May 29 -- Weak Tornadoes -- Lockney, TX Supercell

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The day dawned with great southeasterly surface flow into the southern Panhandle. A complex boundary, combination of a synoptic-scale warm front and an outflow boundary, extended through the Lubbock area and the southern portion of the Texas Panhandle. Note also a weak windshift line that extends acros the Big Country. We believe that this boundary moved through the Lubbock area and brought drier air into the storm that we were targeting (note lower dew points south of the boundary).


A moderately-intense trough in the mid and upper troposphere was centered over the Four Corners region, with 50 knots of flow at 500 mb from the Lubbock area northward. We targeted the area near Lubbock for initiation and hoped that a storm would form and move along the nearly stationary/partially retreating boundary.

The mid and upper (not shown) tropospheric wind field was very favorable for supercellular convection. Hodographs showed a nice loop from low to lower mid levels, and 500 mb flow and 250 mb flow was very favorable for storm ventilation and supercellular shear.


The 850 mb flow was initially southeasterly, although that was only slightly above the ground in the western high Plains. Later in the day it shifted to southerly. In combination with the southeasterly surface flow and southwesterly 500 mb flow, this produced a wind shear profile very favorable for tornadic supercellular convection.


The 1415 UTC satellite showed the first storms going up in the Lubbock area, and the storms responsible for the outflow boundary to the north.


The water vapor image for the same time showed a dry slot advecting northeastward over the same area.


The morning sounding at AMA showed the effects of the cooler air north of the boundary, but the wind profile looked very good.


By 1400 UTC, the AMA sounding still showed the effects of the cooler outflow air to the north, but the temperatures were moderating.. Note the impresive loop in the hodograph.


Dewpoint temperatures seemed to be holding in the mid and upper 60s, with some in the lower 70s in the area. In combination with the temperatures in the 70s suggested pretty low LCLs...and less likeliehood of storms being undercut by cold outflow.


The 0-3 km Energy Helicity Index looked very favorable in our target area.


Later in the day the warm front had continued northward. Here I have simply analyzed the old outflow boundary as a part of the warm front. Note, however, that the weak windshift line/trough noted on the previous chart over the Big Country had shifted northward. The lower dewpoints south of that boundary were brought into the Lubbock area. We believe that this "messed up" the buoyancy/shear balance for the southern storm. In fact, the storm consistently split early in its life cycle. This was a clear sign that things were not "right" for our area.


Initial storms formed just northwest of Lubbock. We immediately became concerned because the storm splitting resulted in left movers that remained existant. This suggested that the shear profiles and/or the buoyancy were not quite in the proper balance.


This is the same storm just northeast of Lubbock. The updraft area on the right flank consistenly became undercut by outflow, although there were occasional signs of rotation in the scud.


This is a zoom of the same updraft area a few minutes later. Note the weak tornado on the right (east) and, possibly, another on the west.


Here is an example of a microburst in the process of undercutting the mesocyclone in the middle foreground.


The scud fingers on the updraft base occasionally showed signs of rotation, while the whole base (in the video) showed very good rotation.