High Risks are rare creatures in the land of severe weather outlooks. When a high risk was issued on January 22, 2017, it understandably sent the weather world on social media into a frenzy. Given that it had been over two years since the last high risk (6/3/14), the reaction was pretty intense. Indeed, many of the classic ingredients you look for when a tornado outbreak is brewing were present. Yet, at the end of the day, and as of this writing there were ten tornado reports from Sunday’s storms.
Did the High Risk Verify?
Ten tornadoes is the lowest tornado count for high risk days since April 13, 2007. The tornado count of ten currently barely trails the April 26, 2009 High Risk in Oklahoma from recent High Risk days. It is possible that tornado number will increase some as more reports are filed. However, the final number of tornadoes probably isn’t going to get above 20 for the entire nation for Sunday.
From a historical perspective, Sunday will likely be at the bottom tier of ‘tornadic’ high risk days in terms of tornado count it appears.
For a bit more perspective, here is how the SPC self-describes a high risk threat:
- 5-HIGH (magenta) – High risk – An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes or a long-lived derecho-producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage. This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe (i.e., violent tornadoes or very damaging convective wind events).
Sunday’s lack of numerous intense/long-tracked tornadoes would tend to indicate it didn’t measure up to the High Risk description above. While numerous is a pretty vague way of putting things, I would suspect more than a couple of events was the intention behind the language there. When coupled with a lower-end tornado count, it appears Sunday was a miss of sorts.
Sunday being a miss doesn’t take away from the forecasting done at the SPC though. It should be noted that high risk misses have happened before, and will almost certainly happen again. However, a great majority of high risk days end up as big severe weather and tornado outbreaks. If a high risk is ever issued for your area, it is wise to take appropriate precautions and prepare for an exceptionally violent weather day as the odds aren’t in your favor.
Consequently, high risks are not something you expect to miss. When High Risks do, it is rather notable because it is a rare event.
For chasers, this presents a good opportunity to look at why an environment didn’t fully pan out. After all, many of the ingredients for a tornado outbreak were definitely in place.
Broadly speaking, it appeared that convection was a mess through much of the day. Isolated storms really couldn’t get going and everything seemed to end up in a clustered mess. Add into the fact that early day storms stuck around quite awhile and you had a recipe for an environment which wasn’t going to have its full potential realized.
When you dig deeper, you find out that the environment itself had a few more subtle flaws as well. Indicies would have produced some pretty model graphics like 0-1km SRH, bulk shear, and even STP. However, the environment itself had a few things that probably kept the potential at bay.
- We posted the sounding above Sunday night on Twitter which generated a good group discussion. The first and most notable thing is that the SSW surface winds helped create a hodograph which was relatively straight. In terms of getting a big outbreak of tornadoes, the most favorable environments are the ones with more isolated to semi-isolated storm modes. This hodograph, coupled with the stronger forcing you typically get in a high risk environment, meant messy storm modes were more likely.
- Another important thing to consider from this sounding is the critical angle. On the TLH sounding above at 18z, the critical angle is 38. For a big/significant tornado event, 38 is really low even for the southeast. You can get by with 55-65 in the Southeast, but on the Plains the closer you are to 90 degrees the better off you are. Given how storms struggled to produce, especially early in the day with plenty of tornado warnings, its possible this was a piece of the puzzle as to why. See more about Critical Angles here and here.
- This was a prime example of not enough cap and too much forcing. The 18z TLH sounding was uncapped as uncapped could be. Given the forcing present in the environment, a lot of storms were going to form. That’s a big problem in getting storms to reach their maximum potential.
A few tornadoes did happen on Sunday. The Albany EF2 (rating as of this writing) seemed to be because of a cell’s interaction with a warm front. The environment around the front was almost certainly better than the ambient environment south of it (as shown by the TLH sounding). Several of the Georgia tornadoes seemed to occur along and near this boundary. A noteworthy thing to keep in mind for sure.
A Few Lessons For The Upcoming Chase Season
To me at least, a few critical lessons were learned and/or reinforced.
First, model indices are just one part of the puzzle. We see it happen every year during the Spring and Summer. This year, there are eventually going to be some bright colors on SigTor model maps that turn out to be a giant convective mess, a cap bust, or something else entirely. Hey we’ll be out there busting with all of you when it happens, so no worries.
Second, I definitely want to continue to pay closer attention to critical angles. The research is intriguing to me, and when making a chase forecast little things like this may prove useful if trying to denote between a couple of targets.
Third, in the bigger environments the little things still matter. As I said above, there were still tornadoes Sunday. Some were clustered around a warm front and others near the Florida Coast. On the bigger days, you definitely want to give yourself every edge even if the overall environment looks significant. I can remember a lot of bigger days with a lot of storms which didn’t produce and only a couple that did. The details matter always for sure.
Fourth, its always best to make your own forecasts as a chaser. Its easy to get caught up in a big SPC Outlook or a lot of chatter on social media with pretty-color bright graphics. But at the end of the day your forecast matters. I’m personally not as flexible on targeting as I used to be thanks to TV coverage — but some guys scored some beautiful storms off of the beaten path this past year when everyone else was in another spot. Always stick to your forecast…always!