Tornado Forecast

I got talked into going out drinking tonight in celebration of Donald Trump eating a tostada lol, so I’m not going to get into much detail tonight. I’m a little buzzed and ready for bed.

The 00Z NAM made a pretty dramatic shift with the location of surface features for Saturday so it either crapped the bed tonight or I’m looking at a longer drive. Not sure which, but I’m leaning towards longer drive lol. The uncertainty on the exact location of the dryline/moisture wrap around is driven by the fact that previous runs were consistent with keeping the surface pattern close to the first picture below, which is the 18Z run. I’m leaning towards the latest 00Z northward shift solution though because both the NAM and GFS are showing it. Not a big deal because we should be able to pin things down tomorrow. Below is the 18Z NAM and then the 00Z NAM dewpoint map (note the  northward shift). 18Z NAM00Z NAM

In addition to the northward shift dewpoints are a tad lower and the moisture wrap around is a touch narrower. I don’t think either of the subtle shifts is a big deal at this point, but it’s not a trend you want to see when you are already flirting with moisture problems so I figured I’d point it out. Regardless of the shift I still think the best tornado potential is focused in two areas. The first being just N/NW of the surface low (moisture wrap around area) where storms should fire first and then off the northern edge of the dryline bulge.  Below is a map based off the 00Z run location and the two areas I’m considering targeting.

00Z NAM forecast map

Sunday’s forecast is a little tricky still and may be  tough targeting call for me. I feel like it’s the outbreak Tuesday again, minus the high quality moisture and the strong instability. Morning storms are forecast to track through parts of Texas and Oklahoma. I only glanced at model data, but it looks like it’s associated with a mid level disturbance that moves through in the morning. The models show this pushing off to the east allowing for clearing and moderate instability to develop ahead of the dryline by late afternoon. That morning convection and it potentially retarding moisture return or instability is my first concern with Sunday. Moisture return into Oklahoma and southern Kansas takes place through the first half of Sunday, so hopefully morning storms don’t inhibit that. 850’s are veered through the morning too, which tends to make me a little nervous about getting good deep moisture packed in tight to the dryline. Winds below 850mb stay backed though and forecast soundings in SW Oklahoma immediately ahead of the dryline showed low 60 dewpoints with the moist layer going all the way up to 850mb/1km area, so I’d imagine that will be okay if it verifies.

The next and bigger concern or at least cause for my uncertainty regarding a target for Sunday is the difference in hodographs from the northern Oklahoma/S Kansas portion of the dryline compared to the area down south closer to the Red River. There is a pretty pronounced S shape to the hodograph, especially farther south. I didn’t look at it real close yet, but it looked like the backing started around or just above 700mb. I’m probably a little touchy to that right now because of last Tuesday’s botched setup, which may or may not have been at least partially caused by a similar problem. I was going to look back at some of that tomorrow and make some comparisons to that setup when I have a little more time. Until then I’ll leave it at that. While the upper portion of the hodograph looks a little worse down south, the lower portion of the hodographs look much better down south. The SW part of Oklahoma and area immediately south of there into northern Texas have large looping hodographs in the lower levels and look pretty solid with 0-1km SRH around 150 at 00Z and ramps it up to 250 or higher by 03Z. Low level shear is not nearly as good farther north near the OK/KS border. I really don’t want to ramble because I’m ready for bed, but I’m wondering how much of the paramaters being showing by the NAM is being influenced by the heavier precip and more clustered storms farther north. I don’t know much about the equations with the NAM and how things like precipitation influence other products like wind fields and surface temps/moisture/instability. That’s something somebody a lot better than me at forecasting would have to evaluate. The NAM does show much heavier precip over NW Oklahoma at 00Z though and I wonder if that’s accurate and how much it’s affecting other fields you look at when trying to forecast conditions for tornadoes. For example look at the CAPE bullseye over that same area at 21Z before all the precip and then the CAPE hole after, which obviously plays into composite indices like sig tornado or supercell composite. Anyway I’ll get into it when I have more time tomorrow. My current thinking is to target closer to I40 along the dryline and kind of split the difference. There will likely be better moisture over the southern half of the state, the models are hinting at that I40 corridor kind of being the transition area to more discrete convection and it’s in the better low level shear being forecast over the southern portion of the dryline. Seems like a good compromise to me. Below is a map I quickly threw together showing where the best tornado potential for Sunday appears to be. Take it with a grain of salt because I did very little forecasting today. I’m focusing on the central portion of the box near I40 right now, but that may change a bit in the next day or two.

Sunday mapAlright, enough for tonight. I need to get some sleep. It’s going to be a rough weekend with a lot of driving so I have to get what sleep I can now. Unless moisture return looks like a deal breaker, I still plan on chasing Saturday, even if I have to go all the way to the CO/WY border to do it lol. It’s May, so you chase, especially on Saturday’s. I’m sure I’ll chase Sunday as well. That could end up being a hell of a drive for me. I was thinking about heading to western Kansas tomorrow night and spending the night there, but since I went out drinking tonight I didn’t get my shit ready which pretty much locks me into staying in Wichita tomorrow night and making the drive early Saturday. If I end up chasing west central or SW Oklahoma Sunday, then that’s another solid drive back south from wherever I end up Saturday night. And then to top it off I have to drive home from Oklahoma Sunday night, putting me home at god knows what hour when I have to work Monday morning. Oh well. Plenty of time to rest this summer. Right now it’s time to try and bag tornadoes. I’ll update again tomorrow afternoon.

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