May 22, 1999

With The VORTEX Armada In West-Central Kansas

We participated in the VORTEX (Verification of Rotation in Tornadoes Experiment) project from May 22-May 26. On May 22, Thom drove NSSL 4 (the van in the far background) and John drove Probe 2 (white vehicle second from left).

The pattern that day featured a large outflow boundary in central KS, with upslope flow to the west. A disturbance coming through eastern Colorado was expected to trigger thunderstorms in a shear environment favorable for tornadic supercells. Unfortunately, the disturbance arrived late, and most of Kansas stayed capped.

Here we are near Hays, KS. Waiting for storms to develop. None of significance did in our area. However, a complex of storms had developed in central Nebraska and had evolved into a bow echo/derecho. This MCS was on its way towards central KS. We were recalled to Norman because of this--a round trip of 680 miles with a 15 minute stop in Hays.

This is the surface analysis just about as we returned to Norman. The derecho had progressed southward to south-central KS. Note the complex outflow boundary stretching across KS. The derecho was in fact a cluster of multicell thunderstorms with severe outflow winds.