Eta model Forecast Hodographs

Helicity was calculated using SHARP (SkewT/Hodograph Analysis and Research Program) for Eta forecast hour 22 (approximate time of the tornado) initialized at 00z, June 2, 1998.

(A) The unedited forecast hodograph.

(B) The storm motion was edited to match the actual motion of the tornadic cell.

(C) The wind direction in the first km. of the forecast sounding was edited to match the backing of the wind produced by the lake breeze on the north shore of Lake Erie, where the initial tornado touchdown occurred..

Helicity values for the three soundings are shown in the table at the bottom. As you can see, the adjustments made in (B) and (C) significantly increased the helicity of this thunderstorm cell.