The parameters existed on Monday for an intense tornado outbreak on the southern Plains had thunderstorms managed to develop in the warm sector. That didn't happen. Even though there was plenty of severe weather from western Texas to southwestern Missouri, it's safe to say that Oklahoma got extremely lucky compared to what could have been.
It's admittedly a little tough to say Oklahoma got "lucky" when there were still damaging tornadoes there and in Texas—some of which likely rated as a significant EF-2 or stronger—and major flash flooding across Oklahoma and parts of Kansas and Missouri. But the overall situation wasn't as bad as it could have been given the potential that existed. Something—possibly unexpected subsidence in the mid-levels of the atmosphere or rising air not rising fast enough near the surface—prevented thunderstorms from blowing up in the most favorable area for tornadoes. That was truly the best outcome given how dire the situation looked going into Monday afternoon.
Comparing SPC’s Sig Tor parameter for yesterday with past events @GCarbin pic.twitter.com/SZCxSxAqDV— NOAA_HWT (@NOAA_HWT) May 21, 2019
The above tweet from NOAA's Hazardous Weather Testbed shows the significant tornado parameter on May 31, 2013—the day of the 2.6-mile wide tornado in El Reno, Oklahoma—compared to what we saw on Monday, when the parameter was twice as high as it was on that awful day six years ago. The environment over the region on Monday was about as favorable for tornadoes as it gets. The atmosphere was ready to spin anything that managed to root itself in central Oklahoma, but nothing really got going until later on when approaching storms had coalesced and the tornado threat began to wane.
The weather doesn't suddenly veer from a predetermined path. Thunderstorms were never going to develop in central Oklahoma when conditions were most favorable for tornadoes. We just didn't know that ahead of time, and that's a failure. The search for answers as to why that wasn't detected and accounted for ahead of time—and how to catch it the next time—will come through plenty of research in the coming months and years. Meteorologists have gotten really good at tornado forecasting over the years, but there's still a lot left to learn.
Rare and memorable severe weather outbreaks are rare and memorable for a reason. It's really hard for all the ingredients to come together at the same time to produce a high-end tornado outbreak. I made note of that going into the day on Monday:
It appears the environment will be capable of supporting a high-end severe weather outbreak. It's hard for big severe weather outbreaks to occur. Lots of things have to go right and it's easy for storms to morph into a sloppy mess on a day like this. Even if the storms on Monday don't reach maximum capacity—and many likely won't!—one storm breaking through to produce one bad tornado is still a big deal.
I won't pretend to have had any special intuition that made me include that blurb. I thought it would be ugly just the same as everyone else. But we've seen lots of seemingly high-end severe weather outbreaks in recent years turn into a sloppy mess. Sloppy clusters of storms and the lack of a sufficient trigger in the warm sector mostly stifled the extreme tornado threat away from the dry line farther west. The setup still produced plenty of tornadoes in parts of the Texas panhandle and western Oklahoma, but it wasn't nearly as bad as it could have been given the dynamics in place.
The most important part of a forecast is getting it right. Messaging is a close second, though—and I'm not convinced (at least not yet) that the high risk yesterday was unwarranted given the extreme parameters in place had a storm been able to form and take advantage of that kind of environment. Can you imagine if it had gone the other way and supercells had blown up around the Oklahoma City area after forecasts downplayed the threat?
Sounding the alarm for a big day that doesn't quite pan out will hurt trust in weather forecasting at least a little bit. You know how averse I am to hype, and yesterday will probably hurt some readers' trust in me. The atmosphere pointed a loaded gun at central Oklahoma on Monday. We're very lucky nothing pulled the trigger.
Thankfully, instead of mourning, today we have an internet full of part-defensive and part-introspective weather folks, storm chasers ticked they didn't see the best day of their lives, residents peeved that they worried over nothing, and officials left explaining why they cancelled classes and moved armies (well, just some planes) based on a potential that went unfulfilled.
Sounding the alarm for a big day that doesn't quite pan out will hurt trust in weather forecasting at least a little bit. You know how averse I am to hype, and yesterday will probably hurt some readers' trust in me. The atmosphere pointed a loaded gun at central Oklahoma on Monday. We're very lucky nothing pulled the trigger.
It's a good thing that people took the threat seriously. Every live shot of Oklahoma City on television yesterday showed the streets virtually empty for most of the day. Yesterday's response shows that people really do trust the forecasts and they really do prepare when things get scary. I hope they still choose to take action the next time.
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