P3.1

an analysis of a prolific tornado producing cyclic supercell thunderstorm

in NUCKOLLS county nebraska, may 24, 2004

High Resolution Figures

Figure 1 Locations and tracks of 11 tornadoes associated with the Nuckolls County storm in Nebraska (source SPC, SeverePlot).

Figure 2 Tornado I (right, near Deshler) at 2115 UTC. View towards the southwest. (Photo: John Monteverdi).

Figure 3 Belleville, KS tornado at 2200 UTC. View towards the northwest. (Photo: Thom Trimble).

Figure 3 Visible satellite imagery at 1932, 2002, 2012 and 2032 UTC showing storm initiation near Hastings.

Figure 3 Subjective analysis of (a) 1513 and (b) 1743 UTC 24 May 2004 surface data. Storm initiation area shown as red box on b. Region with dew point temperatures 68F and greater shown on b.

Figure 4 (a) Base reflectivity, 0.5^o tilt,; (b) storm relative velocity, 0.5^o tilt,; and (c) base reflectivity, 3.4^o tilt, (2051 UTC) from KUEX, at approximate time of Ruskin tornado report (tornado G on Figs. 1 and 2 and also shown in Fig. 5)

Figure 5 The first long-track tornado (G on Fig. 1 and Table 1) associated with the Nuckolls County storm at 2058 UTC, near Ruskin, view to the southwest. (Photograph by Thom Trimble)

Figure 6 Base reflectivity (2105 UTC) from KUEX at 0.5^o and 3.4^o degree tilts, illustrating BWER, as explained in text. T shows the position of the long-track tornadoes near Hebron, seen in Fig. 2. The KUEX radar was intersecting the storm at a range of 56.7 km and at heights of 650 m (0.5^o tilt) and 3366 m (3.4^o degree tilt).

Figure 7 NCEP Reanalyses NAM data, showing key 700 mb features 1800 UTC, 24 May 2004. (a) 700 mb heights d(m) and temperatures (C); (b) 700 mb heights (dm) and vertical velocity (µbar s^-1); (c) 1000-500 mb thickness (dm) and 700 mb absolute vorticity (10^-5 s^-1).

The KTOP (Topeka, KS) rawinsonde ascent was closest to the Nuckolls County storm at 1800 UTC on 24 May. This ascent was deep in the warm air south of the boundary, and showed the lid clearly (not shown) while the KOAX (Omaha, NE –not shown) sounding was just north of the synoptic scale boundary and away from the lid edge.

Figure 8 NCEP reanalysis of surface based CAPE (colors) and CINH (black contours) in J/kg at 1800 UTC 43 May 2004.

Figure 9 1800 UTC 24 May 2004 proximity sounding for Beatrice, Nebraska, obtained by combining (a) KTOP environmental (red) and dew point (blue) lapse rates (from bottom of lid to surface) and (b) KOAX environmental lapse rate (from top of lid) Inset is 1600 proximity hodograph, shown in Fig. 12. Mandatory and significant level wind information for KTOP and KOAX plotted at right.

Figure 10 Proximity Hodograph for the Nuckolls County storm obtained from the 1600 UTC Fairbury (FBYN) profiler and the KTOP wind profile at 1800 UTC, as explained in the text.