hlcater

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.

That MCS threw down an OFB that is favorably oriented to storm motion vector. If it gets time to cook, could get interesting(in W IL) late this afternoon should redevelopment occur.

Will have to watch the behavior of the late morning MCS tomorrow. Truly has the potential to make/break the setup. On one hand, an OFB given off by MCS could serve as a focus for initiation tomorrow afternoon. On another, it could just plow through and overturn the entire warm sector. Honestly, I'm thinking the latter is the more likely of the two. Primarily because of how late the MCS is progged to come through the target area(~17-19z). This inherently brings a whole host of problems and concerns typically associated with the passage of an MCS. If this thing doesn't weaken like it's expected to, cloud debris and an overturned warm sector are serious issues. Heck, even if this thing *does* weaken as forecasted, could still have remnant cloud cover and subsequent hinderance of destabilization. If you can't tell, I'm highly skeptical of the potential here. If the MCS passes favorably(like they always do, right??), maybe we have an event, but prior experience with these sorts of setups is screaming to me that this MCS won't weaken as quickly as expected and that it persists into NW IN before it becomes detached from MUCAPE gradient and weakens. Even if MCS fails to weaken, south and west portions of the warm sector should be alright, but initiation is super questionable over there.

I'd add a 15% hail risk and probably drop the 2% tor. Low-mid 50s dews are the best that can be found today, coupled with mid-upper 70s? That just ain't gon' work. Steep mid level lapse rates between 7.0-7.5 would suggest potential for marginally severe hail with stronger storms though.

the thread that never dies

Tomorrow looks decent, but I think wednesday looks likely to grow upscale into an MCS rather quickly.

That 12z euro was TERRIBLE. In fact, I don’t think I’ve ever seen a worse 10 day run.

Probably. We aren’t at record lows(yet) and still have the rest of may, June and July to go. Shots at 1000 closing fast. Best guess I have right now is 800-900

Guys! The ERTAF is showing some hope in the long range! http://atlas.niu.edu/ertaf/

Well the primary jet really likes the northern conus and Canada, so I think sustained periods of AOA 40kts flow over the plains will be hard to come by. Thinking “day-of” events, upslope and boundaries are going to rule the 2nd half of may. However, with sufficient moisture and instability, this can work.

2nd week of may looks to be dominated by a pretty hefty ridge in the west based on both operational models and their ensembles. Not sure how long it’ll be after this trough early week. I’d hedge to say that it’s gonna be quiet for at least 5 days after that.

I wouldn't call next week's setup ideal... it's got problems. Particularly problems with moisture(especially on the euro side of things) and the GFS digs the trough deep enough such that 500mb orientation is mediocre at best. I'm not seeing an outbreak, but I'm seeing perhaps a few events in the plains from this.

Tornado EMERGENCY in Louisiana for this nasty tornado right here. That thing is meeaannnn.

I think the NAM is suffering from convective feedback, especially across TN. Therefore I’d probably take its output with a grain of salt.

Pretty sure you summed up mike morgan as a whole right there.

You guys are getting (measurable)snow before we are IN IOWA! I highly doubt that's ever happened before.

Bouncing around with the rough placement of this body of cold air. But they all have been remarkably consistent in having this cold air present and have been hinting at storm potential somewhere, but that's where the consistency ends. I'm just happy that we've got a solid mass of seemingly persistent cold air for systems to feed on. Obviously better if the main body of cold air is further west, like you mentioned, but as long as its cold without dry northwest flow, I'll take it. But I do expect the cold(maybe stormy?) look to last, maybe even for those further south.

I've noticed there seems to be a problem with the GFS over-amplifying TCs lately. It was doing this last week too and has in the EPAC as well, although to a lesser extent. I'm pretty sure the GFS just had an update recently and this update brought a bit of an over-amplifying issue it seems. Either way, I wouldn't buy that, although decent strengthening is probable, just not to 870mb.

A strong June EML remains my biggest concern, although its really too far out to make this call, I really dont like that the past several GFS runs all have a very strong capping regime, so even if we do get excellent wind fields and solid CAPE, it may not matter. However, the main part of the trough is in Canada, which probably contributes at least a little to the whole plains being capped off. If the trough is able to slide south some and not eject so far north, I feel like eroding it should become much easier. This trough also has a huge area of 50kts+ 500mb flow, which is excellent for June, would be a shame to see it largely go to waste.

In the EC's defense, the GFS verification scores are quite terrible lately. I saw a graph 2 or 3 days ago showing the scores, and the GFS is way(like significantly) lower than the Euro for the past week or so. I don't exactly know where to find it though.

That low up in near Sioux City is the key, that needs to lift north and/or be not nearly as strong with the CAA or else cyclogenesis will probably have a bit rougher of a time.

Is it just me or does the JTWC have a tendency to over estimate wind speeds. That doesn't look on par with a cat 4 due to a filled eye and no convection north of the center. Wasn't an issue on meranti before it entered the south China sea. Then I think they were over a little. I see lots of storms given ratings, that, based on satellite appearances do not look that steong. However I'm not familiar with the Dvorak classification or whatever thing they use to determine pressure and intensity.