RCNYILWX

One of the turning points in how the pendulum has swung toward too stringent an EF-5 standard was the engineering assessment in the wake of the Joplin tornado. I I'm not mistaken, that assessment found that hardly any/none of the destroyed homes would have withstood EF-3 winds. It seems like, despite Moore receiving an EF-5 designation, that since that Joplin engineering assessment, there's been a granular focus on home construction vs. coverage of damage DI 10 with the highest DOD. Sent from my SM-G998U using Tapatalk

I feel confident in saying that Rochelle-Fairdale on April 9, 2015 was also an EF-5. The wind rowing in the aerial photo from IEMA Air-One looks strikingly similar to that seen in some of the April 27th tornadoes. The survey process for that tornado was rushed imo - we never had an in person QRT consultation, just a virtual one. I'm not sure how that was decided upon, if the QRT felt comfortable going virtual or our since retired MIC pushed for a faster decision to stick with high end EF-4.

To the supposed lack of EF-5s since Moore, if EF-5 were adjusted down to 190+ mph, we'd have seen the "normal" amount of EF-5s over the past 10 years. Particularly with that DI and DOD for houses. As an NWS employee, I think that the agency as a whole has lost the plot when it comes to damage ratings. Having some reference to engineering standards is all well and good, but an impossible standard to reach EF-5 has been set based off building codes that don't exist in much of the country. We've become fixated on finding everything a tornado didn't do as opposed to judging what a tornado did do with respect to totality of damage. If a large swath of a town has catastrophic destruction, it's not the town's fault if they don't have structures built to withstand >200 mph winds. The lower bound on the DIs is used too liberally imo. Vilonia is an example less than a year after Moore of a tornado that by all accounts should have been rated EF-5. Prior to that, there's a good case to be made that Tuscaloosa 2011 should have been EF-5. On the flipside of that, it seems likely that the post-Moore survey standards would have yielded at least a few less EF-5s on April 27, 2011. In recent years, I think Mayflower is probably the best example of how the pendulum has swung well too far in the direction of assigning impossible engineering standards to reach EF-5. Hopefully, the forthcoming updates to the EF scale help bring things back to a more reasonable/realistic place.

Yep, if the most recent Euro and GFS runs are right, the whole subforum isn't going to sniff normal next Monday and Tuesday. Sent from my SM-G998U using Tapatalk

There likely were gravity waves or an undular bore acting upon the stable layer. In these cases with elevated convection, the lower level stable layer ducts the gravity waves or bores, which can then temporarily augment the stable layer. It's more common to see damaging wind as the main threat when there is strong low level stability, getting tornadoes is more rare. I was one of the co-authors on published research regarding the June 30, 2014 double derecho and QLCS tornado outbreak. The northern tornadoes with a MV that passed right near LOT had signs of bore propagation in augmenting the much shallower stable layer north of the stalled OFB/effective warm front. Wouldn't be surprised if there ends up being published research on Tuesday's event in the QCA. Fascinating stuff. Sent from my SM-G998U using Tapatalk

There's definitely a path in which tomorrow underperforms, but don't want to get too caught up in what the CAMs are showing. Since today didn't play out close to the expectations we had for it yesterday, more surprises are probably a decent bet. Pattern and parameter space remain favorable for noteworthy severe, but the uncertain effects of overnight-early AM convection cast a good deal of uncertainty. Recent runs of the RAP continue to show a solid environment out ahead of the cold front in the late AM and early to mid afternoon. Should overnight storms be less widespread, that would seem to be a point in favor of tomorrow living up to its potential closer to peak heating. On the other hand, can also envision scenarios in which overnight-early AM convection causes destructive interference...or the early AM storms are the main show out this way. Will be interesting to see how it plays out.

The 12z NSSL-WRF has a supercell latched on the warm front right into the Chicago metro this evening. 12z NAMnest finally showing storms into the CWA this evening. Regarding tomorrow, unclear if a remnant QLCS/MCS moves across in the early morning, though timing wise and conceptually, redevelopment in late morning over the area would certainly be more concerning for higher end severe over parts of the LOT CWA. A weakening MCS preceding redevelopment could put some leftover OFBs in play, with respect to the tornado threat. Sent from my SM-G998U using Tapatalk

Easiest way to tell that's likely an issue is the super low T/Td spreads and saturated low levels indicating socked in stratus. If dew points get that high, highly unlikely 2m temps will only be 1-3F higher than Td. Sent from my SM-G998U using Tapatalk

I had a feeling that's what you meant, but wanted to clarify for those following the discussion. It's definitely a colloquial thing to call variance in the guidance on capping issues "struggling". Regarding your second point, I'd say that it's fair to say higher end events likely had a strong EML and therefore needed some sort of wave to help break the cap if the large scale synoptic forcing (such as height falls) was lacking. I've brought up April 7, 2020 because of how that event hinged on the cap breaking and there was decided variance on whether the cap would break and coverage of storms. SPC outlooks seemed to largely discount the ECMWF for that event interestingly enough. While Tuesday is not similar synoptically to that 2020 event, time of year, strong EML, and consistency of the ECMWF depiction are interesting parallels. Sent from my SM-G998U using Tapatalk

I wouldn't necessarily call it struggling with the cap. It basically underscores the conditional nature of the threat with eastward extent in the late afternoon and early evening. There's good agreement on a fairly strong cap, but variance on whether there's a wave to break the cap. Without a short-wave, the convergence along the warm front alone likely wouldn't be enough to overcome the minimal forcing and height rises. We won't hit convective T with an EML that stout. The fact the Euro has shown a short-wave and CI multiple runs in a row has my attention though.

*If* the cap breaks as the Euro is showing, the parameter space is high end. For those who recall the wind blown sig hail event on 4/7/20, it had CI pegged for that setup from 6 days out and locked in. It's recently been the most robust with the 500 mb short wave and speed max, enough for CI between 21z and 00z. Because the cap is rather stout, I wouldn't lock in the Euro depiction playing out, but it's interesting that's it's latched onto that scenario. If I were drawing up the outlook for the DVN, LOT, MKX CWA border region and points east, would probably go 15% hatched hail, 15% wind and 2-5% tor. Conditional, but potentially higher end setup late Tuesday afternoon into Tuesday evening, in the 21-03z timeframe. LCLs look a bit marginal for higher tornado probs, but warm front proximity suggests anything close to the front would have that potential if a couple storms go. Edit: Added a gif showing the last several runs of ECMWF 6-hour lightning density valid 06z Wednesday. Edit 2: Added 500 mb heights and vorticity loop from the last several ECMWF runs valid 00z Wednesday [i was on a spring break ski trip last week, though I'll be around and working day shifts this week to add to the discussion. Last Friday was one of the few significant severe events in the LOT cwa that I've missed since I've been out here.]

00Z HRRR variable density (var dens) snow depth output. Shall see what the varsity 00z models show. I won't be here for this one (flying to Colorado to ski during my son's spring break), so this morning was my last AFD for the event. Sent from my SM-G998U using Tapatalk

-NAO ftl. Sent from my SM-G998U using Tapatalk

Morch 2012 forever ruined spring around here. March, April, and usually the first half of May aren't consistently warm at our latitude. But 2012 has made our usual spring weather feel worse and wanting it to be something that it's not. Then when it's legit cold, like this past weekend, it sucks even more. Since I've lived out here, we've only had one April with solid well above normal warmth, in 2017. Other than that, we've had a mix of within range of normal still with late season snow events (particularly 2019), to the relentlessly awful April 2018. This spring looks no different thus far. Hopefully when the blockiness breaks, we can get into an interesting warmer pattern with severe threats and chasing prospects vs. flipping right to summer (albeit not a bad thing temperature wise) like in May 2018.

The common miss northwest or the (less common this season) miss southeast special. Place your bets and run. Picking that this will be the event to jackpot the heart of the metro would be like those who put money on FDU and Princeton to win their first round games. Not smart bets, but felt good when they worked out.

We better not get another shot of -20C at 850 mb lol. Does unfortunately look like a chance for another decent cool shot by late March standards beyond the Thursday-Friday system next week. The ensemble mean snow output next weekend into the following work week hints that some threat for snow may accompany the cool down. Ensemble guidance and teleconnection suggests a relaxation of the predominantly -NAO of late early-mid next week should be followed by another round of -NAO blocking. Until we can fully kick that blocking tendency, we may see a continuation of fairly pronounced cold shots following warm ups. The good news is that there currently aren't any signs of April 2018-like nonsense heading into next month. Sent from my SM-G998U using Tapatalk

I wasn't even looking at specific timing too much since the ingredients were fairly similar on the overnight guidance. Considering the propensity of warm fronts to get hung up by the lake this time of year, the 00z Euro had a plausible look to it. Plus if the wave is lower amplitude, you'd be more likely to have a weaker sfc low initially and gradual intensification more conducive to slower northward movement of the warm front. That's probably even too specific at 6+ days out, though using typical early spring setups as a guide, it's certainly more common for warm fronts to get hung up farther south than for them to rapidly surge north.

Next Thursday checks pattern recognition boxes for a legit severe/tornado threat in the region given a juicy air mass (55-60+ Td) surging northward with a sharpening warm front, 70-90 kt flow at h5, and forecast steep mid-level lapse rates. The forecast lower amplitude 500 mb pattern results in a more favorable wind profile with height, WSW or SW at h5, vs. meridional south or SSW with a negatively tilted trough. In addition, there would be a chance for right moving storms to have residence time near the warm front as opposed to immediately surging north of the boundary. All the usual caveats apply, including meaningful shifts in the currently favorable looking setup, but at this lead time, one of the better late March synoptic patterns in recent years. March 28, 2020 comes to mind and that event not performing to its potential exemplifies the caveats for March setups. Signal is there for a flooding threat as well if the boundary can stay convectively active through the night. At least it's something to monitor and more interesting than the brutal CAD to start this weekend.

Ratios probably were close to 10:1 in the narrow corridor with the warning criteria totals. Certainly overperformed my expectations up there on amounts, but I'd say overall thoughts on how things would play out weren't bad. If I had confidence in the amounts that were observed, particularly in central and northern McHenry County, would have issued the warning. Every event is a learning experience when you work in this field. Sent from my SM-G998U using Tapatalk

It's always been something this season that's resulted in the snow hole from the city and back south and southwest. The issue this afternoon was the stubborn dry wedge. This evening, despite more than cold enough 850 and 925 mb temps, it's brisk east- southeast low level flow that's brought in just enough low level warmth to result in full melting below 1-1.5kft, if you've been following trends on correlation coefficient. Interestingly, the RAP and HRRR had that low level warmth on runs earlier today, but the problem is they don't consistently perform well enough to put as much stock in them vs the other guidance. So ultimately we did get the heavier precip rates here this evening, and similar reflectivity last Friday was ripping aggregates with TSSN, but alas, it just ain't our winter.

Sorry you feel the way you do about our efforts. It's cliche, but in weather forecasting, there's always going to be a bit of 'you win some, you lose some.' However, that being said, I can assure you the headlines are not based "off feeling." When there's a watch in effect and potential to upgrade to a warning, it's a collaborative intra office discussion, in addition to the inter-office collaboration that goes on. Last Thursday, we had about 3 hours worth of discussions on how to handle the existing watch, not exaggerating. Since we inherited a watch on the (Wednesday) day shift yesterday, and it's within a timeframe when we usually make a decision, we're left with a) upgrade the watch or a part of it to a warning; b ) issue a WWA; c) hold onto the watch Options a or b are the typical courses of action. Option C is what we went with for last Friday's event given the unusually large uncertainty up to go time. Preference today (including input up to local management level), was to go with the WWA as our highest confidence option. In that, we explicitly forecast up to 7" amounts in spots for the state line counties. That shows it's not as simple as 6" = definite warning. My own thinking on the decision process was informed on how last Friday played out, with a similar expected 2m temp starting point at precip onset, and the 1-2 hour lag until progressively worse impacts, amidst intense snow rates and TSSN. If part of the evening commute is spent in a lagged ground and pavement response prior to worsening impacts, and 12-hour amounts end up at 6" or less due to shorter duration of sustained heavy rates, plus lighter snow rates Friday AM with temps near to slightly above 32F, that's part of how we felt comfortable going with a WWA. Confidence was not high in widespread 6-7" amounts per non-NCEP guidance being drier, and with much of the accums occurring at a less impactful time of day, we didn't think it necessitated a warning issuance. This of course doesn't imply that we will be right, but shows the process that goes into headline decisions. There's also collaboration between WPC and the WFOs regarding QPF, SLRs and snow and ice amounts. With the milder winter we've had, and no real classic winter storm setups this winter, we've been left with marginal and thus more uncertain synoptic evolutions. There is consistent post event evaluation going on that we use to build mental models of future events. But it doesn't ever make forecasts and headline decisions easy, and there's opportunities for future improvement that come about, from forecasts and headlines to our graphics and DSS.

With every event, the NAM gives more evidence that it should already have been retired. Sent from my SM-G998U using Tapatalk

Obviously intense rates overcome even April sun, but nighttime will definitely help since you don't need sustained heavy rates to accumulate efficiently. Sent from my SM-G998U using Tapatalk

Good call on the slightly farther southeast track. Interestingly, the models that showed mid 970s mb pressures did well. It was a fascinating system overall - like a tropical system with snow, and an incredible amount of TSSN. Without a strong high pressure system to the north or northwest, proximity to the center of the low was the biggest driver in getting into that core of damaging northeast winds. If the only detail you gave for a forecast for the Chicago area was that a 976 mb low would track north of the Ohio River, you'd say most of the metro would have been a lock for heavy snow. The fact that it was a nearly vertically stacked low meant that the mid level lows were more tucked in than a classic winter storm, keeping the deformation area/fronto banding also more tucked in. The radar for a time was very reminiscent of 2/24/16 and the intensity of the banding resulted in strong low level subsidence and drying that overcame good mid-upper level lift and steep lapse rates in place across the central and northern metro. Just not our winter. Sent from my SM-G998U using Tapatalk

Other unfortunate aspect is that all the model run total maps shown by the TV mets are algorithm driven too, and we all own that forecast. My office didn't put out an explicit snow map on more public facing WxStory graphics (it was available on the probabilistic page) on our home page and social media until Thursday PM, but yet "we" forecasted 10" in the metro. QPF and snow depth change maps, plus forecast soundings with omega are the way to go, plus its important to consider whether the DGZ is supersaturated. Looking at the Cobb output page helps too, although even that scientifically more rigorous methodology can have overdone ratios too. Better to play it conservative (ie. pos depth change including var density HRRR product OHweather mentioned) than to get burned with 10:1 and Kuchera ratios. Sent from my SM-G998U using Tapatalk