Reflections on the 2020 Atlantic hurricane season

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Re: Reflections on the 2020 Atlantic hurricane season

#21 Postby CyclonicFury » Thu Dec 03, 2020 9:15 pm

ncforecaster89 wrote:https://www.nhc.noaa.gov/tafb_latest/tws_atl_latest.gif

Reviewing this end of season “preliminary” track map shows a discrepancy between a couple operational intensity (OPI) estimates and peak intensities listed therein.

1) Hanna:
OPI = 80 kt
Map = 75 kt

2) Zeta:
OPI = 95 kt
Map = 90 kt

My best guess is the discrepancy is simply the result of human error in creating the map and not representative of adjusted peak intensities for the hurricanes shown above; especially given they are each candidates for possible slight increases of 5 kt...rather than a decrease as shown there.

I think Hanna and Zeta both peaked right at landfall, which did not correspond with the typical 6 hourly points. The recon data strongly supports 80 kt for Hanna and at least 95 kt for Zeta.
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Re: Reflections on the 2020 Atlantic hurricane season

#22 Postby Ubuntwo » Thu Dec 03, 2020 9:54 pm

ncforecaster89 wrote:https://www.nhc.noaa.gov/tafb_latest/tws_atl_latest.gif

Reviewing this end of season “preliminary” track map shows a discrepancy between a couple operational intensity (OPI) estimates and peak intensities listed therein.

1) Hanna:
OPI = 80 kt
Map = 75 kt

2) Zeta:
OPI = 95 kt
Map = 90 kt

My best guess is the discrepancy is simply the result of human error in creating the map and not representative of adjusted peak intensities for the hurricanes shown above; especially given they are each candidates for possible slight increases of 5 kt...rather than a decrease as shown there.

I believe the map uses BT peak (operationally every 6 hours) instead of advisories. These systems peaked inbetween BT updates.
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Re: Reflections on the 2020 Atlantic hurricane season

#23 Postby ncforecaster89 » Thu Dec 03, 2020 11:20 pm

Ubuntwo wrote:
ncforecaster89 wrote:https://www.nhc.noaa.gov/tafb_latest/tws_atl_latest.gif

Reviewing this end of season “preliminary” track map shows a discrepancy between a couple operational intensity (OPI) estimates and peak intensities listed therein.

1) Hanna:
OPI = 80 kt
Map = 75 kt

2) Zeta:
OPI = 95 kt
Map = 90 kt

My best guess is the discrepancy is simply the result of human error in creating the map and not representative of adjusted peak intensities for the hurricanes shown above; especially given they are each candidates for possible slight increases of 5 kt...rather than a decrease as shown there.

I believe the map uses BT peak (operationally every 6 hours) instead of advisories. These systems peaked inbetween BT updates.


Thank you both (CF & yourself) for pointing that out. I didn't realize that was the case.

That said, it seems like an absurd practice not to use the highest operational estimate regardless of whether it corresponds with the six-hourly BT.
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Re: Reflections on the 2020 Atlantic hurricane season

#24 Postby Shell Mound » Sat Dec 05, 2020 10:43 am

Probably the dispersion or spread of landfalling clusters, along with the sheer number of landfalls, distinguishes 2020 from many other seasons, including those that featured numerous impacts. Very few seasons have featured hurricane impacts from South Texas (Hanna) to the Carolinas (Isaias), to not mention two or more hurricane strikes each on the Yucatán Peninsula (Delta, Zeta, probably Gamma) and Central America (Eta, Iota). Additionally, virtually every coastal state in the Union experienced at least some measurable impacts from tropical cyclones in 2020, with TS+ landfalls on every Gulf state save Mississippi, the Florida peninsula and Keys, the Carolinas, and even New Jersey (!). Only a relative handful of seasons such as 1893 and 1933 can be compared to 2020 in terms of these metrics. As mentioned previously, the ferocity of October/November puts 2020 in its own class—above all the occurrence of two Category-4+ landfalls in November. The only factor that really prevented 2020 from being absolutely historic was the absence of long-lived major hurricanes, primarily in the MDR: this caveat singlehandedly prevented this season from rivalling top-tier (read: top-five) seasons in terms of ACE. The following comparison of hyperactive seasons makes this abundantly clear.

YYYY...NS...MHD.......Ratio*......#TC w/ ≥ 1 MH(C4+) LF...
1926...11...22.75....~207%.....4(3)
1893...12...22.........~183%.....4(1)
2004...15...22.25....~148%.....4(1)
1961...12...16.........~133%.....2(2)
1999...12...14.25....~119%.....3(1)
2017...17...19.25....~113%.....3(3)
1933...20...21.75....~109%.....4(3)
2003...16...16.75....~105%.....0
1996...13...13..........100%......1
1950...16...15.5......~97%.......3(1)
1932...15...13.........~87%.......4(4)
1878...12...10.........~83%.......0
1964...13...9...........~69%.......1(1)
1998...14...9.5........~68%.......1
1955...13...8.5........~65%.......2(1)
2005...28...17.5......~63%.......5(3)
1995...19...11.5......~61%.......3(1)
2010...19...11.........~58%.......1
1886...12...4.5........~38%.......3(1)
1887...19...6.75......~36%.......1
1969...18...6.5........~36%.......2(1)
2020...30...8.75......~29%.......3(3)

*Ratio of major hurricane days (MHD) to total named storms (NS)

Sources: A, B, C

As the data indicate, 2020 easily featured the least impressive output in terms of long-lived major hurricanes vs. total named storms. Many intense storms, to be sure, did occur, as the near-record total of six MH suggests, but only in short, nearshore bursts, rather than sustain MH intensity for days on end. Of hyperactive seasons, 2020 generated the most lacklustre ratio of MHD vs. NS. Unfortunately, virtually all the MHD occurred within a few days of landfall(s) and often involved near-term intensification. This, too, makes 2020 unique in the dataset. Given the predominant steering currents, only the presence of a TUTT in the MDR during the peak of the season likely prevented 2020 from being absolutely apocalyptic in terms of devastation. Otherwise, the very strong subtropical ridge would have likely resulted in multiple Irma- or Isabel-type storms tracking generally westward toward land. Had that outcome taken place, then 2020 likely would have been similar to, say, 1893, 1926, and 2004—if not 2005 or 1933—in terms of ACE and could have easily tied or surpassed 1932’s record of four Category-4+ landfalling cyclones in the Atlantic basin.
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Re: Reflections on the 2020 Atlantic hurricane season

#25 Postby wxman57 » Sat Dec 05, 2020 1:16 pm

Rapid intensification occurs when a storm encounters a much more favorable environment. This indicates that much of the tropics was still hostile this season. Look at the eastern Caribbean. Gonzalo died as it entered. Isaias and Laura struggled there. There were areas where the environment was quite favorable, allowing for a relatively weak storm to quickly strengthen. Otherwise, these storms would have just steadily strengthened without an RI phase.

My favorite question from a client this year: "Why isn't the Greek alphabet in alphabetical order? Why does Eta come after Zeta?"
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Re: Reflections on the 2020 Atlantic hurricane season

#26 Postby Weather Dude » Sat Dec 05, 2020 2:03 pm

wxman57 wrote:Rapid intensification occurs when a storm encounters a much more favorable environment. This indicates that much of the tropics was still hostile this season. Look at the eastern Caribbean. Gonzalo died as it entered. Isaias and Laura struggled there. There were areas where the environment was quite favorable, allowing for a relatively weak storm to quickly strengthen. Otherwise, these storms would have just steadily strengthened without an RI phase.

My favorite question from a client this year: "Why isn't the Greek alphabet in alphabetical order? Why does Eta come after Zeta?"

But Gonzalo was in July though so it wasn't really expected to do much anyway. Laura went on a grand Caribbean tour and plowed right through the islands so it didn't even have a chance to strengthen over there.
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Re: Reflections on the 2020 Atlantic hurricane season

#27 Postby Shell Mound » Sun Dec 06, 2020 2:40 am

Weather Dude wrote:
wxman57 wrote:Rapid intensification occurs when a storm encounters a much more favorable environment. This indicates that much of the tropics was still hostile this season. Look at the eastern Caribbean. Gonzalo died as it entered. Isaias and Laura struggled there. There were areas where the environment was quite favorable, allowing for a relatively weak storm to quickly strengthen. Otherwise, these storms would have just steadily strengthened without an RI phase.

My favorite question from a client this year: "Why isn't the Greek alphabet in alphabetical order? Why does Eta come after Zeta?"

But Gonzalo was in July though so it wasn't really expected to do much anyway. Laura went on a grand Caribbean tour and plowed right through the islands so it didn't even have a chance to strengthen over there.

Technically, Laura formed well east of the islands, but struggled to intensify prior to impact, owing to hostile conditions, despite having formed in the middle of August. On the other hand, Isaias actually developed in the northeastern Caribbean in late July: a feat that is almost unprecedented in the historical database, given that the subtropical ridge and low-level trades are typically strongest in this region at that time. As far as RI is concerned: plenty of storms underwent RI initially and then maintained intensity. Ivan ‘04 and Irma ‘17 are but two good examples. Plenty of EPAC hurricanes and WPAC typhoons underwent similar evolution, too. There is nothing mutually exclusive about RI and subsequent steady state. Even the most conducive seasons are inherently variable, some parts of the basin being more favourable than others, and obviously the atmosphere and ocean are in flux, even in the short term. Atmospheric features such as TUTTs come and go, the MJO changes, and so on. Crucially, favourability is always relative. A storm leaving generally favourable conditions and entering extremely favourable conditions is just as likely to undergo RI as a storm transitioning from hostile to favourable conditions. Ivan and Irma exemplify the former, Andrew ‘92 and Harvey ‘17 the latter. Each storm is unique relative to its environment.
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Re: Reflections on the 2020 Atlantic hurricane season

#28 Postby Ryxn » Tue Dec 15, 2020 2:22 pm

Fun fact! If no additional tropical cyclones form this year, 2020 will be the ONLY Atlantic Hurricane Season to have a Category 5 storm as its final (last-forming) tropical cyclone. This has never happened before 2020. It almost occurred in 1999 with Lenny but that storm was 5 mph short. 2020 is the first year to end the season with a major hurricane since 2016 (Otto) and one of only 12 seasons (or 14 if you count 1905 and 1932) to do so.

Strongest Final Tropical cyclones of a Season (all Cat. 3+)
*1. Iota, 2020 (160 mph)
2. Lenny, 1999 (155 mph)
3. Five, 1910 (150 mph)
4. Paloma, 2008 (145 mph)
5. Six, 1882 (140 mph)
6. Five, 1855 and Nine, 1867 (125 mph)
7. Five, 1873, Five, 1876, Seven, 1912, Thirteen, 1934 and Otto, 2016 (115 mph)
*Strongest Last-Dissipating Tropical Cyclones
1. Fourteen (Cuba), 1932 (175 mph) (ahead of Iota)
8. Four, 1905 (120 mph)

The 1905 and 1932 seasons had final dissipating storms that were at one point in their lives a major hurricane with 1905's Four and 1932's Fourteen (Cuba November). However, only 1932's last-dissipating storm was a major hurricane (Cat. 4) after the dissipation of the season's penultimate dissipating storm (Fifteen).

What makes 2020's case extra insane is that it attempted a Category 5 two times previous to Iota with Laura and Eta (which may have hit it) and Iota came in mid-November after 30 tropical cyclones and still caused 2020 to round off with a Category 5! Talk about a finale. If you come to think of it, October and November 2020 was quiet the final 2 months with likely 6 hurricanes (with Gamma) and an obscene possible 5 majors (with Zeta). This has also NEVER happened before 2020.

Talk about a wacky year!
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Re: Reflections on the 2020 Atlantic hurricane season

#29 Postby Category5Kaiju » Fri Dec 25, 2020 2:28 pm

In all, I think here are my top thoughts about what was so remarkable about this season.

1. The back-to-back landfalls of potent and damaging hurricanes in Louisiana and Central America (particularly Louisiana, which saw 5 total cyclone landfalls this landfalls and the US which saw a total of 12 distinct landfalls, a historic record)

2. 10 storms that rapidly intensified, with a large clustering of intense activity in the Gulf and Caribbean (quite eerily similar to 2005), showing how despite a sub-200 ACE of 180, high ACE does not necessarily give a good indication of catastrophic land impacts

3. Cristobal's rotation surviving even over Wisconsin and Paulette being a zombie hurricane

4. The level of back-loadedness this season possessed, with 4 of the 6 major hurricanes being Greek alphabet named

5. (this is perhaps the most significant and stunning in my opinion) The fact that Eta and Iota occurred. I mean, like what? 2 November majors (the only time in historical records this has happened). Each of them was stronger pressure-wise than Lenny in 1999. Eta was a high-end Cat 4 (could even have been a 5 at one point in its life when recon was unable to sample the storm) while Iota was a Cat 5, the latest on record as well as one of only 2 Cat 5s ever recorded in November. I think Eta and Iota are also historic because they almost certainly will challenge the current way we name storms in the Atlantic, with each of them causing a humanitarian crisis and deserving to have their names uniquely associated with the 2 historic phenomena that unfolded over the course of only 2 weeks.
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Re: Reflections on the 2020 Atlantic hurricane season

#30 Postby Cyclenall » Thu Dec 31, 2020 11:54 pm

Ryxn wrote:Fun fact! If no additional tropical cyclones form this year, 2020 will be the ONLY Atlantic Hurricane Season to have a Category 5 storm as its final (last-forming) tropical cyclone. This has never happened before 2020.

Talk about a wacky year!

That dawned on me a week ago, unless UTC is already in 2021 the ATL only has a few minutes left to produce something so where was that Dec major? A legendary hurricane season is wrapping up.
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Re: Reflections on the 2020 Atlantic hurricane season

#31 Postby ClarCari » Fri Jan 01, 2021 5:07 pm

Practically an inverse of the 2005 season. The L, P, S, and T names in 2020 were quite powerful compared to the weak storms of the same letter in 2005, whilst the D, E, I, K, M, R, and W names of 2005 were stronger than the shlock of 2020’s. Vince and Wilma did memorable things whilst Vicky and Wilfred are laughably forgettable.
Then of course the greeks...
The regular names of 2005 took the spotlight that year and the greek names were interesting forsure but many felt worn out from the more impressive regular named storms that year. Besides Laura, 2020 was the complete opposite, the spotlight of the season was definatley in the greeks.

Also every greek name in 2020 did something completely different than their 2005 counterpart. Alpha was a very interesting Sub-TS in Portugal. Beta was a pitiful TS instead of the impressive major of 2005. Should Gamma receive an arguable upgrade to a Hurricane then it is different than Gamma 2005. Delta 2020 was an impressive major instead of a TS in 2005. Epsilon was a major this time around in 2020. And Zeta was an impressive hurricane in 2020 instead of a notable but still weaker 2005-2006 crossover TS.

If TD 10 is upgrades to a TS in reanalysis, then every tropical cyclone in the Atlantic in 2020 managed to become at least a storm, a rare feat, whereas 2005 had a few depressions not become a TS.
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Re: Reflections on the 2020 Atlantic hurricane season

#32 Postby NorthieStangl » Mon Jan 04, 2021 5:42 pm

I'm surprised that nobody had bought this up yet, but nearly every inch of the eastern United States coastline, from Brownsville in southern Texas all the way up to Eastport in eastern Maine, were under an assortment of tropical advisories at least once during 2020 - except for a single county in the Big Bend region of Florida!

And don't get me started with the sheer large amount of inland advisories - even western North Carolina was under tropical storm warnings because of Zeta, which made landfall four states away in Louisiana!

What a bizarre season.
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