Aug 9, 2012 CTC & Radar Comparison

Given active weather pattern (deepening upper level trough over Great Lakes) with showers and storms over Wisconsin, it wasn't hard to find quick growing cells with at least moderate Cloud Top Cooling (CTC) rates.

There were some breaks in the cloud field over northwestern Wisconsin.  Perhaps this helped oen cell in a line to pulse up.  We were able to spot CTC rates in the moderate range with a value of 17 to 18 over northwestern Washburn County.  Further north in St. Louis County of northeastern Minnesota we observed a CTC value of 12 to 13. See Figure 1 below.

Figure 1. Maximum CTC rates of 17 to 18 over Washburn County.

 We then compared the cells with decent CTC rates with what the WSR-88D Radars depicted.  SEe Figure 2 below for the radar image which corresponds to Figure 1.

Figure 2. Radar image at 1643Z August 9, 2012.

The decent CTC rates would imply an increase in cell intensity observed on radar.  This intensity increase is noted in Figure 3 below, especially in the St. Louis cell which had a 60 dBZ signature.  Of course, these storms were not severe, but it was nice to see that the CTC rate idea enabled us to anticipate an increase in cell intensity.

Figure 3. Radar image at 1706z August 9, 2012.

Rusty Kapela - MKX
Ed Townsend - MKX
Justin Sieglaff - CIMSS