What criteria do you use to determine a worthy "tornado day"?

Discussion in 'Weather In The News' started by Randall Bragg, Mar 28, 2018.

  1. Randall Bragg

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    http://www.ustornadoes.com/2018/03/27/rethinking-conceptualize-tornado-days/

    Here is an interesting take on chase worthy days when you live hundreds of miles outside tornado alley. Jim Tang is a storm chaser who lives in California, and he gives his system and metrics to show how he determines "tornado days" that are worth the time, effort, and money to hunt down twisters.

    Let me know your opinion after reading his article.
     
  2. Warren Faidley

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    Interesting article. The problem with most outbreaks is that the storms are fast moving > 40 mph and they don't always occur in the best landscapes.

    Since I live in Arizona, I have to plan most chases a day in advance if something worthy develops in a short amount of time.

    Over the years, I've worked out my own "priority" list to make a "deep strike" (500+) mile drive worthy.

    1: Location. Forget anything that is in the deep south or will be moving east of 1-35.
    2: Storm speed forecast.
    3: Storm mode forecast: HP vs. classic vs squall line.
    4: Number of potential chase days in good landscapes.
    5: Monkey wrench factors. Risky forecasts, especially when a missing element is not quite in sync. (RH, timing of lift, veer issues, mega cap, etc).
    6: Cost vs. reward. With the decline of the photography industry, I would be reluctant to devote the time, energy and funds to make a last minute chase unless everything was perfect.
    7: Historical factor. No doubt I would miss a "Super Outbreak" set-up just to be there.
     
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  3. Jeff House

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    Follow up article from US Tornadoes also by Jim Tang http://www.ustornadoes.com/2018/03/30/best-time-year-schedule-storm-chasing-vacation/ When is the best time of year to schedule a storm chasing vacation?

    Using statistical analysis Tang concludes the late May timing we've discussed in other threads and I agree. Late April is good for outbreaks but not really chasing, for reasons Warren notes. June performs better than April for chasers, per tornadoes and concentration of them.

    Tang and US Tornadoes sort out what they call clusters, rather than outbreaks, to capture the more chasable days. Article gives details on criteria. June actually has the most clusters. However filtering for quality, minutes of TOG and predictability, late May takes the crown.

    Note that a flexible chasecation is the best. Submit floating leave and watch the forecast. Some early May sequences have been chasable clusters like 2003 2007 and 2015.

    We have debated on here between May and June. Some of those subjective arguments are valid, like crowds and visibility. Still, the quantitative analysis by US Tornadoes concludes late May.
     
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    #3 Jeff House, Apr 3, 2018
    Last edited: Apr 3, 2018
  4. Randall Bragg

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    Agreed Jeff, and I would add May and late May 2013 in Moore, El Reno, and Shawnee, Oklahoma. I'm confused though; are these dates "clusters" or an "outbreak" based on Tang's parameters? I've chased for decades, as a hobby. I rarely travel outside TX/OK/KS. I'm still a Noob when it comes to the technical details of a qualified chase day.

    I rely on the SPC and the experts to determine my target area, and I try to avoid crowds and the professionals to stay out of their way.
     
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  5. JamesCaruso

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    Jim Tang’s analysis is impressive but I’m having a little trouble following the conclusion. Admittedly I didn’t take the time to really study the “tornado cluster” concept, but how do these two statements from the article reconcile:

    “...if you took a two-week chasecation ending on June 12 every year between 1996 and 2017, and you nailed the biggest tornado cluster every time (good luck!), you would’ve experienced a little over 80 clusters. Or around four per year.”

    “...a two-week chasecation that ends on May 31 has resulted in about 30 big tornado days in the past 22 years. In other words, we should expect 1-2 such events if we chase two weeks in late May, and that’s not counting the smaller events that can also yield an incredible chase.”

    From these two statements, it would seem like June is preferred over May if the criteria is number of events. What is it that makes late May better, is it the quality of the events?


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  6. Quincy Vagell

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    It seems that late May has less "big" events than early June, but has a fairly steady stream of medium to big events, while there is a bit more variability in early June. It seems to be more boom or bust in early June, even though there is still fairly steady activity as well in most years. One might have to consider playing the Midwest a bit more (east of I-29) for an early June chasecation, as tornado probabilities increase across Iowa and southern Minnesota, for example.

    My takeaway (might not be exactly what he's saying) is that if you chase in the last two weeks of May, you'll have more tornado chase opportunities and at least a good probability of one or two higher-end events. On the flip side, if you chase for the first two weeks of June (his period overlaps late May a bit for some reason), you'll probably have a couple/few higher-end events, but there will almost certainly be a few down days as well.

    If one chases in late May, unless it's a horrific year, one would expect to probably only have a small handful of down days with little to no tornado activity. Likewise, chasing in early June, there will probably be more down days in comparison to late May, but the big days will have the potential to be as big, if not bigger than late May.

    Some of my biggest days since 2014 have been in mid-June (My best 3-day stretch was June 16-18, 2014 and last year's June 12th was the highlight of the year), but activity becomes much more hit and miss from mid-June on. Not to mention that bigger events become much less common as one heads into late June and beyond. They do happen, but they don't occur every year.

    Early May is an odd period as well. His data suggests there is a secondary (really third) peak over the first 7-10 days of May. There are higher-end events mixed in with some dull periods (most notably 2011). I've had mixed success in early May, but if you look at tornado counts over the past 10-15 years, you'll notice that it's fairly common to see a 3-5 day stretch (or longer) with little to no tornado activity.

    In a perfect world, if one wanted to play the odds and had a full month to take off for storm chasing, I guess you could argue for the first week in May, then the last two weeks in May, spilling over into the first two weeks of June. If one took off the entire month of May, there would probably be a lot of variability and one would almost certainly miss out on some big events in early June.

    My favorite part of June is that tornado activity shifts northward, so you're not always chasing in the same parts of Kansas/Oklahoma/Texas that May commonly features. If one chases regularly in June, expect to see a broader target area, expanding from parts of Wyoming and Montana, eastward into Illinois. While some May activity can and often does spill over into parts of the Midwest, there is a fairly obvious bulls-eye over Oklahoma and adjacent states.

    There's even another little peak in the last week of April, but that involves being willing to chase in parts of Dixie, as well as considerable downtime between events, unless it's 2011...
     
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  7. JamesCaruso

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    Thanks Quincy. Still the average of 4 events per year in the 2 weeks ended 6/12 seems high anecdotally based on my own experience, and those are the exact years I’ve been chasing... But I guess the data doesn’t lie and if his region goes beyond traditional chase terrain that could be a big factor.


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  8. Quincy Vagell

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    I read through his post again and I think there is a difference between "big tornado day" and "cluster."

    If you look at his graph with rolling sums for 14 days, the "yearly average clusters" ranges from about 3.5 for late May to only slightly over 4 for early to mid-June. The latter is probably influenced by some late season big events in the second and third week of June.

    Considering there is not much difference, if one prefers "classic" chasing territory, then late May is probably preferred over June.
     
  9. Warren Faidley

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    The way climatology is currently playing out in the Plains, the last two weeks of May are a toss up. You have potential big days almost anywhere in a multiple state area, but recently the action seems to be following a dryline mixing arc from ABI, CDS, DDC to GLD and points east. More storms are maturing just west of I-35 / OKC which is not a good thing. There seems to be fewer multiple, large target locations as there use to be, e.g., a line from DDC to MAF. During the last week of May into the first week of June I've always stationed myself in AMA - LAA - GLD for the oddball storm if deep RH has worked its way west. It does not take a lot to produce some outstanding tornadoes, especially when disturbances move off the Rockies. (Campo, Simla, etc.) Then again, I'm looking for classic, LP and DL storms as a photographer and I have missed a lot of storms further east as I hate the crummy terrain, and now, the crazy traffic. Early June in all of eastern Colorado, NE New Mexico and SW Nebraska is now a required target given the drought / capping issues further south.
     
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  10. JamesCaruso

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    This is my impression as well - seems like I don’t chase much in the TX PH anymore, certainly not down in the LBB area which has some of the best chase terrain and roads anywhere in the Alley. But this is all anecdotal, and my personal data set is further limited by only having a couple weeks to chase the Plains and tuning in and out to what’s happening the rest of the season... Does the data support this trend??


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  11. Dan Robinson

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    In general, I want to see the following:

    - a robust, wide warm sector (deep moisture) north of I-40 supporting daily MLcapes over 2500 j/kg that is big enough that storms won't leave its eastern periphery before sunset.
    - a solid but breakable EML overtop of the warm sector
    - at least 30 knots of broad 500mb flow overtop of that warm sector, in any direction south of westerly.

    If you have those three over the Plains in the spring, you're going to be in business.
     
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  12. JamesCaruso

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    That’s pretty much my criteria when planning my chase vacation. I can only chase for 2 weeks but I keep a 3 week window open. If “week 1” looks good, I head out and start my 2 week trip. If it doesn’t, I delay until it looks good and then head out. Once I get to the start of “week 2”, I head out no matter what, just to get the full 2-weeks out there - unless it looks utterly worthless.

    So this year for example my window is 5/14-6/2. I will start 5/14 if it looks good that week, otherwise I will wait, I don’t want to start my 2-week clock ticking if nothing’s happening. But by the weekend of 5/19 I’ll be heading out there no matter what, so I get a full 2 weeks before my 6/2 drop-dead return date. If the weekend of 5/19 doesn’t look good, I might stay home just to be with the family but still head out on Monday 5/21.

    With this method, I still never know what the latter portion of the trip will offer, but at least I have a little flexibility and can potentially swap a bad week for a good one.

    The difficult choice is always this: if that first week looks *possibly* “OK” but not great and with plenty of uncertainty, do I still head out or wait and hope for something better? Basically it’s a choice between “week 1” and “week 3”, because the middle week I’m out there no matter what. Of course, there is no visibility whatsoever into “week 3”. It’s like the old Let’s Make A Deal show, take what you have or see what’s behind Door #3. But using Dan’s criteria of good moisture and decent flow, I’m more likely to head out without delay, I don’t need to see a big synoptically evident setup to get me out there that first week. My concern would be that letting anything decent go, I could get a death ridge later in exchange.
     
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  13. Quincy Vagell

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    I decided to look at the West Texas/panhandle region tornado question to see what the data shows. I hadn't ever really looked at it all that closely.

    In 5-year blocks, here are the number of EF/F-2 or stronger tornadoes that were reported in West Texas/Texas panhandle, north of I-10, between April and May. I tried using all tornadoes, but I felt that generally brief EF/F-0 and 1 tornadoes aren't always "worthy" of being a solid tornado chase. Plus the numbers are too high to really qualitatively assess those events. I found the results a bit interesting.

    2012-2016: 25 (5 per year)
    2007-2011: 8 (Just under 2 per year)
    2002-2006: 14 (Just under 3 per year)
    1997-2001: 8 (Just under 2 per year)
    1992-1996: 7 (A little over 1 per year)
    1987-1991: 4 (A little under 1 per year)
    1982-1986: 24 (A little under 4 per year)

    The data is mixed. The 35-year average is for 2-3 significant tornadoes per April/May in the region, but since some of those events had multiple tornadoes, you can estimate that one would maybe get 1 or 2 shots per year at chasing an event with a strong tornado in the area. The odds aren't that high, unless you got the target right each time. With the average, there are some years with no such activity in the area.

    If you look at it year-by-year over the last few years, the sample size is awfully small. Anecdotally, I started regularly chasing the Plains in 2014 and have only had two tornado chases in this area and one was in June, while the other was in November. I honestly have not chased much either between AMA and LBB. I can recall a few HP messes closer to I-20, but aside from the panhandle (I've had a few tornadoes and several high-ranking storm chases), I don't seem to have much chasing luck in the area since 2014. I could have chased the Canadian day, but I made poor judgment in deciding that the setup over that stretch didn't look very impressive. I quickly learned that it does not take much to produce tornadoes in late May...

    Finally, the peak month for tornadoes in the area is May, while the running 10-day tornado average for the Lubbock area peaks in early June, suggesting that late May is also prime time to chase in West Texas. http://www.spc.noaa.gov/exper/envbrowser/
     
    #13 Quincy Vagell, Apr 5, 2018
    Last edited: Apr 5, 2018
  14. Todd Lemery

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    James, I know you got burnt bad last year. I’m pretty confident you aren’t gonna let much slide this year!
     
  15. Jeff House

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    My interpretation of the Tang US Tornadoes article is June offered a greater number of tornado clusters. However late May clusters had more TOG minutes. Colored bar graphs split up TOG minutes by bin.

    I infer June does offer more tornado clusters, and good chasing if one forecasts right. However May offers longer shows, per more TOG minutes in big clusters. They define big as 60+ minutes. I add May is easier forecasting.

    So yes the article text has more total clusters in June (any TOG minutes). At the same time the text (correctly) states more big clusters in May (hour or greater TOG time). Late may is BIG cluster time.

    Separately, I was indeed looking for that early May slight slowdown Quincy mentions. A couple of the graphs (bins) show it slightly. However early may still smokes most of April. If conditions are right early May (what Dan wrote) I go.

    Keep in mind the article is geared to chase vacations, when one seeks a sequence or multiple opportunities in several days. Local chasing is a whole different ball game where of course one chases April.

    Finally I think James has a good system for planning chasecation. Mine is similar except I only get about 7 days total. Fortunately it is truly floating so I go when the weather charts say go.
     
  16. Quincy Vagell

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    Jeff,

    Another quick thought is that SPC annual tornado trends over the past decade or so show a that quite often, the tornado "season" takes a momentary break in early May. A lot of years saw a small flat-line (extreme example is 2011) in early May. This is reflected by a small gap in total tornado reports during the time. In some years, the drop-off is during the first week of May, while other years it's shifted closer toward the second week.

    A few thoughts:
    1. This seems to be offset by high-end/historic events in late April.
    2. Even though early May can be relatively quiet, there have been some higher-end events there as well.

    I completely agree that early May smokes the water out of April.

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