30 MARCH 2005: WEST CENTRAL ILLINOIS









  What a great time yesterday in central and east central Illinois, romping around a virtual supercell playground in very agreeable terrain. Kurt Hulst and I observed five supercells, moving south down the line of storms that trailed back to the southwest. We intercepted the “Peoria storm” in Peoria itself, after having observed an initial supercell to the north which organized briefly. On the PIA cell, which was easily the strongest of the day, we observed three funnels and one non-rotating vertical scud protrusion. We did not observe the “debris whirl” under any funnel that was reported by a citizen.

We chose PIA and the area south of there believing that a more strongly capped environment might maintain discrete cell modes longer while remaining close enough to the upper level energy and surface low to take advantage of favorable shear structures. In fact, the storm activity did not coalesce into a line until late in the period when the actual wind shift associated with the Pacific front overtook convection.

The first cell that caught our attention was near Fairview, with the cell that became the PIA storm to the south of it. Both were isolated, high-based, but organized with strong inflow and evidence of low to mid level rotation via banding and striations. Anvils were soft, however, as it was only about 19:30z and the storms had not moved into the higher theta-e environment or the strong low level jet.

On Stormtrack, someone commented how well-suited the roads northeast of PIA were for Wednesday’s storm motions and this was certainly true, but the roads to the southwest of the city are the opposite, and we struggled to maintain position on the northern storm while still keeping our south option open. At last, we moved north of I-74 and intended to cross the river near Chillicothe or Sparland, but discovered the road to Princeville—and our east option toward the river—was closed. Not just closed in the Kansas sense of the word, with complicated choreographies of workers and walkie talkies and stop signs, but closed as in a tunnel had been filled and the road just stopped at the side of this very large hill.

So we had nothing left to do but turn back toward PIA, and cut across the north side of the big supercell, and as we did the storm really cranked up, earned a tornado warning, and spit dime and nickel size hail. We observed the first of our funnel clouds in PIA, north of the highway, a white tapered tube embedded in rain and very high. We followed this cell for the next two and a half hours, and while it frequently rotated and produced vigorous inflow—yanking all kinds of debris and grass across the road at one point—we never saw anything other than high funnels or lowerings, always followed by some of the coldest and most damp RFD I can remember. At the time of the Metamora tornado report, we were looking directly into the area of rotation, and Metamora was in the storm’s core.

Tried our hand at other storms as well: one near BMI, then another coming into Champaign, but while some of the overshooting tops and backsheared anvils were impressive in the setting sun, none of the storms matched the strength of that Peoria cell.

In all, we chased storms from around 19z to 23:30z—a great way to spend the afternoon. Was good to see Mark Sefried and his chase partner Darrin, who showed us a comfortable mom n’ pop diner where we chilled out and talked about the day’s events. My thanks to Kurt Hulst and the people who called to volunteer nowcasting help. I’ll post some photos tomorrow.