hlcater

Blue box out for much of IA

Can’t wait for OK/TX to have some more setups while the Midwest continues to sleep through peak season.

It was a landspout.

15/7/2 May 1/0/0 June 1/0/0 July 1/1/0 August 3/2/0 September 5/3/1 October 3/1/1 November/December 1/0/0

Figured I'd add the official link.

I wound up chasing today out on a whim, after not originally planning too. Good idea. I had been keeping an eye on a boundary rich in 0-3km CAPE and surface vorticity throughout the day. It was obvious to me that tornadoes would be likely if anything could go up and interact with it, but wasn't terribly confident, and due to other obligations, I couldn't truly chase this day. Though the storms went up late enough that I was able to chase them anyways. I arrived on the original tornado warned storm near Marengo and watched it for a time, it had a nice wall cloud and cycled once or twice, but didn't do too much. The storm still looked good and I continued to follow it, though noting that new convection was beginning to take shape to the south of this storm and would eventually interfere, but the base still looked alright and it was tornado warned, so I opted to stay with the storm. The storm did come quite close to producing a tornado immediately southwest/over Marengo, but it never did. There never was a pronounced RFD cut with this storm and it never made any well-defined intrusions into the updraft. Had this storm had a bit better of an RFD, it might've been able to close off the circulation associated with this wall cloud and produce. As if responding to my wish, the storm did have a really nice RFD push right after the above picture was taken, but perhaps too nice as it totally undercut the base and caused the storm to go outflow dominant -- which it never recovered from. By this point, I was looking for other storms as this one was toast and decided to head to TEC near Williamsburg, instead of turning around and go SW, I decided the best possible course of action was to continue east until the Amanas and then proceed to screw around on dirt roads. While I was busy being an idiot, multiple tornado reports started to come in from the glorified shower behind the Williamsburg cell. I probably could've seen these, but I was just now finding my way to I-80 after an enjoyable experience with said wet dirt roads. Naturally, I flew west about as fast as reasonably possible and ended up being late to the tornado party this little cell was having, but at least I showed up. I saw the final tornado this cell produced -- a wonderfully contrasted elephant trunk that I saw from 8 or 9 miles away. The tornadoes today weren't from the established supercells, but rather meager convection that was trailing it which I thought was interesting, and my late realization of this fact cost me a few tornadoes, along with my poor road choices. Wasn't my best chase ever, but I'm happy with my result. I'll look through my dash video and see if it caught any better pictures than I snapped on my phone. I presume it did, and if so, I'll edit this post and add them. I should also say that I chased Monday in Northern Illinois, but I didn't see much aside from a birdfart 6 miles away and through the rain --- and only because another chaser was able to confirm this feature. Mediocre structure, mediocre contrast, mediocre everything. Didn't deem it worth doing a little writeup for.

Looks like the Linwood tornado is going to get a prelim EF4 rating. Heard something internally that the final windspeed is still up for debate and that Tim Marshall and other engineers were being consulted for portions of the EAX survey path. Probably why there's no DI points in their CWA yet.

Some of the damage from this evening’s Linwood wedge tornado has been very impressive. This, coupled with research conducted by Rich Thompson and Sam Emmserson suggests this was likely a violent(EF4+) tornado. A 0.5 vrot of 90kts and a TDS to 25-30kft(at a minimum, there’s evidence that the TDS may have been potentially 35-40kft, but don’t wanna jump on that) put this firmly within the range where EF4+ is statistically favored.

Another, small, TDS E of Northview now...

So this is gonna be the event people remember from this tornado outbreak sequence...

Note the extremely favorable 200+ 0-3km CAPE on many forecast soundings... one of the single biggest things I think this setup has going for it.

The cap Friday was brutal. Probably as close to a cap bust as you can come while not actually busting, even though many did, especially in IL. If tomorrow isn't disrupted I'll probably be around Galesburg somewhere.

Yea, didn’t look like it hit any significant structures.

Today was a rather challenging forecast, at least for me. What made it difficult was that the warm front had similar parameters from Kankakee all the way towards the East Central Iowa triple point. I had originally targeted Rock Island as models had honed in on initiation along the MS river this morning, and had generally held on to that idea through the early afternoon, so off I went to the Quad Cities, after stumbling around there for a few hours, and winding up in some shadier areas of Rock Island, I found a safe spot to check obs. It became evident that the Quad Cities was no longer the place to be and that the triple point in East Central Iowa was looking increasingly favored over IL, particularly noting the extreme levels of 0-3km CAPE(200-250 J/kg), rich mid 70s dewpoints and the fact that it had been sunny in Iowa the whole day, whereas IL had a late morning MCS and midday supercell. Not to mention that a fairly robust patch of cumulus was evident on visible satellite out in Iowa. After seeing that Iowa was clearly becoming the favored target area, I turned back the way I came, minus one tank of gas lol. Eventually posted up in Williamsburg and watched several towers to the south struggle. After about an hour and a half of watching towers go up and back down on themselves, I became increasingly concerned with the possibility of a cap bust, as subsidence was really putting a hamper on these updrafts, and seemingly winning for the time being. A lone storm finally became established at about 5:45pm and slowly began to acquire supercell characteristics. Core punched through perhaps the lamest core ever(heavy rain and pea size hail -- zzzzzz) but was greeted with a nice, broadly rotating wall cloud, but updraft base was still pretty anemic otherwise. This storm would fight for its life during its entire existence. This wall cloud would persist and evolve with several RFD pushes failing to get the job done. I continued to follow the storm east, and the low-level rotation was getting more and more defined with each successive push of the RFD, but still had a long ways to go. As this supercell approached the warm front, it rapidly got its act together and picked up a tornado warning. Not 10 minutes later, a barrel-shaped tornado dropped below the world's most anemic base, which allowed for some spectacular lighting, to be fair. I'm almost certain that the extra vorticity on the warm front and 225 J/kg of 0-3km CAPE are reasons this storm was able to produce such a formidable tornado despite the storm struggling to maintain a consistently strong updraft. (Music is because I totally botched the real audio -- with radio, some tornado tourettes and talking to other chasers, so I just canned and replaced it with some music.) After this tornado occluded over Iowa City, the storm slowly started to succumb to the subsidence as it never regained anything really resembling a healthy updraft base after this tornado. I followed it towards West Branch before letting it go and heading back to Cedar Rapids. This storm went up, produced a significant tornado and died in under 2 hours, that is the part that surprises me. This wasn't a dominant, robust supercell, this was a supercell that did nothing but fight to stay alive as long as it could, which happened to be just long enough that it was able to produce the most impressive single tornado that I've seen so far. What a fantastic way to start off my 2019 chase season!

If the environment in E IA/N IL looks good tomorrow morning, I'll be out there.

I absolutely think the poor low level lapse rates and deep saturation had a lot to do with it. None of the updrafts were as explosive as expected, evidenced by the weak cores on even the established convection.

Huh? Are you sure you're not watching them replay old footage?

We get it. No need to beat the dead horse here.

99.999% chance destructive interference coming in from that angle and at that intensity.

Looking like a constructive cell merger on the sole remaining discrete supercell near hollis.

Poor lapse rates are probably inhibiting the development in OK. Or at least that's my guess.

SPICY TAKE: The cell spacing right now is far too close to in order to maximize the tornado threat. Probably gonna have to wait for new updrafts to develop that are better separated from what's already becoming grunge. Gonna take some time for dominant storms to come out of that.

I dont think this is worthy of a 60%. This is going to be a significant, possibly historic event, but people need to keep their expectations in check. I've seen comparisons to 4/27/11 on twitter and elsewhere and that's simply not what this is. We aren't gonna get 10 violent tornadoes today. I think 1-2 violent tornadoes is certainly within the realm of possibility and that something as high end as 4/26/91 or 5/3/99 is in the cards if the potential in this event is totally maximized, but something more like 5/24/11 seems like a reasonable outcome at this point.

Perhaps, but I think the warm front is gonna take on a more SW-NE component with time. It may have stalled in the west, but still seems to be continuing to lift northward farther east.