Mikey Gribble
EF5
I was surprised to see that Sunday is actually looking pretty good. There is major differences between the NAM and GFS, especially with the surface pattern, but both models show a respectable tornado threat developing in the southern plains. I just posted on my blog, so I'll just copy and paste that here...
Strong instability, good wind shear, low LCL heights and a breakable cap will all come together Sunday over portions of western and central Kanas for a good shot at a couple tornadic supercells. There is still quite a bit of spread between the NAM and GFS, but they are in general agreement with the paramaters involved that will influence tornado potential.
The surface pattern and location of best tornado threat is pretty different between the NAM and GFS. The GFS has a frontal boundary draped across Kansas. Surface winds will increase and back along and south of the front across the southern half of Kansas. As this happens the frontal boundary is forecast to deform in a northeast to southwest fashion, setting up two particular areas where convergence at the surface is maximized. One over southwest Kansas and another closer to central Kansas. Dewpoints in the upper 60’s and lower 70’s will be wrapped into the surface low and draped along the frontal boundary by late afternoon. Temperatures should be in the 80’s along the boundary, keeping LCL heights low enough for a good tornado threat. Strong instability will develop with surface heating during the afternoon, especially in southwest Kanas where any lingering precip or cloud cover will likely clear out first.
Strong 500mb winds for this time of year will cross over the frontal boundary over southwest into central Kansas, providing strong enough deep layer shear for supercells. Shear profiles are somewhat parallel to the boundary, but I still think convective mode will be semi-discrete supercells, especially over southwest Kansas where 700mb temps will be slightly warmer. Strongly backing low level winds will enlarge hodographs in the lowest 3km, creating an environment quite favorable for tornadoes. The forecast sounding for Liberal is pretty impressive, with a solid combination of thermodynamics and shear. Forecast soundings all the way from Liberal to Great Bend show SR winds at all levels where they need to be for a respectable tornado threat. 1km SR winds around 35kts, 5km at 15-20 and 10km from 30-40kts (which should be adequate for classic supercells, especially in southwest Kansas).
The combination of low LCL’s along the frontal boundary and strong low level shear are whats really bringing the tornado potential together. The lowest 3km of hodographs are good enough for the possibility of a strong tornado or two with any dominant storm on Sunday. Below is a map showing the tornado threat should the GFS verify. My target would be in the Meade to Sublette area with the GFS solution.
The NAM paints a different picture at the surface. In fact a much different picture, but regardless of the geographic seperation with the threat areas between the NAM and GFS, the environment storms would be in with each solution is fairly similiar, which instills more confidence in this forecast than you might otherwise think at first glance. Thermodynamics and shear profiles aren’t quite as good with the GFS, but they are still good enough for a respectable tornado threat. The major difference is that the NAM places the risk area for tornadoes down over the Texas panhandle and another secondary area of enhanced low level winds and tornado potential over the northern Kansas area. This surface pattern with the 12Z NAM is quite a bit different than what the NAM showed with last nights 00Z. Last nights run was more in line with the GFS, so that among other things is why I am believing the GFS with the surface pattern on this one. I’ll still quickly go over what the NAM shows even though I am not buting into it with this forecast though.
The frontal boundary is draped in a much sharper incline along a northeast to southwest direction than what the GFS is showing with the boundary. There are two areas where surface winds back along the frontal boundary. One is over north central Kansas, but the NAM is showing precip all along the frontal boundary from south central Kansas northward, so I’m not going to pay much attention to this northern target. The better area for tornadoes appears to be over the Texas panhandle where surface winds also are backed along the front. Strong instability will develop with good insolation along the boundary in the middle of the Texas panhandle. Strong 500mb winds around 50kts will overspread the area through the day, creating CAPE/shear profiles that are very favorable for supercells. LCL heights are not quite as low as with the GFS solution and the shear profiles aren’t quite as impressive either, but still the environment appears favorable for tornadic supercells.
I am pleasantly surprised with this setup. I’ve only watched the last two runs of each model, but despite some significant differences between them, I am fairly confident in this forecast. Pinning down exactly where the greatest tornado potential will occur is very difficult right now though. I’m just confident that it will develop some place over the southern plains. The NAM doesn’t support the potential for strong tornadoes like the GFS does, but there would still be a solid tornado threat. Below is a map showing where the NAM shows the best tornado potential and then another area where I think the best potential will actually end up being on Sunday (based on a compromise of previous runs).
I will update later with additional information as I continue forecasting tonight.
Strong instability, good wind shear, low LCL heights and a breakable cap will all come together Sunday over portions of western and central Kanas for a good shot at a couple tornadic supercells. There is still quite a bit of spread between the NAM and GFS, but they are in general agreement with the paramaters involved that will influence tornado potential.
The surface pattern and location of best tornado threat is pretty different between the NAM and GFS. The GFS has a frontal boundary draped across Kansas. Surface winds will increase and back along and south of the front across the southern half of Kansas. As this happens the frontal boundary is forecast to deform in a northeast to southwest fashion, setting up two particular areas where convergence at the surface is maximized. One over southwest Kansas and another closer to central Kansas. Dewpoints in the upper 60’s and lower 70’s will be wrapped into the surface low and draped along the frontal boundary by late afternoon. Temperatures should be in the 80’s along the boundary, keeping LCL heights low enough for a good tornado threat. Strong instability will develop with surface heating during the afternoon, especially in southwest Kanas where any lingering precip or cloud cover will likely clear out first.
Strong 500mb winds for this time of year will cross over the frontal boundary over southwest into central Kansas, providing strong enough deep layer shear for supercells. Shear profiles are somewhat parallel to the boundary, but I still think convective mode will be semi-discrete supercells, especially over southwest Kansas where 700mb temps will be slightly warmer. Strongly backing low level winds will enlarge hodographs in the lowest 3km, creating an environment quite favorable for tornadoes. The forecast sounding for Liberal is pretty impressive, with a solid combination of thermodynamics and shear. Forecast soundings all the way from Liberal to Great Bend show SR winds at all levels where they need to be for a respectable tornado threat. 1km SR winds around 35kts, 5km at 15-20 and 10km from 30-40kts (which should be adequate for classic supercells, especially in southwest Kansas).
The combination of low LCL’s along the frontal boundary and strong low level shear are whats really bringing the tornado potential together. The lowest 3km of hodographs are good enough for the possibility of a strong tornado or two with any dominant storm on Sunday. Below is a map showing the tornado threat should the GFS verify. My target would be in the Meade to Sublette area with the GFS solution.
The NAM paints a different picture at the surface. In fact a much different picture, but regardless of the geographic seperation with the threat areas between the NAM and GFS, the environment storms would be in with each solution is fairly similiar, which instills more confidence in this forecast than you might otherwise think at first glance. Thermodynamics and shear profiles aren’t quite as good with the GFS, but they are still good enough for a respectable tornado threat. The major difference is that the NAM places the risk area for tornadoes down over the Texas panhandle and another secondary area of enhanced low level winds and tornado potential over the northern Kansas area. This surface pattern with the 12Z NAM is quite a bit different than what the NAM showed with last nights 00Z. Last nights run was more in line with the GFS, so that among other things is why I am believing the GFS with the surface pattern on this one. I’ll still quickly go over what the NAM shows even though I am not buting into it with this forecast though.
The frontal boundary is draped in a much sharper incline along a northeast to southwest direction than what the GFS is showing with the boundary. There are two areas where surface winds back along the frontal boundary. One is over north central Kansas, but the NAM is showing precip all along the frontal boundary from south central Kansas northward, so I’m not going to pay much attention to this northern target. The better area for tornadoes appears to be over the Texas panhandle where surface winds also are backed along the front. Strong instability will develop with good insolation along the boundary in the middle of the Texas panhandle. Strong 500mb winds around 50kts will overspread the area through the day, creating CAPE/shear profiles that are very favorable for supercells. LCL heights are not quite as low as with the GFS solution and the shear profiles aren’t quite as impressive either, but still the environment appears favorable for tornadic supercells.
I am pleasantly surprised with this setup. I’ve only watched the last two runs of each model, but despite some significant differences between them, I am fairly confident in this forecast. Pinning down exactly where the greatest tornado potential will occur is very difficult right now though. I’m just confident that it will develop some place over the southern plains. The NAM doesn’t support the potential for strong tornadoes like the GFS does, but there would still be a solid tornado threat. Below is a map showing where the NAM shows the best tornado potential and then another area where I think the best potential will actually end up being on Sunday (based on a compromise of previous runs).
I will update later with additional information as I continue forecasting tonight.
