initially expected, which is a good metric.

If you throw out all the math and just let your eyes judge the three seasons I think it's easy to see why 2005 and 1933 were so significant. Just count the orange and red dots. That's significant. Maybe my new metric is seasonal dots (yea, the 1933 dots are bigger). :lol:

1933
Image

2005
Image

2020
Image

1933 was a big big season, and imagine if we were all watching it with 1 minute GOES images?
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Re: Let's discuss ACE as a metric

#49 Postby Zonacane » Sat Sep 11, 2021 3:42 pm

tolakram wrote:
AlphaToOmega wrote:Using my hurricane activity index metric ((S - H) + 2(H - M) + 4M), here are the values for each season since 1967:

2021 so far: 24
2020: 58
2005: 57


SNIPPED

Based on this metric, the most active seasons since 1967 are 2020 (58 points); 2005 (57 points); 2010 (41 points); 1995 and 1969 (40 points each); 2017 (39 points); 2004 (36 points); and 2011, 2008, and 1996 (34 points each). For pre-satellite era active seasons, there is 1933 (43 points), 1950 (39 points), 1916 (35 points), and 1887 (34 points).



I reject any metric that does not put 2005 clearly in front. 2020 was bad, and I agree it's second, but nothing will ever match 2005, and if a metric shows 2020 ahead of 2005 then it's flawed and needs redone.

As somebody who went through the horror show known as Katrina, I agree with you. Somebody impacted by a significant storm in 2020 would not agree with you, however.
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Re: Let's discuss ACE as a metric

#50 Postby aspen » Sat Sep 11, 2021 3:45 pm

I tried to see if I could turn my Instantaneous Cyclone Energy metric into something like ACE, where it gives an instantaneous value for each advisory and they’re all added up. However, it increases way too quickly. I tried it with Guillermo and Felicia, and got 1.785 units for Guillermo and a whopping 79.08 units for Felicia. This is way larger than their difference in ACE. Having both wind and pressure in the equation results in this metric increasing exponentially at high intensities, to a greater degree than ACE.

The normal ICE metric still works well, but it only takes into account peak storm intensity and storm frequency, not duration. However, 2005 still ends up at the top. Here are the ICE scores of the most recent two dozen or so seasons:

2021: 322.41, 13/5/3 (so far)
1977-2016 average: 386.26, 12.2/6.4/2.6

2020: 946.34, 30/14/7
2019: 550.06, 18/6/3
2018: 525.24, 15/8/2
2017: 874.57, 17/10/6
2016: 433.85, 15/7/4
2015: 268.27, 11/4/2
2014: 275.73, 8/6/2
2013: 116.35, 14/2/0 (this is lower than Hurricane Ida’s ICE score)
2012: 453.52, 19/10/2
2011: 469.41, 19/7/4
2010: 764.54, 19/12/5
2009: 215.24, 9/3/2
2008: 611.44, 16/8/5
2007: 445.96, 15/6/2
2006: 230.48, 10/5/2
2005: 1300.35, 28/15/7
2004: 744.05, 15/9/6
2003: 505.24, 16/7/3
2002: 306.71, 14/4/2
2001: 480.95, 15/9/4
2000: 441.31, 15/8/3
1999: 734.47, 12/8/5
1998: 625.63, 14/10/3
1997: 130.34, 8/3/1
1996: 557.60, 14/9/6
1995: 750.56, 19/11/5

Using this metric, the top 5 seasons of the current active era are:

#1: 2005, 1300.35 units
#2: 2020, 946.34 units
#3: 2017, 874.57 units
#4: 2010, 764.54 units
#5: 1995, 750.56 units

While 1995 and 2004 are extremely close in ICE just like they are in ACE, they’re both slightly beaten by 2010 despite it having a lower ACE total, and are all far surpassed by 2017’s ICE. This shows the bias of the metric towards seasons with multiple exceptionally intense storms, and how the duration doesn’t matter at all. That’s the main issue I’ve been hoping to solve with a wind/pressure version of ACE, but so far ICE does its job well as an instantaneous version of ACE.


Also, here are the ICE scores for a few EPac seasons:

2021: 327.25 (so far)
2020: 339.32
2019: 464.41
2018: 1337.94
2015: 1562.25
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Re: Let's discuss ACE as a metric

#51 Postby Shell Mound » Sat Sep 11, 2021 3:45 pm

tolakram wrote:I say we start with ACE, which I do think is a decent measurement, but I also agree it has flaws. I am purposely trying to make this as simple as possible, so let's look at the top 3 seasons.

The standout statistic of 1933 was the fact it was pre-satellite.

1933 - 259 - 20/11/6
2005 - 250 - 31/15/7
2020 - 180 - 31/14/7

1933 was a big big season, and imagine if we were all watching it with 1 minute GOES images?

If satellite and reconnaissance were available back then, 1933 would in all likelihood have surpassed 2005 and 2020. There were at least five storms that attained Category-4 or greater intensity, including at least two Category 5s. These were all verified by observations from ships, so some of the Category 4s could have been Category 5s as well, especially while at sea. 1933 also featured no fewer than five MH landfalls in the basin, four of which occurred with MSW of ≥ 110 kt at landfall: Storms #8 (140 kt in the Bahamas, 110 kt in TX) and #11 (120 kt in the Bahamas, 110 kt in FL), both of which hit the CONUS as MH within 24h of each other! Storm #14 also hit MX’s Yucatán with MSW conservatively estimated at 120 kt.

There were also at least two storms that quite possibly became major hurricanes but were not reanalysed as such. Storm #2, for instance, was reanalysed as having a peak MSW of 95 kt in the Gulf on 5 July, but there a few ships that measured MSLPs of 28.42”–28.51” (962–965 mb). Whether those ships were inside the RMW is unknown, so the reanalysis conservatively went with a MSW of 95 kt. Storm #19 was reanalysed as having a peak MSW value of 60 kt, yet a ship recorded a MSLP value of 28.26” (957 mb). The reanalysis could not locate further information about this observation, but if confirmed, it would support MSW of at least 90 kt (and possibly even higher, if it were recorded outside the exact centre of the eye).

So in all likelihood 1933 featured at least eight major hurricanes, if not more. (Storm #15 likely developed as a CV-type system but was first detected over the subtropics and was analysed as having MSW of 65 kt, based on data from ships, but it could have easily been stronger, owing to sparse coverage.) 1933 also featured multiple long-tracking hurricanes in the Caribbean in June (Storm #2) and July (Storm #5), respectively. It is almost impossible to overstate just how “extreme” this season likely was. Seasonal ACE would have likely come close to 300, had 1933 occurred in the era of satellite and reconnaissance.

Of the pre-satellite, pre-recon years, 1933, 1893, 1926, 1887, 1878, 1932, 1886, and 1906 stand out as having met the criterion for “hyperactivity,” as indicated by seasonal ACE of > 159.6. At a minimum, these years likely featured storm totals (TS or stronger) comparable to those years such as 1969, 1995, 2010, 2011, 2012, and 2019. If one were to adjust for “missing” ACE, all of these years likely featured seasonal ACE ≥ 240 units, given that quite a number of storms peaked while at sea and were long-trackers whose peaks were likely missed. In fact, a preliminary reanalysis found that the late nineteenth century was just as active in the MDR as recent +AMO seasons.
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Re: Let's discuss ACE as a metric

#52 Postby tolakram » Sat Sep 11, 2021 4:39 pm

Zonacane wrote:
tolakram wrote:
AlphaToOmega wrote:Using my hurricane activity index metric ((S - H) + 2(H - M) + 4M), here are the values for each season since 1967:

2021 so far: 24
2020: 58
2005: 57


SNIPPED

Based on this metric, the most active seasons since 1967 are 2020 (58 points); 2005 (57 points); 2010 (41 points); 1995 and 1969 (40 points each); 2017 (39 points); 2004 (36 points); and 2011, 2008, and 1996 (34 points each). For pre-satellite era active seasons, there is 1933 (43 points), 1950 (39 points), 1916 (35 points), and 1887 (34 points).



I reject any metric that does not put 2005 clearly in front. 2020 was bad, and I agree it's second, but nothing will ever match 2005, and if a metric shows 2020 ahead of 2005 then it's flawed and needs redone.

As somebody who went through the horror show known as Katrina, I agree with you. Somebody impacted by a significant storm in 2020 would not agree with you, however.


Right, but impact can't matter here, we're trying to come up with an objective measure of seasonal strength, not impact. I guess I should speak for myself only here, as I haven't asked everyone, but that's my goal. There's no sense trying to measure impact because it only takes one storm (1992, Andrew for example). It may very well be a foolish goal, or it may very well be that ACE is enough.
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Re: Let's discuss ACE as a metric

#53 Postby AlphaToOmega » Sat Sep 11, 2021 4:46 pm

Major hurricane count, hurricane count, and storm count are all good metrics for hurricane season activity. My metric combines all of them and weighs them based on the categorization. A season with a lot of major hurricanes (such as 2005 and 2020) is going to be indicative of favorable conditions, no matter how much ACE they produce. There are multiple ways favorable conditions can manifest: storm spam (September 2020), long-trackers (September 2017), and a bunch of rapidly intensifying storms (October 2020). ACE favors long-trackers, but my metric favors all three because duration is not taken into account.

My metric is defined as (S - H) + 2(H - M) + 4M. Made each term twice the previous for two reasons: the ratio of the hurricane threshold and of the storm thresholds (65/30), and the ratio of the major hurricane threshold and of the hurricane threshold (100/65) are both roughly 2; and 1/2 of all storms are hurricanes, and 1/2 of all hurricanes are major hurricanes on average.

My metric seems to show a useful mix of the quantity and quality of hurricane seasons. The most active seasons since 1967 according to my metric are 2020 (58), 2005 (57), 2010 (41), and 1995/1969 (40). All of these seasons have both a high amount of storms, and they have a high proportion of powerful storms.

Experimenting with other factors yields slightly different results. A system using (S - H) + 3(H - M) + 9M as its formula yielded the most active seasons of 2020/2005 (100), 2017/2010 (73), 1969 (72), and 1995 (71). A system using (S - H) + 4(H - M) + 16M yielded the most active seasons of 2005 (157), 2020 (156), 2017 (119), and 2010 (115). A system using (S - H) + 5(H - M) + 25M yielded the most active seasons of 2005 (228), 2020 (226), 2017 (177), and 2004 (171). A system using (S - H) + 6(H - M) + 36M yielded the most active seasons of 2005 (313), 2020 (310), 2017 (247), and 2004 (240). A system using (S - H) + 7(H - M) + 49M yielded the most active seasons of 2005 (412), 2020 (408), 2017 (329), and 2004 (321). Which one is "best"? It depends on what you consider defines an active hurricane season. However, at the very least this confirms our beliefs that 2013 was less active than 2020.
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Re: Let's discuss ACE as a metric

#54 Postby kevin » Sun Sep 12, 2021 3:03 am

To expand on my previous post I made the peak ACE calculation for every season since the start of the satellite era in 1967. So just to reiterate, this is the sum of the peak velocity squared of all storms (in knots). That sum is then divided by 1000 to make the number easier to work with. So if there were two 80 kt storms that would be (80^2 + 80^2)/1000 = 12.8 points. It's pretty much the same as ACE, but instead of taking a data point every 6 hours I only take 1 data point per storm and because of that I decided only to divide by 1000 instead of 10,000. In cases with unknown windspeed TDs I decided to go for 30 kt so they're also included in some way. I also added a few of the most active pre-satellite era seasons, but beware that the estimates for those season are most likely lower than reality due to missed storms back then. The top 10 most active seasons with this method are:

1. 2005 (207)
2. 2020 (178)
3. 1933* (149)
4. 2017 (143)
5. 2010 (138)
6. 1995 (130)
7. 1950* (129)
8. 1969 (126)
9. 2004 (123)
10. 1999 (120)
* = pre-satellite era

And here's the entire list:

2021 = 68 (so far)
2020 = 178
2019 = 101
2018 = 97
2017 = 143
2016 = 85
2015 = 58
2014 = 54
2013 = 42
2012 = 93
2011 = 97
2010 = 138
2009 = 47
2008 = 115
2007 = 85
2006 = 51
2005 = 207
2004 = 123
2003 = 106
2002 = 60
2001 = 97
2000 = 88
1999 = 120
1998 = 110
1997 = 31
1996 = 95
1995 = 130
1994 = 36
1993 = 35
1992 = 56
1991 = 47
1990 = 68
1989 = 81
1988 = 88
1987 = 35
1986 = 32
1985 = 76
1984 = 62
1983 = 25
1982 = 35
1981 = 83
1980 = 89
1979 = 78
1978 = 71
1977 = 52
1976 = 64
1975 = 80
1974 = 66
1973 = 44
1972 = 38
1971 = 78
1970 = 63
1969 = 126
1968 = 38
1967 = 73
----- (pre-satellite era)
1964 = 98
1961 = 115
1950 = 129
1933 = 149
1932 = 114
1926 = 102
1893 = 96
1887 = 102
1886 = 96
1878 = 83
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Re: Let's discuss ACE as a metric

#55 Postby Category5Kaiju » Sun Sep 12, 2021 7:34 am

Something I have personally been wondering is whether central pressure should be emphasized in a way too much like wind speed is factored into ACE. For each season for example, the metric that I am thinking of, MMCP (mean minimum central pressure), would simply be this equation:

MMCP=(sum of all recorded central pressures of all named storms)/(total number of named storms that form)

The lower MMCP, the more intense an overall season is. It's a pretty simple calculation, but given pressure being a known metric for how intense (and subsequently destructive) a given storm could be if it were to hit land, I felt that this would be something worth thinking of as wind speed is not the full picture.
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Re: Let's discuss ACE as a metric

#56 Postby AlphaToOmega » Sun Sep 12, 2021 7:36 am

Category5Kaiju wrote:Something I have personally been wondering is whether central pressure should be emphasized in a way too much like wind speed is factored into ACE. For each season for example, the metric that I am thinking of, MMCP (mean minimum central pressure), would simply be this equation:

MMCP=(sum of all recorded central pressures of all named storms)/(total number of named storms that form)

The lower MMCP, the more intense an overall season is. It's a pretty simple calculation, but given pressure being a known metric for how intense (and subsequently destructive) a given storm could be if it were to hit land, I felt that this would be something worth thinking of as wind speed is not the full picture.


Minimum central pressure is heavily dependent on the environment. For instance, Hurricane Danny in 2003 had a minimum pressure of 1000 mb.
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Re: Let's discuss ACE as a metric

#57 Postby kevin » Sun Sep 12, 2021 8:44 am

Category5Kaiju wrote:Something I have personally been wondering is whether central pressure should be emphasized in a way too much like wind speed is factored into ACE. For each season for example, the metric that I am thinking of, MMCP (mean minimum central pressure), would simply be this equation:

MMCP=(sum of all recorded central pressures of all named storms)/(total number of named storms that form)

The lower MMCP, the more intense an overall season is. It's a pretty simple calculation, but given pressure being a known metric for how intense (and subsequently destructive) a given storm could be if it were to hit land, I felt that this would be something worth thinking of as wind speed is not the full picture.


You could use v*deltaP for each storm where deltaP is the difference between the minimum central pressure and the environmental background pressure (so if background is 1010 and the storm is 960 then that value is 50). If you want a quick calculation you can assume a standard background of 1013.25 mbar. If you use SI units it should even be an indication of the maximum power density of the storm in W/m^2. But whatever units you use any deltaP times velocity should be a pretty decent indicator of a storm's energy capacity. And like you desire it includes the minimum central pressure. You could do it every 6 hours like ACE or only take 1 value per storm, at peak intensity.
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Re: Let's discuss ACE as a metric

#58 Postby AlphaToOmega » Mon Sep 13, 2021 2:10 pm

Let me ask: which of the following better describes how active 2020 was: Hurricane Paulette or Hurricane Iota? Hurricane Paulette was a Category II long-track hurricane in September. Hurricane Iota was a major Caribbean hurricane in November. By the metric of ACE, Hurricane Paulette produced more ACE (15.9075) than Hurricane Iota (12.3175).

Another example: which of following better describes how active 2005 was: Hurricane Ophelia or Hurricane Beta? Hurricane Ophelia was a Category I long-track hurricane in September. Hurricane Beta was a major Caribbean hurricane in November. By the metric of ACE, Hurricane Phillippe produced more ACE (15.6725) than Hurricane Beta (6.4725).

Do you see the problem with ACE? Long-trackers are not the only way favorable conditions can manifest. What matters is how many storms form and how strong they get; this is what my metric does. It measures how many storms, hurricanes, and major hurricanes form in a season, and it assigns points to each type of storm (1 for storms, 2 for hurricanes, and 4 for major hurricanes).
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Re: Let's discuss ACE as a metric

#59 Postby tolakram » Mon Sep 13, 2021 2:43 pm

AlphaToOmega wrote:Let me ask: which of the following better describes how active 2020 was: Hurricane Paulette or Hurricane Iota? Hurricane Paulette was a Category II long-track hurricane in September. Hurricane Iota was a major Caribbean hurricane in November. By the metric of ACE, Hurricane Paulette produced more ACE (15.9075) than Hurricane Iota (12.3175).

Another example: which of following better describes how active 2005 was: Hurricane Ophelia or Hurricane Beta? Hurricane Ophelia was a Category I long-track hurricane in September. Hurricane Beta was a major Caribbean hurricane in November. By the metric of ACE, Hurricane Phillippe produced more ACE (15.6725) than Hurricane Beta (6.4725).

Do you see the problem with ACE? Long-trackers are not the only way favorable conditions can manifest. What matters is how many storms form and how strong they get; this is what my metric does. It measures how many storms, hurricanes, and major hurricanes form in a season, and it assigns points to each type of storm (1 for storms, 2 for hurricanes, and 4 for major hurricanes).


I would rephrase this: What matters is how many storms form and how strong they get

What matters is how many strong storms form, with strong being up for debate.
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Re: Let's discuss ACE as a metric

#60 Postby AlphaToOmega » Mon Sep 13, 2021 2:58 pm

tolakram wrote:
AlphaToOmega wrote:Let me ask: which of the following better describes how active 2020 was: Hurricane Paulette or Hurricane Iota? Hurricane Paulette was a Category II long-track hurricane in September. Hurricane Iota was a major Caribbean hurricane in November. By the metric of ACE, Hurricane Paulette produced more ACE (15.9075) than Hurricane Iota (12.3175).

Another example: which of following better describes how active 2005 was: Hurricane Ophelia or Hurricane Beta? Hurricane Ophelia was a Category I long-track hurricane in September. Hurricane Beta was a major Caribbean hurricane in November. By the metric of ACE, Hurricane Phillippe produced more ACE (15.6725) than Hurricane Beta (6.4725).

Do you see the problem with ACE? Long-trackers are not the only way favorable conditions can manifest. What matters is how many storms form and how strong they get; this is what my metric does. It measures how many storms, hurricanes, and major hurricanes form in a season, and it assigns points to each type of storm (1 for storms, 2 for hurricanes, and 4 for major hurricanes).


I would rephrase this: What matters is how many storms form and how strong they get

What matters is how many strong storms form, with strong being up for debate.


There is already a metric for that: major hurricane count.
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