They come to do $100 dollars worth of improvements.

Isn't this obvious? A pulls things in(to state it simply) also pulls itself toward things. To a degree hills are things so the tornado will somewhat move toward it. duh.

Down here in Brevard County a couple years ago, there was an F-0 twister that crossed I-95... which would be rather unremarkable were it not for the fact it went directly between a flea market and a trailer park. I still maintain that the damned thing couldn't decide.

I'm trying to find the right words for the effect I've thinking about, but I can't. But imagine if you would, a small plane trying to take off from the surface of a small lake.

It can't, because the uniform surface of the lake is literally holding the plane to the surface of the lake. But if you disturb the surface of the lake by driving around a motorboat for a little bit, disturbing the uniformity of the lake's surface, that plane can take off when the lake's surface no longer has a grip on it.

Okay, what if some buildings disturb the uniformity of the atmosphere and gives tornadoes room to grow in size and strength?

Coelacanth: I'm trying to find the right words for the effect I've thinking about, but I can't. But imagine if you would, a small plane trying to take off from the surface of a small lake.

It can't, because the uniform surface of the lake is literally holding the plane to the surface of the lake. But if you disturb the surface of the lake by driving around a motorboat for a little bit, disturbing the uniformity of the lake's surface, that plane can take off when the lake's surface no longer has a grip on it.

Okay, what if some buildings disturb the uniformity of the atmosphere and gives tornadoes room to grow in size and strength?

Oklahoma would like a word with your theory.

This is not news. There's an area in Ohio, not far from Kent State, that is called "tornado alley" by some of the locals. It's a swath of land with some upslope and the twisters tend to follow it. No one's built on it and there are no trees there.

FTA: "In general, (tornadoes) are relatively rare and it takes a lot of years of record to get something that is statistically meaningful and we're not quite there yet," Knupp said. "Patterns are starting to suggest things that we can form hypotheses on but just looking on locations of patterns, tornado frequency, intensity, path length, that data base is not extensive enough to really carry any scientific weight statistically yet.

"But we can use it to look at patterns and phenomenon and that's what we're doing now."

That's what science is all about.

ds_4815: Down here in Brevard County a couple years ago, there was an F-0 twister that crossed I-95... which would be rather unremarkable were it not for the fact it went directly between a flea market and a trailer park. I still maintain that the damned thing couldn't decide.


LOL !

obvious_tag.jpg

Coelacanth: I'm trying to find the right words for the effect I've thinking about, but I can't. But imagine if you would, a small plane trying to take off from the surface of a small lake.

It can't, because the uniform surface of the lake is literally holding the plane to the surface of the lake. But if you disturb the surface of the lake by driving around a motorboat for a little bit, disturbing the uniformity of the lake's surface, that plane can take off when the lake's surface no longer has a grip on it.

Okay, what if some buildings disturb the uniformity of the atmosphere and gives tornadoes room to grow in size and strength?



Wut?

Coelacanth: What if some buildings disturb the uniformity of the atmosphere and gives tornadoes room to grow in size and strength?

I believe microscale meteorology (e.g. building-caused eddies) could affect this, although obviously the effect would be extremely minimal.

/That, and since microscale is technically

...Well, there goes that "less than sign". As I was saying...

Since microscale is technically less than 1km, many tornadoes fall under this designation as well... any WX-heads who can shed some better light on this?

This just in:

Tornados affected by atmospheric conditions like altitude, humidity and temp.

/DUH

I give you: Sweetwater, Texas. That town has been ravaged time and again by tornadoes. I've witnessed several incredible funnel clouds form right over the town myself.

At the edge of town there's a sheetrock plant that has these massive ovens. The ovens create an upward lift of air. Pretty much a convection current. I think that current draws them to the town.

Contents Under Pressure: "This is not news. There's an area in Ohio...a swath of land with some upslope and the twisters tend to follow it. No one's built on it and there are no trees there."

Actually, that *would* be news to the scientist in TFA. His data suggests the upward slope and peak tend to suffer far less damage than downward slopes. Your local 'tornado alley' would seem to contradict his theory's predictions.

That said, it would be really cool if we could actually engineer our communities to minimize the turbulence that seems to draw tornadoes down; similarly to the way we can engineer cars and planes to minimize turbulent drag. This all makes me wonder if we couldn't engineer and plan windfarms to do double-duty as energy generation -and- as spoilers to direct air-flow in a more desirable manner.

Here in central IL, we have few hills. We do have river valleys though. In my decades of casual observation, towns that are built on the flats receive more tornadoes than towns that are built in valleys or on the bluffs. It has frequently appeared that the tornadoes "hop" when they come to a river valley perpendicularly. I attribue this to winds that blow up or down valleys. Their paths seem to deflect towards and then over valleys before resuming the previous heading when they approach the valleys from an acute angle. I don't think I've ever seen a tornado run "up" a valley.

I've always wondered if big cities deflect can tornadoes by virtue of their "heat bubbles". Cities in the summer being hotter than the surrounding area. I would imagine that it creates a mild pressure center that slows down wind on the windward side and increases wind on the leeward side.

/2 cents

cgraves67: I've always wondered if big cities deflect can tornadoes by virtue of their "heat bubbles". Cities in the summer being hotter than the surrounding area. I would imagine that it creates a mild pressure center that slows down wind on the windward side and increases wind on the leeward side.

Relevant study (new window)

One likely reason I can think of for tornadoes to be more destructive on a downslope is that the vortex gets stretched to stay with the ground, which would tighten the core and increase wind speeds. I'd be interested to know whether there is also a corresponding narrowing of the damage path on downslope portions of tornado paths.

That's just one possible component of this, of course. As has already been mentioned, terrain can also affect the overall wind field, plus other parameters such as moisture. All of these things can play a role in tornado strength.

wxboy: One likely reason I can think of for tornadoes to be more destructive on a downslope is that the vortex gets stretched to stay with the ground, which would tighten the core and increase wind speeds. I'd be interested to know whether there is also a corresponding narrowing of the damage path on downslope portions of tornado paths.

Come to think of it, this core-tightening might apply to the city building situation above. Having the structures cut off inflow from a certain side could cause the whole thing to compensate (believe WellDeadLink touched upon this).

"I thought 'Wow, what's going on here?' " Knupp said. "I continued mapping out the path and the next ridge was Huntsville Mountain. It did the same thing up there. There's a gated neighborhood at the top and there was minimal damage up there. As it went down the slope, it intensified again."

Tornadoes never strike gated communities.

dryknife: Tornadoes never strike gated communities.

"99% of tornadoes fail to hit the richest 1% of communities! #OccupyTornadoAlley"

Water company built a water tower next to my mother house. In tornado country, on top of a hill. If a tornado hits that thing, I hope she has a life preserver.

"that's the finger of the Lord pointing down on diseased spots on the map saying 'why are you farking yo' kin folk?!"

- Joe Rogan

I grew up in a small town with a large mound on the South edge of town and another on the West edge. Tornadoes would time and again reach those mounds and veer off to the side, missing town. The only time it got really bad was when one came right between them and went straight through town. But you know, 90% of the time it works every time!

I experienced an EF-4 on April 27th this year that went right behind my house. I had 6 acres of woods back there completely felled. About 100 yards behind the house is the upslope of a ridge. There was a house behind me a little and to the left that was completely scraped off its foundation, and a house exactly behind mine at the top of the ridge that was dead centered by the tornado that only had 4k of damage. It's amazing to look up there and see all the trees gone on both sides of that house 400 yards away on every side, but the house is fine.

On the downslope of the other side of the ridge, several people were killed.

I got drunk that night.

Since the NWS just texted the shiat outta me (I think I've gotten almost 20 texts in 5 minutes,) about tornado warning for my area, I'm getting a kick...

/ 77006 houston

I just got out of a meeting with my department head about doing my senior research under this guy, so not only am I really getting a kick out of this, but I'm going to show him all of the scientifically relevant theories from this thread.

It's caused by the electromagnetic field that surrounds pink flamingo lawn ornaments adorned with Christmas lights in Spring.

Living in Xenia, Ohio for most of my life, I know a few things about tornadoes. Xenia is at the top of a hill, with the southeast side of town being the crest of the hill, and it sloping downward on the rest of the city. Usually everything on the southeast side that is in the path of the tornadoes are obliterated, and severe damage is done to the rest of the city. With the sole exception of Xenia's biggest trailer park, smack dab in the middle of the north side. Everything around it has been destroyed at one time or another (including the Greene County Fairgrounds, which sits less than a quarter of a mile west), but the trailer park has been untouched every single time.

Aren't most tomatoes were planted by people?

Bunny Deville: I just got out of a meeting with my department head about doing my senior research under this guy, so not only am I really getting a kick out of this, but I'm going to show him all of the scientifically relevant theories from this thread.

I demand credit for mine.

Have heard some 1800's fort in Kansas (?) was built where the indians said there were never any tornadoes.......

And... douchebags

I can sit on my back porch and watch the tornados bounce over my house and down on the other side of the creek. where the nitwits just built the new high school.

Oh, the flaminganity!

Bunny Deville: I just got out of a meeting with my department head about doing my senior research under this guy, so not only am I really getting a kick out of this, but I'm going to show him all of the scientifically relevant theories from this thread.

Tell him to check out the one I mentioned up thread a little. It went over many ridges. The damage was much worse on the downhill sides.

Link (new window)


Google "cherokee valley tornado". It's the valley on the other side of Ringgold. A family of 4 was sucked out of their basement. Most believe it briefly went to EF-5 in that area.

Stayed on the ground 50 miles over ridges the whole way.

Tenga: I experienced an EF-4 on April 27th this year that went right behind my house. I had 6 acres of woods back there completely felled. About 100 yards behind the house is the upslope of a ridge. There was a house behind me a little and to the left that was completely scraped off its foundation, and a house exactly behind mine at the top of the ridge that was dead centered by the tornado that only had 4k of damage. It's amazing to look up there and see all the trees gone on both sides of that house 400 yards away on every side, but the house is fine.

On the downslope of the other side of the ridge, several people were killed.

I got drunk that night.

You don't by chance live in Rabun County, GA do you? They were hit by a monster last spring. I was just up there a few weeks ago and was shocked find an area where the sides of two mountains and a valley were completed devoid of trees for a swath that was at least a mile wide. Many homes had been destroyed or severely damaged. But up on a ridge line, there was a house that seemed untouched.

A tornado will do slightly less damage at the top of a hill than at the bottom. This is due to their wedge shape. The tornado went up the hill, the storm itself doesn't move up, so you end up with more of the funnel touching the ground, meaning a wider tornado. As anyone who has taken high school physics knows, if you increase the radius without changing any other variable, you're going to end up with a smaller force at the edges of the tornado, which is where all the damage occurs.

My really basic theory doesn't take into account that the ridge may upset the updraft (and thus, the downdraft), or if it affects the shear needed to form and maintain a tornado. I'd get a suspicion that it's actually a combination of all of these factors.

/The urban heat island affecting tornados was proven to be bunk when Atlanta/New York were hit with tornados.
//The only thing that protects big cities is their lack of surface area and the rarity of large destructive tornados.

A tornado is more than just the visible funnel. It's an integral part of an organized storm system several miles in diameter, and the general nature of the tornado (size, intensity, direction of movement) is dependent on processes which are storm-scale or larger. Small-scale changes in topography won't change the course of the parent thunderstorm, but anything large enough and sturdy enough to disrupt the wind flow around the tornado (like a hill or a well-built cluster of buildings) can certainly affect its intensity at ground level and possibly cause the end of the funnel to change direction slightly.

The bottom of a tornado is not attached to the ground, and the damage track can be discontinuous even over level ground. The observations in TFA that damage was greater on the downsloping (lee) sides of ridges seems counterintuitive in light of this (what's forcing the funnel to keep contact with the ground?), and in cases where a tornado has crossed over a cliff, there is often a sheltered zone at the base of the cliff where the funnel has skipped over.

Urban heat islands can and do affect thunderstorm formation (increased heat, increased updrafts, increased thunderstorms forming over the city if/when conditions are right), but they don't deflect incoming storms. If anything, since the overall air flow around a heat island is inward to replace the air lost to the updrafts, cities should act as storm magnets, assuming there is any steering effect at all.

/spellcheck doesn't like "counterintuitive"
//or spellcheck

tgambitg: Living in Xenia, Ohio for most of my life, I know a few things about tornadoes. Xenia is at the top of a hill, with the southeast side of town being the crest of the hill, and it sloping downward on the rest of the city. Usually everything on the southeast side that is in the path of the tornadoes are obliterated, and severe damage is done to the rest of the city. With the sole exception of Xenia's biggest trailer park, smack dab in the middle of the north side. Everything around it has been destroyed at one time or another (including the Greene County Fairgrounds, which sits less than a quarter of a mile west), but the trailer park has been untouched every single time.

And parts of your courthouse were found in London, Ohio

/ Things my stepfather used to say to scare the hell outta me so I'd stay inside in the basement and not try to watch tornados
// had about 3 go through good 'ole 43140 that I saw, none of them big or long-lasting; did make for some more interesting hiking behind my buddy's farm.

JackieRabbit: You don't by chance live in Rabun County, GA do you? They were hit by a monster last spring. I was just up there a few weeks ago and was shocked find an area where the sides of two mountains and a valley were completed devoid of trees for a swath that was at least a mile wide. Many homes had been destroyed or severely damaged. But up on a ridge line, there was a house that seemed untouched.

Nope. Bradley County, TN.

I'm about 4 miles north of the Apison, TN portion of this tornado.

Wouldn't some types of locations be more desirable for the construction of expensive homes, and thus less likely to be utilized for low income housing projects, like trailer parks? Just thinking out loud.

Because everyone knows. Land is sexy