hills and tornadoes

Lori Meyer

My brother-in-law is certain that hills and tornadoes are not compatible with one another. He studied meteorology a bit in the air force; however, he does not know what he is talking about. We had lots of fun going back and forth with one another on the subject. The only picture I could find including hills and a tornado was in Alaska and the photo appears to only be a funnel; although, it was reported as a tornado at one point. If anyone has a photo, or knows where one might be, including a tornado in a hilly region, I would be very thankful.
 
I remember many years ago a tornado destroyed a local ski area. This happened at Mohawk Mountain in northern CT, I think sometime back in the eighties. Historically there have been numerous tornadoes in this area, including some very violent ones. In fact I consider the area around the Berkshires, a mountainous area centered in western MA, to be something of a mini-alley. Some tornado track maps I've seen indicate this area gets hit almost as often as many places in the heart of tornado alley (see for example Howard Bluestein's book Tornado Alley, or the map in the April 2004 issue of National Geographic). Clearly, hilly terrain does nothing to suppress tornado formation.
 
Take him along the path of the 05/04/03 tornadoes ... the tornado that crossed near the speedway went down the bluffs on the Kansas side, over the Missouri River, up the river bluffs across from Riverside and up and down some very hilly areas. Johnny Roelands has some good video of the hilly terrain those tornadoes crossed.

The November, 2002 outbreak across Tennessee also occurred in a mountainous area on the east side of the state. Towns like Mossy Grove, TN - that had previously felt totally protected from storms - took a very heavy hit that day, with multiple fatalities. http://www.weather.gov/om/assessments/pdfs/veteran.pdf
 
June 8th 1966 Topeka Kansas. An F5 tornado struck the city, and while doing so, went directly over Burnetts Mound, which, according to the legend, would protect the city from tornadoes.
 
Also lets not forget the F2 tornado that hit Salt Lake City on August 12th, 1999.

And the tornados that hit my county this year on March 12th, crossed several valleys and climd a few hill sides.
 
Mossy Grove is an excellent example. Some other east TN tornado activity was the F1 near Knoxville, TN on April 3 1974 that formed on top of a ridge, dropped into the valley, destroyed a trailer park, and went up the ridge on the opposite side of the valley ( I was on the disaster response team for that event). There was also the east TN outbreak Feb 21, 1993 with several tornadoes that followed ridgelines and dropped into valleys.
Angie
 
As someone who lives in the Ozarks of Arkansas i have also come to several conclusions about this.

I definately think that mtns have the ability to disrupt or even destroy weak tornadoes. Since the majority of tornadoes are weak this can definately explain why some of the mountainous areas of the country seem to have fewer reported tornadoes. (of course this can also be explained by fewer people living in the mountains to report them, but i am not sure this is such a valid argument as used to be since the nws goes out and surveys any areas of reported damage)

I dont think a mtn will make much of a difference for stronger tornadoes (at least initially).

I also think the influence of a mtn or mtn range will affect the whole lower level flow of the storm. I have seen several supercells (not sure if they dropped tornadoes but they were torn warned) that have made their way out of Oklahoma into the mountainous regions of the Ouachita Mtn and they quickly died. Of course the could also be attributed to the climatologically more favorable storm conditions that tend to exist just west into Oklahoma. I have also seen storms that have followed valleys and didnt seem to be affected at all. I used to live in Waldron, AR. Tall east-west mtns (2000-2500) are to the north and to the south stretching about 35 miles west and 20 or so miles east. Most of the time we had severe weather (hail, strong winds) the storms were moving nearly directly from west to east along the path of the valley. And of course there are exceptions with some storms moving through mtns not being affected and some moving through valleys weakening but for the most part i dont think supercellular storms like mtns...especially when they are relatively weak or already weakening.

I also think its possible for mtns to enhance storms and tornado potential. Polk county (Mena) Arkansas seems to have a higher occurance of tornadoes that surrounding counties and Polk county is extremly mountainous.

I am going somewhat off topic now but anyway hope that helps
 
Well I also agree with Brian. In fact when I was on a chase last year (just west of Springfield, Colorado) me and the guys I was chasing with, noted that storms would begin to "spin up" as the passed by a mesa, causeing them to rotate. Below is a picture of a wall cloud that one of the cells produced, as the cell approached the mesa it started to rotate and then once it cleared the mesa the cells rotation weekend and it lost it' wall cloud as well as began to weaken. This was the case for about 3 other cells that followed the same track. (A bit off topic, but the cell just north of us put down a nice big wedge shortly after the wall cloud shown below dissipated.)
Publication3.jpg

(you can see the messa behind the hill that the wall cloud is over)
 
Australia's strongest tornado occurred over very hilly, and heavily forested country. The tornado was rated at least F4, but many believe it was an F5, almost unheard of outside the US.

http://www.psychcentral.com/psypsych/Buladelah_Tornado

The countryside is the eastern slopes of the Dividing Range, the tornado was supposed to have destroyed over 1 million trees. Trees in Buladelah are not small, New South Wales' tallest tree is in Buladelah at around 80m ( 200ft plus ) high. The area is thickly forested with tall timber and rainforest gulleys.

The link below has a picture of the tree and the area - at bery bottom of link page

http://www.mdavid.com.au/trees/bigtrees.html

The area appears to produce a decent supercell or two every year.
 
Hi Lori,

This report may lend some credence to those who believe tornadic circulations are disrupted by “hillyâ€￾ terrain:

THE TORNADO CONTINUED TO ABOUT 1 MILE EAST OF VIOLA WHERE THE DAMAGE PATH THEN BROKE AS IT ENCOUNTERED A STEEP BLUFF...AND THE PATH THEN BECAME MORE SPORADIC.
http://www.crh.noaa.gov/arx/events/aug182005_tors.php

Scroll down to “Viola, Vernon County, WI: 4:05 pm - 4:40 pmâ€￾ for the remainder of the event summary.

While I don’t believe this summary is in any way suggesting this happens often, it would appear that terrain may have disrupted this particular, somewhat weak, tornado.

Pat

PS This was the same system that produced the Stoughton, WI F3 last year.
 
Thank you all for the ammunition. I did mention that weak tornadoes may be disrupted by hilly terrain; however, I have read that strong tornadoes can actually gain strength when entering a valley between hills.
 
Hi Lori,

This report may lend some credence to those who believe tornadic circulations are disrupted by “hillyâ€￾ terrain:

THE TORNADO CONTINUED TO ABOUT 1 MILE EAST OF VIOLA WHERE THE DAMAGE PATH THEN BROKE AS IT ENCOUNTERED A STEEP BLUFF...AND THE PATH THEN BECAME MORE SPORADIC.
http://www.crh.noaa.gov/arx/events/aug182005_tors.php

Scroll down to “Viola, Vernon County, WI: 4:05 pm - 4:40 pmâ€￾ for the remainder of the event summary.

While I don’t believe this summary is in any way suggesting this happens often, it would appear that terrain may have disrupted this particular, somewhat weak, tornado.

Pat

PS This was the same system that produced the Stoughton, WI F3 last year.
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...and most of my neighborhood is located on a hill, didn't seem to do us much good. My mother took this picture of one of the houses:

082005damage12.jpg


In fact, the whole vicinity is rather hilly:

081805I.jpg
 
While the "Viola Tornado" wouldn't be classified as "weak" as it was, probably, a lower end F2, I appreciate your point.

Great discussion question, BTW.

Pat

...and most of my neighborhood is located on a hill, didn't seem to do us much good. My mother took this picture of one of the houses

In fact, the whole vicinity is rather hilly:

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I know the terrain is "hilly", but two separate supercells produced each tornado (I think the cell that produced the Stoughten tornado formed a bit to the SE of the Viola supercell). The circulation that was disrupted didn't cease to exist after the "hill" encounter btw, it may have just been hindered by it.

Pat
 
I think someone mentioned this tornado, but there was one that I think went through a mountainous region in wyoming. I've been searching for a pic of the damage. I saw a pic of the damage once in a book and it was pretty amazing. Anyone know where to find it, I've been googling with no luck.
 
I think someone mentioned this tornado, but there was one that I think went through a mountainous region in wyoming. I've been searching for a pic of the damage. I saw a pic of the damage once in a book and it was pretty amazing. Anyone know where to find it, I've been googling with no luck.
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I believe you are referring to the July 21, 1987 tornado that crossed the Continental Divide in Wyoming and was rated F4...if you have access to any old printed versions of Storm Data, the July '87 issue has a nice write up with lots of pictures and maps. I am sure there are other publications out there with info on this as well, just not sure where or what..

Rob
 
Go on amazon.com and buy the book called "Extreme weather". It has alot of information about weather and extreme weather and has many photos including the f4 that crossed the continental divide. It has alot of usefull information with over 300 pages and is worth the money.

In the book it says, "The f4 tornado moved through the teton wilderness and mowed down many trees some above 10,000 feet in the rocky mountains in whyoming just northeast of moran junction on july 21, 1987. A mile-wide, f4 cut a destructive path for 24 miles and crossed the continental divide at an elevation of 10,170 feet."
 
The November 15th, 1989 Huntsville Alabama tornado (F4) went up and over Monte Sano mountain:

.... From the intersection of Whitesburg Road and Airport Road, the tornado moved up Garth Mountain, as it continued on a northeast course. This took the tornado into a heavily wooded section. As it crossed the top of Garth Mountain and moved down the east side, it struck Jones Valley Elementary School on Garth Road. Thirty-seven children, five teachers, and seven painters were in the school when the tornado struck. The children were part of an Extended Daycare Program conducted at the school. The lead teacher of the day-care program moved the children from the second floor of the school building into a small open area under the stairway on the first floor. This action, first suggested by the school principal as she left for the day, saved the lives of the children.

One woman was killed in an automobile driving along Garth Road en route to the school.

From the school, the tornado crossed Garth Road and moved across a portion of Jones Valley Subdivision, a development of well-constructed single family homes. The tornado severely damaged or destroyed a number of homes in the Jones Valley subdivision. It continued across Jones Valley moving up Monte Sano Mountain. The area from Monte Sano Mountain to the end of the tornado path is rural with only scattered structures. The tornado continued to destroy or severely damage whatever structures it encountered.

The tornado topped Monte Sano Mountain and moved down the east side crossing US 431. It traveled through this valley in the vicinity of Dug Hill before moving up and over Chestnut Knob. From Chestnut Knob the tornado traversed the Flint River valley referred to as Salty Bottoms, crossing the Flint River and US 72 (Lee Highway). It crossed US 72 one mile southeast of Brownsboro.

The tornado continued on an east-northeast track over Reed Mountain to a small lake at the headwaters of the Killingsworth Cove Branch, a small creek which feeds into the Flint River. The tornado path ended at the southeast tip of this small lake.

The total path length was 18.5 miles from the initial beginning on the Redstone Arsenal to it's end at the headwaters of Killingsworth Cove Branch. The damage path was generally about one half mile wide; however, it reached nearly one mile in width in the Flint River/US 72 area. The tornado was classified as an F4 on the Fujita Tornado Scale.
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This also happened in the 1974 outbreak:

Myth: Tornadoes don't go up and down steep or high hills. Fact: A tornado that hit Guin, Ala., stayed on the ground as it climbed the 1,640-foot Monte Sano Mountain and grew in intensity as it descended the northeast slope. The Blue Ridge tornado of that day formed in the mountains at 1,800 feet just east of Mulberry Gap and crossed a 3,000- foot ridge before moving down to the bottom of the canyon. The tornado finally climbed to the 3,300-foot top of Rich Nob before dissipating.

Myth: Tornadoes will not follow terrain into steep valleys. Fact: The tornado that wiped out three schools in Monticello, Ind., descended a 60-foot bluff over the Tippecanoe River as it moved out of the town and damaged homes at its base.
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I know of numerous mountain strikes. Your Brother-In-Law is most definately wrong.
 
I know of numerous mountain strikes. Your Brother-In-Law is most definately wrong.
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Wrong, 100% of the time? I'll grant, maybe, 99%.

See my earlier post. Probably just a rare situation, but the damage path did seem to be disrupted to some degree. Of course one could argue that this would have happened in any event; but a nearly vertical hill does create some wonder as to why the disruption happened at precisely the moment the circulation encountered the hill. Something to ponder, which was the point of my earlier post!

Most people know tornadoes have moved over hills before without any, noticable change of intensity; but do they always perform this feat without disruption? That's probably the real question.

Pat
 
What's more, hills obscure low-level surface features and therefore, from a statistical point of view, will have a lower amount of people witnessing the tornado. Less construction in mountainous and hilly terrain (often due to the expense of construction in such areas) means less people to witness the destruction.

Furthermore, radar, which provides a fair number of warnings, only operates in line-of-site, meaning that the hillier the terrain, the less the radar can "observe" what's happening in the lowest levels of a storm. This also leads to bias against reporting of storms in these areas.

I can remember in the early 1990s when I was first chasing, maps of tornado reports followed highways. It's not that the highways begat more tornadoes, only that there were more witnesses along highways and the associated towns on either side.

I can tell you that localized hills can enhance lift, or change wind currents to either enhance or diminish storm-relative features. But by themselves, hills do not offer protection in any traditional sense. Very good discussion :).
 
The November 15th, 1989 Huntsville Alabama tornado (F4) went up and over Monte Sano mountain:
This also happened in the 1974 outbreak:
I know of numerous mountain strikes. Your Brother-In-Law is most definately wrong.
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Those were strong tornadoes from particularly strong storms. I have no doubts that weaker tornadoes are greatly affected by mtns. Also the terrain of the mtn itself will have a lot to do with how it will affect the tornado. I am sure the more rugged the terrain is in terms of elevational difference between mtn-valleys the more negative impacts there will be. We are talking about a mere handfull of known mountain crossing tornadoes. If mtns didnt impact them we should have many more examples of mtn crossing tornadoes. I think that somewhat comfirms the theory that on average only the more intense tornadoes would be successfull in crossing mountainous areas. I would be interested to know if during any of the storm and tornado modeling that has been done - what were the effects of rough terrain on the results (if that was tested).

10-20 years ago i would buy the "theres no one out there to report one" but these days with all the outdoor enthusiasts and even storm chasers/spotters i dont buy it. I also wonder how different each of our ideas of what a mtn or hill is.
 
Living in east TN most of my life, I observed many systems get disrupted by the Cumberland Mountains as they moved east out of middle TN. The Cumberlands are barely 3000 feet high, so there is something about topography disrupting lower level flow. However, the rare system that survived the trip over the mountains, would at least maintain it's strength, if not take advantage of the orographic lift (the 1993 outbreak and the 2002 events I mentioned in my previous post are examples). I would say that 90% of the time, the Cumberlands would disrupt the system to the point that while middle TN would get severe storms and/or tornadoes, the most east TN would get would be just garden variety storms or rain.
Angie
 
Living in east TN most of my life, I observed many systems get disrupted by the Cumberland Mountains as they moved east out of middle TN. The Cumberlands are barely 3000 feet high, so there is something about topography disrupting lower level flow. However, the rare system that survived the trip over the mountains, would at least maintain it's strength, if not take advantage of the orographic lift (the 1993 outbreak and the 2002 events I mentioned in my previous post are examples). I would say that 90% of the time, the Cumberlands would disrupt the system to the point that while middle TN would get severe storms and/or tornadoes, the most east TN would get would be just garden variety storms or rain.
Angie
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You are about right...it would all depend on the dynamics of the storm system. Whether they could overcome the terrain or not. I have witnessed on many occasions in the Lower Mississippi Valley/Gulf Coast Region of tornadoes forming and then going up hills and discipating. I have also witnessed the more powerful tornadoes just ride up the mtns and go down the other side and continue to "eat" everything standing.
 
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