Jim Steenburgh Analysis of Salt Lake Inversions

Tony Crocker

Tony Crocker

Administrator
Staff member
The recent Salt Lake weather has made an inviting target, but I've decided to conclude my comments by referring the issue to a professional source that both admin and I respect.


Jim Steenburgh":3i2mfiyk said:
The inversion season is Nov-Feb. Only rarely do we see inversion-like phenomenon in early March. The reason for this is that in March the sun is high enough and the days are long enough that it can quick burn off any cold pools that exist in the valleys. I have seen a couple of weak inversions the first week of march, usually when there is snow on the ground in the valley.

I haven't done much of an analysis of dry spells in the Wasatch. From an average snowfall perspective, things don't change much at Alta from month to month. Some people believe inversions and dry spells are more common in January, but I've never seen a good analysis of this. The conditions that lead to inversions are associated with large-scale upper-level ridges, so inversions tend to be associated with below average snowfall in the mountains.

Although I don't know a good dry spell analysis, I do have access to an analysis of air pollution in the valley by week of year (1 being the first week of January, see attached). This shows very clearly the inversion season from Nov-Feb. It could be argued that bad air quality events are slightly more frequent in January than other periods. I'm not sure if one can say that also indicates more dry spells. January may have more events simply because there is a greater likelihood of snow on the ground then.

Sorry I can't completely answer your question. Even with these dry spells, the Wasatch still probably have the most reliable snowpack and snowfall likelihood in the western US. The best odds for powder anywhere in the world is Hokkaido in January.
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SaltLakeInversions.png
 
There is no "mid-January inversion."

There is, however, an annual mid-January debate in this forum about the existence of said mid-January inversion.
 
as an engineer, i'm down with statistics.......

tony do you have any statistical analysis on hepa filtration masks?? obviously looking for something that filters out PM2.5 and greater..........
 
Tony Crocker":q9qi6zxa said:
And I'll print and frame the post where admin admits the Utah mid-January dry spell is not any more likely than during many other parts of the ski season. Oh, wait, we haven't seen that one yet.
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You haven't seen it because your clouded memory and gross misunderstanding of time series statistics has caused you to significantly altered what he originally wrote and his original premise when you try to make your point. It was like arguing with a box of hammers.
 
Marc_C":1vskybxa said:
Tony Crocker":1vskybxa said:
And I'll print and frame the post where admin admits the Utah mid-January dry spell is not any more likely than during many other parts of the ski season. Oh, wait, we haven't seen that one yet.
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You haven't seen it because your clouded memory and gross misunderstanding of time series statistics has caused you to significantly altered what he originally wrote and his original premise when you try to make your point. It was like arguing with a box of hammers.
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So you believe there's a higher likely hood of a mid January inverson or believe its just as likely during most of the winter?

Sent from my SCH-I545 using Tapatalk
 
Marc_C":w0rjp65g said:
Marc_C":w0rjp65g said:
socal":w0rjp65g said:
So you believe there's a higher likely hood of a mid January inverson or believe its just as likely during most of the winter?
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Read the original thread. No point in rehashing it here.
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Ok
Marc_C":w0rjp65g said:
Us locals are merely saying that the multi-day inversions *tend* to occur and clump *around* 3-7 days into January and *usually* *tend* to change pattern in the last 5-7 days of the month. Yes, that's vague as hell, hence the phrasing "we usually get some dry spells (meaning inversions) in the middle part of the month", with middle being pretty loosely defined. Our local TV news weather readers (only one is actually a meteorologist) say as much.
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and
Marc_C":w0rjp65g said:
And they usually tend to happen mid-January. Sometimes there's an outlier in December or February, but over the past 12 years of direct experience, if there's one time period I don't recommend to visitors, it's from about Jan 5 to Jan 25, or thereabouts. That may or may not be true next season, but it is this year, and last,...
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So given Jim Steenburgh said


From an average snowfall perspective, things don't change much at Alta from month to month. Some people believe inversions and dry spells are more common in January, but I've never seen a good analysis of this.
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I'll just restate my original question to you, "So you believe there's a higher likely hood of a mid January inversion or believe its just as likely during most of the winter?
 
Jim Steenburgh has demonstrated that the peak incidence of Salt Lake inversions runs from Week -2 through Week 4, meaning second half of December and ALL of January. A skier who heeds MarcC's spurious advice and comes to ski Utah on Dec. 26, Jan. 1 or Jan. 25 is as likely to see a dry spell AND and an inversion as if he arrives on Jan. 10 or Jan. 15. Perhaps visitors should avoid the inversion season altogether. Then MarcC and the Utah locals can have Alta's 90+ inches of January snowfall to themselves, no matter when it falls during the month. :lol:

With regard to dry spells during and outside of inversion season, Alta has helpfully provided us with daily data for the past 9 seasons. January averages 15.6 snowless days while March averages 15.1 snowless days.

MarcC":3b5oz7gd said:
gross misunderstanding of time series statistics
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Here are the longest streaks of snowless days during those 2 months:
Jan: 11,10,9,9,8,8,5,5,5,4,4,4,4,4,3
Mar: 12,11,9,9,8,5,5,5,4,4,4,3,3,3,3
 
Tony Crocker":3jow095y said:
Jim Steenburgh has demonstrated that the peak incidence of Salt Lake inversions runs from Week -2 through Week 4, meaning second half of December and ALL of January.
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Uh, no he hasn't. He's demonstrated that peak particulate matter pollution occurs during those timeframes. He has not demonstrated that's the peak for inversions. While inversions do indeed trap particulate matter, they're not the only cause of increased particulate matter levels -- therein lies the danger of taking statistics and making them appear to prove anything that you want them to. Steenburgh himself wrote to you:

Although I don't know a good dry spell analysis, I do have access to an analysis of air pollution in the valley by week of year
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And you continue to inaccurately put word in other people's mouths despite admonitions to cease such behavior:

Tony Crocker":3jow095y said:
A skier who heeds MarcC's spurious advice and comes to ski Utah on Dec. 26, Jan. 1 or Jan. 25 is as likely to see a dry spell AND and an inversion as if he arrives on Jan. 10 or Jan. 15.
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Nowhere did Marc_C offer any such "advice."
 
admin":2dswgn30 said:
Nowhere did Marc_C offer any such "advice."
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:-k
MarcC":2dswgn30 said:
Us locals are merely saying that the multi-day inversions *tend* to occur and clump *around* 3-7 days into January and *usually* *tend* to change pattern in the last 5-7 days of the month.
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Nice to see that perhaps admin no longer believes mid-January is no more likely to see dry spells than the surrounding weeks of inversion season.

I will make a standing bet for any upcoming season that Alta receives at least 45 inches of snow between Jan. 5 and Jan. 25, MarcC's designated "dry period" as quoted above. Any takers?
 
Tony Crocker":6bj8qqex said:
admin":6bj8qqex said:
Nowhere did Marc_C offer any such "advice."
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:-k
MarcC":6bj8qqex said:
Us locals are merely saying that the multi-day inversions *tend* to occur and clump *around* 3-7 days into January and *usually* *tend* to change pattern in the last 5-7 days of the month.
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I'm still waiting to see where Marc_C advised visitors to avoid skiing Utah in mid-January.

Tony Crocker":6bj8qqex said:
Nice to see that perhaps admin no longer believes mid-January is no more likely to see dry spells than the surrounding weeks of inversion season.
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I've neither said nor implied that I've abandoned my point.

Tony Crocker":6bj8qqex said:
I will make a standing bet for any upcoming season that Alta receives at least 45 inches of snow between Jan. 5 and Jan. 25, MarcC's designated "dry period" as quoted above. Any takers?
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For someone who's ostensibly so intelligent, you really do have a hard time grasping this point. Averages mean nothing. If Alta records 50 inches on January 4 and 50 inches on January 29, it still gets 100 inches on the month, the same as if it got a little bit of snow every three days adding up to 100 inches in the month. And what in the world does a single season's data point have to prove?

But as long as you insist upon focusing on a single season, our annual mid-January inversion arrives next week, right on schedule. So, whether or not "Alta receives at least 45 inches of snow between Jan. 5 and Jan. 25" the mid-January inversion will happen anyway, further proving my point that averages mean nothing.
 
Admin":3pakkef6 said:
Tony Crocker":3pakkef6 said:
admin":3pakkef6 said:
Nowhere did Marc_C offer any such "advice."
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:-k
MarcC":3pakkef6 said:
Us locals are merely saying that the multi-day inversions *tend* to occur and clump *around* 3-7 days into January and *usually* *tend* to change pattern in the last 5-7 days of the month.
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I'm still waiting to see where Marc_C advised visitors to avoid skiing Utah in mid-January.
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Here you go

Marc_C":3pakkef6 said:
Sometimes there's an outlier in December or February, but over the past 12 years of direct experience, if there's one time period I don't recommend to visitors, it's from about Jan 5 to Jan 25, or thereabouts. That may or may not be true next season, but it is this year, and last,...
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http://www.firsttracksonline.com/boards/viewtopic.php?f=3&t=10743&p=67836&hilit=inversion#p67837
 
MarcC":xwnmtz1a said:
if there's one time period I don't recommend to visitors, it's from about Jan 5 to Jan 25
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In order to make that recommendation, presumably MarcC believe that expected snowfall is substantially less than most 20 day periods of the season. How much less? Time to put your money where your mouth is.
admin":xwnmtz1a said:
the mid-January inversion will happen anyway, further proving my point that averages mean nothing.
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Just like the New Year's inversion, and the mid-December inversion, right? All of these inversions are equally and relatively frequent. Many years they happen, some years they don't. Similarly, big dumps can happen in mid-December, at New Years or in mid-January, all with modest but similar frequency. Therefore a comment like
MarcC":xwnmtz1a said:
if there's one time period I don't recommend to visitors, it's from about Jan 5 to Jan 25
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is false and misleading, and I'm pleased to see admin not endorsing it.
 
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