Should the terms waterspout, landspout etc be dropped?

[Sam Jowett]

Why don't you try and refute my points Martin?... I suspect because there's no logical argument that can. Whatever the sway of opinion, it doesn't negate the other argument... take global warming scepticism for instance!

I'd like to continue this discussion in a constructive manner if that's ok?

The naming system used in the US is actually more thorough than the UK, as tornadoes are categorised according to both whether they are over land or water, and whether they're produced by a meso updraught or not. The UK only goes half way really, categorising according to whether over land or water. Landspout is rarely used in the UK in my experience.

Both conventions mislead the public in terms of them all being tornadoes though. It's technically their strength and diametre that determines their impact and these can be measured more clearly on a scale than varying naming conventions.

I wonder how the public would perceive the threat of an F3 landspout or waterspout, compared to an F3 tornado?

 

[rdale]

"waterspouts regularly come ashore and survive in the UK, so long as the vorticity and updraught survive."

Do they ever form over land? No. How long do they survive inland? I can't believe it's more than a few minutes?

"waterspouts don't come ashore much, because the alignment of the convergence zone remains offshore and this is what provides the vorticity for the updraught to stretch. Would you agree?"

I'm not familiar with Florida waterspouts - I'm talking about Great Lakes ones. They do come ashore, and fall apart within 50 feet of making landfall. Never any further inland.

"Therefore, doesn't that prove that waterspouts and tornadoes are the same?"

No, it shows exactly my point - they can't be intermixed. A tornado can go over water with no change at all, then back to land on the other side. Waterspouts cannot. Tornadoes can form over land, over water, or anywhere else as long as they are related to CB. Waterspouts form out of fair-weather cumulus (not storms) over water only (not land.) Hard to say they are the same.

- Rob

 

[JF Massicotte]

Don't waterspoud and landspouts almost have the same generation process, the main difference being that the updraugh comes from water's heat on one case and from heaten ground on the other?


I would stick with the idea to keep term tornado when they occur but there still is a MAJOR difference when it comes on forecasting them!


Si I would say that they all are tornadoes, but experimented chasers/forecasters/any 'ers related to weather should keep telling the difference between them.

 

[Sam Jowett]

Tornadoes rarely survive more than 10 minutes in the UK anyway to be honest Rob, so a few minutes is probably as long as they survive, yes. This isn't because the tornado is different in any particular way though, it's because the parent environment can't sustain the updraught and vorticity for as long as a supercell would. The more finely balanced the environment producing the tornado, the more delicate to changes that tornado is going to be.

When do waterspouts form over the Great Lakes? I'd guess during the fall when the water can provide the instability? If so, it's surely the fact that the boundary layer instability is much less once the updraught comes ashore... much like when they come over the UK coast. So once again, the change in the environment and not a different kind of tornado.

I assume you must have land breeze/lake breeze effects providing short lived vorticity to passing updraughts as well... again only going to be short lived because of the change in the environment.

The main difference with meso produced tornadoes, is that the storm creates the vorticity, so as long as the instability is sustained and the environment conducive to a mesocyclone, the storm can generate the vorticity necessary to sustain a tornado. This is the only reason supercell tornadoes tend to be more long lived and stronger... the storm carries the right environment with it.

Sounds like we agree on the meteorology, just not how the events should be labelled: i.e. tornadoes, waterspouts, landspouts are all produced in the same way, but the environment producing them may be very different. Shouldn't that environment be classified separately, rather than included in the tornado terminology?

Agreed JF... there's a great variety of conditions that can produce tornadoes, some can sustain them and produce strong events better than others. This must continue to be clearly recognised and I wouldn't want to divert attention away from that.

 

[rdale]

"the environment producing them may be very different."

Bold and italics on the "very" in there...

"Shouldn't that environment be classified separately, rather than included in the tornado terminology?"

No. A waterspout carries no threat to anyone other than a stray boater on the lake and a shed near shore. That's it. Never any worse. So why confused the public? You can't have a tornado on the ground without a warning, but you won't find anyone saying we need to go wall-to-wall because a waterspout is going to spend 30 seconds on shore.

So let's keep the definition how it's been, and use the description to tell you the environment. You'll have a hard time finding a meteorologist who will refer to a true waterspout as a tornado...

 

[Sam Jowett]

"A waterspout carries no threat to anyone other than a stray boater on the lake and a shed near shore. That's it. Never any worse. So why confused the public? You can't have a tornado on the ground without a warning, but you won't find anyone saying we need to go wall-to-wall because a waterspout is going to spend 30 seconds on shore."

That may be the case with the Great Lakes waterspouts, but I don't think it holds the world over. One of the most damaging tornadoes in recent years in the UK (F2 or so) started its life offshore and spread a few miles inland I believe. Either way, it caused quite a bit of damage in the coastal town there.

My point being that they can be destructive if the environment brings them ashore and remains conducive enough to sustain them.

We're talking from different perspectives I suppose, as you have a much greater variety of vortices there, in terms of strength and size. In the UK environment, a tornado produced by a meso is often similar strength to that produced by a convergence line. This means that the variety of terms can be more clearly differentiated in the US than the UK. This is why it's not good to have apathy towards waterspouts in the UK, when on average they're stronger than tornadoes that form over the land!

Wouldn't be reasonable to expect the US to change their terms to satisfy the UK I guess , but global consistency I think is worthwhile. I can see your perspective regarding large disparity between environments, but can you see mine with regards all vortices being produced by the same process?

 

[rdale]

I see your perspective - but again, nobody outside this forum cares. The public doesn't. Meteorologists don't. We have waterspouts, and we have tornadoes over water. Simple, explains all about the environment, and is accepted.

 

[Martin North]

Why don't you try and refute my points Martin?... I suspect because there's no logical argument that can. Whatever the sway of opinion, it doesn't negate the other argument... take global warming scepticism for instance!

I'd like to continue this discussion in a constructive manner if that's ok?

Deary me Sam...do you always get this touchy when you don't get your own way....?

I have been constructive and I have nothing to refute. I know the processes of tornadogenesis as well you know...

The fact that Waterspouts and Landspouts are in effect tornadoes is neither here nor there. I'm not in dispute with that.

The problem here, as I see it, is the fact that you want to rename certain meteorological phenomena (as laid out...named and described in glossaries/guides) to meet your own personal (amongst others) agenda or whim.

Now is that constructive enough for you...?

 

[B Ozanne]

It doesn't matter what we call it, it's still gonna happen and people still won't pay attention. You have to remember, outside of these weather boards and the meteorlogical community in general - nobody cares.

I'm not sure I care.

I was burning some brush in Vermont and the smoke started to rotate. As the column contracted it began to rotate faster. Was that a tornado?

 

[rdale]

"As the column contracted it began to rotate faster. Was that a tornado?"

Of course not - even the simplest of definitions wouldn't accept that.

 

[Steven Williams]

I've just skim read this thread. my thoughts...

The term 'waterspout' has been around a long time and is here to stay. No question about that.

The term 'landspout' is a relative newbie but I like it. It is useful to have a term for a non-mesocyclonic tornado.

 

[B Doss]

I never really liked the term landspout and never thought they should be intially reported to the public as anything but a tornado. There seems to be a surfacing attitude that a tornado warning that is relayed to the public in landspout language somehow diminishes the danger to the point that some do not fully appreciate the threat to life and property. Warn it as a tornado, document it as a non-mesocyclone tornado.

 

[MJ Poore]

As a Brit myself I find this thread rather embarrssing. The views here from the UK seem to represent those of the TORRO organisation, which is not affiliated to any university, or credible scientific body (if that's harsh, then I am sorry) . I don't believe all or most serious meteorolgists in the UK call landpsouts or whirlwinds tornadoes as do this TORRO organisation.

This in effect is a form of propaganda, and it gives rise to statements like the claims that the UK experinces more tornadoes per area than anywhere else. Which I believe is nonsense. I live in S Africa and have lived in the UK for quite a while as well. Where I live now there are hundreds of landspouts and whirlwinds here everyday. But nobody is calling them tornadoes, quite rightly.

 

[Sam Jowett]

Another issue in the UK I guess is where do you draw the line between a mesocyclonic tornado and a non-mesocyclonic tornado. A mesocyclone technically has to display persistent rotation to be defined as such, but what really counts as persistent? Although a few LT supercells probably occur every year in the UK, full size supercells born from a tropical airmass are very rare, simply because we don't have the land mass to support the necessary conditions.

What we do get regularly of course is short lived rotation within the updraught. Whilst not persistent, so not being classed as a mesocyclone, this is probably the most common situation for producing tornadoes in the UK... or would these be termed landspouts? As I said earlier, landspout isn't really used in the UK, probably due to the lack of mesocyclones!

I'm sorry if my comments have embarrassed you Mungo, but they are only opinions after all. They're held be me and not TORRO specifically... some there agree, more don't. Whether or not the organisation has specific affiliations is surely irrelevant... what's important is that a group of qualified and amateur meteorologists are seeking to study severe weather in the UK. Why attack that?

I thought the misconceptions and vagaries of the spout terminology would be an interesting point of discussion. Science never moves forward if people don't question things. It's not propaganda for anything either... as I've just stated above, if you don't count landspouts as tornadoes, you could probably count the UK's annual total on one hand. Considering the amount of us that chase on the Plains, it should be obvious that we know the place to go to see a tornado!

Anyway, back on topic. Where exactly do you draw the line between a tornado and landspout / tornadic waterspout and true waterspout if both are produced by a rotating updraught? Does the rotating updraught need to be persistent enough to be called a mesocyclone? Also, what is the ceiling wind speed for a landspout / true waterspout? If a short lived rotating updraught produces a landspout, but the rotating updraught becomes long lived enough to "become" a mesocyclone, does the landspout "turn into" a tornado? These all seem to be vagaries that need defining to me.

 

[Paul Knightley]

Get a grip Sam!

When are you going to drop this meatless bone...

You no more shot me down here than anywhere else. This arguement is on three boards now and you are losing across all three.

Time for you, I suggest, to be elegant in defeat and drop the subject...

"Losing" doesn't mean a thing Martin! It's the quality of the responses you should be looking at.

Right, let's boil this down to a few points:

Tornadoes are rotating columns of air, pendant from cumliform clouds and in contact with the surface. They appear to develop when vertical vorticity is stretched by a passing updraught. The vorticity can be created in many ways; e.g.

through tilting of streamwise vorticity (which itself may be generated by a storm-scale feature, perhaps the forward-flank downdraught/gust front of a supercell, downdraught/gust-front of a multi/singlecell storm, sea breeze boundary, in fact, any mesoscale baroclinic feature)

through interactions between several storms, perhaps intersecting boundaries.

through features present in the pre-storm environement, such as a horizontal convective roll.

vortex shedding from islands/headlands

convergence zones

and quite possibly, many other situations!


Now - my point is that a passing updraught can ingest this vorticity, and the result can be a tornado. This is not dependant on the updraught rotating (i.e. a mesocyclone), and not dependant on whether the storm is over land or so.

Now of course I understand that tornadoes developing beneath low-level mesocyclones are usually intrisically more intense than those which are not, but this is probably due to the fact that such updraughts are themselves more violent and long-lived than non-rotating updraughts.
So classifying tornadoes but any other name seems pointless to me. Of couse, waterspout is entrenched in history and I'm aware that it's probably not going anywhere - however, that doesn't mean it's right.

And as for 'landspouts' - well, many tornadoes in the USA (and defininately the UK, and likely elsewhere) are probably not associated with supercells, so does that mean that they should be classified as landspouts? No - classify them for what they are - tornadoes.
That's my take on things anyway, and I'm sure people will disagree!