hills and tornadoes

[Pat Lawrence]

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:

[/b]

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

 

[Robert Edmonds]

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.

 

[Rob Satkus]

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.
[/b]

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

 

[MatthewCarman]

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."

 

[Chris Sokol]

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.
[/b]

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.
[/b]

I know of numerous mountain strikes. Your Brother-In-Law is most definately wrong.

 

[Pat Lawrence]

I know of numerous mountain strikes. Your Brother-In-Law is most definately wrong.
[/b]

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

 

[Jason Persoff]

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 .

 

[Brian Emfinger]

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.
[/b]

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.

 

[Angie Norris]

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

 

[Brett Adair]

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
[/b]

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.

 

[Kevin Myatt]

mid-April 1996, an F4 tornado kills half a dozen and stays on the ground for 30 miles of extremely rugged terrain in Stone and Izard Counties, Arkansas ... there is some video I've seen of the tornado literally blowing on top of and down 1,000-foot ridges ... I walked amid the ruins of homes flattened deep in river valleys between steep ridges ...

 

[Jason Persoff]

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.
[/b]

I think your point is good: being originally from Denver, I note that my friends in Jacksonville FL consider a mountain any natural hill that allows you to see above the tree line (LOL); my standards are a touch more stringent .

As for the former comment, post-hoc storm analysis only takes place when damage is reported. Storms occuring over very hilly terrain do not register similarly to those on the Plains unless a Doppler radar station is nearby. No matter how many outdoorsmen (outdoorspeople?) there are, statistically there is still a lower probability of reporting in that area. My point wasn't that there isn't an increase in reporting in these areas (cell phones are now nearly ubiquitous even in areas I am shocked to find a signal), and so I concur that reporting in these areas is much improved. Still I would posit that the actual events that occur are more numerous than reports available.

 

[Khristian Snyder]

I have a really good one:

Says its the highest elevation tornado in the US

Occured in the Sierra Nevada here in California:

http://tornado.sfsu.edu/RockwellPassTornado/index.html

 

[Steve_Stuck]

I have a really good one:

Says its the highest elevation tornado in the US

Occured in the Sierra Nevada here in California:

http://tornado.sfsu.edu/RockwellPassTornado/index.html

[/b]

This has been posted already, but is a great example. I think they estimated the touchdown at 12,000 feet

 

[StephenLevine]

On June 2nd, I believe it was in 1999, a significant tornado hit Mt. Washington, a hilly bluff overlooking downtown Pittsburgh PA and the 3 Rivers.
It did significant damage to homes and trees in the area.
Photos of the storm revealed a stovepipe- type structure approaching the mountain from the West.