Changing TC classification standards

[CyclonicFury]

Continuing a discussion started on the Kirk thread to a more general thread about TC classification.

There seems to be a lot of systems these days that are questioned by mets such as Wxman57 and crankywxguy for instance. NHC has started to classify more "borderline" systems, such as Colin in 2016, Emily in 2017, etc. While I personally think both warranted classification, the same cannot be said for some other knowledgeable mets.

I personally think anything with convection and a well defined circulation should be classified, but according to some, organized convection is a requirement for classification. What are your thoughts on the changing standards of TC classification?

2018 may have 11 named storms already, but a couple decades ago, the total could be a few less than that.

[Kingarabian]

Yeah it's certainly interesting.

And also it seems that the NHC waits for much more definitive evidence that a system qualifies to be classified in the EPAC compared to the ATL.

[Sciencerocks]

Kirk was a tropical storm.

Had closed LLC
Had Tropical storm force winds
Had convection

What do you wish to do? Demand 45 knots to upgrade a system to tropical storm?

lol

[Sciencerocks]

Yeah it's certainly interesting.

And also it seems that the NHC waits for much more definitive evidence that a system qualifies to be classified in the EPAC compared to the ATL.

A lot of those eastern pacific systems could easily be upgraded 12-24 hours earlier if the nhc set the same standards as the Atlantic. Doesn't mean that they're NOT right in the Atlantic...so think about it.

The question is what is a tropical cyclone?
1. Closed circulation
2. Convection

For a depression there's no standard for minimum winds either.

[CyclonicFury]

Kirk was a tropical storm.

Had closed LLC
Had Tropical storm force winds
Had convection

What do you wish to do? Demand 45 knots to upgrade a system to tropical storm?

lol

I agree that classifying Kirk was the right call, especially this morning when it looked better.

There have certainly been some questionable systems classified though. Alberto early this season in its early life is an example. The convection was poorly organized and the low-level center was weak and well removed from the convection. Alberto eventually became better organized to become a bonafide subtropical storm, but there often seems to be a "rush" to name systems that pose a threat to the US. If the same system was in the subtropical Atlantic in the offseason it would not have been classified (at least not if it improved in organization later).

It's debatable what "organized deep convection" really means. Does the convection have to cover the center? Apparently not since TD 11 was classified last night.

[Hammy]

I think the classification should be much less subjective if nothing else. What constitutes "organized deep convection"? It could differ from one met to another, and I'm certain there are things that were upgrade by one NHC met that may not have been upgraded had another been on shift at the time, and vice versa. Anything with a closed circulation (obviously something that isn't open for debate) should qualify so long as there is deep convection associated with the circulation (rather than just the center itself) as a result of the system itself--this would also eliminate the current inconsistencies of keeping something like Joyce as a depression for days while not upgrading formative system in the same shape. So I largely agree that more "borderline" systems should be classified if they're organized enough to produce convection and have a LLC.

There's also the fact that, when comparing say to the 1970s, smaller systems or ones that might have looked less organized than they were would likely have gone unclassified due to the resolution of the satellite data compared to now, as well as the lack of scatterometer data, which plays a part in more borderline systems being classified today.

That leaves subtropical systems, which I'm not certain there is a fully objective criteria to lay out given the line between a non-tropical hybrid and a classifiable subtropical system is extremely blurry.

[Ntxw]

Yeah it's certainly interesting.

And also it seems that the NHC waits for much more definitive evidence that a system qualifies to be classified in the EPAC compared to the ATL.

A lot of those eastern pacific systems could easily be upgraded 12-24 hours earlier if the nhc set the same standards as the Atlantic. Doesn't mean that they're NOT right in the Atlantic...so think about it.

The question is what is a tropical cyclone?
1. Closed circulation
2. Convection

For a depression there's no standard for minimum winds either.

Not only that but you would also open a whole new can of worms for the WPAC and EPAC subtropics and above. If you think the spurious lows being classified, there are even more of them ignored in the Pacific. The Kona lows north of Hawaii would have a field day being named. Numerous missed.

[Shell Mound]

Continuing a discussion started on the Kirk thread to a more general thread about TC classification.

There seems to be a lot of systems these days that are questioned by mets such as Wxman57 and crankywxguy for instance. NHC has started to classify more "borderline" systems, such as Colin in 2016, Emily in 2017, etc. While I personally think both warranted classification, the same cannot be said for some other knowledgeable mets.

I personally think anything with convection and a well defined circulation should be classified, but according to some, organized convection is a requirement for classification. What are your thoughts on the changing standards of TC classification?

2018 may have 11 named storms already, but a couple decades ago, the total could be a few less than that.

The main argument against Colin was that it lacked a well-defined low-level centre, but rather was part of a baroclinic monsoon circulation with several small areas of vorticity, with the strongest winds several hundred miles distant from the supposed centre. Colin was heavily involved with a nearby mid-level trough and was arguably not fully tropical to begin with. Its circulation was extremely broad, even for a hybrid-type system, much less a tropical storm. As for Emily: it developed beneath a mid-level trough and was situated at the tail-end of a frontal boundary at the time of its classification. Additionally, surface observations from Gordon (2018) in South Florida indicate that the circulation was only closed at the mid levels, and that aircraft recorded temporary winds associated with the strongest convection that were not representative of the circulation, which featured much lower winds at the standard 10 m. I have heard many arguments that the NHC is overestimating the intensity and organisation of systems by taking into account the strongest winds reported by aircraft instead of contextualising the environment and circulation (e.g., effects of shear and dry air on the reduction from flight level to 10 m, the erroneous effects of downbursts and microbursts on reported winds, et al.).