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2014-06-03 MISC: NE/IA

Glad to hear I wasn't the only one that was having "issues"! Definitely had some tense moments yesterday. The GPS tracking I used to plot my spot on the radar always seemed to be working and spot on, i.e. if I was in a town, it showed I was in that town on radar. So it seemed to be the position of the storm that was off
 
Ditto. When the first TOR was issued, GRL3 said I was well in the clear from the hook, yet I and Bill Robertson had to drive south a couple miles to drive INTO the northern fringe of the TOR polygon. Then, we never had severe winds, but they got interesting, and it was raining pretty good off and on despite GRL3 saying it shouldn't be raining at all. I think we were in sort of a low-level rain foot surrounding the *alleged* tornado that the radar couldn't see.

This was all early on, until we got a few miles SE of Ord, when everything got calm.
 
Having chased yesterday, I saw three problems:

1) Jeff already touched on this a little, but 1.8+ pwat and 40-45kt 9-11km SR winds pretty much meant everything would be far on the HP side of the scale. Anytime you have something HP, you have weaker updrafts and better chance for outflow dominant storms. This in turn will mean a larger cold pool, and consequently higher chances for an MCS to develop. If there had been slightly less moisture in the air, or if the upper dynamics were a little stronger, those supercells riding the front could have been prolific tornado machines. If storms popped further south like the 13Z HRRR progged, I think the upper air support would have been better in this area as well, so they would've less likely been as HP. They all ended up being prolific rain shaft and gustnado machines - I'm still wondering if there was even a single legit tornado from those specific storms.

2) Crappy surface pattern. Your prime tornado area was in between the two boundaries (wf and ofb/wf hybrid thingy):

http://i.imgur.com/4ayF5i6.gif
http://i.imgur.com/0cIfPnf.gif

Warm front plays tend to work well if you have a nice closed surface low 100 miles away, and a fat instability axis nuzzling up to the front. We didn't have either of those yesterday which already makes the warm front play problematic. Now if the 13Z HRRR was right, and cells popped NW of Kearney like they were forecast, there would have been isolated cells with no nearby cold pool marching through that 10+ STP. Low level lapse rates suggested two deformation axes and focal points for convective development - one west of North Platte, and one near Kearney (you can kind of see this on the STP image above). I'm *guessing* this had something to with the early convection outflow and the two surface lows back on the western Nebraska border, but would love to hear a proper explanation. The end result is that there wasn't enough "focus" for storms to go up NW of Kearney and march into the good air, which leads nicely into...

3) The EML. That was a hot, hot EML nosing into Nebraska. If surface features were more focused, or the cap was slightly weaker, maybe some storms could have popped in central NE before dark. They didn't, so the only chaseable option left was the HP junk on the warm front.

I'd say the high risk derecho scenario busted even harder, but I don't know much about derechoes or why that happened.

My question is this: How do you get the more classic supercell without the higher PWATS? Aren't they a product of high dewpoints? And isn't that moisture needed for higher CAPE values and lower LCLs?
 
Not necessarily. You can have tornadoes with 50° dewpoints, as long as you have abundant sunshine, lower surface temps for the LCLs, and very steep lapse rates. Of course everything else like the shear and firing mechanism are involved. This goes much better for higher terrain such as the high plains out west. 4/20/2010 saw a nice cone tornado west of Amarillo with a spread of around 70/50. Very steep lapse rates and a decent pocket of CAPE value with a very slow moving storm due south, and everything just fell into place perfectly.. Now of course, when you have sun scorching down on 70+° dewpoints, that's when you get those obscene CAPE values over 5000. And if you have a decently sheared environment and a breakable cap...the Earth's crust will be getting a gash.
 
I'd say the high risk derecho scenario busted even harder, but I don't know much about derechoes or why that happened.

Too much separation of updrafts and a worked over warm sector were a part of it. Most derechos are a result of extreme instability and decently strong deep-layer shear values around 35-40 knots with a mostly unidirectional profile with wide open warm sectors. Yesterday got complicated due to the surging OFBs throughout the day and multiple cold pool interactions making it difficult for one large line to become congealed/established.
 
I'm absolutely beat from some pretty serious white-knuckle driving that I did yesterday from Ord to I-80 at the height of that insanity yesteday. Thank God my chase partner / cousin Doren Berge and I had rented a brand new all-wheel-4x4 SUV, as if we had been in a 2 wheeler, I'm not sure we would have fared too well. Lost our front passenger window near Scotia that I'll have to pay for...I'm really happy about that. We saw at least 6-8 separate tornadoes yesterday. None had much of a condensation funnel, but there was zero doubt that these were actual tornadoes, as the rotation was low, often huge and fast. A child could have recognized these as tornadoes. Thinking back, I guess we saw 2 that had full condensation funnels. Some of them were actually quite large and a couple were multi-vortex. At times we saw more than one on the ground at once. These were not gustnadoes. At every instance, they were undercut by the brutal south moving front. We remarked to each other that had these not been undercut, we believe we would have had some large, long-tracked high-end tornadoes. Most of our tornado observations were from just south of Scotia and in Valley, Greeley and Nance counties. The largest was a multi-vortex in southern Nance county.
Earlier in the day, a cousin who manages a bank up in O'Neill Nebraska (Holt Co.) called me on my cell and said they had everybody in the bank, both employees and customers, huddling downstairs in the basement of the bank. The sirens were blasting in O'Neill he said, and he also mentioned that the town of Bassett, which is probably an hour drive west of O'Neill.....had winds over 100 miles per hour. Doren and I surmised that when that storm...or others in the area near there collapsed, this is what must have driven the southbound winds to surge at such a ridiculous pace. Truthfully, since we chased today in the Nebr. panhandle today and had a long drive to get in position, we didn't have time to analyze what actually happened or how other chasers fared. We did run into Jeff and Kathryn Piotrowski today at a steakhouse at lunchtime in Paxton Nebraska, and evidently Kathryn filmed a classic tornado just north of Ord yesterday. Doren and I had actually rolled into Ord a few minutes after they blew the sirens, and got caught in the tornadic/meso wide circulation as we drove to shelter at some spot on the abandoned airfield. Perhaps this is where we lost our passenger window, as we were getting hammered by extremely strong winds that blew debris as us from several different directions as the circulation passed over us. I really figured we'd #%^@* the pooch with that move, and when I looked at Doren his eyes were big as saucers. The thin, wrapping rain curtains were circling around us, as the local police escorted everybody on the road in the north part of Ord out of harm's way. I'll give them credit, they did a great job at rounding motorists up and giving them an escort to safety. Once the meso went over where we were parked, we tacked our way southward, keeping ourselves in the thick of things until we finally hit I-80...where we pointed ourselves towards North Platte in an effort to get a little closer to the Day 2 action. All-in-all....it was a very exciting day, we saw tornadoes, and experienced many of nature's flavors that most people try to avoid. This is what we sign up for each spring, and Doren and I are still out for another few weeks. With any luck, we'll stay safe and have some magnificent photo opportunites as we go along. I'm confident we will. In closing, it needs to be said that my birth state of Nebraska dodged several big bullets yesterday. Had these storms and tornadoes not been continually undercut.....there was a lot of misery and destruction that most likely would have taken place.
 
We saw at least 6-8 separate tornadoes yesterday. None had much of a condensation funnel, but there was zero doubt that these were actual tornadoes, as the rotation was low, often huge and fast. A child could have recognized these as tornadoes. Thinking back, I guess we saw 2 that had full condensation funnels. Some of them were actually quite large and a couple were multi-vortex. At times we saw more than one on the ground at once. These were not gustnadoes.

I guess I'm a child/bad chaser then :D

Gustnadoes can do EF-1 damage, and with as gusty as those storms were, the potential was certainly there. Rotation strength and condensation have little to do with tornado vs. gustnado - it's completely dependent on whether there is an attached mesocyclone, which I saw zero indication of. Very happy to be proven wrong, but I saw no indication of organized rotation near that multi-vortex swirl as impressive as it was.
 
Not necessarily. You can have tornadoes with 50° dewpoints, as long as you have abundant sunshine, lower surface temps for the LCLs, and very steep lapse rates. Of course everything else like the shear and firing mechanism are involved. This goes much better for higher terrain such as the high plains out west. 4/20/2010 saw a nice cone tornado west of Amarillo with a spread of around 70/50. Very steep lapse rates and a decent pocket of CAPE value with a very slow moving storm due south, and everything just fell into place perfectly.. Now of course, when you have sun scorching down on 70+° dewpoints, that's when you get those obscene CAPE values over 5000. And if you have a decently sheared environment and a breakable cap...the Earth's crust will be getting a gash.

Thanks for the input. I guess since I have never chased farther west than the Lincoln, Nebraska area (and that was just in May for the first time) I have never had the chance to experience chasing the high plains like that. Mostly it's just been Illinois or eastern Iowa, and it's essentially all HP storms.
 
My question is this: How do you get the more classic supercell without the higher PWATS? Aren't they a product of high dewpoints? And isn't that moisture needed for higher CAPE values and lower LCLs?

A few things to touch on here...

High PWATs alone don't mean HP vs. Classic. An HP storm is just a storm with a weaker updraft that can't vent precipitation away from its core efficiently. Extreme CAPE, lower moisture, and better anvil winds can all help - and like most things in meteorology the mix of individual components is what's important. In this case we didn't have the extreme CAPE, lower moisture, or better anvil winds so these cells were pretty much doomed to be far to the HP side of the scale. One thing I've noticed with high humidity summer storms in the upper midwest is that they tend to need 3000-4000 MLCAPE to maintain a balanced storm mode that is more conducive to tornadoes. You fall below that and you tend to just get the type of HP gusty storms we saw on 6/3.

Also, precipitable water is a measurement of the water content in a column of air, of which the surface dewpoints are just a very small component. You can easily have a shallow moisture layer at the surface and be drier above. Higher CAPE values either need warmer parcel temperatures or cooler environment temperatures, and neither are completely tied to moisture content. They're tied to maximum moisture content, but that's irrelevant when assessing CAPE.

CAPE is also a really poor discriminator of tornadic potential. The beefiest tornado I've seen (4/14/12) was only in something like 2000 MLCAPE.
 
Rob, I don't know why you felt I was addressing any comment I made towards you. I haven't even read your post yet. Yes, in my 25 yrs. of chasing, I've seen more than a few gustnadoes. I sure wasn't attacking you....just writing about my personal experiences.

;;
 
Rob, I don't know why you felt I was addressing any comment I made towards you. I haven't even read your post yet. Yes, in my 25 yrs. of chasing, I've seen more than a few gustnadoes. I sure wasn't attacking you....just writing about my personal experiences.

Don't worry, I didn't take it personally. Very little in the chasing community has the ability to affect me anymore - it's really all about the storms themselves and a handful of good friends :)

I brought it up because while you implied that there were clearly tornadoes south/east of Ord as the system progressed, everything from my perspective says they were strong gustnadoes. I have zero tornadoes this year, and I would *love* to have some of those intense swirls actually be tornadoes but I honestly don't think there was a single tornado once that storm left Ord. We rode the inflow notch from Ord past Fullerton and never saw anything that suggested anything besides a kickass outflow HP machine.

The Basehunters had a pretty good view of the swirls in question:

https://www.youtube.com/watch?v=9-6Z2i8rlJE&feature=youtu.be
 
I can say with certainty that the vortices that happened north of Seward around 7:00 were strong gustnadoes, since we were just over a mile north of them.
 
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