Tornado Forecast 051519

I’m seriously worried about that cap over the open warm sector with Friday’s setup. That in my mind is the one big fly in the ointment for the SW Kansas and Texas panhandle portion of the target area. What’s weird is that if you read the Norman NWS discussion and the DDC NWS discussion they seem very confident in at least scattered storms off the dryline. Those guys definitely know better than I do, but despite their confidence I am still extremely worried and am bracing myself emotionally for a blue sky cap bust lol. You do get strong moisture convergence along the dryline, especially in SW Kansas and the high resolution NAM and regular NAM both show towers/light showers trying to come off the dryline in that area, but neither has shown any sort of sustained convection across the SW Kansas or Texas panhandle portion of the dryline. BTW if you look at the 00Z NAM simulated reflectivity and saw the precip over the target area at 21Z pictured below, I believe that’s elevated bullshit the NAM is wrongly kicking off the dryline down in the panhandle at 18Z. That’s not surface based precip coming off the dryline at 21Z like you might think.

00Z NAM from COD showing 21Z simulated reflectivity

The GFS has shown an isolated storm or two occasionally, but I have no faith in the GFS precip output. Getting a sustained storm issues aside, the environment looks quite good for tornadic supercells late in the day, with the strongest parameters consistently being located in that SW Kansas into the northern Texas panhandle corridor, which is what I’ve been focused on. I still really like my Meade, KS target and I am sticking to it. The only adjustment I would make would be if I thought that moving up or down the dryline was necessary because there wasn’t going to be a sustained storm coming off the dryline in SW Kansas. I think it has as good of a shot as anywhere though when looking at the dryline between I70 and Amarillo.

I’m going to get into a little more detailed discussion tonight since we’re getting closer and the finer scale details are what really matter on this. I’ve avoided getting into that up to this point strictly because it’s too far out, but I have been looking at the details pretty closely with Friday’s setup for several days. I mentioned a day or two ago the temperature anomaly that starts over the Texas panhandle portion of the warm sector and spreads up into Kansas through the day. The surface temps over that area ahead of the dryline are a good 6 degrees cooler than the ambient warm sector. That pocket of lower surface temps syncs up exactly with the lower surface based CAPE and stronger CINH. Why is it there? Welp, from what I can tell it’s the NAM’s response to heavier cloud cover and warm air advection at 850mb. The NAM has been extremely consistent in showing that. It starts over the Texas panhandle at 12Z and advects north through the early afternoon which keeps surface heating down ahead of the dryline from the NE Texas panhandle into SW Kansas. Below is a few screen grabs from COD 00Z NAM showing this evolution through the day. The first pic is 18Z cloud cover, note the heavier cloud cover moving up out of the TX panhandle into Kansas which is inhibiting surface heating with the NAM (I outlined the cloud cover in black that I’m talking about).

The next screen grab below is the surface temps at 18Z, showing the temperature anomaly that syncs up with the cloud cover. There is a good 6 degree or so drop in surface temps associated with that. Again it’s outlined in black.

And finally below is the 00Z CAPE/CINH output from the NAM where you can clearly see how the lower surface temps equates to reduced CAPE and increased CINH ahead of the dryline across the NE Texas panhandle and SW Kansas. There is no CINH along the dryline where there was better surface heating, so if that were to verify, you may get storms trying to come off the dryline in SW Kansas, but they’d struggle and fizzle in the model world.

Also note the very unstable and uncapped warm sector farther north in NW Kansas and southern Nebraska which is the portion of the warm sector north of the cloud cover and gets good heating through the early afternoon. All this is very easy to see if you loop the NAM and again, it has been extremely consistent in showing it. In the model world, that pocket of less stable air and high inhibition is a deal breaker for surface based storms coming off the dryline in SW Kansas and the panhandle, which is where the strongest wind shear is for tornadoes. So the big question is whether this is going to be a real world problem or is it just a model world problem. I have no idea lol. I just spout off shit on here and hope the people reading know less than I do so I look like I know what I’m talking about lol. No I joke, but I do only know enough to be dangerous. I have a fair amount of experience and I studied mesoscale and storm scale meteorology a little when I was getting started as a youngster, but I am not strong at the fundamentals of diagnosing things like cloud cover associated with warm air advection (I suck at synoptic scale meteorology too btw). The good people at NWS and SPC are good at that and they don’t seem to think it’s that big of an issue so I have to defer to them on these types of matters. Normally I’m a firm believer in following my own forecast regardless of what others like SPC say, but on things like this and whether or not the cap will break and we’ll have sustained storms over the warm sector, I know my own weaknesses and I defer to others, so I will participate in the Friday cap bust lol.

Storms still look to be much more certain over the northern portion of the warm sector coming off the triple point in SW Nebraska, which is farther south in the latest runs btw. The low level shear is not nearly as strong up there though and any tornado potential would be isolated to the triple point and near warm front environment. Given storm motions and the orientation of the front, I don’t think that window is very large and the residence time for supercells tracking through that corridor of greater tornado potential won’t be very long. I love a triple point chase, but when the low level shear is only strong enough to be supportive of tornadoes in the near warm front environment you need right mover storm motions to be somewhat in alignment with the orientation of the front so the storm can either root in the boundary and track down it or at least maximize it’s residence time in that near warm front environment before it moves north of it and becomes elevated. That difference between projected storm motions and front orientation up there is just too big for that to happen IMO and it’s a pretty sharp warm front so storms will probably get elevated pretty quickly as they cross it. I think the best chance is literally right at the triple point where you may have possibly have a little longer residence time in that favorable window. I’d target there if I was chasing up there and I think it has the best shot at a tornado or two. I do think we’ll see a tornado report or two out of that spot and it’s the area I boxed in on the map. The exact location of that triple point will likely change, but you just change your target with it. The concept that you target the first storm coming off the triple point remains regardless of the exact location of that triple point.

As for the southern target, at this point in time I think I’m targeting Meade, KS, but I also think the I40 and just south of there in the TX panhandle portion of the dryline may be a better target. It kind of depends on the NAM verifying though with the pocket of lower surface temps over the NE panhandle and SW Kansas. Assuming the NAM is totally accurate, then the Texas panhandle target would clear out a little earlier in the afternoon allowing for more surface heating and a wider uncapped warm sector for storms to work with. It’s also on the southern edge of the strong low level jet and stronger SRH. Best overlap of low level shear and workable warm sector. I don’t know though. I like the environment better in SW Kansas, I can help with coverage if I stay up here and my gut makes me think the NAM is overdoing the lack of surface heating over the warm sector in SW Kansas. BTW I say all these very specific details about the NAM three days out not because I think it’s going to play out exactly like that so I give it that level of validity. I say it just because I do think that scenario is a possibility and it’s a good exercise to prepare for quick and effective chase day targeting decisions based off how it’s actually playing out and you’re going off observations trying to figure out where to move to in the final hours before initiation. It’s also just good practice to spend time evaluating the details trying to find subtle mesoscale strengths and weaknesses between one specific target and another. Anyway, point being don’t take those very specific model details too seriously this far out. So that being said as things stand now I think my strategy would be to target Meade, KS hoping for the best, but be there at least a couple hours early so I can watch satellite and current conditions and adjust south into the Texas panhandle if I need to. Any sustained storms in the southern target area I outlined on my tornado threat map would likely pose a tornado threat and we could even see a strong tornado threat if things play out right.

Alright I’m too tired to get into the extended range tonight. I’ll hit on that tomorrow. Basically I think maybe a couple lower end tornadoes Saturday, but needle in the haystack type chasing. Sunday is a down day in the plains. Monday through Thursday there is tornado potential every day, but the trend with the GFS has definitely been to back off the tornado threat as we get closer for each setup. I don’t know. It could be tough chasing with localized areas of enhanced potential on given days. There will definitely be tornadoes, but you are going to have to put more work into it than I thought you would a few days ago. I’ll get into the specifics more tomorrow.

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