Forecast Update

Well it looks like I definitely made the right call on not chasing yesterday. The storm pics I saw from the one severe storm was a high based piece of shit lol. I won’t lie though, there was a few minutes when that one severe storm hit the warm front where it right turned for 2-3 radar scans. When I saw that, I was like son of bitch that thing is going bite into the front and manage to track down it. No dice though. I knew storm motions had too strong of a northerly component to be able to propagate along that front. You needed another 15 degrees or so of alignment between the storm motions and the front orientation for that to work. It did scare me for a few minutes though. Even if it could have held and tracked down the front, LCL heights were just too high to get the job done. That was an easy call when I saw by lunch time that dewpoints weren’t going to clear 57.

Looking ahead, I’ve been watching the setup for Texas/Louisiana on Saturday. I just got done reading some posts on facebook about it where some chasers are trying to act like it’s a flawless setup. Come on lol. That’s absurd and you either aren’t objective or you don’t forecast much if you think that. I can find plenty wrong with this one. Before I get into this, this not an official forecast post. I haven’t looked at this setup close enough yet, but I’ll start digging into it with the 00Z runs tonight. That being said, issue number one that can be an absolute deal breaker and kills more setups than anything in the southeastern US is convective evolution. Crapvection all over the warm sector through the morning is a big problem and it’s being forecast. The models also have that somewhat clearing out or at least allowing for advection to keep bringing in more moist unstable air from south of the thicker cloud cover/precip as initial early morning convection pushes north. I saw other chasers mention the warm sector was capped which would suppress convection and allow instability to build up Saturday. That’s bullshit. There no surface based CINH after 15Z. That’s about as uncapped as it gets. I’m not in the habit of calling out forecast posts and telling somebody they’re full of shit on social media, but I almost did it on that one lol. Truth be told, I don’t think you ever can really know how convection will unfold through the morning and early afternoon on setups like this one. None of the models do a very good job accurately predicting precipitation/convective evolution. I can tell you that widespread precipitation across the warm sector through the day should be a big concern and a potential disruption to any tornado threat on Saturday. The other big issue I have with this setup is one that isn’t getting mentioned nearly as much and that is meridional 500mb flow (which means 500mb winds are southerly, rather than southwesterly) and very little curvature in the 850-500mb layer. I am a directional shear junkie. I can hardly remember any setups that played out good for tornadoes where you have very little turning in the 850-500 layer. Now there is some decent turning in the 850-500 layer during the afternoon on Saturday, but that better directional shear is along the warm front where low level winds back. Problem with that is that the area where you have better directional shear you also tend to have more clustered convection where storm scale interactions will be detrimental to tornado potential. Basically you have your best shear profiles you also have the highest probability of clustered in storms and precip screwing things up. Below is a zoomed in view of the supercell composite for 21Z Saturday from COD. I’m in a hurry so I don’t have time to mark up the pic, but note the best directional shear along the front, south of there you don’t get much turning at all (fyi supercell composite shows 850 and 500 winds, so it’s a quick easy way to evaluate turning in that layer over the warm sector). Where low level winds back along the northern portion of the warm sector near the warm front, you are also more likely to have storm interactions and widespread precipitation messing things up. It doesn’t take much room for a storm to go tornadic so it’s not a deal breaker, but when your best shear coincides with the best area for convective evolution to disrupt things, that’s a red flag. You know you’ll have cleaner air farther south, but the shear profiles have little to no turning down there also and you just don’t see many good tornadic storms in environments with little to no turning in the 850-500 layer.

You do have a much better directional component to shear profiles out over Louisiana (our to 500mb winds have a more SW component to them rather than a strong meridional component like they do farther west), but that’s also where morning storms look to be tracking through during the afternoon and convection wants to fill in faster over Louisiana with that lead band. I was looking more at the secondary band the NAM has forming back closer to the surface low during the afternoon. If you could get clearing out ahead of that (behind any morning precipitation), it may have a better chance because I think storms may tend to stay a bit more discrete

That’s my quick ramblings on the forecast. I was leaving work early this afternoon because my plan was to do my taxes tonight so I could bail tomorrow afternoon and head to Texas. As much as I hate the lack of directional shear and have major concerns about widespread precipitation and convective evolution screwing the tornado potential up with this one, I still think that it’s probably worth the gamble since it’s on a weekend and it really doesn’t take much clearing or storm separation to get a tornado down when you have high quality moisture pumping in off the gulf through the day. That planned got all screwed up though when we got a call from our biggest customer and we had to go see them at 5pm this afternoon. I just got home from that like an hour ago so now there’s really no chance for me to get my taxes done tonight. I’m going to try and at least get started and if I can I may try to leave work early tomorrow, finish my taxes up and then hit the road and knock out part of the drive to Texas tomorrow evening. I’m up in the air on that. I can’t risk not getting my taxes done and I don’t want to be screwing with them Sunday night when Game of Thrones comes on. I will be checking model data tonight, but I won’t have time to update again since I’m dealing with that. I’ll try to get a few quick thoughts posted sometime tomorrow by lunch though, so check back then if you’re interested.

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