an interesting (maybe stupid) question

Laura Good Buffalo

Yes, I'm a newbie, so bear with me....
I have noticed that often storms develop just west of us, and then consistently go either just north or just south of us,within 15mi either direction. anyone know what would cause this effect? :?
 
To be quite honest - chance.

There's no poof that rivers, streams, lakes, or buildings deter tornadoes or storms. Being as no mountains exist in NE, that covers any topographical anomolies. I'd say you've just been getting lucky (or unlucky, depending on your opinion :wink: )
 
To be quite honest - chance.

There's no poof that rivers, streams, lakes, or buildings deter tornadoes or storms. Being as no mountains exist in NE, that covers any topographical anomolies. I'd say you've just been getting lucky (or unlucky, depending on your opinion :wink: )


Unless you live in Norman Oklahoma......
 
I've heard some that have hypothesized the urban heat-island affect can slightly deflect storms, but do I believe it? Hell no! Tornadoes/storms propagate through the "atmosphere." Which means the "atmosphere" governs where the storms go - not concrete jungles...

Regards -
 
Well, the thing is that urban heat rises and alters the local atmosphere. In some cases, such as Atlanta, the heat island provides an area of improved lift in a generally moist summer environment, increasing frequency of airmass storms east of the city.

Here in Phoenix, the drier conditions create a heat island that's locally enhanced cap, effectively killing some--not all--storms that attempt to enter the city. Some storms that attempt to enter Phoenix off higher terrain to the E and N simply lose relative humidity to terrain and perish, but many are moving on the same altitudinal plane. These storms are often riding their outflow pool. When they reach the interior city, they peter out, but the outflow travels through the city and, when it emerges on the other side, generates new storms.

On upcoming days when the monsoon puts AZ in a SLGHT RISK, check the SPC Mesoscale Analysis page: you can often see the higher CIN over the PHX area.
 
To address Laura's question, since Chadron has no heat island to contend with, I'd guess it's the Pine Ridge that may have an effect, but I can't imagine it would consistently alter stormtracks in that area. If anything it would seem to be a good lift enhancer for the area.
 
Joe, I'd attribute the Salt River Valley's (Phoenix met area) relative lack of precipitation to lower elevation, i.e. orographic descent, rather than lack of moisture. If anything, the urban area is more humid than the outlying deserts due to cultivation and open water.
 
I suppose I could see possibly a very large metropolis affecting the local environment just enough to slightly weaken thunderstorms. I guess when I think of local affects on convection, I'm looking at it at a standpoint of (can the urban heat-island affect weaken deep convection?). In my opinion, no - because deep convection feeds off of mid-level and upper-level energy, as well as a broad low-level inflow layer. I wouldn't think the "average" urban area would be large enough to cause enough fluctuation at either layer to disrupt the maintenance of convection. If what we're talking about here are weak, air-mass thundershowers, then okay, maybe I'd understand that...

Regards -
 
:( It sounds just like the same situation that I have here in Goehner NE.
I call it the "Boil of Bordom" Its a invisible bubble that surrounds some areas that chasers live and keeps all interesting weather away from them.
I am thinking about having an exorist (spelling?) come in and get rid of it.

Dennis
 
I have so many times seen storms here at the head of Lake Superior "split"....they come across the state and then when they hit the lake area, they either split around Duluth (head of the lake) or just completely fall apart. Lake Superior causes it's own unique weather patterns.

i.e. Yesterday's heat away from Lake Superior was in the mid 90's-100F. Right at the lake it was upper 60's. But then finally a strong SW wind got the heat down to the shore and pushed the "lake air" over the lake. In one hour, the temps when from 71 to 96F!! I kid you not.

But later in the year after the lake warms up a bit, storms will actually intensify over the lake because the added warm moist air. But the first half of the summer, Lake Superior is a real storm killer.
 
heres a theory. Imagine over a 2 month period, the law of averages takes storm paths from 15 miles north (15 miles being the number she gave) and from 15 miles south of Chadron, in about 2 mile intervals. So if you were to keep track on a map of these storm tracks, at the end of the 2 month period, you would have 8 tracks north of town, and 8 tracks south of town, and only 1 going through Chadron, as the town is only 1.5 miles wide. Now, in her head, she has just seen 17 storms go through the immediate area, but only 1 of them has directly hit the town. I can see where that may make someone think the town deters storms, when in reality, it had been hit with a storm, at the same frequency that any other 2 mile wide parcel in the surrounding area has been hit. Now obviously it will not be this cut and dry, but you get the idea.

Thoughts???

Doug Raflik
[email protected]
]http://www.wxnut.net[/u]
 
I've also noticed that there's an area in the northeast suburbs of Dallas, in Eastern Collin County and Northeastern Dallas County, roughly along and east of US 75, that gets spared every time a heavy rain event strikes the Dallas Metroplex. During the 5 years I was living there, I hardly ever heard a tornado siren or remember a tornado warning being issued (that could be though because I didn't have Internet or TV for much of those 5 years).

Another area that has been devoid of supercellular activity, at least during the last couple of years, has been Texas County and Cimarron County in the Oklahoma Panhandle. There was action there during the 80's and 90's, but so far not yet in this century.

Just some observations. And maybe it's just me.
 
I have noticed that. . . <snip> . . .what would cause this effect? :?

Hi Laura, from a fellow newbie Nebraskan!

I've snipped your question, because it highlights a potential problem. You have made an observation (informally, I'm guessing - over how long a period of time?) and based on that observation you have decided that there must be an "effect" or mechanism at work. There may be, but there are several assumptions at work in your question:

1) Your observations are valid
2) Your observations have been made over a statistically significant period of time.
3) What you are observing is driven by a single mechanism (effect) or particular combination of mechanisms.

Oftentimes, we can take an observation and turn it into a hypothesis that we then evaluate with confirmation bias (we give more weight to evidence that supports our hypothesis and devalue evidence that would tend to disprove it). Even scientists need to be on guard against allowing confirmation bias to creep into their research.

This sort of confirmation bias has led people into thinking that their particular town or area was immune to tornadoes (for instance:
"Sometimes even local legends can contribute to a perception of invincibility:

EXAMPLE: Tornado, Waco, Texas, May 15, 1953. An Indian legend held that the area was immune to tornadoes. This was even printed in a pamphlet by the Chamber of Commerce (Moore, 1958:3)."
--from Disaster Response, Chapter 2 (The Apathy Problem).


So the question might better be: Is there an effect or is it possible that I'm not using enough observations (data points) to show that there isn't any statistical effect?

Darren Addy
Kearney, NE
 
Thanx for your input, Darren. as for your questions- I have lived here almost eight years, and we have had one strong storm hit town. one tornado, probably F0 or F1, about 7 mi n. of town. at least 3 fairly strong storms have hit the state park, 8 mi s of town, this year, with two tornados hitting that area since I have lived here. storms also consistently hit the slim buttes/ Oglala S.D. area, with one f3 in 1999. this is from 15 mi ( slim buttes) to 30 mi n of us (Oglala). the 1999 storm also produced tornadoes in grass creek and Kyle on the rez. and then there was the storm early this month. it was really great to watch it develop just north of us but we got nothing out of it .I believe there was a tornado around Potato creek. another thing I have noticed is that storms consistently start building just east of us, with frequent watches and warnings in Sheridan co (Rushville) and Cherry co (Valentine). Valentine seems to get hit pretty consistently. curious about that one, too?? :wink:
 
Lake Michigan seems to have an effect on storms in Wisconsin. I live 3 miles west of Lake Michigan. When the lake is cool (water temps 40s and 50s) in the spring, storms do weaken and/or die when they approach the lake. Later in summer though, (July, August, early September), when the lake temperature reaches the low to mid 70s, storms don't weaken. It always ruins my parade to see a strong supercell move at me all the way across Wisconsin, and then die right as it enters my county. Granted, when I have the opportunity, I do drive west to intercept any decent storms before they have the chance to die.
 
Lake Michigan seems to have an effect on storms in Wisconsin. I live 3 miles west of Lake Michigan. When the lake is cool (water temps 40s and 50s) in the spring, storms do weaken and/or die when they approach the lake. Later in summer though, (July, August, early September), when the lake temperature reaches the low to mid 70s, storms don't weaken. It always ruins my parade to see a strong supercell move at me all the way across Wisconsin, and then die right as it enters my county. Granted, when I have the opportunity, I do drive west to intercept any decent storms before they have the chance to die.

Oh....I relate to the "ruin the parade" syndrome! It happens so much here too!
 
The "town" becomes an arbitrary point of reference which is given greater importance than any other point on the map. For example, if Chadron had been built where the State Park is, would you be wondering right now: "I wonder what is so strange about that area 8 miles north? I notice that storms always seem to go north or south of it?" Doubtful that it would even be noticed (or significant enough to you that you would consider some effect as the cause).

The surrounding area is probably filled with areas that you could say a similar thing about, except that we don't notice them because there is no town there.

I'll leave it to others more expert to decide whether 8 years is a statistically adequate period of time for conclusions to be drawn. Also, not sure about the Chadron area, but Nebraska -in general- is going into Drought Year 6. We had some relief in May/June of this year, but we may still be in what is considered a drought. If that was true for your area, then it would mean that 75% of your observation period has been characterized by fewer percipitation events than normal, which could partially explain why Chadron hasn't had a direct hit. If fewer bullets are flying then it is easier to be missed!

Darren Addy
Kearney, NE
 
yes I must admit I didn't take the drought into consideration. and like you , with the exception of this may/june, we definitely have been in a drought. it sure would be nice to get a few more hits, though :?
 
and Darren, I've been meaning to get on StormWiki. I've got some pretty cool pics of some of the storms that have passed us up. that's the one good thing about them going around, I get really great 15-25 mi shots of developing cells. will work on getting on soon.
 
Aahhh, Lake Michigan. It's southern tip has been responsible for many urban/small stream floods in recent years. It starts out has a hot heavily capped summer day. By evening, a weak cold front, outflow boundary, or some other kind of cap buster moves down across the IL/WI border, turning winds from the east just ahead of it. It's clear blue sky to BOOM! as the atmosphere immediately goes nuclear in the course of what seems like just a few moments. Within minutes there is a line or train of SLOW-MOVING, constantly backbuilding thunderstorms from just north of Chicago, west/southwest to the Quad Cities. It is awesome to watch this happen. I've seen blinding rain, and strobbing lightning for six sustained hours from one of these events.
 
Joe, I'd attribute the Salt River Valley's (Phoenix met area) relative lack of precipitation to lower elevation, i.e. orographic descent, rather than lack of moisture. If anything, the urban area is more humid than the outlying deserts due to cultivation and open water.

Well, this makes sense, and as I mentioned certainly the storms coming off high terrain N and E are susceptible to this scenario, but many storms moving across the desert floor also peter out at the urban edge.

One thing that I didn't consider before was the apparently decreasing number of storms within city limits. When I was growing up here, the active monsoon seasons saw many storms in inner PHX. Having been gone 9 summers and back for the last 2, I saw a dramatic reduction in storm number in PHX, but I realized that may be more a drought factor than of the heat island.

I agree the urban area is more humid, but i think that the humidity in combination with heat-storing concrete disallows nocturnal cooling and thus perpetuates local heat. How high this heat goes I do not know, but without cooler air aloft you can't have lift, and this seems to be the problem.
 
Doug & Darren, way to think scientifically. Indeed the discussion should have started with such a post. Perception followed by analysis.

Not that spontaneous unresearched theories aren't also fun :)
 
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