2018-05-27 Event: TX, OK, KS

[Michael Wilkinson]

I’ve been on chasecation since May 16. It’s been enjoyable and a good learning experience, but no significant tornadoes yet. I have seven days left. We took off the last two days to photograph Rocky Mountain wildlife.

Texas panhandle looks as good as anything from the last two weeks. The HRRR has a couple of spots at 00z with SRH 0-1 at over 100, LCLs below 1500, and adequate ML CAPE. Anyone think it’s worth an eight hour drive, considering that Monday’s setup might be good not too far from where I’m at now in Ft. Collins, CO?

 

[Marc R. O'Leary]

You should include CO in this thread as parts of the state have already breached 60° dews. We don't get up that high very often.

 

[JamesCaruso]

And now add Wyoming because we all know what happened there...

Did anyone here target WY and if so can you explain why? The winds there were still northeast at noon MDT when we made the decision to target eastern CO instead, and late afternoon dewpoint forecasts looked questionable on some models. 500mb flow was modeled to be almost backed to the southeast. Hard to go back and remember all the data I looked at and when, but I don’t recall anything looking particularly intriguing about southeast WY today. There’s what we know with hindsight, but with data and models available at noon MDT, how many of you would have targeted the Cheyenne area? Kicking myself now and still trying to learn from the mistakes I am still making even after all these years...

 

[JamesCaruso]

It looked like winds were more northeast than east, which is why I wasn’t too excited about SE WY, and I figured upper support looked to be about the same over the whole area, maybe potentially even backed slightly at 500MB over SE WY. Am I wrong? How much of the tornado was a “mesoscale accident” versus something I should have seen in the data? Really frustrated about this miss, after scrambling to fly out here at the last minute for this!


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[Brett Nickeson]

It looked like winds were more northeast than east, which is why I wasn’t too excited about SE WY, and I figured upper support looked to be about the same over the whole area, maybe potentially even backed slightly at 500MB over SE WY. Am I wrong? How much of the tornado was a “mesoscale accident” versus something I should have seen in the data? Really frustrated about this miss, after scrambling to fly out here at the last minute for this!

This will serve as a bit of a postscript targeting summary, but I chose SE WY for several reasons:
1) The northeast flow up there was transporting some pretty good moisture for the area characterized by low to mid 50's dewpoints. That's more than enough for significant storms, especially when it can pool a bit against the Laramie range. Northeast winds up there aren't quite the same as what they are on the plains. Usually we think of northeast winds as being stable and north of a warm front, but in this instance on the high plains they acted as the transport for good moisture and unstable air.
2) With near northerly storm motions before any deviant right motion, the ENE surface winds have the same storm relative vectors as a southeast wind would have on a easterly moving storm. We flip over those hodos, so the ones in SE WY were near the same but rotated about 90 degrees.
3) 0-6 km shear was quite a bit better in SE WY. Going off of memory it was something like 45 knots compared to 30 or so for western KS and eastern CO.
4) Multiple CAMs, primarily my beloved HRRR, were showing one or two nice slow-moving cells with strong updraft helicity tracks in this area. Contrast that with the storm mode mess it was showing in eastern CO. I love the HRRR for determining storm mode. As a photographer, it can help me decide if I want to play an alternate target that might remain a bit more discrete or move a little slower than an area with potentially better sig parameters.
5) Visual clues. When I stopped in Ogallala to figure out where I wanted to target, the clouds over eastern CO were showing evidence of sinking stable air as they had a lot of hanging virga. That can often times be a clue that the lid strength is a bit strong. I know Skip is a huge proponent of that parameter and posted a map yesterday on facebook showing it being quite a bit stronger in eastern CO than WY. I don't really use it, but the visual clues seemed to match up with what the map was saying.

 

[JamesCaruso]

This will serve as a bit of a postscript targeting summary, but I chose SE WY for several reasons:
1) The northeast flow up there was transporting some pretty good moisture for the area characterized by low to mid 50's dewpoints. That's more than enough for significant storms, especially when it can pool a bit against the Laramie range. Northeast winds up there aren't quite the same as what they are on the plains. Usually we think of northeast winds as being stable and north of a warm front, but in this instance on the high plains they acted as the transport for good moisture and unstable air.
2) With near northerly storm motions before any deviant right motion, the ENE surface winds have the same storm relative vectors as a southeast wind would have on a easterly moving storm. We flip over those hodos, so the ones in SE WY were near the same but rotated about 90 degrees.
3) 0-6 km shear was quite a bit better in SE WY. Going off of memory it was something like 45 knots compared to 30 or so for western KS and eastern CO.
4) Multiple CAMs, primarily my beloved HRRR, were showing one or two nice slow-moving cells with strong updraft helicity tracks in this area. Contrast that with the storm mode mess it was showing in eastern CO. I love the HRRR for determining storm mode. As a photographer, it can help me decide if I want to play an alternate target that might remain a bit more discrete or move a little slower than an area with potentially better sig parameters.
5) Visual clues. When I stopped in Ogallala to figure out where I wanted to target, the clouds over eastern CO were showing evidence of sinking stable air as they had a lot of hanging virga. That can often times be a clue that the lid strength is a bit strong. I know Skip is a huge proponent of that parameter and posted a map yesterday on facebook showing it being quite a bit stronger in eastern CO than WY. I don't really use it, but the visual clues seemed to match up with what the map was saying.

Thank you Brett, that was very helpful! We need more post mortems like that - I often wished there was a version of an SPC outlook written in past tense [emoji848]Anyway actually being able to learn something from a failure makes it easier to take, so I appreciate it. I feel stupid still making mistakes like this after 20+ years of chasing, but at a max of two weeks a year and not having a ton of time to study meteorology throughout the year, I guess I should give myself a break ... [emoji52]


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[Michael Snyder]

If I remember correctly I chased SE WY, because of better shear, winds at the surface were from a decent moisture source, and well just because its Wyoming.

I scored big time, I was right behind Timmer as the huge tornado just emerged out of the rain near Federal, WY. I caught 3 other tornadoes viewing from Happy Jack Road and then a bit east on the dirt road that goes back north to Federal.

Write up to come...