STORM2K

We've all seen the pictures...a horizontal column of rotating air (that formed prior to a thunderstorm's arrival in the area) is pushed upward by a thunderstorm's updraft into a vertical position and is stretched out until it creates spinning in the entire length of thunderstorm, all the way down to the ground.

For example, from the NSSL guide on tornadoes:

Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.


Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.


An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.


I have a problem with this, however...mainly, how is that even physically possible? For example, you walk around in a pool and create a vertical whirlpool (same concept as the tubes being formed in the air, just backwards)...so if I suddenly reverse direction and start walking in a straight line, I'm going to cause the whirlpool to turn 90 degrees on it's axis? Um...not hardly, more like my motion against the current is going to completely kill any forward momentum and the whirlpool will simply cease to exist, save for in my mind (granted, this is all assuming the whirl I create doesn't sweep me off my feet first! )

With the current idea of how tornadoes develop, the updraft cutting through the rotating air should cause any rotation to cease, it may slow parts of the updraft down some (due to the updraft having to overcome the downward moving air on it's way up), but it will certainly not create rotation, not on the scale seen when tornadoes develop, anyway. The sides of the tubes not totally obliterated by the upward ascension may be lifted up some, but any rotation associated with that should spin down and die away (thanks to it now being away from the source that was causing it to rotate in the first place).

I think tornado formation has more to do with how the inflow to a storm is set up. Obviously a thunderstorm is a low pressure system, air is being evacuated upward by an updraft, which creates the lower pressure...nature must have things balanced, so air rushes inward from outside to relieve the vacuum created by the upward moving air...that is basic thunderstorm behavior. Friction has to be added in, as well. Maybe there is a relationship between inflow (both direction and speed, since the inflow would be coming in from many sides, including both outside the storm and from the downdraft) and the amount of friction the winds have to overcome in order to start rotating (let alone develop a tornado). If the friction is great enough, the air could get to the updraft region and just rise because it is all out of steam.

Or...moving in a slightly different direction that is a bit easier for me to grasp with a non-college mind...

In the case of multicell and single cell storms, inflow speed from outside the storm is typically about equal to the inflow speed from what is being pulled in from the downdraft. Per the Advanced Spotters book, most single cell storms only last about 20 to 30 minutes (your pulse storms). There never really is a time when the up/downdraft are both established...more the storm just collapses after a point. Inflow would generally be about equal from all sides in terms of wind. In multicell storms, the updrafts and downdrafts are usually about the same strength, so winds coming in from outside the storm and from the downdraft would usually be about equal, thus mostly not causing a fuss when they collide.

When it comes to supercells, the wind being pulled in is far greater than the other two storm types. The winds inbound from outside the storm are generally stronger than the winds being pulled into the updraft from the downdraft region...this is where the problem starts. If you have two cars moving along at 20 mph in opposite directions and they collide, they generally just smash into each other and leave a mess. If you have the same two cars and one is traveling at 20 mph, while the other is doing 30 or 40 mph, the faster one will overrun the slower one and both will rotate to some degree upon impact...same concept here. The faster winds (coming in from the SE) reach the updraft area quicker than the downdraft winds...some of these winds are going to "overshoot" the main updraft area and keep going, where they impact the slower downdraft winds, sparking rotation (thanks to speed shear). Both areas are still going to rise (because they are still in the area of updraft, just not in the center), but they are going to rotate as they rise. The rotation starts off the ground because the main inflow would be elevated...friction above the ground is less, so there is a quicker response time for the winds to funnel in (no pun intended ). The lower levels slowly start responding, and as they do, this rotation lowers to the ground. Thanks to friction, however, the rotation generally will decrease in size (tighten up).

Eventually, something interferes with the inflow at some level, and the tornado dissipates. It could simply be the tornado is weak and a forested area screwed it up (or buildings), so it lifts off the ground until the friction levels allow the ground winds to resume a rotation. In the case of the bigger, longer lived tornadoes, it could be that the winds being pulled in are interfered with by another storm, the inbound winds briefly slow down, causing a loss of rotation and the storm has to reorganize, or simply the downdraft gained some strength (which could result in the storm strengthening, causing the downdraft winds to flow down faster).

This would help explain a few things...one, why do tornadoes mainly rotate counterclockwise (as many as 9 in 10)? Southerly and Southeasterly winds flowing in at rapid speeds and colliding with slower, west winds would force the west winds to bend to the north...this deflection would create a counterclockwise rotation as it continued. In this case, it would take a pretty unique set of circumstances to generate a clockwise rotating tornado. The winds coming in from the west would have to be stronger than the winds coming from the South and Southeast, to deflect those winds to the east to create the clockwise rotation...something that is usually not common, given the way supercells are set up.

This would also help explain why single and multicell storms generally do not produce tornadoes (they can do so, yes, but generally, no). This would also explain why the southernmost cell on a squall line behaves more like a supercell and can produce a tornado, it has the inflow needed to generate the rotation, without the frictional interruptions of other storms. This would also help explain why the rotation is generally in the back of the updraft region, behind the main rain free base, but before the downdraft region...the "overshooting" of the stronger, inflow winds. Also, if the downdraft winds were stronger, the storm could theoretically produce a tornado, but any inflow would very shortly be overrun by the collapsing system, and any tornado that did develop would quickly dissipate after a very short, weak life.

And...I just realized (as posted on my facebook) "So...I go on S2K to write a topic on why I disagree with the current idea behind how tornadoes develop, and instead, I end up basically writing a rough thesis paper on my ideas of how they develop...and I'm not even in college! *facepalm*"

Anyone wish to add thoughts to this?

No takers? No comments?

Well I dont have a scientific or what so ever helpful comment for your cause...I thought thats what you wanted But I think that you put alot of effort into this, and really your post actually made me understand tornadoes (I had no idea before I read this days ago) but to me, it sounds reasonable. But I'm sure most people who viewed it probably thought the same thing...You did a really good job on this!

Thanks! Any comment about it is welcoming, it can create debate and spark new ideas and what not.

Hey guys. Which maps are you using. My favorite is down, somehow.

Tim, that is a well thought out theory/thesis. I have always wondered how the explanation of how a tornado forms really works, especially with the factors you note involved. What I find interesting about your thoughts is that in a way I think it helps explain how the current theory works and at the same time still raises the same questions I have. Friction most definitely plays a part in the "destruction" of tornadoes as well as probably their formation. The lack of friction in the plains I think explains to some degree how they grow large and are long tracked there as opposed to in other regions with more topography(not that there aren't long trackers in areas with topography). A big question I have is what makes the tornado weaken to the point it isn't viable after it has managed to wind up into a destructive funnel? I would think it has to be some of the same forces that form it, possibly as you say, colliding with themselves and breaking the rotation down. I would love to hear the thoughts of pro-mets on this since they have had the schooling and the in depth explanation/understanding of how it "works" that I haven't had.

I can tune in a little bit here, but I am not a met. First, brunota...go to Grad school. You have the mind and obvious aptitude for the research there, and already have some research topics.

Next, I would like to say that this model for tornado formation is very well studied, and I really do not feel that it will change any time soon. With that said, supplements are being added to the model all the time. The reason the model works is because of is complexity. We do not just have the two aforementioned 'cars' acting against each other, but also up to 5 other ingredients that must come together for tornadoes. Starting with the car analogy though, these cars do not ever collide in supercells! In order for tornadogenesis to occur, there must be vertical shear available. Car 1 and car 2 need to be going in different directions and usually have to be 100mb or more apart.

As for the lift, per my understanding, there is a mix of surface heating and a LLJ (or another vertical wind) create for uplift. It's not necessarily the thunderstorm sucking the rotating barrel into it.

All of this said, this is just base knowledge for me. I'm not entirely sure everything is correct, and if something is not please correct me.

I understand the theories behind it, to the best of my knowledge...but still think the barrels would be shredded when they got lifted. Perhaps the barrels are just a sign that the conditions are right to produce a tornado (a by product), versus the actual mechanism that produces them?

As far as downdraft winds never mixing with the updraft, how is it possible that they would never mix? The vacuum left behind by the air rushing upwards would pull air in from all sides...it wouldn't sit there and go "oh, you're from the downdraft and totally not cool, sorry, cool air molecules only!". Now, the downdraft air is cooler than the air surrounding the system, so obviously too much entrainment would kill off the storm. I will say, though, that the cooler air would not rise as far up, due to warmer air being lighter.