Coming up with an objective way to rank chase days/seasons

Discussion in 'Advanced weather & chasing' started by Dan Robinson, Mar 20, 2018.

  1. Dan Robinson

    Dan Robinson WxLibrary Editor
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    I've had this in a notes file for a while as something to try and develop, and wanted to toss it out for some discussion. I thought it might be interesting to come up with an objective way to rank chase events - a sort of "QI" or "quality index" that we might be able to use in analogs and rankings of better meteorological setups.

    The main factors I used are:

    - PTs (Primary Target areas): Number of target areas that the majority of chasers were positioned in.
    - DPHTs, PTs: Daytime photogenic tornadoes in all primary target areas
    - DPHTs, STs: Daytime photogenic tornadoes in all secondary target areas (smaller percentage of chasers)
    - PTs with tornadoes (photogenic or not)
    - PTs with good lightning
    - Minutes DPHTs: the greatest total time (in minutes) that daytime photogenic tornadoes were in progress out of all storms
    - Minutes Structure: the greatest total time (in minutes) that remarkable storm structure was present out of all storms
    - Storm speed in knots

    I tried to come up with a formula that would somewhat match what we'd mostly agree on as being better events. What I did is take all of those factors above, give them each a multiplier that reflects their relative weight in determining the quality of a chase day (daytime photogenic tornadoes being the biggest one), then dividing it by the number of target areas. The spreadsheet formula is as follows:

    =ROUNDUP((((D2*150)+(G2)+(E2*30)+(F2*15)+(H2)*(60-J2)+(I2/30)*(60-J2))/C2)/100)

    C = PTs
    D = DPHTs, PTs
    E = DPHTs, STs
    F = PTs with tornadoes
    G = PTs with good lightning
    H = Minutes DPHTs
    I = Minutes Structure
    J = Storm Speed

    This image is a screencap of the formula in action for a selection of events. Some of the time figures may be a little off, I just entered my best estimate.

    quality2.jpg

    Anything 3 and up should be something we'd all agree is a good event, anything over 10 should be exceptional.

    For months or seasons, a possible ranking could simply be the sum of QIs from all chase events.
     
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    #1 Dan Robinson, Mar 20, 2018
    Last edited: Mar 20, 2018
  2. John Moore

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    I'm not sure how to do it in a formula, but I think 5/25/16 should have come out higher. I was at the 5/24 and the 5/25 event, and many of us thought the 5/25 was a best of career storm, or close to it. 5/24 was amazing in the quantity of TOR's and the number of simultaneous ones, but 5/25 had stunning structure, was very photogenic with good lighting, and ambled along leisurely for a very long time.
     
  3. Dan Robinson

    Dan Robinson WxLibrary Editor
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    The only reason that date didn't rank higher is because there were two targets that day, and only one of them produced a photogenic tornado before dark. This formula considers all primary chase targets of a day together instead of just one storm. The other target attracted close to half of chasers, and since it busted, brought down the score for that day.

    A storm-level ranking that takes into account total photogenic tornadoes, total time that photogenic tornadoes were in progress and storm speed would probably place 5/25/16 in the top 5.

    The formula for single storms using the same variables should be:

    =ROUNDUP((((D2*150)+(G2)+(F2*15)+(H2)*(60-J2)+(I2/30)*(60-J2)))/100)
     
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  4. Michael Snyder

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    5/25 was nice, but I'll disagree massively on it being the better day vs Dodge City, the hand-offs, the 3+ photogenic tornadoes, the multiple tornadoes down at the same time.
     
  5. Dan Robinson

    Dan Robinson WxLibrary Editor
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    Here is the storm-level formula applied (we'll call it QI-S) - 5/25/16 places 3rd with this method:

    quality-s.jpg

    Again, 3 and up is good, 10 and up is exceptional.

    Spreadsheet formula is as follows for anyone who wants to play around with it:

    =ROUNDUP((((C2*150)+(E2)+(D2*15)+(F2)*(60-H2)+(G2/30)*(60-H2)))/100)

    Total number of tornadoes overall (photogenic and non-photogenic) is probably a factor that should be included (that would raise Leoti's score for example) but I'll tackle that some other time.
     
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  6. Jeff Duda

    Jeff Duda Resident meteorological expert
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    This is a good idea and it appears to be unmasking some good results, but just keep in mind that there is still substantial subjectivity in it, especially with what is regarded as a "photogenic" tornado or storm structure. Also, are you using the average forward speed of only the photogenic storms, of all storms in the primary target area(s), of only tornadic storms whether they were photogenic or not, or something else?

    As long as your classifications can be defended well, I say this is as good a measure of a chase quality as any. But as with everything in life, your mileage may vary - some people will have career days with events rated QI 5 and under, whereas many people (like me) will find ways to screw up a QI 25+ type event and therefore won't think much of the day in retrospect.

    Also, someone is going to have to maintain this database. I take it you will handle that, Dan.
     
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  7. JF Massicotte

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    Chasing will always be somewhat subjective. I like how he tries to account for the success likelihood into his index. However, one improvement that could be made is add a measure of how predictable the PT is. For example, Bennington had one primary target, but the forecast confidence wasn't too high, so a chaser living in OKC will likely not take a PTO for that day. That's different for chaser on a chasecation with nothing else to do than to try that one PT.

    Adding a factor for the primary target predictability or confidence could adjust the scale a little bit. I know it would just add subjectivity, but I think it is relevant in our case here.
     
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  8. Dan Robinson

    Dan Robinson WxLibrary Editor
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    Here are some ideas for definitions and refining the index, along with suggested multipliers and factor values. These multipliers and factors will take some finessing to make this work, these are just preliminary.

    Primary targets: traditionally evident targets where the majority of chasers ended up. Including but not limited to dryline bulges, warm fronts, triple points, outflow boundaries, boundary intersections etc. There can be multiple primary targets in a single setup (common during big outbreaks)

    Secondary target: non-traditional target areas such as cold-core, DVCZ, upslope or Midwest warm/stationary front storms where only a few chasers deliberately target. Note that these types of targets can become primary if the traditional target areas are too marginal or not present.

    Daytime photogenic tornado: a relatively complete tornado structure consisting of a funnel and/or debris from ground to cloud base, clearly visible for at least 180 degrees surrounding the tornado.

    Good structure: well-developed and symmetric supercell structure, including high-contrast striations, banding and inflow tails.

    Good terrain: flat with few trees or hills (western Kansas)

    Mixed terrain: mostly flat with few trees and hills (eastern Kansas)

    Poor terrain: mostly trees and/or hills, few views (eastern Oklahoma)

    Event-Level QI Formula (QI-E):

    1.) Start with Speed multiplier (greater for slower-moving storms) = 60 minus the storm speed in knots

    2.) Go through the following for all primary targets total:

    Count of all daytime photogenic tornadoes, x 150
    Total time in minutes that photogenic tornadoes were visible from a reasonable chase position x (speed multiplier)
    Total time in minutes that good storm structure was visible from a reasonable chase position, divided by 60, then x (speed multiplier)
    Count of tornadoes visible from typical chase positions x 15
    Tornadoes only visible in HP notch x 5
    Good lightning = 15 (no multiplier)
    Terrain factor (no multiplier):
    --Happened in good terrain = 50
    --Happened in mixed terrain = 0
    --Happened in poor terrain = -50
    Road factor (no multiplier):
    --1-mile grid, mostly gravel or paved = 50
    --2-mile grid or less, few paved = 0
    --No grid, few to no paved secondaries = -50
    Forecastability (no multiplier):
    --Synoptically evident days in advance = 50
    --Evident in morning-of data = 0
    --Not evident until less than 3 hours prior to start = -50
    Rare feature factors:
    --Number of instances of multiple simultaneous tornadoes x 40
    --Number of instances of tornadoes directly sunlit x 30
    --Number of instances of audible roar x 30
    Negative factors:
    Problematic chaser traffic = -100
    Number of tornadoes that caused significant damage x -70
    Number of tornadoes that caused fatalities x -200

    3.) Redo the above for secondary targets, then divide the secondary target sum by 3.

    4.) Add primary and secondary target total, then divide this by the number of primary targets.

    5.) Divide this by 100 for the final QI.

    Storm Level QI formula (QI-S):

    Sum of the primary target portion of the formula above, divided by 100.

    I'm leaving out storm mode and supercell type, since it can be assumed most by-definition photogenic tornadoes are going to be with classic supercells. Lower-visibility tornadoes in HPs are already accommodated in the above formula.
     
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    #8 Dan Robinson, Mar 21, 2018
    Last edited: Mar 21, 2018
  9. JeremyS

    JeremyS EF2

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    Hey Dan- Any consideration to the tornado outbreak in southern Minnesota 6/17/10? First day I ever saw a tornado and I believe I saw 6 that day. All visible tornadoes of all shapes and sizes. I saw tornadoes for almost 3 hours straight pretty much!
     
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  10. Drew T

    Drew T EF4

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    I think that's where subjectivity comes into play. Seeing a single tornado on the ground for an hour and a half IMO is a once in a chase career thing, but we see storms drop multiple tornadoes every 5-10 years or so. Maybe not to the extent of DDC, but having missed both, I would have much rather seen Chapman than DDC. I personally thought that was much more impressive from a duration and being able to maintain that type of strength for that long. I don't know if I'll ever have another shot at a Chapman. I think I'll have a much more likely chance seeing a DDC type storm again. Just my opinion, but again, that's where subjectivity comes into play.
     
  11. Dan Robinson

    Dan Robinson WxLibrary Editor
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    This weekend I'll make a web page with a javascript calculator that everyone can play with - both by manipulating the different multipliers and factors and entering data for chase events.

    I didn't chase this event, but it should definitely rank high based on what I know about it. To rank the event and each storm, I would need:

    Total daytime photogenic tornadoes.
    Total tornadoes that were visible to chasers.
    Total time that photogenic tornadoes were visible to chasers.
    Was the lightning good (frequent/close/photogenic)?
    Was structure good? How long did it last?
    Storm speed in knots.
    Terrain (good, mixed or poor)
    Road network quality
    How evident was the forecast?
    Did the tornadoes cause significant damage, injuries or deaths?
    Were there any rare features (two or more tornadoes at once, horizontal vortices, sunlit tornadoes, audible roars)?
     
  12. Dan Robinson

    Dan Robinson WxLibrary Editor
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    I did some more work on the QI-S formula this afternoon using some of the expanded metrics. Here is the spreadsheet formula, Ill call this version 2:

    =ROUNDUP(((C2*150)+(J2*50)+(K2*50)+(L2*50)+(M2*30)+(N2*30)+(O2*30)+(P2*-75)+(Q2*-75)+(R2*-150)+(S2*-500)+(D2*15)+(H2*30)+(I2*5)+(E2)*(60-G2)+(F2/30)*(60-G2))/100)

    And the results of this second-run analysis:

    qi-s.jpg

    I created a javascript calculator on my web site where you can play around with the different factors and multipliers used in the formula that control how much weight each metric has in determining the final QI:

    http://stormhighway.com/qi.php

    You can also download the OpenOffice spreadsheet file here:

    http://stormhighway.com/qi/quality-storms.ods

    I'm finding it tricky to deal with the human impact metrics. I think the QI should take a big hit for events that cause deaths, injuries and damage, but working that out here hasn't been very easy as you can see.

    My thoughts at this stage are to raise the various multipliers so that the top-end events like Dodge City approach 100, which would give some of the lesser events some room to avoid being knocked below zero by negative factors.

    If any of you would like to do some experimenting with the numbers and let me know your thoughts, it would be helpful!
     
    #12 Dan Robinson, Mar 26, 2018
    Last edited: Mar 26, 2018
  13. Dan Robinson

    Dan Robinson WxLibrary Editor
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    After some further adjusting today, I am making these changes:

    - Increased the weight of photogenic tornadoes, tornadoes, lightning and rare features.
    - Added "historic" metric for a record-breaking event or remarkably rare tornado(es) configuration
    - Added an anticyclonic tornado metric
    - Added a "major disaster" metric, defined as a tornado that destroys more than 1/3 of a town and/or causes more than 10 deaths.
    - Added a final result called "QI-S base" that shows what the result would have been absent human impact factors.

    Here is a screenshot of the spreadsheet output with these changes (I'll call this v3):

    qi-s-v3.png

    I'll update the web page and calculator later today.
     
  14. Dan Robinson

    Dan Robinson WxLibrary Editor
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  15. Warren Faidley

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    Interesting index. Where do you get all that time for such fun? I've always based the quality of severe events strictly by the photographic / video opportunities, but that's likely because of my photography background. Campo would rate a solid ten, although I was not there. Had Campo been shot in the early 1980's (producing a good transparency), it would have been close to a 500k + income tornado over the next 20 years. It was an obvious forecast if you were in the region and the road was perfect. It remained on the ground long enough to capture with good contrast. I guess the index depends on the reason behind being there, to just witness a tornado or have serious designs on filming it.
     
  16. samuel stone

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    Personally i love this, i've always tried to do similar things myself with much less success. Being primarily a Kansas chaser, I also love seeing so many amazing Kansas days which I've chased in the index, all the way from Harper and Mulvane 2004 to Chapman 2016!!
     
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  17. Dan Robinson

    Dan Robinson WxLibrary Editor
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    I ran June 17, 2010 and June 4, 2015 through the calculator, though since I did not chase either of those, I had to estimate many of the metrics from chase reports I saw online. If anyone is more familiar with those days and could enter the data to the best of your memory here, that would be helpful:

    http://stormhighway.com/qi.php

    The June 17, 2010 QI-S came out to 49. Simla's came out to 78, handily beating out Dodge City for the #1 spot. I would really like to get some confirmation on that day's metrics though instead of using estimates. I used the following specs for the Simla day:

    6 photogenic tornadoes
    15 total visible tornadoes
    1 anticyclonic
    90 minutes of photogenic tornadoes
    120 minutes of good structure

    Also, if any chase vets know of days prior to 2000 that have a shot at making the top 10, please let me know!
     
  18. JeremyS

    JeremyS EF2

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    My personal experience and somewhat reduced memory from nearly 8 years ago.... I've also attached a pdf from the Minneapolis WFO of the event. I am focused on the southern Minnesota tornadoes.
    http://www.crh.noaa.gov/Image/mpx/StormReports/17June2010.pdf

    This file lists 25 tornadoes in southern Minnesota all during the late afternoon and evening.
    I see in the PDF, that 24 of the 25 tornadoes were videographed or photographed.
    Shows tornadoes from 345-845pm.
    I do remember a fair amount of lightning and a lot of those were the positive CG strikes.
    Great structure. No issues with rain wrapped tornadoes, etc.
    I remember storm speeds of 20-35 mph.
    Terrain was also fairly good. Not a ton of trees, some hilly farmland, but other than that no real issues.
    Road networks was fine.
    Day 1 had a fairly large moderate risk with a 10% hatched tornado risk. Day 2 outlook for this day was a slight risk with a large 30% outlook.
    Tornadoes did cause some significant damage to farmsteads. There was 1 fatality and a couple of injuries.
    Tornadoes included 1 EF-4 and 3 EF-3's and 3 EF-2's. A couple of instances of 2 tornadoes on the ground at once. I witnessed horizontal vortices on the EF-4 tornado. The EF-4 was on the ground for 45 minutes, a mile wide at times, and threw a car 3200 feet!
     
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  19. JeremyS

    JeremyS EF2

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    I just made a post about the Minnesota tornadoes, not seeing you had made this one a few minutes earlier as I was typing up my reply!
     
  20. Dan Robinson

    Dan Robinson WxLibrary Editor
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    Thanks for the info! The highest tornado count I saw from a chaser was 13 from Roger Hill, so I used that as the max for that southern target. I guessed 5 photogenic tornadoes on that storm based on the photos I saw from Roger's, Skip Talbot's and Jeff Duda's chase logs. That southern target had a base score of 56 when not counting for the fact that the F4 caused a death and injuries.
     
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  21. Dean Baron

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    Dan,

    Just a small detail. Your date for the Dupree storm is wrong. It was on 6/16/10, the day before the big Minnesota outbreak on 6/17/10.
     
  22. Dan Robinson

    Dan Robinson WxLibrary Editor
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    Version 5 updated:

    QI-S = ((DPT*350)+(FL*50)+(H*400)+(TF*50)+(RF*50)+(R*50)+(TRF*-75)+(D*-75)+(I*-150)+(FT*-500)+(MD*-1500)+(L*50)+(T*50)+(HT*5)+(DPTmins*1.1)*(60-speed)+(Smins/30)*(60-speed))/100

    Here are the rankings with the new tweaks and corrections along with a few more events added:

    qi-s-v5.jpg

    http://stormhighway.com/qi.php
     
    #22 Dan Robinson, Mar 29, 2018
    Last edited: Mar 31, 2018
  23. Chad M

    Chad M EF0

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    Where would 5/9/16 rank on the list ?

    Definitely one of the days I regret missing, especially being somewhat close to home.
     
  24. Dan Robinson

    Dan Robinson WxLibrary Editor
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    I added a few more events (including Eads and Katie) to the spreadsheet as well as updating the formula to "version 6" which increases the weight of all of the various factors to spread out the results between roughly 0 and 100:

    qi-s-v6.png

    In this new version, a score of 10 is "good", 20 is "excellent", 30 and up is "exceptional".

    The calculator has also been updated:
    http://stormhighway.com/qi.php
     

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    #24 Dan Robinson, Mar 31, 2018
    Last edited: Mar 31, 2018
  25. JamesCaruso

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    Quincy, thanks for the objective analysis. Nice to see quantified what we all anecdotally know to be true.

    Question though, why do you consider the 5/28 Colorado landspouts event to NOT be a “localized and fairly short-lived event”? Maybe I’m just biased because I missed it, and admittedly I’m not sure how long it lasted (but doubt it was much longer than the WY 5/27 tornado), but wouldn’t you agree 5/27 it was most certainly a fairly localized mesoscale accident?

    Also I think 5/29 in KS/OK is worthy of being included in the list of noteworthy chase days - not great, but at least as good as 5/27and 5/28.
     

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