STORM2K

I've come across a Wikipedia article titled "Cyclones Katrina and Victor–Cindy". The tittle implies these are different storms and I was originally wondering why they shared an article. Basically, according to the BoM, Victor-Cindy (second named received after moving into SIO) came from the remnant low that was formerly Katrina as the low persisted into the Indian ocean.

I quote:
"The remnants of Katrina continued to move west towards the coast and finally moved north and weakened substantially east of Cairns. A weak circulation persisted for a further two weeks and drifted westwards across north Australian and into the Indian Ocean."
"Victor formed in the Indian Ocean, most likely from the remnants of Katrina which decayed in the Coral Sea two weeks previously."
"The time period from the formation of the low from which tropical cyclone Katrina formed in the Coral Sea, through until it could no longer be identified as a low in the central Indian Ocean was at least 50 days."
(from: http://www.bom.gov.au/jshess/docs/2000/chappel.pdf)

So my question: are Katrina and Victor-Cindy the same system? Because at least one source refers to them that way and the "50 day" sentence implies so. But

"See the portion of this summary covering the South Indian Ocean basin for the final chapter in the life of what can be referred to as Tropical Cyclone Katrina/Victor/Cindy." (although it is stated that this summary is preliminary information)
(from: https://australiasevereweather.com/cyclones/1998/summ9802.htm)

I'm asking because on any track they're considered separate systems.

Edit: I found a BoM thing that considers them the same system

Link: http://web.archive.org/web/20150924004343/http://www.bom.gov.au/climate/ntregion/statements/tropical/dtds-199802.pdf

Long satellite movie spanning the lives of the two systems...

[youtube]https://youtu.be/wArZoeBnJLE[/youtube]

Sort of. The NHC would probably retain the name if it all occurred in the same basin today. I am not sure what Australian policy is. It looks like the ITCZ was wanting to spin up something new north of Australia and the remnants helped. Not sure if I would call that the same system, but the NHC keeps names if remnants are trackable (ie. not bifurcating), even if the system evolves into something completely different when it regenerates (ie converting from post-tropical to subtropical)). Harvey in 2017 was initially a weak tropical storm that degenerated back into a remnant open wave at one point. When a system crosses basins, the general protocol is to change the name (Victor->Cindy). It literally gets a new name as soon as it crosses a specific longitude point or in the case of the Atlantic, when a storm crosses over basins in latin America. If the remnants have degenerated too much and there is no longer an observable vorticity pattern that you can follow, then it may get a new name. Even if a system retains a name, it often both sort of is the same system and not at the same time-like Lee in 2017. Either way it cannot be called the longest lasting tropical cyclones because it was not a tropical cyclone between Katrina and Vince. It degenerated in the intermediate time, hit land, and then finally drifted and interacted with the ITCZ. How it is named is determined by the basin, agency, and their discretion.It existed as just a remnant for a period of its life. I haven't heard of this system until this post and simply watched the satellite video someone posted. When the system crossed into the Indian ocean, it became Cindy. These names are very coincidental, I must say.

It would hardly be unheard of for a weak Atlantic tropical storm to hit central America, degenerate into an open trough or remnants, and then eventually reform to become a significant hurricane over the Pacific. At that point though, the storm would be over a completely different basin (and one that is actually negatively correlated to the Atlantic). That is similar to what is going on here.

In addition to all that's mentioned, the group of Wikipedia editors started to unofficially combine some articles for these systems where one formed from the remnants of the other, even if they are in different basins and named differently, but clarify in the article that they are two distinct storms. The most notable case is Amanda and Cristobal (2020), whose articles were merged primarily because their impacts have significant overlaps.

If you check the Talk page, you'll see that there was a time when the article was named "Tropical Storm Amanda-Cristobal", due to the personal opinions of a small group of contributors (if not just one) that, if systems like Harvey and Lee 2017 were seen as the same storm, then Amanda and Cristobal also should - as the only difference is that they were in different basins whereas Harvey stayed in the Atlantic the whole time. However, treating "Amanda-Cristobal" as the same storm is purely subjective and is not supported by the NHC's official classification. That's why the Wikipedia articles had an extensive discussion and decided to change it to the current title, "Tropical storms Amanda and Cristobal".

This does raise a (somewhat philosphical) question: If a storm dissipates and its remnants later regenerates, does it count as the same storm? And what determines whether it's counted as the same storm?

The answer seems to be wildly inconsistent across basins and across agencies. I believe the NHC's current policy is that a name change happens if and only if its dissipation and regeneration are in different basins. So Harvey 1.0 and Harvey 2.0 kept the same name, as does Genevieve 2014 (which formed in EPAC, moved into CPAC and dissipated, then regenerated in CPAC but kept the name Genevieve instead of a CPAC name, and later even moved into WPAC where it became a Cat 5); whereas ATL-EPAC crossovers (Grace/Marty 2021) and the less common EPAC-ATL crossovers (Amanda/Cristobal) received different names, unless they cross as a fully intact tropical cyclone (Bonnie 2022).

But whether this should be done is the question. Meteorologically speaking, there's not much difference between the evolution of Harvey 1.0 to Harvey 2.0 vs the frequent ATL-EPAC regenerations; or more analogously, Eta 1.0 to Eta 2.0, which also dissipated in Central America, just that it tracked north instead of west. One may speculate that this is for clarity in communication if the 1.0 and 2.0 versions affect the same basin, but they don't always work for the better - Ivan 2.0 probably caused a lot of confusion when it reformed in the Gulf right where it tracked through as a Cat 4 a week earlier.

Naming conventions seem to be even less consistent in other basins. Freddy this year started in the Australian region and got an Australian name, then crossed into SWIO, dissipated and regenerated. It broke the duration and ACE records for a single storm worldwide, but they (especially ACE) relied on its second life after regeneration in SWIO. You can argue that it could have received an SWIO name (Fabien) in an alternative universe.

Likewise, the Katrina/Victor-Cindy example is perhaps one of the most bizarre. At that time, not only did the Australian region (managed by BoM) have three different naming lists by different warning centres under BoM (thus Katrina became Victor when it regenerated in a different part of the region), but Australian-SWIO crossovers also had name changes automatically after crossing the boundary (thus Victor became Cindy). Yet, Katrina retained its name when moving from the Australian region to SPAC, a different area of responsibility.

Bottom line is, I really wish there can be more consistency on this.