Surprise supercell intercept

VORTEX2 has been conducting missions in Nebraska for the past few days. It has been pretty disappointing most days. The Plains continue to be pretty quiet. Strong jet stream winds, frequently necessary to provide a source of rotation for supercell thunderstorms, and tornadoes, are flowing only in the far northern tier of states, in North Dakota and South Dakota. Hot moist air, necessary to provide the energy for thunderstorms to form in the first place, has been confined to the far south. So, there have been few places where the conditions for rotating thunderstorms have overlapped.

One of those places was Alliance, Nebraska on Wednesday. VORTEX2 started in Ogallala, Nebraska, and went north to get under the edge of the jet stream. We spent much of the day in a nice town, Hemingford, Nebraska, waiting for storms to develop. We met a lot of the townspeople and even gave a tour to an elementary school class.

In mid afternoon storms began to percolate west of town. Then the chase began. We debated whether to drive north or southeast since there were storms in both areas. The choice was not very clear, and there were a variety of opinions. Both choices had merit. The southern storm was stronger, but the northern storm was in an environment more likely to cause it to become a supercell. It was my turn to be 'mission scientist' who serves as a tie breaker when the 'Steering Committee' of VORTEX2, can't reach a unanimous decision. So, I said, let's go southeast after the 'bird in the hand', the stronger storm. We stayed ahead of that storm for about an hour, and considered deploying the huge VORTEX2 armada around it. But, it never matured into a supercell, so was very unlikely to make a tornado. Would it morph into a supercell when it hit a cold front? Would it never change? Again, we did not know and it fell to me to break the tie by deciding to give up and head back west.

As we headed back to Alliance, Nebraska, most of the Steering Committee, including me, were not optmistic. We were discussing whether to wait for a while, or just to give up and let our crews get dinner at some reasonable hour (at real, non-fast-food, restaurants which are often closed when we roll into towns at 10pm). But, one of our group was more optimistic and recommended that we try a little longer. He sure was right. A weak storm near Alliance quickly got organized. It became a supercell. And supercells are what make tornadoes? We quickly deployed our radars, Sticknets were dropped, mobile mesonets drove back and forth. We finally had a mission, an intercept, on a viable storm, an interesting supercell.

The storm had a hook echo and rotation. One team observed a gustnado, which is a small, tornado-like spin up below a storm. VORTEX2 collected data on the storm for about an hour before it moved away from any paved roads. It never made a tornado. But, finally, we had intercepted a 'real' storm. We were very glad that we had driven all the way to northwest Nebraska, and that we had been tenacious and had not given up. It was also nice to see how the project leaders worked as a group, even when we had different opinions. As it turns out, neither the original choices of north or south were correct, a storm in the middle that all but one of us, including me, wanted to give up on, became the supercell, and we were there.

Today we're moved even more northward, to South Dakota. Chances are only slight for a supercell. But, like we saw on Wednesday, the chances are not zero. Even if chances are slight, VORTEX2 needs to be in the right place at the right time if another surprise happens this afternoon.