Extended Forecast Update

Just a quick update on the extended forecast since I haven’t posted in the last couple days. BTW, usually the frequency of posts you’re going to see out of me is directly proportional to how good the tornado potential is, so if I’m not saying much, then it’s probably because there isn’t much to talk about lol.

I’ve been watching the GFS pretty closely to get a feel for when it will get active again. I mentioned some potential for this Friday and Saturday in my last post, along with the potential problem of not getting any surface based storms. That’s a big problem if you’re after tornadoes and it’s looking more likely that it’s going to verify. I’m not going to get into the problems with the trough and this setup, but the only chance I think there is may be for SE Wyoming on Friday where they may eek out a low end tornado. It’s not looking good Saturday either and it’s doubtful there will be any surface based storms or tornadoes.

The next possibility seems to be around Wednesday of next week when a very weak short wave may work through somewhat zonal flow across the plains. Now the models are still jumping around quite a bit run to run, but for the most part they’ve consistently shown this weak shortwave coming through mid week. It isn’t much to look at if you’re just scrolling through 500mb charts, but it’s got my attention for a couple reasons. One is that throughout the forecast period there should be pretty favorable trajectories in the low levels bringing moisture up from the gulf and Caribbean, so it’s logical to assume there will be pretty solid moisture already in place across the plains for this shortwave to work with. With good moisture/instability, you can offset weakness in deep layer shear to some extent, so even with a small weak wave, you can still get some solid tornadic storms, at least over a small area. I also think there is likely to be good directional shear. With a small, low amplitude wave like has been forecast, you’re not going to get screwed on directional shear like you can with a higher amplitude trough that has a positive tilt. It may be over a compact area, but the potential is there for some good tornadic storms if the GFS stays on track. I’m certainly keeping an eye on it. Still a long ways out, but the consistency on showing a weak shortwave working through the somewhat zonal flow and the fact that model data, common sense and climatology point towards decent moisture being available, I am somewhat optimistic about chase potential with this disturbance.

Things get a little murkier beyond Wednesday. By that I mean I really don’t have any idea what is going to happen lol. The models have jumped around a lot with any specifics regarding the upper air pattern, but in general there have consistently been signals for a more active pattern for the last 10 days or so of May. Several runs of the GFS have shown significant tornado outbreak type setups, but they just as quickly vanish in the next run lol. When you’re looking that far out and there is little run to run consistency, you really can’t pay any attention to details. I try to focus on moisture, upper level winds and the trends from run to run with both when I’m watching models that far out. As I mentioned above, trajectories over the Caribbean and gulf appear to be pretty favorable through the forecast period, so moisture likely won’t be a major issue with any trough we get. We just need a stronger trough to come through the plains (that doesn’t have a nasty positive tilt and is shitting the bed like this weekends trough). The GFS keeps wanting to bring SW flow into the plains with fairly strong waves working through it starting around a week from tomorrow and then it keeps a good wave train pattern going through the plains up into the end of May. That is what you’d expect this time of year, so climatology is on our side here. May 20-30 has delivered more consistently for me over the years than any other stretch of storm season. I’m fairly certain that statistically the peak of tornado season is in that May 20-30 period along with the peak of tornado season historically for Kansas (I think May 26th is the statistical peak for Kansas). I know this, if it does get active then I will definitely be out there. I haven’t used much vacation with as slow as this year has been and I am itching to chase. I really hope we get a multi day event where I can hit the road and stay in hotels for a few days. Those are always fun. Exhausting, but fun.

Alright, that’s it for the night. The theme here is don’t overlook that weak shortwave that may come through the middle of next week and there is reason for optimism with the back half of May looking more active.

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