Glen Romine
EF5
Yeah, the blob does seem to be seperate, yet that said there was evidence of a small downdraft on the back side of the blob (not the center of the blob) - the spatial scale being much smaller than the typical RFD. The blob is colocated with a strong jetlet feature - with cyclonic shear on the left side and anticyclonic shear on the right side. It appears to be tied with the descent of the tornado cyclone from mid-levels. Further, as the blob reaaches the ground, it is associated with a surge in the gust front, with numerous very small vortices (not tornadoes - but might be associated with small gustnado appearance spinups) spinning up along the gust front edge, particularly on the cyclonic side of the surge. It is further hypothesized (not in the Rasmussen work) that through vortex mergers into the gust front occlusion of these small spinups that this could serve as a seed for the tornado cyclone aloft to lock in phase with. Observations of these surface vortices have been made by both the DOWs and the UMass radar operated by Bluestein's team.
While there are several cases of blobs for tornadic cases using radar data only, more work needs to be done to make sure blobs don't appear often times when no tornado occurs. Also, this may be an evolution only associated with a particular mode of tornadogenesis, and then would not have general applicability. As with most observations of 'features', it is very difficult to determine if the blob is causing a phenomena, or if the phenomena is causing the blob. At this point, too many puzzles pieces are missing to definitively say one way or the other.
I think Jeff Wear's video is quite possibly a blob phenomena - at least it looks to have the right visual characteristics. If I had the radar data handy, I'd try looking for a blob feature with this case (but I don't).
If the vortex2 field project happens - this is certainly a feature that folks will be looking at closely - and hopefully get some better sampling of to better undertand the dynamics and thermodynamics behind it. Numerical models have offered some clues - but the observations to confirm/deny what we see is as yet unavailable.
I'm not aware of Aaron's involvement in this research - but perhaps he has additional insight to share on the subject.
Glen
While there are several cases of blobs for tornadic cases using radar data only, more work needs to be done to make sure blobs don't appear often times when no tornado occurs. Also, this may be an evolution only associated with a particular mode of tornadogenesis, and then would not have general applicability. As with most observations of 'features', it is very difficult to determine if the blob is causing a phenomena, or if the phenomena is causing the blob. At this point, too many puzzles pieces are missing to definitively say one way or the other.
I think Jeff Wear's video is quite possibly a blob phenomena - at least it looks to have the right visual characteristics. If I had the radar data handy, I'd try looking for a blob feature with this case (but I don't).
If the vortex2 field project happens - this is certainly a feature that folks will be looking at closely - and hopefully get some better sampling of to better undertand the dynamics and thermodynamics behind it. Numerical models have offered some clues - but the observations to confirm/deny what we see is as yet unavailable.
I'm not aware of Aaron's involvement in this research - but perhaps he has additional insight to share on the subject.
Glen
