Have Certain Things Fundamentally Changed About Atlantic Hurricane Seasons?

[Category5Kaiju]

So, let me preface this question by saying that I've had quite a bit of contemplation on it due to recent events but that it's been something I've wondered for some time.

Between an 11-year, ongoing streak of 155+ mph hurricanes per season, devastating Gulf landfalls, practically no major hurricane landfalls on the East Coast (especially Florida), etc., we've seen an impressive stretch of years that showcased activity in a manner that hurricane seasons and periods in the past rarely exhibited. Is this just a freak occurrence in the grand scheme of things, or do you think that certain aspects of Atlantic activity have genuinely changed, for better or for worse? And if so, why would that be the case?

[tolakram]

No.

Remember recently when no majors had hit the US in years? This question was asked back then as well.

[Ubuntwo]

I don't believe so. You could have asked this question in 1950 after a decade+ onslaught of hurricanes targeting Florida. Patterns are cyclical and can span many seasons.

[weeniepatrol]

I'm a firm believer in Natures' tendency for balance and therefore its tendency for reversion to the mean.

But, at some point we have to start asking if we are exceeding a mere reversion to the mean.

11 category 5s in the 2016-2025 surpasses the previous record of 9 during 1998-2007.

Of course, that last decade was followed by the cat 5 drought between Felix of 2007 and Matthew of 2016. There's a lot of natural variability at play which causes cycles on a decadal timescale, no doubt. But when do we say "okay, this is getting to be a bit much"?

[tolakram]

I'm a firm believer in Natures' tendency for balance and therefore its tendency for reversion to the mean.

But, at some point we have to start asking if we are exceeding a mere reversion to the mean.

11 category 5s in the 2016-2025 surpasses the previous record of 9 during 1998-2007.

Of course, that last decade was followed by the cat 5 drought between Felix of 2007 and Matthew of 2016. There's a lot of natural variability at play which causes cycles on a decadal timescale, no doubt. But when do we say "okay, this is getting to be a bit much"?

It's not a case of believing in it, just to parse your wording a bit. Unless an average is changing it will be met via the variability over time. These short term proclamations of change are problematic, plus as you go back in time the means of detection and accurate categorization drops. Would we even notice that Erin reached cat 5 in the 50's? I'm also allergic to this categorization, as a small cat 5 is a lot different from a large cat 5.

Back to averages, we need this in order to create a usable metric in my opinion:

1. Define what we are averaging, is it a reliable measure? I'd say no as categories are horribly problematic and detection of short term changes has improved over time.

2. Define the timescale that we think should meet the average. Is the timescale large enough?

3. If we note a change over the timescale is there anything else that could explain it? I'd answer detection again, but for me we already failed #1

[LarryWx]

So, let me preface this question by saying that I've had quite a bit of contemplation on it due to recent events but that it's been something I've wondered for some time.

Between an 11-year, ongoing streak of 155+ mph hurricanes per season, devastating Gulf landfalls, practically no major hurricane landfalls on the East Coast (especially Florida), etc., we've seen an impressive stretch of years that showcased activity in a manner that hurricane seasons and periods in the past rarely exhibited. Is this just a freak occurrence in the grand scheme of things, or do you think that certain aspects of Atlantic activity have genuinely changed, for better or for worse? And if so, why would that be the case?

I think there’s a very good chance that climate change is the single most significant influence on the Atlantic with its large # of 155+ mph storms as well as a stronger mid Sept-Nov. Also, CC MAY also be leading to a more inactive W Pacific overall, but who knows?

Regarding there being no MH hits on FL E coast since 2005:
-seems most likely to be mainly random to me. The E coast of FL isn’t but ~400 miles long, small enough to be missed for decades from a MH.
- Besides, Irma, Matthew, and Dorian just missed.
-1966-91 had no MH in E FL. Also, none occurred 1872-1887.
-Hoping the MHs keep avoiding FL E coast! The FL home insurance industry among other things could be devastated.

[Teban54]

I'm nowhere near as professionally involved in weather as many members here are, but I did some quick secondary research years ago for a college writing course.

My recollection is that in the North Atlantic, global warming may result in

• No significant changes in frequency of hurricanes (maybe even a slight decrease)
• BUT: Higher intensity of hurricanes, such as RI episodes

So I won't be surprised at all if the streak of 155+ mph hurricanes isn't just a coincidence.

[Woofde]

It's incredibly difficult to gauge the effects of Climate Change on the hurricane season. We unfortunately just don't have that much accurate data. I do believe it is having some effect likely aiding in the top end of systems, but there is no way to be 100% positive. There are too many cycles which are >30 years and variability is large even in a non modified climate. It's not even just CO2, aerosols play a huge part as we saw the previous years with records breaking SSTs due to sulphur emissions reductions.

The previous decade has been anomalously active though that is for sure. I don't think there is a definitive answer to this question yet, if the next 10 years follow in the footsteps of the previous 10, then I believe the answer is yes something has changed. Theory does support this.

It is worth stating that 10 years of no below average seasons is incredibly unlikely and eyebrow raising. While I wouldn't give a definite answer yet, if I were forced to guess, I would say yes we are witnessing a large change overall in the basin. The large scale heating cannot be ignored.

[Teban54]

Minor quote in an otherwise excellent comment:

It's incredibly difficult to gauge the effects of Climate Change on the hurricane season. We unfortunately just don't have that much accurate data.

IIRC, some or most of those studies weren't statistical (analyzing past activities), but model-based. They create hypothetical scenarios with climate change, then observe their downstream effects on hurricane activity in the models.

Of course, the caveat is that our modeling abilities are still far from perfectly capturing the real world - "all models are wrong, but some models are useful".

[WeatherBoy2000]

So, let me preface this question by saying that I've had quite a bit of contemplation on it due to recent events but that it's been something I've wondered for some time.

Between an 11-year, ongoing streak of 155+ mph hurricanes per season, devastating Gulf landfalls, practically no major hurricane landfalls on the East Coast (especially Florida), etc., we've seen an impressive stretch of years that showcased activity in a manner that hurricane seasons and periods in the past rarely exhibited. Is this just a freak occurrence in the grand scheme of things, or do you think that certain aspects of Atlantic activity have genuinely changed, for better or for worse? And if so, why would that be the case?

After Betsy in 1965, there weren't any east coast major landfalls until Hugo in 1989, that was a 24-year gap. It's important to look at the past first before saying that the climate is fundamentally changing in one way or the other. So far, it's only been 21 years since Jeanne.

I think the biggest climate change indicator is the 11-year streak of 155mph+ hurricanes, there's nothing remotely comparable to it on record prior to 2015. It's long enough now that even with the more questionable records of the past, I think we can confidently say that it is unusual. It also most falls in line with what you'd expect with warmer oceans due to climate change and tropical cyclones. Logically, warmer oceans would generally yield stronger cyclones.

[Hypercane_Kyle]

I’d say the rate of nuclear rapid intensification episodes has greatly increased over the past decade. That is a fundamental result of SSTs being warmer for longer periods of the year.

[Ulf]

My recollection is that in the North Atlantic, global warming may result in

• No significant changes in frequency of hurricanes (maybe even a slight decrease)
• BUT: Higher intensity of hurricanes, such as RI episodes

So I won't be surprised at all if the streak of 155+ mph hurricanes isn't just a coincidence.

To add to this. While the frequency of hurricanes is not changing, the number of named storms per season has definitely increased significantly. We are at the point where even El Niño years feature above average activity based on number of named storms alone even if most of them tend to be weak and/or short lived tropical storm/cat 1 slop.

After all, the last below average season was 2015, ten years ago. Before this, the Atlantic would get at least one slow season every three or four years.