4/09/19 Forecast

Well, after looking over the 00Z runs I really don’t see anything that makes me think different on the potential for tomorrow. I’ve been trying to take a close look at moisture return starting up and comparing it to the NAM to get a feel for how good of a handle it has on it since that’s a real critical aspect of tomorrow’s setup. For at least the last day the NAM has been pretty consistent with return flow starting up over the Brownsvilled/Corpus Christi area in south Texas right around 7pm tonight with mid 60’s starting to nudge on shore. That has in fact happened. I looked at the Corpus Christi sounding and the moisture is very shallow, despite the high surface dewpoints being seen there right now. The NAM also had that initial nose of moisture being exceptionally shallow though so I don’t know that it’s a big concern. So after glancing things over I think the NAM has actually handled things pretty well so far. It does have some pretty miraculous moisture return with dewpoints as high as 62 pooling up near the triple point by tomorrow afternoon, so it obviously makes you skeptical, but like I said so far I haven’t seen anything indicating it’s way off. The HRRR on the other hand is a solid 5 degrees lower with dewpoints over the warm sector tomorrow afternoon. For now I’m going to stick with the NAM. I haven’t kept real good track of it, but I think it’s done a decent job so far with the surface pattern on other setups this year. One thing I’ll definitely check tomorrow morning is the FWD and OUN soundings. That should tell us a lot more about the moisture quality we are going to be working with. I also made a note of the NAM showing 56 degree dewpoints nosing into Kansas by 15Z and 60 degrees by 18Z. I’m curious to see if that verifies and between that and morning soundings you should have a pretty good idea of whether or not the NAM is juicing moisture or not by 1pm.

Now if the NAM is telling the truth, then I think it’s worth chasing. I glanced over 00Z soundings from Amarillo and SW of there and that is a nice EML with steep lapse rates, so combined with 60 degree dewpoints and strong deep layer shear, the environment is definitely supportive of supercells. There is going to be a lot of convergence near the triple point and I think there is a decent shot of getting a surface based storm off the triple point if 60 degree dewpoints do in fact verify. The NAM is showing a storm developing right there at the triple point and best I can tell it tracks right along the warm front, but it seems to be on the warm side or right on it, so you have to assume it’s surface based or close to it. One thing that is a bit concerning is that the warm front seems to have a little more east to west orientation than in previous runs and forecast RM storm motions right ahead of any triple point storm, which means it may start to cross the front and become elevated. It would really need to propagate to the right in order to stay along the front with the current orientation the NAM is predicting. That is a concern, but I think it’s one of those concerns where you have to go and just see how it plays out.

So now if we get a sustained surface based storm, then is it going to be able to produce tornadoes? I think it’s got a decent shot. The UH tracks have been pretty impressive so far with any storm coming off the triple point, but that doesn’t speak to surface based rotation/storms mind you. I believe the storms would rotate pretty hard given the hodographs just northeast of the surface low in the path any triple point storm would take. Below is the NAM and NAM NEST forecast soundings and hodographs for the area immediately NE of the triple point.

Note the CINH is manageable minus the borderline -50 on Sfc based parcel with the NAM. The hodographs are pretty solid, especially the lower one. There’s also a pretty large difference between the two. It looks like my lower one I pulled a little closer to the front because surface winds are backed more and storm motions are more northerly. Note also how strong of a northerly component the RM storm motions have. Again storms wanting to cross the front and become elevated is one of my bigger concerns once you clear the even getting a surface based storm hurdle. Maybe you get one that develops a little farther south along the dryline though, giving it more residence time in the warm sector. Or maybe a storm can turn hard right and stay along the boundary. As I said earlier though I think that’s just one of those things where you need to go and hope for the best, plus I need a warm up chase so I think I’ll bite. With the strong 0-1km SRH and workable LCL heights, if a storm can stay in that environment for a period of time I think it could produce a tornado. There are some serious caveats here and I know SPC has stayed away from talking much about the outside chance of a tornadic supercell, but I think the potential is there and the chance is high enough that if you’re close by it’s worth a go. If nothing else you get to dust the equipment off and make sure everything is working good before we get a serious setup.

I’m too worn out to make a map right now, but my preliminary target is probably some place close to Osborne, KS. I may need to adjust that a bit depending upon exactly where the triple point will setup. I also want to see that moisture is on track tomorrow morning before I pull the trigger. If we aren’t going to get 60 degree dewpoints then that very well may be a deal breaker. I want to see how the HRRR handles precipitation too. My plan is to leave Wichita around noon if I go so luckily I’ll have plenty of time to comb over the forecast tomorrow morning before I need to make a final decision. I’ll try to make some quick updates in the morning on how things are looking, so check back then if you’re interested.

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