Urban Heating?

Pete Smith

I often notice (especially this year) that when storms roll through the St. Louis vicinity, they seem to die out, only to refire in southern Illinois.....Has this anything to do with the "Urban Heat Island" effect? If so, why wouldn't the storms strengthen or at least maintain?
 
Examples? Keep in mind if you only look at base reflectivity on radar, storms will often appear to weaken near the radar then restrengthen far away due to the beam height changing.
 
It is TRUE. I have lived in STL almost my whole life and this can be verified.

Want proof? Check this out:

http://www.failedsuccess.com/index.php?/we..._weather_story/

Another oddity is the tornado climatology, our fatal tornadoes are usually in the fall and winter and at night.
Except for the F4 we had May 27, 1896, which was the costliest tornado in US history.

But since the Arch was built, there has not been 1 fatality from a tornado in the City of Saint Louis.

Yes, I know the article is satire. Enjoy.
 
"Has this anything to do with the "Urban Heat Island" effect?"

No, it's the "storms never hit me here in xxx, they always go around and strike yyy." Then you talk to the people in city yyy, and they say they always hit city zzz...
 
Examples? Keep in mind if you only look at base reflectivity on radar, storms will often appear to weaken near the radar then restrengthen far away due to the beam height changing.
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That happens a lot more than we think in areas all over the country. Kinda like rdale said "storms weaken as they move right over _______ because of _________." In Ft.Smith, AR some people think its a anomalous east wind that causes their storms to weaken when in reality its just the storms approaching and moving directly over the radar.
 
I don't really buy the "arch" effect Matt, but storms do seem to grow in western/mid MO only to crap out around St. Louis, only to regenerate once entering Illinois.....To comment on base reflectory: that may be true when it comes to base reflectory, but all too often I experience this here. I'll see a nice cell on radar, then, Poof! its gone. Yeah we get strong storms, but supercells are few and far between.
 
There is a big river running right through Saint Louis that is much colder, this time of year, than it's surroundings. I don't have any evidence, but I wouldn't be surprised if the river creates microscale river breezes that penetrate inland during the afternoon. This could easily kill storms as they approached the city.

Just another theory.
 
I used to live a few miles from the Mississippi in the Quad Cities, and recently moved out about 25 miles to the east in the "country." People around here say that we get more storms than the QC, and to be honest it does seem like we "get it" out here more frequently than the QC. I'm sure it's a coincidence but sort of interesting I guess.
 
Check out the radar this evening, yet again STL is saved by the awesome power of the Arch.
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Yep. Severe warned storms in Pike Cty have withered away to nothing while passing to the north...Im sure they'll refire in Illinois lol. Although the convection to the north does look somewhat tempting, think i'll sit this one out.
 
Stanley Changnon, Jr. of the Illinois State Water Survey
did a lot of research over the years with urban areas
and climate. Some of his research involved studying
Chicago and Saint Louis. Google and search the
AMS archives for more of his work.

Mike
 
Keep in mind that climo generally favors more storms in the southeast U.S. with a decreasing trend as you move north and west of there. One of my former profs wrote an article in BAMS discussing convective weather holes and concluded there were none with the potential exception of Grand Forks, ND (where I just happen to live). This does not take into account potential severe weather holes. Synoptic climo may enhance certain severe variables over one area and limit them elsewhere. Finding holes based on reports alone is tricky is these tend to be focued in populated areas.

I have seen a couple of studies that suggest there is a better chance of rain just downwind from a city than over the city (Atlanta and St. Louis come to mind). I don't know if these were peer reviewed. Keeping with the general theme in the eastern half of the U.S. that climo dictates there are more storms to your south, the results are certainly questionable unless the climo variation can be incorporated in the study (such as looking at obs in all directions).
 
Something somewhat similar happens when I lived in Douglass, KS (20 SE of Wichita). It usually only happened in late May-July during the overnight hours from storms that moved in from E. Colorado/W. Kansas where they started. Most of the time, these storms would start to intensify within a county or two from Wichita and get into Sedgwick County (where Wichita is located), and start to lose their intensity to the point where it is an average to slightly above average storm. The line moves into Butler, Sumner, and Cowley counties (counties E, S, and SE of Sedgwick County, respectively) and will intensify anywhere from near severe to a spotted report of significant winds (70+). Wichita gets as much severe weather as any part of the surrounding area, but during the overnight with a line or bowing out line, this scenario occurs more than a few times.
 
I'll see a nice cell on radar, then, Poof! its gone. Yeah we get strong storms, but supercells are few and far between.
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Going back to what RDale said.. the same can be said for any one location. I'm sure you can just pick any small town, like little Windsor, IL and ask them how often they are hit by a large supercell, and their answer isn't going to be any more frequent than yours.

I dont know if that makes any sense or not. But any ONE stationary location isnt going to be hit by a major storm every time convection occurs in that general area. Its not a storm killing effect, its just the way weather happens! Storms fire, and storms die out. Sometimes they fire back up. But to take any one place and say that it deflects storms doesnt hold much ground.

I feel the same way when people harp on the "NORMAN BUBBLE" Oh nooo, supercells and tornadoes never hit us directly in Norman, OK. Yet, Oklahoma City I believe is the city most frequently hit by tornadoes in the US. In 2004 or 03 (sorry, brain fart) the city was hit by tornadoes on back to back days. Arguably the strongest tornado to date hit OKC in 1999. No, these didnt hit Norman directly, but were mere miles from the city. Just because you don't get a daily dose of extreme weather in your front yard doesnt mean your city repells it.

Something somewhat similar happens when I lived in Douglass, KS (20 SE of Wichita). It usually only happened in late May-July during the overnight hours from storms that moved in from E. Colorado/W. Kansas where they started. Most of the time, these storms would start to intensify within a county or two from Wichita and get into Sedgwick County (where Wichita is located), and start to lose their intensity to the point where it is an average to slightly above average storm. The line moves into Butler, Sumner, and Cowley counties (counties E, S, and SE of Sedgwick County, respectively) and will intensify anywhere from near severe to a spotted report of significant winds (70+). Wichita gets as much severe weather as any part of the surrounding area, but during the overnight with a line or bowing out line, this scenario occurs more than a few times.
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To address this observation.. storms do pulse up and down from severe levels. A storm or storm complex, regardless of form wont always maintain significant severe levels. I dont doubt what you've seen, but I do believe the fact that it happens over a given location is merely a coincidence.
 
You city dwellers think you have it bad! In over 12 years of observing (and chasing) storms in the central Appalachians, I have seen an unmistakeable (maybe even obvious) pattern of storm dissipation due to a set of environmental factors. Storms will die 90% of the time upon approaching the Ohio River and the state of West Virginia. This 'Appalachian zone of dissipation' runs from the Tennessee-Kentucky border up to around Akron-Canton-Pittsburgh. This is no imagined phenomena either - watch it happen anytime.

In observing the storms and talking with local mets, I've come up with the following 'real' (non-imaginary) factors that supress convection as it approaches and crosses the state line from Ohio. Many of these are borderline obvious, but are worth mentioning.

1.) Inflow cutoff/damming - Southerly and easterly flow at and near the surface is physically cut off or suppressed by the high terrain of the Appalachians, which runs along the VA/WV border up through central PA and south along the NC/TN border.

2.) Orographic subsidence - Southerly or easterly flow crossing the mountains encourages sinking motion and downsloping effects (warming and drying, lowering of surface moisture and resultant CAPE). I have seen 'reverse drylines' take shape west of the mountains during strong downsloping. Td drops of 30F+ can be observed between Charleston and Lexington during these events, for example. Unlike CO, our terrain is a curse rather than a blessing - no DCVZ for us over here unfortunately.

3.) Timing/Diurnal effect - Climatology seems to favor storm initiation in Indiana and western Ohio by mid-afternoon in spring and summer, resulting in convection arriving at the border at or after sunset, simply due to timing issues. Loss of daytime heating alone or combined with the other factors results in storms dissipating.

On the rare occasion that storms initiate right on the border, inside of WV, or just into Ohio, storms can maintain their intensity. But most established complexes from the midwest will not make it to the crest of the mountains. Most will have no lightning left by the state line and no precip by the time it reaches the I-79 corridor.
 
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